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Pesticide Residue Analysis - Science topic

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How can I calculate concentation (mg/kg) of sample by using area of peak during analyzing the pesticide residues by HPLC?
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Using the same HPLC method, a multi-level calibration table must be created using proper standards for comparison.
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I would like to test a biological method of screening vegetables/fruits for the presence of pesticide residue. Since a biological agent is used, the extraction solvent should be non-toxic.
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QuEChERS sample preparation
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estimate time of residence
toxicology
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I found this interesting document in which it is it stipulated that people who live near a hazardous waste site, might be exposed to endrin from contaminated air, dirt, or water:
Stay safe
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many researchers have analyzed pesticide residue in soil by using GC/MS or GC-ECD. But my lab has GC-FID. can I get the result by using GC-FID?
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No. You will need an MS detector to gain an additional dimension of analysis. Retention time alone is not enough for pesticide ID. Either GC-MS and/or LC-MS (or better yet, LC-MS/MS) are needed for basic quant and ID. Using just GC-FID alone may provide only a limited amount of information (qualitative) so even when used with proper standards may or may not be enough for your application.
Please define your exact goals and objectives, then research your question online using a keyword search for examples.
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I would like to ask which Blank type you use for measuring the LOD, LOQ peaks in relation to the blank peak?
are you using matrix-matched blank - if the sample contains analyte+ acetonitrile + Aerosol. Should we use the blank as (acetonitrile and Aerosol )
or you are using the Mobile phase as a blank?
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Tomasz Grabowski that is very helpful thank you so much !!
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Hi,
I'm setting up a pesticide residue screening method on a Waters UPLC-MS/MS system. Most application notes suggest a 10 mM Ammonium Acetate buffer, but I'm seeing better results (so far) with a 5 mM Ammonium Acetate buffer. Can any one with more experience on pesticide residue screening comment on why a 10 mM buffer might give better performance?
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Give also learned something
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Usually several methods are used to calculate uncertainty. At the time of analytical method development and validation for pesticide residue determination, it is necessary to estimate uncertainty. Could you please tell me which method is comparatively easy to estimate uncertainty in the case of pesticide residue analysis using GC-MS and/or LC-MS/MS. Thanks in advance for your kind cooperation.
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If I correctly understand your question then the easiest way to calculate the uncertainty is:
U = RSD x t (P; n - 1)
where U - is uncertainty,
RSD - relative standard deviation of 9 results of Recovery (for example, from accuracy).
t - Student coefficient
P - probability, ussualy 95 %.
n - number of Recovery results, in this case 9.
I hope I give you correct answer.
If I did not correct understand you would excuse me in advance and please do not hesitate me to ask.
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Kindly suggest precise and suitable method of extraction of pesticides and their residue analysis via. GC_MS.
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Dear Rachit Kashyap,
Thanks for your interest in this area. To determine pesticide residues in pome fruit, QuEChERS extraction and cleanup technique in combination to GC-MS and/or LC-MS/MS would be the best option. However, I am giving you 2 article for the estimation of pesticide residues from melon fruit and eggplant, you may follow this article. I think these article will be helpful for you.
For eggplant (DOI 10.1007/s12161-014-9898-3)
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I run full scan for Dimethomorph (a fungicide) in GC-MS/MS, and it gives two peaks with different retention times 11.1 and 11.3. I increased temperature from 280 to 320°C and peaks little bit come closer but this is final temperature limit of column and i can't go beyond. Can anybody explain what is possible reason and how i can overcome it. For assistance spectrum is attached below. Thanks
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Thanks @marcos steola giving detailed answer, sum up area for both peaks is best option, thanks again
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Hello,
I have a question how to make the 4ppm standard mixture, and I should prepare it by mixing 205 pesticide standards in a bottle.
I have looked up a method to produce the 4ppm standard, and I should find out what 25,000 means.
Let me show the process of producing the 4ppm pesticide standard.
First,
201 of 1000ug/ml * 100ul pipetting = 20,100
1 of 100ug/ml * 1000ul pipetting = 1,000
3 of 2000ug/ml * 150ul pipetting = 150
Thus, the sum is 21,250
Second, 25,000 is suddenly calculated as follows.
25,000 - 21,250 = 3,750
3mL and 750uL of Acetone was used to prepare 4ppm standard mixture.
I still have no idea the second process.
Why 25,000 was computed?
I need you help. ;-(
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Each stock pesticide standard having ppm values:
201 std (1000ppm), 1 (100ppm) & 3 (2000ppm)
Aim is obtaining 4 ppm in final dilution
Step-I now calculation is 100ppm/25mL is 4 ppm
So, take each stock standard to get 100-ppm solution
Step-II 201 *1000ppm*100uL (0.1mL) we get 100ppm of each
Similarly, 1 * 100ppm * 1000uL (1mL), 100 ppm
3 * 2000ppm * 50uL (0.05mL), each 100 ppm
Now overall volume is 21,250uL (21.25mL) ( 250000uL- 21250uL = 3.75mL)
According to the step-I, we need total final volume should be 25mL, that’s why 3.75mL of acetone for the remaining volume.
