Pesticide Analysis - Science topic

For pesticide analysis in water using the Thermo Scientific Trace 1300 GC-MS, follow the QuEChERS method for sample preparation, then analyze with appropriate GC parameters and quantify using external calibration. Establish retention times through method validation and utilize software like TraceFinder for data processing.

For assessing the environmental fate of pesticides, LogKoc (the organic carbon-water partition coefficient) is the most appropriate adsorption parameter, as it indicates the pesticides' retention in soil versus their mobility in water. This provides a clearer understanding of their potential for leaching and environmental impact.

Using the same HPLC method, a multi-level calibration table must be created using proper standards for comparison.

Atrazine can nicely be analysed by GC-MS, by HPLC-MS/MS; and well enough by HPLC-UV or DAD. I am not aware anyone does Atrazine by fluorescence because as You pointed out it does not make a serious signal.

I was determining antibacterial activity of jade plant and I extracted by methanol in Soxhlet extraction the extract was water soluble so I dissolve it using distilled water and perform susceptibility test for different isolate.

Check out https://www.researchgate.net/publication/345322889_Multi-residue_Analysis_of_Pesticides_in_Turmeric_Powder_and_Rhizome_Using_Gas_Chromatography_Tandem_Mass_Spectrometry

If the method you found is for herbicide with halogens (Cl probably) and you want to measure low concentrations and you have a dirty matrix, it will not work. The FID is most probable not sensitive and specific enough. And forget about the TCD.

"but many studies have been carried out with the help of FID detector."

10, 20 or 30 years back maybe, and what sort of studies? Current studies of halogenated herbicides, I doubt they use a FID or even an ECD, or the concentrations must be high. Current studies will be with GCMS or GCMSMS.

I suggest to upgrade your equipment.

There are many factors are responsible to get more precise results using GC-MS/MS for the determination of pesticide residues. The main responsible factors are outlined below:

1. Use external standard

2. Use Matrix matched calibration standard to minimize the matrix effect

3. The method used for analysis should be validated following the EC document: SANTE/12682/2019 as it is well accepted and nicely described for the method validation guidelines using GC-MS/MS.

4. Prepare the working standard solutions correctly.

5. To extract the desired pesticides using QuEChERS extraction method.

6. To cleanup the analytes appropriately by adding the proper amount of solvent, sorbent and reagents, incase of cleanup try to avoid the use of GCB or use a minimum amount.

Dear Nicolas Pala

I also think that it is feasible with both variants.

In my experience, 13C-labeled standards are considerably more expensive than deuterated standards, so it also depends on your budget.

It would also be possible to combine e.g. deuterated standards as recovery standards, 13C standards as quantification standards.

I hope you will find the right answer for you.

With kind regards and stay healthy

Jaochim Horst

You can use simply a Soxhlet extraction or even shake the soil with organic solvent. Compare few to get best recovery. If the pesticide is not so volatile, you can evaporate part of the solvent from extract to increase the sensitivity of your method.

regards,

GB

Rinse the syringe several times with the solvent of that type of pesticides

Thanks Noel W Davies for correcting my concepts 🙂

Dear Noel,

Many thanks for your efforts in the identification of our spectra.

I also came out with the same formula C8H4Cl4N2O2. I looked to that recent article of colleagues of EAWAG in Switzerland “New relevant pesticide transformation products in groundwater detected using target and suspect screening for agricultural and urban micropollutants with LC-HRMS” Kiefer etal 2019, with an important database as Supporting Information of possible transformation products of pesticides.

One of the specific pesticides discussed is the fungicide chlorothalonil and its possible transformation products detected in groundwater samples. One of the known transformation products in soil is 1,3-dicarbamoyl-2,4,5,6-tetrachlorobenzene (C8H4Cl4N2O2).

Thanks @R.Girijan Menon

This may also help

https://web.vscht.cz/~hajslovj/publications/lehotay_gctrends_trac_vol21_p686-697.pdf

Hello Daniel J F Santos ,

Yes it will. You can see the below document.

S. Wagner, "Environmental Fate of Imidacloprid," Sacramento, CA, 2016.

Furthermore, the coupling of UV light increased the degradation of Imidacloprid by ozonation. You can check my paper if you would like to.

Best.

Busra S. Baghirzade

Portable Detection Instruments are an interesting field but until now they are not allowed in the official analysis neither as screening before the more expensive official analytical methods.

