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I am trying to get a CV of Hydrogen Peroxide on Prussian Blue which I electrochemically deposited on screen printed carbon electrode.
I am using hydrogen peroxide as the signature molecule to electrochemically detect lactate. I read a few articles which have done this, and they refer to redox peak a 0 V as a signature potential step to do chronoamperometry, but I haven't been seeing this peak.
The best sensor response I get is at a potential step of -0.55V instead of 0V but I don't get any corresponding peak in the CV at this potential.
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I do have experience of detecting hydrogen peroxide from a lactate oxidase enzyme using prussian blue, if I saw your data I may be able to help - I don't check researchgate a lot you can find me here - https://www.zimmerpeacocktech.com/contact-support/
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How to do electrochemical detection of trace heavy metal ions detection without using stripping voltammetry?
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If you have only detect the heavy metal ions you can use cyclic voltammetry. But if you want to quantify as well then anodic stripping voltammetry is the best option!
You can use other alternate techniques:
Amperometry
Potentiometry
Electrochemical Impedance Spectroscopy (EIS)
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Dear all
I am trying to do an electrochemical detection of cholesterol and triglyceride, so kindly help me with some valuable inputs. Kindly help me with some reference for the same .
Thank You In Advance
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For cholesterol: You have to add surfactant like Triton X-100. For e.g if you want to prepare 30 mg/ml stock solution, then add 60 mg of cholesterol to 1 ml of Triton X-100 and stir it under heating at ~ 90-95 deg C until the solution become transparent. Then add 1 ml of IPA, allow it to stir for 2 min, bring to room temperature. You can store it in 4 deg C and prepare the dilutions in whichever solvent you want when DI water.
For triglycerides: If you are using triolein, mix it first with Triton X-100 and then with Tris-HCl buffer. heating is not needed. This solution will be milky but homogeneous. Prepare the dilutions in water or PBS whichever solvent is needed.
Hope this helps
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Peak appearing ~ at 0.58 V - 0.56 V.
Scan rates tested: 50 mV/s, 100 mV/s, 200 mV/s, and 500 mV/s. for 50 cycles at max.
Electrolytes used: 0.1 M NaOH, 0.1 M Phosphate buffer solution (pH-7.4) separately.
Cleaning methods tried: pulsed ultrasonication of 1 min, multiple times cleaning using 0.3 micron alumina slurry.
Reference electrode: Ag/AgCl
Counter electrode: Pt wire
CV system and GCE: Metrohm Autolab
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If you contact me here I will help - https://www.zimmerpeacocktech.com/contact-support/
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Why lead oxide nanoparticles cannot be used in electrochemical detection of heavy metals? Although it can be envisaged as suitable anodes for decontamination of waters containing organic polluants.
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Because lead is a heavy metal..quite toxic just like Cd, Hg, etc etc..
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I wanna calculate the efficiency of an electrochemical detection of heavy metal ion using SWASV
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Javier Ernesto Vilaso Cadre, bravo!
There is indeed no such thing as “efficiency”, which is quantified for (electro)chemical sensors, and “efficient” is a confusing term in regard to them. If we look at the IUPAC Orange Book, we will see that “efficiency” is among the terms used in photochemistry and in light scattering. One can talk about luminous efficiency, quantum efficiency (quantum yield), scattering efficiency, and other concepts of physics. The charge-transfer efficiency is directly related to radiation detectors (charge-transfer devices) rather than electrochemical detectors. Sometimes there is a mention of efficient (analytical) methodology but not in quantitative terms. To sum up, “efficiency” is not among the terms characterizing analytical properties of an electrochemical sensor.
Regards,
Rouvim Kadis
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Hi everyone
I'm looking for Laviron's equation for adsorption controlled process, could anyone help me?
thanks
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This image contains Laviron's equation for adsorption-controlled process.
You can read the article titled: "Trace analysis of Ponceau 4R in soft drinks using differential pulse stripping voltammetry at SWCNTs composite electrodes based on PEDOT:PSS derivatives"
You can also follow the last question I asked.
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If I use TiO2 sensors for quantification of organic matter in a matrix where quantification using this photocatalytic substance has not been tested, would this be a good topic for an article? I know there are many articles on the use of TiO2 for sensing applications, and obviously this is not a recent topic. But are these sensors still a good option and a valuable research topic?
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Dear Javier Ernesto Vilaso Cadre, I think yes regarding many advantages related to economy/performance, ease of processing and formulation, to answer the required end use criteria. Please have a look at the following recent review. My Regards
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I use gold ultramicroelectrode (~ 10 um * 10 um) as working electrode. After electrochemical polishing, 2 uM haipin probe (3'- HS-SH-C6-CGCCAATATTTATGGCA - MB -5' TCEP reduction) was droped into the surface of ultramicroelectrode. Incubate at 4 ℃ overnight. After washing with deionized water, three-electrode mode was used to detect the MB signal in PBS by using SWV method. But I can get stable signal.
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Hi Kai Sun ,
Try also to block the void spaces with thiols. So after the immobilization of DNA, try to fill the void spaces with thiols such as 6-mercapto-1-hexanol in PBS pH 7.4 for 60 min.
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I am giving potential to my sample which is anodic region from -1000mV to 200mV, and i get a current response both having positive and negative sign..
I am confused about current flow, as per my understanding current need to flow in one direction as this potential range which i am applying is anodically active region. Then why current change its sign??
Plz help...
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Since your LSV experiment has a potential window that goes from negative (-1V) to positive (+0.2V), it is likely that you will get a current that follows the same trend, so this is not unusual.
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When using the modifiedcarbon paste electrode (CPE) for electrochemical detection, most of the time the response is weak, how can we improve the response?
I think that one of the main factors is the used paraffin oil? What do you think of this?
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well, many times is a matter of the paraffin to carbon ratio used. The name "carbon paste electrode" usually misleads people to think that the mixture should be a paste, when in reality the amount of paraffin should be quite small and the carbon remains like a loose powder that can be compresed to a solid homogeneus state. but, by my experience if the mixture looks like an actual paste then it has to much paraffin an the response is usually small
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I'm working on electrochemical sensing drug molecule. My workstation is Origalys (origaflex 500). In papersa particular concentration is reported for every sensing studies like 200micromolar etc. How to do chronoamperometry for the sensing application and what is the relevance of this concentration. How to get this value of concentration
Please share your ideas
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When using chronoamperometry you would first need to be in steady state using either a rotating electrode or a stirring bar in your experimental electrochemical solution. Then, you would need to apply a potential to monitor the response in current. But first, does your analyte has a specific redox potential value ? How do you plan to sense the response ? Is it direct detection of the analyte of indirect ? Which electrode are you using (material, geometry, surface modification …) ? Are you building a biosensor ? I thank you in advance for providing more details so we could help further.
Once you set up your apparatus and answered all these questions, I suggest to add known concentrations of analyte of increasing values (both in concentration and volume added) into the electrochemical solution in order to build a calibration curve.
Best regards
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Ferrocene (Fc) has been regarded as a helpful catalyst for the electro-oxidation of dopamine, ascorbic acid, Levodopa, etc., at different potentials.
If anyone suggests to me any literature about why ferrocene works as a catalyst for particular analogs (e.g., dopamine, ascorbic acid, uric acid), not for others (e.g., glucose), that will be helpful.