That’s it. I hope you understand.
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Nowadays, I have conducted a seminar from our students about effects of pesticides to human health, so I would need some article about this subject.
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Hello Dear comrades/Peers,
I worked earlier with PGPR and focuses on soil microbiology. But, now working in a lab major in pesticide and its residue analysis. So, I want to start a project merger of Pesticide residue and PGPR followed by bio-remediation.
So, can you help me in this regard; how can I start this kind of project with previous record of such activities. I am working as PhD student at KNU, Korea.
Thanks in advance.
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Mr. Sarkar,
You can spike the pesticide in soil and also compare natural the soil respiration activity or autoclave soil and add spike PGRs and measure same. You can refer Thesis chapter 5, in following link, where instead of phytate you can add pesticide.
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In residue analysis sample preperation is time and solvent consuming. so its may be better to use preperative HPLC for sample preperation.
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Preparative chromatography is a scaled up for separation, purification of solutes in quantitative terms from a given sample. Sample preparation has to be done beforehand. Sample preparation should not be confused with preparative chromatography.
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Dear All
LC MS TOF can carry out non target analysis, in addition the isotopic profile for the obtained data make the identification of these compounds more easier and reduce false positive results. It gives also lower LOQ higher resolution. However, for routine analysis is it require more maintainance, or there are some limitation for using such technique.
For whom is working with lc ms tof, if you have additional benefits or some alarms from using lc ms tof for pesticide residue analysis, please tell me, if their are articles supporting your opinion please send it to me too.
Thank you
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There are many instruments out there and instrument manufacturers and their sales support are experts without question. However, having worked for government and a public company my experience is that funds are hard to come buy. You cannot afford to buy the wrong instrument. If you do your carerer could be jeopardized.  Ask yourself why you are buuying an instrument? What do you plan to do with it both in the present and the future? Send extracts of samples which have been spiked (or are known to be contaminated) and cleaned up for the  analytes and matrices of interest.  All instrument manufacturers will be more than glad to analyze and show what they can do. Do not forget the data system, not all are equal. . We almost lost $0.5M client because we employed a trap instrument (not orbitrap) many  years ago to attain increased sensitivity for a large monitoring program utilizing fish bile. It was a disaster because data did not fit with conventional quadrupole because traps dump ions when full. Sample analyses are critical to making an informed decision.
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Dear All 
For a MRM method involve more than 300 pesticide, can one carry out a spiking /fortified sample daily by a representative number of pesticide(10 to 30) rather than spiking by 300 pesticides in order to minimize the consumbtion of the prepared mixture (300 pest) and used it only for preparing calibration. While, preparing a mixture of lower n. pesticide(representitive based on solupility, pKa, stability,..) to be used for spiks preparation. 
for the validation, spiking will be carried out using all the pesticides.
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Most multicomponent methods use a subset of compounds for matrix spiking (see USEPA method 8760 and 8270, for example), in combination with a series of surrogate standards like Dr. Chamkasem discusses. You would ideally like to use a series of pesticides that encompasses a wide range of pK values, planarity, volatility, thermal stability, etc so that you can show recovery for similar compounds as well as problematic compounds. Normally you would spike one sample per analytical batch with this mixture as well as a "blank" sample (called a fortified analytical blank) which would be a similar matrix to your samples (for example, dried mixed vegetable matter that you rehydrated prior to analysis). 
Additionally, since you are using MS/MS you can easily incorporate deuterated analogs of compounds (like the d10-chlorpyrifos mentioned) as surrogates to demonstrate your ability to recover pesticides in each sample. AOAC method 2007.01 references deuterated terphenyl as a surrogate; I personally use a mix of 5 deuterated compounds that we carry through the entire extraction, cleanup/concentration and analysis process. We can then verify our analytical method by checking the surrogate recoveries for each of these compounds in every sample, whereas we would only check the recovery in one sample. If you have a wide mixture of samples that you are analyzing the surrogates add another layer of assurance that your analytical technique is valid. 
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To my knowledge, ozone treatment is the Best way to remove pesticide residues. After carefully searching the database, the related paper only describe the treatment time points,  ozone concentration , vegetabels and fruit types. If anyone know the mechanism or published papers' link w hould you please tell me. Thanks in advanced!
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 Have you ever checked the change in quality of fruits after ozonation, especially the ascorbic acid content?
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I would like to know the opinion of experts in the matter, about this issue of special concern for me.
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Dear all,
Thank you very much for your answers.
