Questions related to PEAKS
I analyzed spearmint essential oil sample, the chromatogram showed 2 peaks very close to each other, one of them at RT 13.74 detected as carvone, and the other one at RT 13.88 detected with name of a compound that is not well known in spearmint..could this second peak be stereoisomer of carvone that has not been recognized by the GCMS?!
Or what else could it be ?!
I took the CV of nickel ferrite using carbon black as the counter electrode, the voltammogram shows multiple reduction peaks. why does that happen?
I am running standard VFA samples, but the gap between each peak is wider. I changed the column with a new one and still have the same issue. The initial oven Temp is 110c, then the next 130c (ramp 1), then the maximum goes up to 200c (ramp 2). Total gas flow is set to 30ml/min.
I have used the same methods before and always got consistent results with less gap between the peaks.
Dear All, i m facing this problem on HighScore Plus XRD software,when i m trying to search and match to get details ,i get this note : No condidate found .
i already selected peaks and added Databases COD21 and PDF2.
could you please help me !.
I am new to the XRD, and when I analyzing the Au particle (micron size), I see some abnormal split of the peaks happened. I suspects that the splitting is due to the K alpha 1 and K alpha 2 of the copper. I doing the XRD on d8 advance power XRD machine. And I have done the SEM to confirm that the Au is pure. I check up some of the K alpha 1 and K alpha 2 splitting, it seem like they would cause 0.2% of difference in the d spacing( which is confirmed my all five peaks), but the intensity should be around 2:1, also the splitting should be more obvious with the increasing of the 2 Theta, those two are not my case. I wonder what should I do to confirm if it is due to the K alpha 1 and K alpha 2 splitting.
I am studying about triboelectricity, and I have a question why some open circuit voltages some out as single-peak and some output voltages comes out as double-peak.
1. The first one has only one peak which shows both the voltage for contacting and separating in one peak. For example, the positive slope represents pressing, and the negative slope in the peak represents releasing.
2. The second one has two peaks that have opposite signs to each other. For example, when pressing, the voltage shows distinct positive peak. Then the voltage comes to equilibrium. And then when released, the voltage has a negative peak. After that, the voltage comes to equilibrium.
I want to know what is the difference between those two.
I have been running a batch of samples with the hplc machine and I have noticed that each time I run another batch of samples, the retention time of the peaks shift backwards.
For example, a week ago the retention time for one of my standards was 3.4 minutes but it has been shifting each day and now the retention time is 1.9 minutes for the exact same standard.
Is there a way to fix this problem?
I have seen endless publications that show that phosphorus has no spin-orbit coupling, although the peaks fit exactly that. Most of what I seen, for example, is 132.8 eV for P-C and 133.7 eV for phosphate. But it actually fits the 0.87 eV spin-orbit coupling.
Is there any reason that a P2p spectra won't show coupling??
Hi people, any body working with Bruker's LCMS EVO TQ here? We are facing an issue with vit. D2 in serum and blood. Blanks and Cal 0 showing peaks for vit. D2 while QC for vit D2 is fine. And no issues with vitamin D3 blanks and Cal 0 at all. Only D2 showing contamination. We recently changed extraction column and every thing was OK for few days and now this problem started. Any suggestions would be highly appreciated. Thank you 🙏
Lately I'm synthesizing a compound,
(the structure of this compound is in the picture)
I found out the 1H-NMR of this product are all broad peaks. I suppose it might be due to the present of mixture of rotamers (conformational isomers), as stated by the related literature. (Bournaud, C.; Chung, F.; Pérez Luna, A.; Pasco, M.; Errasti, G.; Lecourt, T.; Micouin, L. Synthesis 2009, 869– 887.)
So, I decided to do VT-NMR to see if I can get sharp peaks in my spectra, and luckily, most of the peaks became sharp at 75 degree(as shown in the picture). I choosed dmso-d6 as my D-solvent, because high temperature(> 60 degree) is needed to observed sharp peaks. (I've tried chloroform-d6 before, the peaks remained broad at 60 degree)
But a singlet is observed around 8.24 ppm, I suppose it might be the signal of chloroform-d6 that I used before, (or the signal of CHCl3, because I often use CHCl3 to get rid of n-hexane and ethyl acetate after column, in order to have a clean 1H-NMR spectra without any solvent peak).