Ok

I suggest to review the following properties of this xenobiotic before to commence with oral study

pKa, acid-base stability, gastric irritation and chemical-food interaction.

you have to buffer its optimum pH since weak acids will have more serum level that may be toxic.

you can also assess acid-base stability within hours at 37 C.

gastric irritation could be predicted from SAR.

Then oxoid food contents adsorption could also be assessed by spectrophotometry.

Provided that there were no previous studies that role out those parameters

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.

It is slowly, it is almost within three months

Please have a look at this useful RG link.

Hello,

Use amber color sterilized (Heat upto 300 celsius temperature) glass bottles for the collection of water samples and better if you can collect around 2L water sample. Preserve your samples with 10ml of chloroform/1L of water sample. Transport samples in cold room condition and store samples in the cold room until start analysis. You can use both solid phase extraction or liquid liquid extraction for the extraction of pesticides from collected water samples. After concentrating, pesticides samples can inject to HPLC, LCMS or GCMS machines. Use EPA methods for the protocols.

Hello, spiking if preferable for all 74 pesticides that you want to analyse in your food samples to be able to calculate Recovery. Also better to use some internal standard besides of your pesticides for more reliable results. I think you should at first validate your method before use in food testing.

Above all mentioned is best practice.

But if you want to spike fro 5 to 10 pesticides you shuld chose mach different from each other for better results.

Hope this info will help you.

Good luck!

it depends on molar extension coefficient value

for example: if it is 100000 L/moll. cm then 0.000001 M solution would give 0.1 absorbance

We extracted DDT, DDE Aldrin and PCBs from fish tissue using Accelerated solvent extraction, then SPE but often found we still have too much lipid so we would freeze our extracts (hexanes) to remove the lipids. We found cold centrifuging helped to separate the frozen lipids from the hexane. We would use acidic cleanup when we were only testing for PCBs and PBDEs.

use LCMS using the pesticide molecule as a reference and then you compare the two spectra and masses of pesticide molecules and an extract of honey

1. use surfactant to to ensure complete runoff that prevents droplets remaining at leaf edge.

2. Use runoff and when you think that all leaves are covered, check the bottom side. You will find in many cases that it is not covered until you keep spraying more and more.

3. Try to use a fan with a slight air flow while you are spraying to "mix" the leaves to ensure that the underside is covered.

If it is a filter effect the magnitude is related to both the concentration and the median distance excitation/emission traves to exit the solution.  These effects are testable empirically using fluorescence cells of different dimensions.

@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.

I am beginning work on occupational exposure to pesticides, and exchanging ideas would be great, Paresh. We have HPLC and GC-MS in my lab and looking to acquire other suitable instruments for this work.

Bruce.

I really appreciate your help. I did the analysis and it went all right.

Thank you very much.

Rice Co has a WG formulation that does not presents those problems 

in Indian storage system Celphos is widely used in warehouses which containing phosphine gas to control storage pests

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

Thanks for your detailed answer. The problem here is that I'm working with different taxa (and hundreds of species, from plants, carabid to birds...) in field plots over the whole country.... so it's going to be tricky if not impossible.

My main problem is to combine in an index different molecules. Unfortunately, and though this isn't really satisfying, I'll have to stick to the treatment frequency index...

Thanks again for taking the time to answer

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.

For the sake of the discussion, I have added the recent regulation on glyphosate in which is also stated: “Member States shall ensure that plant protection products containing glyphosate do not contain the co-formulant POE-tallowamine (CAS No 61791-26-2)”.

Best regards,

Roberto

You may dissolve the active ingredient in a suitable solvent. That is solution A. Then use an adjuvant and an emulsifier (Solution B). mix both solutions atleast for 30 minutes ; 150-200 RPM. You get a EC formulation now.This is general formula. But the composition varies from active ingredients. If you can specify the active ingredient; i shall provide you the composition of formulation

Hello Morgan,

These papers may be useful:

10.1016/j.envpol.2014.02.028

10.1007/s00216-014-7757-0

10.1002/etc.514

10.1021/es902256m

10.1016/j.talanta.2008.09.047

Kinds regards,

Bea

I think for analyze both  of FAMES and pesticides DB-5 is better than DB-1.

with regards

maryam

Be aware that extract clean-up with PSA should be avoided in case of acidic analyses. 