Shivani and Abdalla, I was rather thinking in multiresidue analysis of several type of pesticides in vegetable matrices.
Armando, I agree with you in that pKa is the key. This situation can be managed with more or less success when the type of pesticides of samples are known. However, the problem increases with field samples of unknown record. In these cases, could not be the pH control counterproductive? What is your opinion?
Does anybody have more suggestions/opinions? Thanks in advance!
JJ
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we are working on a.m mentioned compound,
would like to know the acceptable limit of Imidacloprid in South Korea.
The Limits in European Union id 1 mg/kg for cotton kernel extract.
dr vipul doshi
venus lab
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Acceptable limit of Imidacloprid in South Korea.limits 1 ppm i.e. 1mg in 1000ml of water as a solvent.
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A part from GC-MS analysis, is there any simpler method for pesticide residues quantification in fruit and vegetable samples?
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QUECHERS is the preferred method, the many articles with various variations of the method. The method is primarily used with LC-MSMS, but GC-MSMS has been developed also.   
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I try to quantify paraquat/diquat in potato using LC/MS similar to the attached method but using different LC column. I use standard in solvent with internal standard (IS) to correct for matrix effect (paraquat has enhancement). The issue is the response of the analytes and IS is not consistent in sample matrix so the number is way off (sometimes is too low, sometimes is too high). I injected the same blank matrix with analytes 5 times and response was not the same. The run is isocratic so the matrix of the first injection may show up in the second or even the third injection. The paper use matrix-matched standard with IS (which is over kill) and it may be necessary to do it. I e-mailed the authors but so far no response. any comments are welcome.
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@Heydebreck  I will check on this but the final decision for what I remember, you have to spike at just before extraction because at the low level, I found that the matrix will absorb a finite amount of analyte and it will be corrected by adding standard at the beginning. Most of the time, I prefer to add IS just before analysis to correct for only matrix suppression and save money. Most of the method on internet (even QuPPe) prefer to add at just before extraction.  By adding IS just before extraction will disguise the poor extraction method and if you have poor recovery, you need to fix it and not using IS to compensate.
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I am interested, where Glyphosate and its metabolites can already be found in the environment as wildlife plants and animals and agricultural plants and animals, soil biomes and rivers. Do you know good survey studies with dedected concentrations and dedected limits of Glyphosate and AMPA in plant parts like roots, stem, bark, leaves or fruits and in animal organs and urine? Here in Austria glyphosate residues in European hare (Lepus europaeus) are just of special interest in stomach and urine. Many thanks for your answers! J HUMER
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This glyphosate monograph with many good references may be of interest
Best regards!
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only explanation of this two terms 
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What kind of risk are you trying to do the assessment? An environmental risk assessment or human exposure risk assessment?
Definitions:
- Acceptable Daily Intake (ADI): Estimate of the amount of a substance in food or drinking water, expressed on a body-mass basis (usually mg/kg body weight), which can be ingested daily over a lifetime by humans without appreciable health risk. For calculation of the daily intake per person, a standard body mass of 60 kg is used. ADI is normally used for food additives (tolerable daily intake is used for contaminants).
 - Risk Quotient (RQ): Is calculated from an estimated exposure (PEC), divided by an estimated effect (PNEC). If a value less than 1, then there is an acceptable risk. In contrast, if the RQ greater than 1, there is an unacceptable level of risk and measures to reduce exposure should be taken.
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I want your help to find a laboratory for pesticide residue analysis by chromatography ?
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Pesticide Residue Analysis, Microcoulometric Gas Chromatography of Pesticides
D. M. Coulson, L. A. Cavanagh, J. E. de Vries and Barbara Walther
Journal of Agricultural and Food Chemistry
Vol. 8: Issue. 5: Pages. 399-402
Publication Date: May 1960
DOI: 10.1021/jf60111a018
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I am currently trying to narrow down which set of salts (AOAC, EN, Original) should be used to extract imidacloprid residues from dairy cattle manure using QuEChERS method, as well the sorbents to be used for cleanup using d-SPE. Our initial extractions using just acetonitrile and water (80/20) yielded a dark, yellowish-brown liquid. Samples are to be run on HPLC after extraction. Any comments would be appreciated! 
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If the cow manure is dry then you need to hydrate the sample prior to QuEChERS. We take 3 grams of a dry sample and add 12 mL of water prior to extraction.
My procedure is to add the water to the dry sample and mix well (shaking). Add 15 mL of acetonitrile with 0.1% acetic acid and shake well. Add the QuEChERS extraction salts (I prefer the AOAC method) and shake well. Centrifuge to separate the phases. 
Imidacloprid will not be lost on GCB, so you most definitely want to use PSA/C18/GCB for cleanup. I am assuming that you are using LC-MS, not GC-MS. If so, you should be able to see <10 ppb of the imidacloprid in the cow manure using this method.