Thanks.
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Hi. I hope the following article could help you: https://hal.archives-ouvertes.fr/hal-03066386/document
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I am using screen printed carbon electrode (scpe) for cyclic voltammetry in my sensing studies. The electrolyte is PBS solution (pH=7). I got the CV for bare SCPE without much noise but after coating of the nanomaterial I couldnt get any proper response instead very high noise in the CV. I tried with two different nanomaterials and tried two different coating methods (without and with binder), but the observation is same.
I am attaching the picture of noise I got.
Please discuss your valuable suggestions for solving this issue. I haven't done any pretreatment for the scpe before coating the sample
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In electrohemistry, noise ideally needs to be removed t source since electrochemical devices are typically non-linear for most of the i-V characteristics and noise will be rectified leading to current offsets. It is possible that it is simply a coincidence that the nanoparticle modification happened before the noise increased. Do a quick Fourier transform and see what the dominant frequencies are- this could let you know if it is pick-up from the power supply- as this will be 50 Hz (UK and Europe, or 60 Hz US) and probably the odd harmonics, but make sure that the sampling frequency is as high as possible, but at least >100 Hz. Did you change the sampling frequency after the treatment? Your noise might previously have been aliased to very low frequencies and not seen. Also, what reference electrode are you using? If this is the one on the screen printed electrode, these are pretty terrible at the best of times, but some alteration in the surface chemistry could lead to increase Ref-solution impedance. Changes in contact resistance after the treatment is another possibility.There are some useful tips on noise in our paper "Lifting the lid on the potentiostat" and the electronic supplementary information shows real world examples: Physical Chemistry Chemical Physics (2021) 23 8300.
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Can we perform electrochemical detection process of analytes by only using water without any supporting electrolytes?
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Thank you Dr. Khaled Faisal Qasim for your contribution
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Iron vanadate catalyst was coated over SPCE and the EIS curve was measured in the presence of 5 mM K3[Fe(CN)6] and K4[Fe(CN)6]/0.1 M of KCl solution.
Thanks in advance!
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Dear Ganesh-Kesavan,
for more help you have to:
1) re-plot, please, Nyquist Z'_-Z'', both (Z',-Z'') axes under the SAME (Z)scale, (0, 4500) 0hm, e.g. origin(s)=0, and Z'max=-Z''max=4500 0hm.
2) Also, show, please, a Bode plot(s), or note the frequency limits of your Z-measurement.
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Hello, i have a question about Cyclic voltammetry. I made planar sensor with all 3 electrodes (WE,RE,CE) with AgNP ink. Problem is when i try clean the surface with only 0.1M KCl, the current reach 100 or 1000 times more then it should. Almost same results are if there is added 5mM ferro/ferri on 0.1M KCl. I tried to use printed silver RE with classic WE (Pt) and CE (Pt) and printed silver CE with classic RE (Ag/AgCl/KCl) and WE (Pt) and current of 5mM ferro/ferri in 0.1M KCl was in expected window (under 100 uA). Then i tried printed silver WE with classic CE and RE and current was again in units of mA. My knowledge of chemistry is very low so i dont know if there is some kind of reaction.
My main question is why and what happens and if different buffer intead of KCl can work. If you can redirect me to some web page or article it would be great. Thank you.
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Thank you Dagwin Wachholz Junior and Teemu Tuovinen for your answers. I will try Potassium nitrate as buffer for fully Ag sensors and I try print another sensors with Carbon WE. If these atempts fail, I will try phosphate buffer. Again thank you both for help.
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While testing my target X, it has an oxidation potential at 0.5V. For the interference test, a mixture of my target X and an interfering ion Y was done. While running CV or DPV the oxidation potential has shifted. How to explain that?
Also, what does mean if I get a large oxidation peak instead of a sharp one?
Thank you!
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The change of the peak shape and the oxidation potential indicates that the interference ion Y affects the CV. The interference ion Y can broaden the peak shape and oxidation potential in three ways at least. 1. interference ion Y reacts with the analyte X to form a new compound; 2. The Y may be adsorbed or interact with the working electrode. Consequently, the electrode surface has been changed to show the broaden peak and shifted oxidation potential; 3. The Y is added so much that it changes the electrolyte solution significantly. The reorganization energy of the X has been affected to the CV.
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I tried with DI water but it cannot fully dissolve melatonin.Some people suggested to use little ethanol. But i have a confusion that if i use ethanol then it may have interference duringelectrochemical detection.I need some good suggestions.
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Thank you very much@Firas A. Al-Lolage
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I'm trying to determine the best way to detect changing dopamine levels in primary neuronal cultures under different treatments/stresses. The literature seems very hard to follow as methods and equipment used are not explained very well. I've found that electrochemical detectors coupled to a HPLC seem to be fairly standard, but it's very difficult to understand which company is the best to buy a detector from, from ESA no longer sell? and whether they will fit with most HPLCs? Or whether this is now an out dated method and there is a better way?
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In my opinion, electrochemical detection is still quite a useful and relatively simple way to detect dopamine. Dopamine is highly electroactive, i.e., is oxidized at fairly low potantials, therefore, the method can be very selective.
It can be determined either using amperometry in liquid-flow techniques, such as HPLC. However, bulk techniques such as voltammetry can be also used. As an "electrochemical detector" in HPLC basically any potentiostat capable of performing amperometry can be used (look at potentiostats from Metrohm). Then a very simple electrochemical cell is constructed, very often in wall-jet arrangement, and it is connected to virtually any HPLC system (see for two examples of detection cell arangement). Also, you have to choose your working electrode. In my opinion, boron-doped diamond is a good candidate (https://pubs.rsc.org/en/content/articlehtml/2015/cp/c4cp04022h). This paper could help as well.
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Hi Research gate community,
I'm currently working on HPLC/Electrochemical detection method development for a peptide Hepcidin-25 (also known as iron regulator). After trying different gradient profiles with phosphate and acetate buffers in acetonitrile and methanol respectively, I came to the conclusion that Hepcidin-25 is not electrochemically active.
So I began searching about techniques that can be used to make amino acids and peptides electrochemical active and found that the most popular technique is derivatizing with OPA/ beta-mercaptoethanol or OPA/sulfite, for aminoacids. Although this technique was never applied to peptides, I'm willing to try and check if some amino acids in the peptide are going to be derivatized. Biuret's method was found to be successful for peptides, but it was never used with HPLC and required a very high potential to oxidized for some peptides.
Does anyone know if there are any other methods that may be worth exploring to make this peptide electroactive? or otherwise, I have no option but to collaborate with labs equipped with HPLC-MS/MS.
Thanks in advance!
Amino acid sequence of Human Hepcidin 25 is:
Asp-thr-his-phe-pro-ile-cys-ile-phe-cys-cys-gly-cys-cys-his-arg-ser-lys-cys-gly-met-cys-cys-lys-thr
Mobile phases combinations tried:
(A: 50 mM NaH2PO4 (pH~2) in water, B: 100mM NaH2PO4/ acetonitrile/methanol 30/60/10 (v/v/v) pH~2) and
(A: 100 mM Lithium acetate in water, B: 100 mM Lithium acetate/ methanol/ acetonitrile 10/80/10 (v/v/v))
Column: C18, 4.6 mm x 250 mm, 5 um, 300A
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Hello,
There are a few different ways to approach your problem.