I've put my compound under vacuum about one week, before I conduct the VT-NMR,(and there's still solvent remain...),and I'm sure that the compound is pure, without any impurity.
I'm asking how can I get rid of chloroform or other solvents before I conduct VT-NMR?
I am not familiar with different analysis modes of mass spectrometry so I seek your help.
I wish to understand the difference between DIA and DDA analysis.
I understand that DDA searches the top N number of the highest-intensity precursor ion peaks to go through MSMS, then after a certain amount of time, it selects the next N number of peaks and so on.
I also know that DIA is not top N but rather chooses an isolation window and fragments EVERY ion in that window.
Heres my question, if DDA keeps selecting top N and the next and the next, doesn't that also mean that eventually every ion will be fragmented? like DIA? am I completely missing something?
To me this sounds like tomato tomato so I appreciate all the help I can get
I prepared CdS and I got sharp peaks with high intensity in the XRD pattern. The peaks at 2𝜃 do not correspond to ICSD of the XRD patterns of cubic and hexagonal CdS nanocrystals. How can I discuss that?
I have been struggling with the crystallinity of synthesized cobalt nanowires or iron carbide nanoparticles with some previously established chemical/hydrothermal methods. Each time, I take XRD spectra, I can see broad peaks instead of sharp ones. The peaks are normally in proper places, though. This might be due to low crystalline quality of the synthesized sample, if I am not wrong.
Would anyone be help to suggest me a way of solving this issue, please? Or, is it a washing problem? I would be grateful for the help.
I am investigating the redox behavior of Diene compounds by cyclic voltammetry in anaerobic environment. My electrodes include carbon glassy electrode as working electrode, platinum as counter and silver/silver chloride as reference. My solvent is THF and supporting electrolyte Tetra(n-butyl)ammonium Hexafluorophosphate. The problem I have is that I cannot see the redox peaks for these electron transfers. Can anyone give me some advice on how to optimize the situation?
To determine microplastic chemical content, I recently analyzed some samples. By using the KBr method, Infrared (IR) spectra were obtained using the IRprestige-21 model. I got 19-28 peaks in a band and the metadata was in ASCII file format. The database only contains transmittance values in ##.###### format. For a particular polymer, I need a single-band graph with the required peak. In Origin Pro software, I was unable to do it. Could anyone assist me with this matter? Your assistance will be greatly appreciated. Thanks in advance.
I did raman spectra of SiO2 thin film of around 800 nm thickness on grown on Si(100). But i am not clear about the peak of SiO2. Where it is/are actually in the attached file?
Hello all i have a problem. I recently got a new RP-HPLC column with a guard column as well, after connecting them and starting the first runs i noticed that my sample (70% purity) elutes into two peaks if i use an injection volume of 5 ul. However once i increased it to 10 ul the two peaks will elute at one but with a shoulder (which i always assumed as impurities before). Shouldnt it be the otherway around? I thought if i overload the column a double peak of one component would more likely to appear.
I want to understand the XRD characterization having different diffraction peaks of EDTA
Please check the attached UV-Vis. spectra of Beta cyclodextrin hydrate, which exhibited peaks at 225 and 272 and a shoulder peak. Please help me write a reason behind it. I searched the literature, but it doesn't match with the published manuscripts except for one paper where they didn't explain.
Recently we have performed DSC experiment in some glassy alloys of SeTeSnIn system. I have attached the DSC scans for your inspection. We have obtained similar DSC scans at other heating rates too.
We need your help in explanation of these DSC scans.
It seems that this splitting is happening due to phase separation.
We think that 1 peak (Endo) is corresponding to glass transition and 2 peak (Exo) represents crystallization. But we are confused with other peaks
I took an IRF using deionized water in the TCSPC system, in which the decay profile showed multiple peaks instead of smooth exponential decay.
I am getting unwanted bands, primer dimers and smears in conventional PCR. I have to sequence the pcr products, so for getting clear peaks in the sequencing result, I have to bring clear bands in the pcr. Increasing the melting/annealing temperature did not solve the problem. What else can resolve the problem?
I want to get the reason for shifting the peaks with increasing the concentration of hydrogen peroxide. Because in this plot I confirm that my sample is detecting the hydrogen peroxide in the milk as a real sample.