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There are other methods for pesticides residues analysis in soil (exception chromatography) !
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Dear Slamene,
Unfortunately, most of the available methods are by GC/ECD or LC-MS.
You may see the following link:
Hoping this will be helpful,
Rafik
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Actually i'm looking for the sampling rates (cal) of POCIS technology, in order to calibrate them for very high temperature and low velocity (a lake in Burkina Faso).
I'm looking for 50 types of pesticides, from different family type
  1. Organochlorates
  2. Organophosphates (Chlorpyrifos-methyl / Diazinon / Omethoate / Profenofos / Triazophos)
  3. Avermectin (Emamectine Benzoate)
  4. Carbamate (Carbofuran)
  5. Neonicotinoid (Acetamiprid/Imidachloprid)
  6. Pyrethroid (Cyalothrin Lambda / Cypermethrin / Deltamethrin)
  7. Tetranortriterpenoid (Azadirectin)
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I am working on detection of pesticides (especially Organochlorines) in river water. So I am interested to know that in between QuEChERS and SPE which extraction technique provides better detection. Thanx in advance .
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Thanks Nikolaos and Melanie for your suggestions.
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I am working in pesticide residues analysis. I need to know about the different methods for conversion of cotton lint into cotton powder to determine the pesticide residues in it.
Thanks in Advance,
Mahmoud.
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you need to dry it by freezing. i tried liquid nitrogen once but it did not appeal to me too much. the grinding machine did not work. so i shifted to keeping it in freezers for weeks. it was tedious and unsuccessful. what is left an instrument using the freezing shock. but was not available at time. 
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I want to gain experience in the field of pesticide residue analysis using LC_MS/MS and GC_MS/MS (TRIPLE QUADRAPOLE) SO i want to read a lot of thesis to gain experience from it
thank you in advance
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Hi Mahmoud,
I belong to the Research Institute for Pesticides and Water (IUPA). Our thesis are written mainly in spanish but here is the link to our publications so you can check some articles on pesticides by LC-MS/MS and GC-MS/MS with different ionization sources.
Best Regards,
Carlos
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I want to know about the different sample preparations of food in pesticide residues analysis
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analysis of pesticide in cotton 
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Is there any specific method for extraction of pesticide residue from human urine sample?
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You can do salting out with acetonitrile and inject. Use the the link below and replace the apple with your sample.
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Accepted methodology, solvent for analysis, solvent ratios with time plan, black tea sample extraction procedure for minimum matrices and colour figments effects.
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Are you trying this fungicide residue or deposit,no problem,you can mix the black tea ,in ice temp.. then take 5 gr for analysis best solvent is acetinitryl  , 10 to 15 ml  and for color sepration  PSA in needed , in extraction procedure PH is important.
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I am going to analysis of fish samples for organo-chlorine pesticides residues. I have only GC-ECD detector. As well I wish to use the QuEChERS method. Here we havent facility to access AOAC etc. So, any one can help me to find the detail (step by step) method (AOAC or EU or any standard methods) for above analysis?
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try my method on PCB in fish. Food Chemistry 192(2016)900-906 or look at my profile.
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IS ANY PROVEN TOXIC IMPACT OF ORGANO CHLORO PESTICIDES IN HUMAN being?
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Hi Susan
The kepone (chlordecone) has caused acute toxicity in workers of the Hopewell plant, leading to the ban of this organochlorine in the USA, in the 1970's
until now environmental pollution is though to cause hormone-like disorders and pathologies in the Caribbean
some paper deal with this topic
Adir, J., Y. H. Caplan, B. C. Thompson (1978). "Kepone serum half-life in humans." Life Sciences 22(8): 699-702
Boylan, J. J., J. L. Egle, P. S. Guzelian (1978). "Cholestyramine: use as a new therapeutic approach for chlordecone (kepone) poisoning." Science 199(4331): 893-5