With 8 Cys present, hepcidin-25 should be electrochemically active. It may be that your sample is oxidized and no longer detectable. The easiest way to address this is to treat the samples (standards and biological0, first with a reducing reagent like dithiothreitol (DTT). Selvi shows how to do this with glutathione.
(Selvi, M. Bharath. "Biochemical Mechanisms of Homocysteine and its Role in RETINAL VASCULAR DISEASES." PhD diss., BITS Pilani, 2015.
See also: Sakhi, A.K., Russnes, K.M., Smeland, S., Blomhoff, R. and Gundersen, T.E., 2006. Simultaneous quantification of reduced and oxidized glutathione in plasma using a two-dimensional chromatographic system with parallel porous graphitized carbon columns coupled with fluorescence and coulometric electrochemical detection. Journal of Chromatography A, 1104(1-2), pp.179-189.
Zhang, M. and Pfeiffer, C.M., 2004. Comparing the ESA HPLC total homocysteine assay with electrochemical detection to the CDC in-house HPLC assay with fluorescence detection. Clinica chimica acta, 340(1-2), pp.195-200.}
Standards of glutathione or oxidized glutathione (10 µg/mL) are made in buffer. 50 µL of standard is mixed with 5 µL of 50 mM DTT at room temperature for 10 minutes. 10 µL of the mixture is injected into an HPLC (Buffer: 0.1% trifluoroacetic acid, 2% acetonitrile, 98% MilliQ water; Flow rate: 1 mL/min; Pressure: 400 bar; Temperature: 27.7 °C; ECD with glassy carbon electrode; Range: 1 µA; E cell: 0.90; Voltage: 1.16V; Column: ODS Hypersil C-18, 5 µm particle size, 150 X 4.6 mm).
Note that the moles of disulfide bonds per gram of oxidized GSSG is different than the moles of disulfide bonds (possible) in hepcidin-25 by ~1.75:1. So you might want to make the DTT solution a little stronger (~90 mM). You could also add more 50 mM DTT solution but that will dilute your sample.
Since you are open to other methods, I have attached a chapter on thiol-reactive fluorescent dyes that you can use to label Hepcidin-25. Again, remember the stoichiometry and be sure to first reduce any disulfide bonds in Hepcidin-25 (intra- or inter=molecular) and also use enough thiol-reactive dye to label all 8 Cys.
Best regards,
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First, i coated Hexanedithiol on to the gold surface and then blocking remain gold surface used Mercaptohexanol. After that Benzoquinone was coated on gold surface. We reduced the benzoquinone using electricity. Finaly, thiolated peptide was coated on to the gold. And measured using SWV.
(Buffer-4mM Fe(CN)3-/4- )
Question 1. We can't observed clean peak in SWV. How can i get a clean peak?
Question 2. Some research papers suggest that SWV should measured many times to get stable and clean peaks. Is this suggest
correct?
Thank you for interest to my questions.
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Chaehwan Cho check your frequency. You need to run your experiment on different frequency e.g. 5, 10 or 15 and choose the one that is very clear. I am very much sure you will resolved your issue and will get very clear results.
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I have seen many researchers including Prof Alan Bond measure the effective areas by measurement of the peak current obtained as a function of scan rate under linear sweep voltammetric conditions for the one-electron oxidation of Fc [1.0 mM in CH3CN (0.1 M Bu4NPF6)] or reduction of [Fe(CN)6] 3- [1.0 mM in water (0.5 M KCl)] and use of the Randles-Sevcik equation.
The classic IUPAC paper (Trasatti and Petrii 1991, https://www.sciencedirect.com/science/article/pii/002207289280162W) provided us with some other important recommendations in different conditions (one example is via reduction of gold oxide)!
I would like to know whether there are any disadvantages of using the Randles-Sevcik equation for measuring the area? Do you prefer any other methods over this one while working with a reversible reaction on gold disk electrode?
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Firstly, there is an important distinction to be made between the “surface area” and “geometric area” of an electrode. Surface specific methods, such as gold oxide stripping, will tell you about the former, as pointed out by Danny O'Hare , in his response. Redox mediator methods, such as the oxidation of Fc or reduction of [Fe(CN)6]3- will tell you about the latter. This is because even an atomically rough surface will look “flat” on the scale of the diffusion layer, hence the diffusion limited current is sensitive to the geometric area, rather than the true surface area (note that the ratio between the two, surface area/geometric area, is the “roughness factor” of your electrode).
As for your original question, while it is true that Prof Bond often uses the Randles-Sevcik Method to calibrate the geometric area of electrodes used in electroanalysis, two important assumptions need to be made in this case:
1) The reaction is electrochemically reversible (Nernstian) on the timescale of the experiment –this is always true for Fc on metal electrodes at scan rates less than 1 V/s, but may not be true for the case of [Fe(CN)6]3-, which can exhibit some deviation from reversibility on some electrodes.
2) The contribution from uncompensated resistance, that is iRu, is negligible.
The voltammetric peak current, ip, is influence by both the electron-transfer kinetics (k0) and iRu, making it a less than ideal form of analysis.
Another method that you could try is semiintegration, which converts your peak-shaped transient voltammogram into a sigmoidal-shaped semiintegral voltammogram. Unlike the peak current, the diffusion-limited plateau of a semiintegral voltammogram is insensitive to both k0 and iRu.
Details can be found in: Bentley, C. L.; Bond, A. M.; Hollenkamp, A. F.; Mahon, P. J.; Zhang, J., Advantages available in the application of the semi-integral electroanalysis technique for the determination of diffusion coefficients in the highly viscous ionic liquid 1-methyl-3-octylimidazolium hexafluorophosphate. Anal Chem 2013, 85 (4), 2239-45.
Hope this helps,
Cameron Bentley
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We have synthesized graphene foam via hydrothermal route. When we carry out electrochemical tests in the KOH solution,
the foam gets fragmented. Is it possible to use a Carbon conductive adhesive tape to fix the foam?
I would appreciate if any one could help.
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Dear Ali Farzaneh many thanks for your helpful comment.
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I am looking for information regarding Differential pulse voltammetry method to detect organic contaminant using nano biosensor, .... i have also question regarding their advantages to other methods such as USING GC and GCMS.
What is its strong feature?
i need some quantitive source and information  to compare its cost and accuracy and its process of dpv to gc.
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Dear Shariat Mobasser with DPV you will see the change in the current response with the potential and the change in the current will be proportional to the contaminant present. In DPV it is very important to known the exact potential range of working. With the change in the analyte i.e contaminant in your case the potential range may vary. CV will give you the potential values. DPV is extremely sensitive.
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Hello, we are using the method described here, , for an application in our lab. In short, we add biotin UTPs to an isothermal reaction, followed by incubation with SA-magnetic beads and SA-HRP, and finally TMB for colorimetric analysis. In our initial experiment, we had high colorimetric background in our no template control sample.
After incubation with beads and HRP and magnetic isolation, we wash three times with five times the reaction volume using 0.5% Triton in PBS.
We repeated, using molecular grade water as our product, eliminating BSA in our SA-HRP diluent, since BSA can contain biotin. This increased background.
We repeated again and increased BSA in our SA-HRP diluent. This helped a bit, but we still see high background.