For making standard solutions, first we have to make single stock solution for each compound, then as a second step prepare mixed working solution (based on your system sensitivity you can adjust  concentration by further dilution, expressed as ug/mL ).  Final result can be calculated as below:

 (Peak Area of Sample/Peak Area of Standard )x Concentration of Mixed Standard Solution , ug/mLx (Dilution volume of sample, mL /Sample Weight, g ).

 An emulsion is a mixture of two or more liquids that are normally immiscible (unmixable or unblendable emulsion should be used when both phases, dispersed and continuous, are liquids. In an emulsion, one liquid (the dispersed phase) is dispersed in the other (the continuous phase).. Emulsions, being liquids, do not exhibit a static internal structure. The droplets dispersed in the liquid matrix (called the “dispersion medium”) are usually assumed to be statistically distributed. The said ingredient makes more emulsifiable the formulation  I guess

I agree with Dr.Timothy A Ebert, moreover, It should be kept in mind for residue analysis that a number of pesticides are water soluble and almost non in to hexane  type solvents while some are opposite of this nature

You need to tell first, what prompted you to go for this ? To be more precise in answering.

To extract OCs andOPs the best solution is to use an appropiate solvent for them and sonicate in an adequate proportion (i.e. 3:1) following by centrifugation if the objective is a further analysis. Then to anayze the extract by GC or LC-MS. There few "good solvents" for this. The selection can be decide considering the next step. For example if you like to check them after extraction by LC-MS MeOH should be a good candidate. In the case of GC-MS EtAc it should be very adequate.

I would recommend two choices to try out.

1) do the solvent exchange from acetonitrile to acetone or toluene.

2) if you want to do acetonitrile, you can try to use spit injection with split ratio of 1:1 or 1:3. Jack Cochran from Restek has a paper that you would not loose sensitivity much. However, acetonitrile may give the response to the ECD so if you need to use ECD, I would do the solvent exchange.

Thank you Francois. I hadn't seen this paper.

All above answers are correct, just wana mention that one of the best and so reliable reference for these questions is "NCBI pubchem compound".

http://pubchem.ncbi.nlm.nih.gov/compound/3017   for Diazinon

http://pubchem.ncbi.nlm.nih.gov/compound/40585  for Deltamethrine

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.

We currently detect carbofuran between 275 and 280 nm in biological samples (plasma / urine) with no interferences. MS is definitely more sensitive (even GCMS works for carbofuran)

Dear Amal,

These papers may be helpful:

Olá Emanuel, 

obrigada! Thanks! I didn't know that article. I found it on our platform (https://www.researchgate.net/publication/271557244_A_Review_of_sensor_technology_for_in-field_phosphate_monitoring). It is summarizing sensors for phosphate detection on the ground using sensors. 

The conclusion for spectral sensors was that you would need a field/site specific calibration, what I agree. If you do not do a field specific calibration than uncertainties become large. The question however remains how we could bring the field measurement (which is already prone to uncertainties) to the satellite or airplane level. For many applications it would probably enough to get the general level of pollution without having extensive expensive and time-consuming field measurements. Once there is the indication for pollution then of course measures on the field scale should be implemented.  

até mais Theresa

Dear Gary, would be nice to know which compounds you have in mind....

Anyway In my view all quetchers based methods are screening methods that have as an outcome only have aserious look or forget about it there is no problem.

If serious quantitation is required a thorough extraction (soxhlet or ASE) slould be combined with lipid removal eg by size exclusion chromatography also called gel permeation and eventual sorption cormatography e.g. by silica gel chromatography. 

This approach has been acknowledged on both sides of the atlatic in official food analysis.

Kind regards

Kai

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.

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.

In case you have samples of standards available to you, and in case there is a good UV chromophore (epsilon > 1000, preferably more) UV-based methods should be more reliable than the typical MS methods. Assay precision will largely depend on strictly following the protocols for sample isolation/preparation.

However, some herbicide AIs are only very weakly UV-active. In such case MS is the way to go.