Cannon, S. B., J. M. Veazey, Jr., R. S. Jackson, V. W. Burse, C. Hayes, W. E. Straub, P. J. Landrigan, J. A. Liddle (1978). "Epidemic kepone poisoning in chemical workers." American Journal of Epidemiology 107(6): 529-37
Cohn, W. J., J. J. Boylan, R. V. Blanke, M. W. Fariss, J. R. Howell, P. S. Guzelian (1978). "Treatment of chlordecone (Kepone) toxicity with cholestyramine. Results of a controlled clinical trial." New England Journal of Medicine 298(5): 243-8
Martinez, A. J., J. R. Taylor, P. J. Dyck, S. A. Houff, E. Isaacs (1978). "Chlordecone intoxication in man. II. Ultrastructure of peripheral nerves and skeletal muscle." Neurology 28(7): 631-5
Taylor, J. R., J. B. Selhorst, S. A. Houff, A. J. Martinez (1978). "Chlordecone intoxication in man. I. Clinical observations." Neurology 28(7): 626-30
Larson, P. S., J. L. Egle, Jr., G. R. Hennigar, R. W. Lane, J. F. Borzelleca (1979). "Acute, subchronic, and chronic toxicity of chlordecone." Toxicology and Applied Pharmacology 48(1 Pt 1): 29-41. http://dx.doi.org/10.1016/S0041-008X(79)80005-8
Fariss, M. W., R. V. Blanke, J. J. Saady, P. S. Guzelian (1980). "Demonstration of major metabolic pathways for chlordecone (kepone) in humans." Drug Metabolism and Disposition 8(6): 434-8
Saunders, L., P. Kadhel, N. Costet, F. Rouget, C. Monfort, J.-P. Thome, L. Guldner, S. Cordier, L. Multigner (2014). "Hypertensive disorders of pregnancy and gestational diabetes mellitus among French Caribbean women chronically exposed to chlordecone." Environment International 68: 171-176. http://dx.doi.org/10.1016/j.envint.2014.03.024
Kadhel, P., C. Monfort, N. Costet, F. Rouget, J.-P. Thome, L. Multigner, S. Cordier (2014). "Chlordecone Exposure, Length of Gestation, and Risk of Preterm Birth." American Journal of Epidemiology 179(5): 536-544. http://dx.doi.org/10.1093/aje/kwt313
Boucher, O., M.-N. Simard, G. Muckle, F. Rouget, P. Kadhel, H. Bataille, V. Chajes, R. Dallaire, C. Monfort, J.-P. Thome, L. Multigner, S. Cordier (2013). "Exposure to an organochlorine pesticide (chlordecone) and development of 18-month-old infants." Neurotoxicology 35: 162-168. http://dx.doi.org/10.1016/j.neuro.2013.01.007
Dallaire, R., G. Muckle, F. Rouget, P. Kadhel, H. Bataille, L. Guldner, S. Seurin, V. Chajès, C. Monfort, O. Boucher, J. P. Thomé, S. W. Jacobson, L. Multigner, S. Cordier (2012). "Cognitive, visual, and motor development of 7-month-old Guadeloupean infants exposed to chlordecone." Environmental Research 118: 79-85. http://dx.doi.org/10.1016/j.envres.2012.07.006
Clere, N., E. Lauret, Y. Malthiery, R. Andriantsitohaina, S. Faure (2012). "Estrogen receptor alpha as a key target of organochlorines to promote angiogenesis." Angiogenesis 15(4): 745-760. http://dx.doi.org/10.1007/s10456-012-9288-7
Multigner, L., J. R. Ndong, A. Giusti, M. Romana, H. Delacroix-Maillard, S. Cordier, B. Jegou, J. P. Thome, P. Blanchet (2010). "Chlordecone exposure and risk of prostate cancer." J Clin Oncol 28(21): 3457-62. http://dx.doi.org/10.1200/JCO.2009.27.2153
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Explain more on Garcia et al (1990) method of using glass tubings.
Talk also about the Y-tube olfactometer
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Olfactometer studies are usually preferred to know attraction towards a volatile. Repellency  study require different parameters viz., feeding deterrence,oviposion repellence etc. The study should be in open choice condition first and confirmation in no-choice test.
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Following butanol extraction procedure or pesticide contaminated soils, can I freeze dry the solid and liquid portions of the soil for the determination of residual concentration and bioavailable fractions respectively?
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The butanol will quickly start to boil  under the strong vaccuum combined with freeze drying. This and the vaccuum can lead to significant losses of chemicals.
You should check for the volatility of the pesticides you plan to analyze. You may better evaporate the solvent using a rotavap and/or N2 gas stream.
Use a fume hood to not contaminate the lab with butanol vapour.
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I want to analyze residue of insecticide / fungicide in plant sample and insect. Further I want  to do residue analysis in soil also by using HPLC. 
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Thank you
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I am currently reviewing literature in regards to my undergraduate thesis on Assessment of Cocoa Farmers practices on disposal of Pesticides Waste in Southwestern Nigeria. I need research articles relating to the field and will really appreciate you if you can provide me with some articles.
Thanks.
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 Thank you Dr. Mirza for making the book available for download. I will check it out.
Kind regards.
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How to increase the recovery of OPPs from vegetables using GC?