Could the beads and HRP be interacting with each other causing the background? Something else?
Thank you in advance!
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The reason is poor coating on the surface of magnetic nanoparticles. This allows interaction of peroxide with iron core that catalyzes it causing TMB to change color.
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Hello,
I read two research papers regarding electrochemical detection of two analytes: potassium ferrocyanide and hydrogen peroxide. I notice that the resulting i-t curve for each experiment looks different from the other. Why is that ( potassium ferrocyanide samples generate a rapid current increase followed by a rapid current decrease while H2O2 samples generate a rapid current increase followed by a graduate current decrease)? Also, how can I integrate the charge values for the hydrogen peroxide curve, in term of integration limits? I attached an image that shows both curves.
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Dear Motaz,
It is simple! The only difference is the way experiments are done. In both cases you apply a potential to get a current, in the first case is the oxidation of ferro to ferricyanide, directly or as an electron transfer mediator in a glucose enzymatic sensor. Glucose oxidase oxidizes glucose to gluconolactone and then ferricyanide is reduced to ferrocyanide. You apply a potential to oxidize ferrocyanide.The anodic current is proportional to the concentration of glucose (or the charge, integral of current with time, area under the curve, can be related to the number of moles by Faraday's law).
In the second case it seems that the curve i-t corresponds to the reduction of hydrogen peroxide (be careful with the signs, in common literature anodic current is positive and cathodic current negative. I'd have to check it better in this paper).
In any case, in the first case there is no any stirring, you deposit a drop on the paper and ferro is oxidized and current is decreasing according to Cottrell equation (there is o any stirring).This was not done on a flow cell but a paper cell, ferrocyanide is consumed from one to the other (coulometry).
In the second case you have a conventional cell with three electrodes (Pt counter, Ag/AgCl reference, and the modified working electrode) and you stir the solution. Since you stir the solution, you get a plateau instead of a peak because you are transporting new molecules to the electrode surface by forced convection. Molecules arrive to the electrode and are oxidized or reduced, and in the plateau you have the limiting current (as soon as they get to the electrode they are oxidized, the rate of mass transport equals the rate of electron transfer). If we don't stir, then the concentration on the surface electrode decreases (there is no efficient mass transport) and the current decreases (as happens in the first case).
There are two phenomena: 1) electron transfer, 2) mass transport. The difference between both is the mass transport. In the first case there is only diffusion and in the second case we add forced convection.
Concerning the charge, in the first case is the area under the curve, many software have this possibility, or you can even calculate with triangles (triangulation?). In the second case, you can take the current obtained with time, but I don't see the aim. In the first case we did it because we demonstrated the possibility of performing coulometric measurements.
Good luck!
Best,
Teresa
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I work on the determination of the three component system of heavy metal ions (Pb2+, Cu2+, Cd2+) in water by an anodic stripping voltammetry technique on a thin film of mercury on the glassy carbon electrode. According to my observations, there is no interference between the determination of such metal ions. I have some samples that were in contact with an adsorbent. After adsorption equilibrium, the solution was separated. I want to know how much of the mentioned metals are retained in the solution. My advisor insisted on the standard addition of three metals in sperate runs, and it will be so tricky because of the high number of samples. Do I want to know what if, all three metals added simultaneously in the standard addition process?
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Hi Mohammad,
My point is as M. Toner's, do as your advisor indicates... no need to explain why, there are multiple reasons...
Related to the standard addition methodology, it is very useful to avoid matrix interferences. If you know there are no this type of interferences you can use external calibration. However, you can have different matrices, so then it is better to use standard additions.
About adding all-at-once (Pb, Cd, Cu) or one-by-one, obviously analysis time is an important parameter and it would be desirable to add all in the same addition. Initially, I don't see any inconvenience, but it will depend on the concentration level. If the concentration is very high you can "overlap" peaks (e.g. Pb and Cd are very close) and make measurement difficult. As C.Radu says, there are a lot of bibliography on ASV and probably this is well documented.
On the other hand, although ASV is an excellent technique, you can also consider the proposal of M. Farooq and use AAS as a validation technique, if the species to be determined are the same (maybe different results respond to different species of the same element).
Apart from this, society requires low-cost and decentralised analyses and the use of gases, flames, expensive and technologically complicate instrumentation (not portable) is not in this trend. In any case, both enter in the toolbox of analytical techniques and have specific excellent applications.
Best regards and good luck
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Hello scholars,
Recently, I have been working on AOR. I have obtained interesting results, however, the result is a bit disturbing as it comes with noise in the curve. Below is a picture of such. I have read up some of the suggestions presented to similar circumstances in RDE measurement for ORR. I have not been able to overcome the challenge. For my circumstance, am working using Pt wire/coil as counter, Ag/AgCl as reference and GC as working electrode in 1M NaOH.
NB:
1. No leakage in RE as I have checked a couple of times and I have about 3 of these REs at my disposal, so I can interchange and check if there is any leakage (issues) with either of them. The aligator clips look good and have also interchanged with spare.
2. No mechanical vibration / interference as the lab is set up in the basement of the building and the experimental setup is on a standardized experimental bench. In addition, am not working on a hanging electrode.
3. From the picture, I have worked between -0.7eV and 0.6eV. However, I do work also in the range of 0eV and 1.4eV
4. The experimental solution has been prepared hours prior to the the measurement, and given enough time to acclimatize to the room temperature. As regard to the GC electrodes, I follow the standard rules. Polishing via the "8" pattern using 0.05um polishing alumina once in 5 days on the polish and DIW for rinsing.
Do you have any other suggestion?
Thank you
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Try to increase the sample interval and sensitivity to 0.005 it might help (I remember something regarding the ratio between scan rate and sample interval)
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Why the amperometic curve (under stirring condition) will has perfect straight line (Figure 1) but some of them will have slanted line (Figure 2) ?
The current of oxidation of analyte (Electroactive sp.) in amperometric curve should decrease after the increement as the analyte is oxidized by the modified electrode and the concentration of analyte is decreasing?
Please advise. Thanks.
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Hello,
In the stirring condition, diffusion process occurs fast, that's why you observed straight line in the calibration curve. However, At certain level of analyte concentration, there may be possibility to saturate the electrochemical sensing platform or products may bind with the electrochemical sensing platform and reduces the amperometric response for the analytes. In few cases at high concentration of the analytes, the current responses decreased due to formation of complex formation or intermediates which hinders the electrochemical process.
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Hello all,
I'm looking to improve the sensitivity of a mediated carbon electrode. The mediating compound is being added via solvent casting post electrode printing, so any additional treatment/ modification can be applied at any stage.
So far I have tried using MWCNTs, Pyyrole, nafion, and various potentials of anodisation using NaOH, and cycling in H2SO4.
Can anyone suggest other methods/ protocols that may improve my electrode sensitivity without creating too much background?
Regards.
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Hi,
Apart from all that has been saitd, it seems very important too, to eliminate the solvent in order to decrease capacitive current. You can try to cure them more time.
Good luck and best regards
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My work is on biomolecule sensing by potentiometry (CA, CV, etc.). Concentration of each individual biomolecule can be easily monitored by variation in current or voltage, but how to check selectivity i.e. which specific biomolecule is present in a mixture of different biomolecules. In case of heavy metals the redox potential difference is high which is not the case in biomolecules. So please suggest me how to sense or discriminate specific biomolecule (ex. amino acid).