I have done FTIR to get results in favor of Microplastics. I got many peaks in different wavenumbers (from 400-4000 cm-1).
Please suggest to me, how can I analyze the data.
How would I know, the peaks I got are that plastics variant or something else?
Thanks in advance.
I have synthesized sulfide nanoparticles using biosynthesis approach of size 20 nm. Previously reported papers shows both UV and PL peaks. UV graph shows only peak of protein at 280nm while PL show broad band.
Say we have an XRD pattern that shows peaks for both (111) and (222) planes. Does it mean the crystal has a property that a similiar material that shows only the (111) peak doesn't have?
Thanks in advance
I am analyzing the gene sequence of my target gene in Brassica juncea. In that there is some ambiguities in the gene sequence which is appearing after few clear peaks in the sequence. I am attaching the chromatogram for your reference. We again re-sequenced them. Same results occurred after few clear peaks. Suggest me possible reasons for this and how can I confirm that.
I am working in Barium ruthenate triple perovskites. I have been observing proper downward peaks at about 30 K, with the minima shifting to higher temperature for higher frequencies. The magnitude of the dips is also higher for higher frequencies. An exactly opposite trend is seen in the imaginary part of ac susceptibility data at the same temperature. There is no transition visible at 30 K in the DC magnetization or heat capacity data. The measurement was carried out in the Quantum Design SVSM MPMS3 multiple times and from multiple instruments at a magnetic field of 3 oe. I have observed this in two different Barium ruthenate triple perovskite compounds of mine. I had also carried out the ac susceptiility measurement in ACMS option of QD PPMS with 13 Oe magnetic field and this anomaly at 30 K is absent. Figures are given for reference.
I am trying to define the peaks of my synthesized powders and while researching how to do it properly I came across several youtube videos. After baseline corrections and smoothing the graph, one of the videos went through an extra step where they stripped k-alfa2. My question is, is this step necessary? If yes, then can someone explain why? I couldn't find any further information regarding this.
With or without upwelling the copepoda Paracalanus quasimodo is present in high abundance in Cabo Frio. What would happen if this species was lost in the region, would the second most abundant species (Temora turbinata) take its place? Both preferentially herbivorous and highly related to the phytoplankton peaks present all year round.
In the few literature, it was mentioned that the binding energy of Si 2p1/2 was higher than Si 2p3/2, while some authors made the just opposite statement about these peaks. I am so confused about which one is right. Please help me in clarifying my doubts.
how to minimise negative peaks in HPLC using uv detector at 210 nm, not always it is coming, only some times
what factors leads to negative peaks in hplc
I run a compound on HLPC at four different wavelengths (205,215, 254, and 306nm), and my solvents are 30% IPA and 70% Hexane. Absorbance peaks are shown at the same time in those wavelengths. However, the intensity of those peaks are different, and one of peaks disappears in one of the four wavelengths. My questions are how to choose best wavelengths to determine %ee and whether or not I should stay consistent at one wavelength ( because one of the peaks disappeared. It is almost a straight line on a spectrum).
I am new to HPLC. Please help me explain more, and all comments are appreciated.
We are conducting an experiment to measure the mean axial velocity component of an axial swirler by LDV. We are getting two different values of the peaks in the mean axial velocity. What is the margin of error that is acceptable for the above-given values?
Lower shifts in characteristic XRD peaks of metal-oxide/chalcogenide composites...
I simulated a cylindrical TSV in Lumerical FDTD and measured reflectance with different radius. The reflectance curve getting more oscillation and peaks are shifting with change in radius. Is there any way to analyse the interference and diffraction effect?
I have synthesised an organometallic compound Fe (II), and I got an nmr spectrum as expected, except for 2 peaks that were actually present but their intensities were too low resulting in a very low integral value. I was able to find the corresponding carbon peaks after running a C-NMR, so I am not sure why am I getting these strange integral values for these 2 peaks specifically. Could it be due to paramagnetism?
I have tried to purify a chemical sample. I performed multiple runs with the same method at specific wavelength. The first run gave me numerous significant peaks in the middle of the run. The second run of the exact same sample gave me a huge peak in the initial bit of the run and the peaks that were seen in the first run could not be seen the second run. I did a third run of the diluted sample and I got a spectrum similar to first run. Could somebody please explain what’s happening here.