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GC itself has nothing to do with the recovery of the anlayte. However, what you see may be the apparent low recovery as a result of your extraction method and solvent as Ravi mentioned above. To check the real recovery, you need to prepare the matrix blank going thru the same method as the spiked sample and add the expected amount of pesticides to it. The matrix will cancel out matrix effect and you can measure the recovery of your method. OP is more polar than chlorinated pesticide, so if you do solvent transfer to more non-polar solvent (for GC injection), your OP may not partition well. Use QuEChERS extraction method and inject the actonitrile extract (after the clearnup) with no solvent partition to hexane or toluenen. Or you can dry down the acetonitrile (not to dryness, cause you may loose the pesticide during the drying process and add acetone to it so the final solvent is acetone. I don't do OP by GC anymore because I have LC/MS for that.
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I am doing experiment in rice leaves with different rice pesticides.
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you can do clean-up for your extract by three layers, one represent the silica gel ; the second one composed of both silicagel ,and charcoal(the longest one), and the third one is anhydrous sodium sulfate as i did in my project for multi-residue analysis
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I am using Quechers method to extract diazinon from grapes. I followed the original Quechers method. I first contaminated the grapes with pesticides then analyze the residue levels. After blending 200 g grapes, I will take three portions of blended grapes (each portion 10 g) and analyze them using LC/MS/MS. But my results showed that, within the three portions of the same batch, the difference are quiet significant. For example, they can be like 0.1ppm, 0.06ppm and 0.05ppm. Is this normal? I felt the three value should be pretty close since I blended them thoroughly.
I am using a commercial blender for blending. I wonder how can I tell if the grape is blended into homogeneous? I set the blender at high speed and blended for 3min. Is that long enough?
Also,  after the blending, should I measured the 10 g portion immediately? Or I should wait for a while to let it equilibrate?
Will any of these affect my final results?
Do I need to add some water to the 10 g portion before addition of acetonitrile and salts?
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You probably has a hot spot. Try this, blend the blank grape well, weigh 10 g into 3 tubes and spike analyte to it. You can vortex to mix the standard to matrix and store it for a while. This way it guarantee that you have equal amount of analyte in each tube and then you can evaluate your method. Grape has lots of water, no need to add more water.
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I have tried to work with the QuEChERS method and used different salts, but the recoveries are very poor. The method must operate for more than ~ 600 different pesticides and I work with GC-MS/MS and HPLC-MS/MS.The methode should be practible for routine analysis.
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take a look at my publication on Avocado by LC/MS and GC/MS in my profile. For spice, you need QuEChERS extraction with SPE in the cartridge format not dispersive SPE it is more dirty.
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I work on birds in an agricultural landscape whose primary diet consists of insects and grains. I want to find out the pesticide residue in crops. What part of the plant should I sample and should I collect soil samples? 
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Hello, that is a good topic,
About your question, it's depend of your goals, because if you want to make the risks assessment on your birds, you don't need the soil samples, you can take the fruits for example.
but if you want to know the transfer from soil to plants, and then to your birds, yeah you need to collect the soil samples, and for the plants you take all parts, and make analysis for each part [( roots, stems, fruits (or grain)]
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What should farmers do to avoid pesticides ? thanks everybody.
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use of the right pesticide preferrably non- persistent chemicals, recommended dose and  harvest interval.  Good agricultural practice should be observed.
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I have tried to clean up procedure with florisil and silica in QuEChERS process for soil pesticide residues but recoveries are very high during method development.
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Are you using the GC? If it is, you may have matrix effect. If you use LC/MS, you should see matrix suppression. If you use standard in solvent, you will see low recovery on the LC/MS and high recovery in the GC method.
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With sample:solvent ratio of 1:2 (5 g with 10 mL acetonitrile), you have good overall recovery. I used 0.5 g of oil with 30 mL acetonitrile just to maintain amount of oil at 0.5 g for fear of damaging the GC column. The idea of freezing should help out a lot to get rid of the oil. The method is good for lower the LOW to 10 ppb.
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I have already develop a method using 0.5 g oil and 25-30 mL acetonitrile to increase solvent/sample ratio and got good recovery. However, with a smaller sample size, my LOQ is much higher. See my profile on publication of pesticide in olive oil.
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See above
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Dear Researcher
You can use ion exchange chromatography technique. 
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While doing pesticide remediation of soil with bacterium, why it is difficult to remediate soil compared to water?
Thanks for the suggestions.
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Dear Kunal,
Soil is totally heterogeneous system,. If you talk about bio-remediation of heavy metals or other contaminants from soil, then you have to go for Sequential exatration of heavy metals or contaminants. In soil heavy metal is bound in mainly four form: (1) Soluble/ extractable form (2) Bound to carbonates (3) Bound to iron and manganese oxides  (4) Bound to organic matter (5) residual fraction while water ishomogenous. So so can easily see how complex is the soil as a system of soil-metal complex.
    Moreover, in soil availability of heavy metals for plants or microbes is very very less as compared t water.
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Detailed method for extraction of insecticide residue for HPLC.