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Hi Ishu Singhal ,
I have few suggestions for you.
You must do (know) the following:
1. What is the charge of your molecule (analyte) at the working pH? (you can get this from the pka of the molecule).
2. What are the charges of the other interfering molecules.(you can get this from the pka of the molecules).
3. Does your molecule have specific interactions such as pi-pi with your electrode material or thin film.
4. Are there any materials in the literature that showing selectivity towards your analyte.
5. Design an electrode material based the factors above.
6. Use Differential pulse voltammetry technique to know the selectivity of the platform towards your molecule.
7. Do some control experiments such as blank, molecule of interest, and the interfering molecule one by one. Compare their responses and come to a conclusion.
I hope that these steps will surely help you.
Have a great time...
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I'm performing a photolytic reaction that liberates a species that is electroactive and detected amperometrically on a Pt electrode. The illumination occurs directly on the Pt working electrode and results in an increase in background current even when evaluating a blank sample.
Is this due to photocurrent in the Pt working? I thought this was more prevalent in semiconductors. Or perhaps it's photoelectric effect?
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Hello, Zheng, I also found similar effects in a green ns laser irradiated Pt electrode. I am looking forward to see if there are any updates on this thread.
Best,
LW
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I want to reduce NaBO2 to NaBH4 on a catalyst (electrode). Kindly provide me suggestions of how can I confirm that the reduction of NaBO2 to NaBH4 is taking place or not?
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IR. Peaks around 2300-2400 cm-1 can't be confused with much else. not the best technique for aqueous solution though, you;d have to isolate and dry. Raman better for aqueous solution, A1 totally symmetric BH4 str breathing mode at 2310 cm-1. such peaks provide positive fully diagnostic evidence.
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We use this acid bath to clean electrochem glassware. A recently prepared one has turned faint yellow after 3 or 4 uses. We've been trying to rule out possible sources of contamination. Could KCl contamination be the cause?
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Maybe formation of HCl (from contamination with KCl ) and, consequently, aqua regia? The regular colour of aqua regia is a faint yellow.
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The material or compound could be in solution from where it could be electro-deposited onto a second surface but the deposited layer of material from solution becomes non-conducting after deposition.
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Hi,
I suggest to you use the polymer with low conductive or any composites which deposites on the surface .
Regards,
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Various methods as finding capacitance have already been discussed in some papers but it seems that reliable figures and data is not available. BET is out of question as metal catalyst is carbon supported. Is there any other method that could be used to determine the electroactive surface area of non-noble metals.
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Hi,
The electrochemically active surface area depends on the specific reaction for each electrode. A possible approach:
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I'm calibrating Hg/Au amalgam electrodes for Fe(II) in redox analysis. Based on literature, I should be able to do this at 100 mV/s scan rates with a 100nA/V sensitivity. However, this rate is too noisy. While reducing my scan rate to 10 mV/s helped with noise, I still have a peak issue. I should be seeing a peak around -1.5 to -1.4 V, and instead its closer to -1.6 V. Is this an issue with a faulty Ag/AgCl reference trode? Or a Working Electrode polishing issue? I plated using 0.16M Hg(II)Cl2. Or even my supporting electrolyte? (0.02 M NaCl)
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Dear Jeff,
It's essential to know the sources noise of square wave voltammetry due to the following reasons:
- The scan rate that includes not enough to cover all potentials with current.
- The reference electrode that you used with high resistance, use a another electrode as Hg2SO4/Hg.
- The electrolyte of solution high resistance / high conductivity.
- essential the dives set not calibrated in correct way/ or from the long time
- pre-treatment of working electrode not enough to prepare it.
- Might be bubble form on the surface of the reference electrode.
- Use trace support electrolyte to reduce the fast migration of ions towards the surface of working electrode.
- Pass the nitrogen gas with high purity in solution of electrolyte before run the EXP. To reduce the OXYGEN oxidation.
Best wishes,
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I have arsenic precursors like arsenic tirioxide,  i need to prepare AS(III) solution for the electrochemical detection.  Is it need to dilute arsenic precursor in acid to make AS(III)? or else we can use any base?  If we need to use acid or base what is the required concentration of acid or base in the preparation?
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To dissolve As(III) oxide, you have to put As2O3 in a glass beaker, add water, heat mixture close to boiling point and while keeping that temperature, start adding the peaces of solidus NaOH, while constantly stir the solution. Peaces of NaOH have to be added successively, next peace have to be added when previous is completely dissolved. When As2O3 is completely dissolved, leave solution to cool and then neutralize (set pH to desired value) with appropriate acid. I used 2M solution of sulphuric acid.
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What is the difference of a species preadsorbed at the electrode and having the species suspended in the electrolyte? 
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Hi Marlene,
In addition the above answers I recommend you to take CVs at different scan rates, to find out the surface confinement of the electroactive species under study. up on ploting  the graph for E(potential) vs v(scan rate) ,you should get a straight line passing through the origin. if it is diffusion controled the straight line you got will be for E vs square root of the the scane rate.
A
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Dear researcher
i am working on electrochemical detection of DNA and proteins after adsorption of Fc-DNA probe or Fc-aptamers on reduced graphene oxide modified electrodes. But, the sqaure wave voltammetry signal is not stable with time. always there is 5 to 10% decrease in the swv signal which cannot be used for further measurement. does anyone saw this issue before and how can we figure out it. many publications have been published in this field bit none talk about the stability of the adsorbed DNA containing redox tag.
regards
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Dear,
Although my main experience is with gold-thiol chemistry, the problem seems very similar. After modification of the electrode surface there will always be loss due to non specific adsorption. This may be due to weak interactions or crowding of the electrode surface. Depending on your modification method, I would consider a loss of 5-10% reasonable. Normally I used to include "desorption" step in the modification method. This is essentially an additional incubation which mimics the conditions of the test (but without the analyte).  Normally losses should become smaller after this. To distinguish between stability of Fc or the desorption of DNA probe, you could  use a unmodified DNA probe  and use  for example Co(phen) to characterize the electrode. If the loss is similar under these conditions then the problem originates in the probe adsorption not the ferrocene labeling or Fc stability. Hope this helps.
Kind regards,                          Mike
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hello everyone, I am a beginner in the field of biosensors and I am working on rGO based SPE for glucose detection. I am facing some problems such that the redox peaks are occuring in the negative potential and the peak to peak seperation is too high than 59 mV. what are the possible reasons? Need some expert advise. please find the attachment
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Dear Anas
This kind of behavior is typicl fro SPE with carbon electrodes. Usually is the combination of carbon / silver ink. I should recomend you to use mateprics carbon/grafite inkk. It could improve the performance of your SPE. 
product SRCE-001 Resistive carbon ink for electrochemical sensors
Regards
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Because, I am getting negative intercept for my dopamine sensor (diffusion controlled process). When i am plotting the peak current vs square root of scan rate, i am getting negative intercept. But when i plot with scan rate it shows positive intercept. So, what is reason behind this, and what the intercept stands for......