This all depended on the pesticide itself. Can you for example use gas chromatography for analyzing this pesticide? I think if the compound has reasonable molecular weight and is not a very high melting solid then it will be resolved via gas chromatography. If this the case, you can then use an internal standard which is a compound that is not active chemically and that has a gas chromatographic retention time comparable  to that of the pesticide. You make solutions of known concentrations (as an example a 1:1 mole ratio) of the pesticide and the internal standard and inject them on the GC and get areas under the peaks for both the standard and the pesticide. From these areas (ratio of areas) you get something call response factor. Let us assume that the area of the gas chromatographic pesticide peak was 40 and that of the internal standard was 80, then the response factor is 2. For real analysis, you mix known amount of the standard (known number of moles) with the pesticide (unknown concentration) and you measure the areas under the peaks. Number of moles of pesticide can be calculated by multiplying the ratio of its area compared to that of the standard times 2 times the number of moles of the standard. Hope this helps. 

Thanks, could you tell me which article can help me more.

here's the method. Note that it has more than one tabs.

the components such as methiocarb, niclosamide , metaldehyde  etc are major molluscicidat components extracted from calamansi rind. Likewise , oil extracted from pummel has a good mulluscicidal property . you can try out some citrons , they could serve your puepose but its rind -derived oil hold some promise.

Detailed bioassay to establish synergism and additivity is a recognized method. Stick to it and identifying the deviation from normal are the recognized methods.

Dr. Mirza Arshad Ali Beg 

 Thank you Dr. Mirza for making the book available for download. I will check it out.

Kind regards.

Diet feeding assay having know concentrations of insecticidal protein. Rearing till pupation is important. Ensure the Plutella be parasitised just before initiation of assay.

I think it is difficult to use GCMS to identify the compound(s) that have effect (GC MS has degraded all compounds) . I think you can use other chromatography methods such as Column chromatography, TLC (preparative) or HPLC (preparative) to separate the compound(s). From these, you can have fractions that contain single/mixture compounds for pest experiments., than you can identify the the active component from the active-fraction(s) using GC MS or LC MS or others (NMR)

Catarina, 

could you specify a little more your question? What crop, what surface, which pesticides? What environment? Aerial applications (by airplane) on rice fields or manual applications on field crops or in greenhouses? Are you looking at pesticide residues on the crops or in the soil? or in the water?  Insecticides, herbicides? Irrigated crops? There are so many factors to have in mind that a simple calculation (or not so simple) seems to lead far from reality. And then, predict what? The absence of insects (pest insects or beneficials, vertebrates?) in the crop area or in what distance to the pesticide applications? One year seems to me a very short period. If you precise your question, perhaps we can help with brainstorming?

Internal standard (IS) is used to compensate matrix suppression of your target analyte, so it should be exactly the same (except a bit heavier) so it is eluted at the same time as the native analyte. It is not practical to do 300 IS because it is way to expensive. When I screen, I use standard in solvent to estimate the amount of pesticide in the sample. If it is below tolerance, you let it go. If it is about or above tolerance, I use standard addition to compensate for matrix suppression. Contact me if you need details of how to do it.

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)]

Hi, in my opinion,  for mortality is better Sun-Shepard formula:

another non invasive biomonitoring tool are feathers... maybe this publication could be useful.

best regards

stefania

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.

10 times the SD is one definition of LOQ. USEPA also defines LOQ as the lowest concentration in your standard curve, which is the definition that I prefer since there is no uncertainty in that. Thus, if your standard curve for the compound of interest runs from 0.1 mg/Kg (ppm) to 10 ppm, your LOQ would be 0.1 ppm times the concentration/dilution factor for the sample.

Your LOQ is not in any way dependent upon the MRL; rather, it is dependent upon instrumental or method criteria. Your low standard should be roughly 3-5 times your limit of detection (LOD) which you can derive statistically. However, you should run your low standard at a concentration that affords you adequate precision at the low standard (typically defined as <40% RSD).

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.

For sure,  option 2 is the best. It is always preferable to use fragments ( clearly established) than isotopes becasue they have to be consider more selective and with the ion ratio interval defined in experimental conditions. 

Obviously it is a general rule, in some especific cases Cl or Br isotopes are very helpful and even the first choice but ths selection is case by case.

Additionaly to say that; at very low concentration high variations in intensity can be related with the resolution provided by the instrument

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.

You can use GC-MS in Full Scan mode. But, you need have a specialized column to different groups of pesticide.

Dear Kwamina,

Garlic, ginger and vodka, beer, wine. This mixture must be very expensive!

Stability: hydrolytically stable DT50 at pH 4-9 (25 ° C)> 1 years. DT50 with water photolysis 5-30 d.