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First of all you should extract out bound residues of pesticides and its derivatives from the soil by solvent extraction method(Sohxlet extraction) and then check their solubility in solvents to make them inject-able into HPLC instrument. HPLC techniques are used with C-18 reverse phase column with UV detector for pesticide residue analysis.HPLC is the principal separation technique for identification of the pesticides in environmental samples and for quantitative analysis of analytes. At each stage of the HPLC procedure the chromatographer should possess basic skills that substantially help in accomplishing HPLC experiments correctly, to obtain reliable, repeatable, and reproducible results.Reversed-phase liquid chromatography (RPLC) with ultraviolet (UV) detection mode is most widely adopted, owing to its ability to perform efficient separation of very polar to apolar pesticides and the universal character of the detection mode. Therefore, a large part will deal with reversed-phase liquid chromatography/ultraviolet (RPLC/UV) applications showing its excellent separation performance and detectability of compounds not directly amenable to gas chromatography (GC).The more  elective/sensitive detection modes, fluorescence detection (FD) and mass spectrometry (MS) as applied in pesticides residue analysis will be discussed with emphasis on the increasing importance of MS for identification and quantification of polar pesticides in various types of samples.
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multi_residue method for the analysis of hormones in meat liver heart fat using
LC_MS/MS and or GC_MS/MS
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Analyst. 2000 Apr;125(4):711-4.
Determination of estrone and 17 beta-estradiol in human hair by gas chromatography-mass spectrometry.
Choi MH1, Kim KR, Chung BC.
Author information
Abstract
An efficient procedure is described for the determination of estrone and 17 beta-estradiol in hair by gas chromatography-mass spectrometry (GC-MS). The method involves alkyloxycarbonylation with isobutyl chloroformate (isoBCF) of phenolic hydroxy groups after alkaline digestion of hair samples. The resulting isobutyloxycarbonyl derivatives of estrone and 17 beta-estradiol are extracted with hexane and subjected to chlorodifluoroacetyl derivatization in order to protect the remaining alcoholic hydroxy groups. When GC-MS with selected ion monitoring (SIM) was used, the quantitative ions were at m/z 270 and 384 in the electron ionization mass spectra for estrone and 17 beta-estradiol, respectively. The detection limits for SIM of the steroids were 1 and 2 pg, respectively, and the SIM responses were linear with correlation coefficients varying from 0.991 to 0.994 in the concentration range 0.2-4.0 ng g-1 for the estrogens studied. The detection of estrone and 17 beta-estradiol in hair samples was possible in the concentration range of 0.24-1.30 ng g-1. The concentrations of the two estrogens detected were different in male and female hair samples.
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I am testing pesticide residues and my last step of extraction is to transfer 0.4ml acetonitrile containing cyprodinil into 1ml of HPLC water. I wonder if cyprodinil is stable in this situatoin if I store my final samples for days before final HPLC analysis?
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Stability: hydrolytically stable DT50 at pH 4-9 (25 ° C)> 1 years. DT50 with water photolysis 5-30 d.
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I'm looking for field or lysimeter tracer studies (particularly using Bromide but other conservative tracers are more than welcome too) which are of long enough duration to capture not just breakthrough and peak concentration but also the final exit of the solute from the profile. Many studies list only the first two results, presumably due to the extensive times required for the tracer to totally exit the profile. I am particularly looking for studies within Ireland or England, and failing that the rest of the EU.
If anyone could suggest some papers that would be much appreciated! Thanks everyone.
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Here's one in Germany where the tracer tests lasted over 300 days and exhibits a long tail:
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In many countries, more and more people like eating organic rice as a new life style of healthy food; however, the yield of this rice is normally low and there are many requirements for field preparation in comparison with those of non-organic rice, which lead farmers to be afraid to invest. If the world turns to produce this kind of rice then we might be faced with the problem of food security since with a low quantity of rice it is not enough to provide for people.
What should be our advice for people or their Government? Producing non-organic rice with a high quantity of rice to provide for the world or the organic rice?
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In the interest of food security and people's health, it is advisable to follow integrated nutrient and pest & disease management methods. Use of novel cropping systems will also help to reduce chemical load on the environment. Organic rice production can be a niche area for selected consumers.
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I am using LC/MS/MS to detect pesticide residues (Diazinon, Cyprodinil, and Imidacloprid) on fresh produce. I got the standard pesticides from sigma and tried them on the lc/ms in my lab. But the lc/ms shows no peaks when I inject the 1ppm pesticide solution (in acetonitrile) directly into the lc/ms. But when I dissolve the pesticides in methanol and inject the 1ppm pesticide into the lc/ms, there are obvious peaks. I never saw any similar problems in any articles. Does any one also have the similar issue or know the reason and solutions?
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The proton donating abilities of MeOH are stronger than acetonitrile, in other words solute are more easy to ionize in MeOH than in acetonitrile when using ESI interface. 