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Generally, a process that is completely diffusion controlled shows the intercept at 0. However, sometimes the process is diffusion controlled but it is not the only process occurring on the electrode surface. You can also have a look of one of my articles where the same phenomenon occurred to me:
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I'm going to try an electroanalytical methodology for sucralose determination. Sucralose is a sugar substitute, in fact, a sugar-like substance with three chlorine atoms instead of hydroxygroups.
How can I modify a conducting polymer, in order to immobilize covalently the sucralose molecule?
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Thanks!
We pretend to use the presence of the chlorine atoms in the sucralose molecule, in order to immobilize sucralose by them. It would be more selective.
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I found it for Cyclic Voltammetry (Peak intensity is proportional to the square root of the scan rate), but not for DPV...
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From the attached paper, peak current decreases as function of scan rate for a surface confined redox process. 
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Hi,
I am working on electrochemical sensing of metals using Square Wave Stripping voltammetry, I am getting good results ( prominent peaks of analytes) but also there appears peak between 2-4 mV vs. SCE when there is no analyte in system. Is there any method for base-line correction???
My WE is GCE modified with Au-NPs, RE is Calomel 3.5 M KCl, Pt as CE. I am using ultrapure water for buffer synthesis. Do clean cell and WE carefully i am very confused how to remove this error.
What should i do?
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Is the peak present without the Au-NPs? I would bet that the peak you see is coming from some quinone groups of the carbon.
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I have got Rct value of bare GCE of 80 kohm cm2. Please help me to explain why Rct value is high for bare GCE?
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Cleaning is critical step. Some day we should spend time to do it. After polishing remove all AL resíduos with ddwater
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here I have used 3 electrode system, with different types of electrodes such as 6M KOH, 5M NaCl and electrodes are graphene coated Nickel Foams. Is this same potential window can be applied for the CV as well as GCD? I want to know the way how to find out this potential window
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for carbon-based EDLC type electrode , you have to use 0 to -1 V in KOH electrolyte, you can use 0 to 0.8 V in NaCl electrolyte.  For metal oxide, metal sulfide type pseudocapacitor electrode, you have to use 0 to 0.5 or 0.6 V in KOH. using NaCl for pseudocapacitor electrode will not give a good result. The potential window is normally determined by performing CV until there is the occurrence of HER in negative side and OER in the positive side. HER and OER denote the breakdown of aqueous electrolyte and it will be shown by sharp increase in current density. 
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I was trying to polymerize aniline onto GCE and use for heavy metal detection. But the modified GCE shows a huge oxidation peak in square wave stripping voltammogram and none of the metal ions oxidation peak can be observed. But similar sensor has been established and published with successful detection of Pb.
I'm using three electrodes system with GCE, Ag/AgCl, Pt wire for CV and SWSV. Here is what I have done:
1). CV polymerize aniline onto GCE in 0.1M H2SO4 for 10 cycles using classical parameters for polyaniline.
2). Dip modified GCE into distilled water for 3 mins for removal of monomer if any.
3). Put modified GCE into spiked testing solution and run SWSV with 300s pre-depo. time and other classical parameters for Pb detection.
Graphs showed below are 1)untreated GCE in testing solution with 10ppb Pb. 2)Modified GCE in exact same testing solution in 1). 3)A typical voltammogram for polyaniline modified GCE for Pb detection.
My question is:
1) What may cause the oxidation peak in graph 2.
2) If it's related to the CV of aniline, how can I get rid of it? Or how can I make sure that the surface treatment is stable and won't get oxidized in following testing procedure?
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Here you go.
Glassy carbon electrode modified by conductive polyaniline coating for determination of trace lead and camium ions in acetate buffer solution
By Zhaomeng Wang, Erjia Liu, Xing Zhao
Thin Solid Films 519(2011) 5285-5289
By the way, after zoom in range -1.0 to -0.3v in Fig. 2. I could not see any oxidation peak which actually is the issue.
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I have prepared supercapacitor electrode. Its is Graphene Oxide coated on Ni foam.
I measured it within three electrode system. Pt electrode as counter electrode and Ag/AgCl electrode as reference electrode, connected them manually in 6M NaOH electrolyte solution. I have tried the cyclic voltammetry in 1 V difference but CV curve is not square shaped. When I reduce the voltage difference up to 0.6 V its starting to given the square shape and further decrement (0.3 V) its given the ideal CV curve.
I need your comment about this matter, I fell this small voltage gap is not enough for publication. Using your experience anyone can comments what should I improved in my electrode ?
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The shape of the CV curve varies with the electrolyte and the property of the material used. As you are using a neutral aqueous electrolyte and an EDLC material, it should give a square shape which you are able to produce until 0.3V. That means your material is reversible for supercapacitor application up to 0.3 V in 6M NaOH. Try other alkaline and acid electrolytes where you may be able to increase the potential window. The CV curves should be free from water redox peaks and improper cleaning method of Nickel foam can produce redox peaks. Need to take a CV of a cleaned nickel foam before coating and determine whether it consist of any redox peak. The redox peak shouldn't be an issue as you are getting a square peak up to 0.3 V; so try to change the molarity of electrolyte or use different electrolytes.
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I am not fully clear about the experimental procedures to do stochastic microsensing and how to interpret the patterns obtained from the stochastic microsensor. I would appreciate as detailed analytical information as possible. 
Thanks in advance.
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Hello Arif,
I hope you find the following useful:
Karatzas: A TUTORIAL INTRODUCTION TO STOCHASTIC
ANALYSIS AND ITS APPLICATIONS.
Schmidt: Stochastic sensors.
Gupta et al.: On a Stochastic Sensor Selection Algorithm with
Applications in Sensor Scheduling and Sensor Coverage.
Kind regards,
Jules
***Edit, another: Singh & Lemay, Stochastic Processes in Electrochemistry.
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I'm working with a L3Mo(0)(CO)3 complex. Performing CV at acidic pH with 0.1 M, I observe a reversible MoI/0 couple. Shifting to basic conditions by the addition of NaOH, I observe a large irreversible oxidation. I can add HOTf to shift the pH back to <7 and can recover my reversible couple, almost completely. What process could be occuring under alkaline conditions? I initially though it might be decomposition to Mo-oxide. How could I probe this? Thank you for any help or insight you can offer.
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You're sure the ligand isn't getting protonated/deprotonated (remember I know very little if nothing about CV) and you're possibly seeing ligand redox waves? Depending on the acidity you could be protonating the CO ligand to make an aldehyde. There's also the possibility of making and decomposing the Mo(CO)3L3H]+. this is all probably wrong, but that's what I can see from some quick searches and thinking about M(CO)x chem. 
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Hi All, I deeply appreciate any suggestion for a cost effective method to measure sulfur compound during sulfidic spent caustic treatment by electro-fenton method? Is there any colorimetric method rather than chromatography analysis? 
Regards 
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A good starting point for ideas is Feigl's books Spot Tests in Organic/Inorganic Analysis (I don't have the inorganic one).
A simple test for 2- and 4-valent sulfur uses Raney nickel and HCl to give hydrogen sulfide, which can be detected (for example) with lead acetate paper or solution.
I once set this up in a flow system (post-column LC detection), using a phase separator borrowed from the hydride generator accessory of an atomic absorption spectrometer. Surprisingly, this doesn't seem to have been published, so please do so if you take up the idea.
Important safety warning: nickel salts are carcinogenic and particular care is required here because of aerosol formation.