I synthesized Mn-Zn ferrite powder. In the FTIR spectrum, there are four peaks at wavelengths less than 1000, two of which are related to Fe3+_O2-. What are the other two related to?
I have a DSC result run from -90oC to 100oC in a heat/cool/heat cycle.
Tg, crystallisation and melting peaks are observed in the heat run. However the cool run, the crystallisation peaks are not reflected. What is the course of this from the polymer?
I am using a C30 column for carotenoid analysis. I bought the column recently and using it for the first time. When I use the column in LC-MS scan mode, I clearly see the UV-Vis peaks for my standards, but TIC has a lot of noise and I don't see the m/z peaks corresponding to my standards. Instead, I see peaks with a repeating m/z around 14, like a polymer. I used methanol: MTBE ranging from 95:5 to 50:50 as the mobile phase. I washed the column overnight also. Still, I don't see peaks for my standards, but polymer-like peaks. Does anybody have a similar experience? Any suggestions to resolve this issue? Thank you.
I have a sample of carbon paper. There is no coating on the carbon paper and it is high graphitic and electrically conductive.
From trying to fit a peaks in C 1s spectrum, I think I have found C=C (284.5 eV), C-O (287.5 eV), C-C (286.6 eV), C=O(287.9 eV), O-C=O (288.9 eV), and shakeup (291.0 eV).
With C-C is skew Voigh and the rest is Voigh line shape.
However, for O 1s, I can fit in 1 Voigh peak at 532.8 eV which I think it is C-O.
Since I was able to fit multiple oxygen functional groups in C 1s, does O 1s also need to have C=O and O-C=O as well?
I synthesized the nanocomposite of GO@SiO2
The XRD result shows multiple peaks at a low intensity ranging from 10.2 to 28.
What do these peaks indicate and why this has happened? Any ideas?
Honestly grateful if you shed some light on this issue.
We are in need of a reference for our experiment and cannot find good data anywhere. We are not sure if the peaks that we are seeing correspond to our sodium azide or they are not.
We conducted a lab practical on Raman spectroscopy, specifically focusing on the spectrum of a Gold and Palladium mixture. I would like to ask why there are no clearly defined peaks observed, unlike in other spectra.
P.S. x-axis is Wavenumber and y-axis is Intensity.
I'm trying to determine a concentration of isododecane in one of the products. I prepared a standard solution of isododecane in dichloromethane. The concentration was high, about 1% wt. However, I don't see any peaks even at the very broad scanning range.
Agilent 7890A/6975 MSD
Splitless. 1 ul inj volume. 70Cx1min-20C/min-280Cx4min.
DB-HeavyWax column. 30mx0.25
At these conditions I see few residual peaks from DCM (as compared to pure DCM) but not the C12H26. What could go wrong?
For the enzymatic activity assay, I have to use 4-Hydroxybenzoic acid. I have kept it in the refrigerator. In the first experiment, I saw one peak but, after 3 weeks I was 2 peaks during UV spect.
Do you have any idea or guess?
I'm trying every way to check FWHM for certain peaks of Raman spectra in Spectragryph. But for some, it just appears --. I adjusted all possible parameters. I don't want to use a lot of software in my analysis. I tried WIRE and the same thing happened. They are not "doubtful" peaks. They are real ones. Does anyone know how I can see FWHM of these hellish peaks? Thanks.
I am trying to do refinement of magnetic garnet ferrite material; I have extracted the values of lattice parameters and atomic coordinates from CIF file. I am facing one problem every time i.e., the intensity of the observed peak (represented in black line) is not changing, it’s almost showing a straight line. While other peaks are varying. Initially on first run the observed peaks (black line) are visible but as I start refining it, after 2-3 steps the peaks shifted to very low intensities. Kindly suggest me some solution.
Thanking you all
My starting material was natural graphite flakes, xrd showing the standard peaks. Post processing my sample has the distinct 002 peak (sharp) but with slight shift to the left side and significant drop in the intensity (nearly 45%-50%). The physical properties of the samples definitely have changed (appearance, SEM). I've assured that the processing yields MLG and FLG. How can I used the xrd data to support this claim? Is it mandatory to do peak fitting before I compare the two samples?