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These two chemicals are being used extensively in crop protection along with other group of insecticides. Am researching to find out native soil bacteria to degrade these two pesticides effectively. So hope may some kind of bacterial groups are specifically involved in degradation.
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The metabolism of neonicotinoid insecticide thiamethoxam by soil enrichment cultures, and the bacterial diversity and plant growth-promoting properties of the cultured isolates. J Environ Sci Health B. 2014 Jun 3;49(6):381-90. doi: 10.1080/03601234.2014.894761
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When do you buy a pesticide standard of reference material, has a determinated shelf life. Once it´s finished, how do you managed? do you extend the shelf life, and if you do, how do you managed with it? Do you take a control of them with another standard o how ?
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Dear Alejandra,
The efficacy of pesticide preparations are influenced by many factors of their production most of them you cannot control or evaluate. Thus, the first rule is to use always ”fresh” samples or those whose shelf life is still valid. Generally, many pesticides, mainly WP and EC formulations can keep their efficacy even after their shelf life thus comparing their efficacy with fresh preparations you can calibrate them. In case of Bacillus thuringiensis (Bt) preparations there are so called international unit (IU) values which serve to calibrate even fresh commercial preparations. When working with Bt preparations I asked IU samples from the Pasteur Institute in Paris.
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in validation a procedure of pesticide residue analysis,Specificity defined as the ability of the detector (supported by selectivity of extraction and cleanup) to provide signals that effectively identify the analyte. according to SANCO/12571/2013, these signals should be less than  30 % of RL( reporting limit).
my question :1- how can i attain Specificity from standard (analyt in solvent),(analyt in matrix) or ( by spiking the matrix then exctractin, cleanup, injection and determination the detector response)?
2- specificity should be attained for an analyte for each matrix? 
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According to SANCO/12571/2013 guidelines the criteria for specificity is response in reagent blank and blank control samples should be < 30% of RL. So, standard and blank matrix (non-spiked) after processing are to be analysed. It is to ensure that the peak obtained is specifically from the analyte and not from matrix. Blank control samples of each matrix has to be run.
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When using the instrument (GC or HPLC) for pesticide residue analysis, we found that there are many peaks that are not pesticides we already know , Also the peaks are not from chemicals of pretreatment and matrix. Then how do we know whether composition of these peaks is toxic or not ?
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Dear Hong
In addition to the comments already made, please consider this:
- What kind of samples are you dealing with? In case of environmental samples or biological experiments: think of metabolites and degradation products (hydrolysis, photolysis).
- If you are really sure that sample preparation or matrix do not contribute to your unknowns and you are dealing with commercial pesticide preparations rather than pure substances: check for additives.
- On your final question "Then how do we know whether composition of these peaks is toxic or not ?": chemical analytics is not able to tell you. This is subject to toxicological studies. Once you know the substance, you either will find respective data published (hopefully) or you got to get such studies done. Eventually you may try to estimate from similar substances but that's a unsteady and questionable path.
In any case it is essential to apply mass spectrometry to identify your unknowns, as previously suggested. In case your samples can be analyzed by GC (maybe after derivatization), I'd strongly suggest to use GC-MS. The spectra mostly show sufficient fragmentation to allow interpretation from scratch, but in most cases a proper library will do the job.
I hope it helps
Peter
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What is the most preferred solvent for dissolving a sample prior to injection on GC/MSD especially for pesticide analysis? 
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It completely depends upon your sample and the pesticides you're looking for. As a general screening method QuEChERS is an outstanding method; we directly inject the acetonitrile without any major problems using large volume/low split ratio injections. Acetonitrile/QuEChERS is not good for some compounds. In those cases you're better off using a polar solvent with solvent exchange into MeCl2 or hexane.
As long as you're careful with your injection technique any solvent lighter than toluene will perform adequately.
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The interference effects of pesticides.
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when I work the interefering effects of pesticides which have same electroactive group but have different substition give same region peaks especially carbamat gruops pesticides. if i change solution, solvent etc, their interefering effects can be grand the peaks region
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I am analyzing some pesticide residues in soil with HPLC-UV. I have tried different extraction and clean-up methods using acetonitrile or ethyl acetate as sovents and PSA or GCB as dispersive SPE sorbents. However lots of peaks related to impurities appear on the chromatogam when I inject the samples to HPLC-UV. Is there any cheap and effective way I can reduce these impurities in the extracted samples?
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Any soil extracted with such solvents will always produce an extract that contains not only the target compounds you want to analyse but also many other organic substances present in the soil. There are a number of SPE cartridges designed to adsorb some of the unwanted compounds - you have to look at the commercial catalogues and decide which one to use. Apart from that, florisil columns are also good. In any case, HPLC-UV chromatographs always show a number of unknown peaks...All you should aim for is a clear baseline.