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I had fabricated a oxide based thin film over metal layer. We have electrochemical workstation in our lab. 
1)On what basis i had to set the voltage range for CV curve
2)Is there any standard values for a material to achieve like this much capacitance is needed at this area to be a good capacitor
3)Can any other test regarding capacitor can be done using electrochemical workstation? If yes I also need the basics and experimental methods.
Thanks a lot in advance
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I think you are dealing with (metal-insulator-metal) known as MIM structure.
It all depends what kind of insulator you have in between the two metal electrodes.
First of all the insulating film must have a high resistivity, and a low dielectric loss.
1) If you selected insulator has a dielectric constant, you will be able to measure some capacitance.
2) If both you metal contacts are non rectifying at either side of the insulator, you will have a well defined MIM structure.
You will measure capacitance, now why would you like to do C-V. You cad C-V, but then why?
If you have a ferroelectric as the insulator you will get a certain specfic shap of the C-V curve.
It all depends what kind of an insulator you have, is it polar, or non polar.
------------------
If you simply evaluating a film for capacitor application, I would say, you must test the following.
1) Its capacitance, then calculate the dielectric constant, by knowing the thickness of your oxide film, and electrode area.
2) Measure the tan delta at a certain frequency.
3) Measure both capacitance and tan delta as a function of frequency.
4) Measure the dielectric breakdown voltage of your thin film capacitor.
5) Measure the capacitance and loss at a certain frequency and vary the temperature.
you can do a lot of measurements , once you havea good MIM structure.
K. Sreenivas
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We are a new research group in Electrochemsitry at Universidad de Lima in Peru.  We currently do not have resources to buy a new potentiostat, so ask if any of your groups has a potentiostat that is no longer used and is in good condition for CV measures. We could take care of the shipping and others. 
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Hi Subramabya,
Thanks for your complements. We are doing continuous research in Electrochemial Instrumentation. And our next version will be including FRA along with higher current ranges without much increment in the costing. Our basic objective is to support resource poor research institutes.
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Hi everyone,  we are having an issue with our Dionex ICS 5000.  We are analysis phenol levels in alcohol samples from different distilleries within the company using HILIC and electrochemical detection (glassy carbon electrode) and gradient elution.  We were running our samples very happily on an old Dionex ICS 500 machine, but about a year ago we upgraded to the ICS 5000 and have had issues with peak height in our phenol analysis ever since.  Basically our peak heights sequentially drop with each sample we run until no peaks are detected (this only happens with phenols and not with our carbohydrate analysis on the same system but with a different column and eluents).  We have tried everything from multiple different cleaning methods for the glassy carbon electrode, changing both the reference and glassy electrodes, changing the detector, buying new reagents, changing the column, and getting thermo involved and nothing has worked.  We are now back to using the old ICS 500 as it has never had this issue.  Thermo don't seem to have any idea of what could be the cause either.  Can anyone help?  Many thanks
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Hi Angela,
I am so pleased that you resolved the situation.
Kind regards,
Ade
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I quantifying the Dopa mine,Serotonin,Norephinephrin by HPLC with Electrochemical detection (ECD). I want quantify Epinephrine Acetylcholin,GABA,Glutamate,endorphin and Histamines.
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I agree with John. You can use the same protocol with HPLC-ECD for quantification of epinephrine. But for quantification of gaba and glutamate, you have to use a  method of OPA derivatization, for acetylcholine you need to apply a post column IMER.
All these methods use different columns.
And for endorphin or histamin, the problem is the same : these compounds are electroactive (they can be measured by ECD) but in completely different conditions from those used for catechols.
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I have been trying to use inNO Model-T from Innovative Instruments Inc. in order to detect NO release from some nytrosil ruthenium (II) coordination complexes, but a lot of problems have happened. The background is very noisy and the sensibility of the sensors is very low. I have followed all the instructions provided by the manufacturer, but it was no use. What can I do? I have noticed the manual of the detector says there is a Potential Measuring Cable which allows you to correct the potential applied by the device. Do this work?
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Hi Florêncio,
Unfortunately I have no experience with your method you mentioned, but I'm working a lot with NO-Bioimaging. I assume that you have access to an epifluorescence microscope. If you have to do more experiments, I would suggest you to try these novel NO probes (see link). We use these probes in our lab and it works pretty well to visualize NO in single cells in a dynamic and concentration dependent manner. 
Good Luck
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I will use it to find MA and SA, respectively. Can be the mass-transport correction equation used for it? for example i-1 = iD*imeasured/iD-imeasured. But there is no a plateau in OER polarization curve. How can I find kinetic current for OER? Thank you all.
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I believe that most researchers simply report the iR-corrected voltage vs measured current for kinetic analysis of OER.   Calculating MA is easy because you just divide measured current my mass of catalyst, however SA may be more complicated.  I have attached links to papers by Jaramillo et al. which detail methods to calculate ECSA of non-Pt catalysts.  This involves plotting the C(dl) vs scan rate and deriving the ECSA from the slope of this line. Although this isn't a perfect method because it may not normalize to the number of active sites (most likely Fe sites, see papers by Boettcher et al.) it is a useful method to compare non-PGM electrocatalysts by normalizing to an effective surface area.  If you are instead studying OER on PGM catalysts in acid, I believe there are good papers by Gasteriger & Shao-Horn on calculating SA.
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what are the functionalization details and how would be the device fabrication?
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Graphen peer see cannot detect analyte in samples. Also hepatites is broad concept. You mean hepatite virus? inflammation?
If is virus as said Denis you need to detect antibody or genome. Graphene only increase the sensibility of biosensors.  
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Our chemistry department just acquired a Gamry Interface 1000 for electrochemical detection. We also bought a Dr. Bob's cell to start learning how to use the potentiostat. I want to know what simple RedOx reactions I could try with this cell just to get a sense of how the potentiostat and the electrodes work. Any help will be really appreciated. Thanks!
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Usually, the first electrochemical experiments were done in potassium ferrocyanide. The redox reaction is with the transfer of one electron. For supporting electrolyte I think pH 4 or 5 is the best choose. 
First, the electrodes should be prepared. Counter electrode should be well washed, as well the reference electrode. The working electrode is the most important part. Should be very clean. If is a carbon electrode, as glassy carbon, it should be polished (even is was never used) using diamond particles or alumina.
The next steps:
- all electrodes in electrochemical cell, in supporting electrolyte (only)
- Cyclic voltammetry (CV) from initial potential 0 V to maximum potential + 0.7 V and back to the minimum potential -0.1 V.  The step potential 2 mV and the scan rate 50 mV/s (several scans)
-After the electrode was conditioned in suporting electrolyte CVs in potassium ferrocyanide can be done, at the same condition. A concentration of 250 uM can be OK.
On the positive going scan the oxidation peak of potassium ferrocyanide will appear around 250 mV (vs. Ag/AgCl - as reference electrode). On the negative scan, the catodic peak (reduction) should appeared at 60 mV less than oxidation, with a similar current.
The difference of 60 mV between peak potentials corresponds to the transfer of one electron. Also, the redox potentials not depend on the pH of supporting electrolyte.
If instead of potassium ferrocyanide it will be used catechol or hydroquinone the difference between peak potentials (oxidation - reduction) should be 30 mV; the transfer of two electrons. Also, the redox potentials, in this case, depend on the electrolyte pH, which means that the redox reaction take place with protons transfer.
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I record ORR by RDE method. My the current density for ORR usually ranges 4-5 mA/cm2 at 1600 rpm in acid or basic electrolyte. However, the current density appears near 6 at mA/cm2 at 1600 rpm in some good papers. I want to try to get tha same current density with those papers. What is wrong with my experiment? Please tell me some comments on it. Which flow rate of oxygen during measurement is suitable?
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You cannot literally compare your number with ones on the papers.  You have to think in relative terms, instead.  The good papers you referred to must have an internal reference, i.e. a commercial catalyst that you can also buy or already have. Find out how much their catalyst is better than their reference and compare yours with your reference.  After that, you can follow all the suggestions that have been made thus far.    
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I want to apply magnetic field in the three electrode system (Electrochemical cells), field strength is 720. G or 0.072 T, any one can help for this?
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I have gone through few methods to hydroxylise the polysilicon surface as the following:
- Fenton reaction
- boiling in HNO3 1hr
- 1:3 (H2SO4:H202) 90c
Are these methods good for hydroxylating polysi surface? Or is there any other good method for this process?
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We work with H2O2/NH3/Milli Q (1:1:5) 70°C 30 min.
Best regards
Christian
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I fabricated elecrtochemical biosenser for glucose detection and i showed the response time but i can not understand  the reviewer comment of (A comment on the time constant of the sensor response would also be helpful for comparison). from the i-t test i showed the respons time but i coiuld not understand what maening  time constant of the sensor response?
second Q:
one of the reviewer asked Why the Fe-O band shifted from Fe3O4 to magnetite- prussian blue (PB)?
I characterize Fe3O4  and composite Fe3O4 PB nanoparticles by IR and the result  of Fe3o4 showed absorption peak of Fe-O bonds at 573 cm-1 and for IR of  composite Fe3O4-PB it showed absorption peak of Fe-O bonds at 596 cm-1. according to the literature both band attributed to the Fe-O bonds.
so he asked why there is defferent in the bans of Fe-O in Fe3O4 and Fe-O band in composite Fe3O4-PB?
Also he asked why there is no negative transmittance in IR spectra?
Iam accaching the FTIR spectra of pure Fe3O4 nanoparticles (a) and magnetite PB nano-composites (b).
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About the biosensor 'time constant' please check my answer at the related question: https://www.researchgate.net/post/Can_anyone_help_me_understand_a_comment_on_the_time_constant_of_the_sensor_response
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I have been using HPLC UV methods for some amines, now i am willing to switch over to electrochemical detection, but the LOD i'm getting is same as UV detector. i'm not able to detect below 50 ng/ml concentration. May you please share your experience with HPLC -ECD? what modifications in ampreometric analysis can enhance the signal of ECD? 
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There are too many choices to be made:  sample preparation, column, mobile phase, electrode material, applied potential, column internal diameter.  There are perhaps 1000 papers (or more) that demonstrate this. I was one of the "inventors" of this method back in 1972, but many improvements have occurred since then.  In some cases LC/MSMS can also work well.  It is very important to know which amines: serotonin is different than dopamine, norepinephrine is different than epinephrine etc. Plasma is different than tissue.   It can be difficult to get good results without spending some time examining the literature and understanding electrochemistry to some extent.  Concentration detection limits below 1 ng/mL of plasma, for example, are very feasible, with experience and care to details.  Yes. As Sanket has suggested, many procedures involve a preconcentration step on a small amount of acid washed aluminum oxide. Many of these compounds are easily oxidized at physiological pH.  Often the first step is to lower the pH and precipitate proteins.
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Hi all,
I am trying to formulate a relationship to convert the corrosion current density (micro amperes per sq. centimeter) to penetration depth (millimeter per year). 
Could someone help me out how this conversion is made?
Thank you so much.
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Dear Anuruddha
The attached link will help you to convert data between the most common corrosion units in usage especially what you asked about ; 
Regards.
Alobaidi Haitham M.
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Dear Colleagues
I have a question regarding gradual I-V curve in ReRAM. Actually the Top and bottom electrodes are Au and ITO, respectively. The insulator is polymer but I got gradual curve, what should be the inferred switching mechanism considering that Au is not an active electrode? In log-log plot it shows ohmic contact with slope of 1.2, but I think it shouldn't be filamentary because the change is not abrupt.
Would you please give me a comment?
Regards
Niloufar (Neli)
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You can fit with other models also like SCLC, TAT ets. But the slope clearly reflects the filamentary conduction mechanism. The sharpness of the switching also depends on the thickness of the active material. If it is too thick then the changes may not be abrupt. What is the thickness of the insulating polymer? 
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I am working electrochemical Immunosensor for detection of protein (toxin).I am modified GC electrode surface for cobalt phthalocyanine as redox mediator than Immunosensor reaction of antibody and antigen interaction reaction.100ng to 1 ng detection I got signal. But zero concentration of protein also given signal Why? How to solve the problem. Can you give me  advice?
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Non modified GCE does not show any oxidation peak, except for electrolyte solution (ferrocyanide) 
Once you decorate the surface you should do cyclic voltammetry to see if there are some peak and regist
  1. Once you decorate the surface you should do cyclic voltammetry to see if there are some peak and regist
  2. Try to measure the baseline first (only buffer solution without analyte)
  3. Measure the zero concentration 
  4. Than others concentrations (the adsorption of remain analyte on electrode surface may show the signal even removed by positive potential, if use electrodeposition technique).
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 Hello all,
I'm gonna ask the experts in electrochemical corrosion testing. when I get corrosion rate from electrochemcial test such as Tafel test or Rp/Ec trend, is that exactly the corrosion rate estimation in that type of material or just as indication for corrosion process ? especially we use accelerated tests. and I read some question answers here imply the corrosion rate from polarization resistance maybe will be different from another test because the corrosion depends on the time. 
Thanks in advance 
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The results of your electrochemical tests provide an accurate indication of the corrosion rate.  However, this measurement is only accurate for the material, electrolyte and test conditions in your test.  I may or may not be a reasonable indication of the corrosion rate that would be experienced for that material outside of the laboratory.  Corrosion processes can be very simple or they can be extremely complicated.  It all depends upon the material, the environment and the effect that corrosion products and bi-products have upon the system.  It depends upon how well your test sample reflects the metallurgy and chemistry of the materials used outside of the lab.  So the only answer that can be given is that "it depends".  It depends upon how accurately your test simulates the real application.  It depends upon whether you have identified, captured and controlled all of the important parameters for your corrosion process.  It depends upon whether the acceleration process that you used for your lab test skewed the results too much.  It depends ...
So, for a general corrosion test design question such as this, the only answer that can be given is that the electrochemical measurement of corrosion provides a snapshot indication of the corrosion that is occurring on the metal that you have placed into a controlled environment in the lab.  Whether this provides an accurate assessment of the corrosion beyond that specific test is dependent upon far too many variables to discuss for such a general question.
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Related to Insitu electrochemical detection
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Cu(NO3)2 is a salt which is completely disasscoaietd in Water, just like NaCl. You might review physical chemistry to better understand the nature of different types of chemical bonds (or forces). There is no covalent or strong coordinate bonding between Cu ions and nitrate.
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