I would like to thank Javier Hern&#225;ndez-Borges and Cecilia Ortega-Zamora for their invaluable support. I also want to thank the Universidad EAN and the Universidad de La Laguna.

1. Preparation of the stock solutions
NOTE: It is recommended to wear nitrile gloves, a lab coat, and safety glasses during the entire protocol.
<ol>
	<li>Prepare a stock solution in acetone at 400 mg/L from a commercial mix of OCPs (see Table of Materials) at 2,000 mg/L in hexane:toluene (1:1) in a 25 mL volumetric flask. Table 1 shows each of the selected OCPs.</li>
	<li>Prepare the subsequent stock solutions in acetone at concentrations o...

<ol>
	<li>Sabzevari, S., Hofman, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+worldwide+review+of+currently+used+pesticides'+monitoring+in+agricultural+soils.">A worldwide review of currently used pesticides' monitoring in agricultural soils.</a> Science of The Total Environment. 812, 152344 (2022).</li><li>Tzanetou, E. N., Karasali, H. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comprehensive+review+of+organochlorine+pesticide+monitoring+in+agricultural+soils:+The+silent+threat+of+a+conventional+agricultural+past.">Comprehensive review of organochlorine pesticide monitoring in agricultural soils: The silent threat of a conventional agricultural past.</a> Agriculture. 12 (5), 728 (2022).</li><li>Farenhorst, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Importance+of+soil+organic+matter+fractions+in+soil-landscape+and+regional+assessments+of+pesticide+sorption+and+leaching+in+soil.">Importance of soil organic matter fractions in soil-landscape and regional assessments of pesticide sorption and leaching in soil.</a> Soil Science Society of America Journal. 70 (3), 1005-1012 (2006).</li><li>Silva, V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pesticide+residues+in+European+agricultural+soils+-+A+hidden+reality+unfolded.">Pesticide residues in European agricultural soils - A hidden reality unfolded.</a> Science of The Total Environment. 653, 1532-1545 (2019).</li><li>Vischetti, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sub-lethal+effects+of+pesticides+on+the+DNA+of+soil+organisms+as+early+ecotoxicological+biomarkers.">Sub-lethal effects of pesticides on the DNA of soil organisms as early ecotoxicological biomarkers.</a> Frontiers in Microbiology. 11, 1892 (2020).</li><li>Alengebawy, A., Abdelkhalek, S. T., Qureshi, S. R., Wang, M. -. Q. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Heavy+metals+and+pesticides+toxicity+in+agricultural+soil+and+plants:+Ecological+risks+and+human+health+implications.">Heavy metals and pesticides toxicity in agricultural soil and plants: Ecological risks and human health implications.</a> Toxics. 9 (3), 42 (2021).</li><li>Zikankuba, V. L., Mwanyika, G., Ntwenya, J. E., James, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pesticide+regulations+and+their+malpractice+implications+on+food+and+environment+safety.">Pesticide regulations and their malpractice implications on food and environment safety.</a> Cogent Food &amp; Agriculture. 5 (1), 1601544 (2019).</li><li>Varela-Mart&#237;nez, D. A., Gonz&#225;lez-S&#225;lamo, J., Gonz&#225;lez-Curbelo, M. &. #. 1. 9. 3. ;., Hern&#225;ndez-Borges, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quick,+Easy,+Cheap,+Effective,+Rugged+and+Safe+(QuEChERS)+extraction.">Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) extraction.</a> Handbooks in Separation Science. , 399-437 (2020).</li><li>Anastassiades, M., Lehotay, S. J., &#352;tajnbaher, D., Schenck, F. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fast+and+easy+multiresidue+method+employing+acetonitrile+extraction/partitioning+and+&amp;#34;dispersive+solid-phase+extraction&amp;#34;+for+the+determination+of+pesticide+residues+in+produce.">Fast and easy multiresidue method employing acetonitrile extraction/partitioning and &amp;#34;dispersive solid-phase extraction&amp;#34; for the determination of pesticide residues in produce.</a> Journal of AOAC International. 86 (2), 412-431 (2003).</li><li>Gonz&#225;lez-Curbelo, M. &. #. 1. 9. 3. ;., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evolution+and+applications+of+the+QuEChERS+method.">Evolution and applications of the QuEChERS method.</a> Trends in Analytical Chemistry. 71, 169-185 (2015).</li><li>European Union. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=European+Regulation+(EC)+NO+396/2005+of+the+European+Parliament+and+of+the+Council+of+23+February+2005+on+maximum+residue+levels+of+pesticides+in+or+on+food+and+feed+of+plant+and+animal+origin+and+amending+Council+Directive+91/414/EEC.">European Regulation (EC) NO 396/2005 of the European Parliament and of the Council of 23 February 2005 on maximum residue levels of pesticides in or on food and feed of plant and animal origin and amending Council Directive 91/414/EEC.</a> Official Journal of the European Union. 70, 1-16 (2005).</li><li>Kwon, H., Lehotay, S. J., Geis-Asteggiante, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Variability+of+matrix+effects+in+liquid+and+gas+chromatography-mass+spectrometry+analysis+of+pesticide+residues+after+QuEChERS+sample+preparation+of+different+food+crops.">Variability of matrix effects in liquid and gas chromatography-mass spectrometry analysis of pesticide residues after QuEChERS sample preparation of different food crops.</a> Journal of Chromatography A. 1270, 235-245 (2012).</li><li>Lehotay, S. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Determination+of+pesticide+residues+in+foods+by+acetonitrile+extraction+and+partitioning+with+magnesium+sulfate:+Collaborative+study.">Determination of pesticide residues in foods by acetonitrile extraction and partitioning with magnesium sulfate: Collaborative study.</a> Journal of AOAC International. 90 (2), 485-520 (2007).</li><li>European Committee for Standardization (CEN). <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Standard+Method+EN+15662.+Food+of+plant+origin-Determination+of+pesticide+residues+using+GC-MS+and/or+LC-MS/MS+following+acetonitrile+extraction/partitioning+and+clean-up+by+dispersive+SPE-QuEChERS+method.">Standard Method EN 15662. Food of plant origin-Determination of pesticide residues using GC-MS and/or LC-MS/MS following acetonitrile extraction/partitioning and clean-up by dispersive SPE-QuEChERS method.</a> European Committee for Standardization. , (2008).</li><li>Gonz&#225;lez-Curbelo, M. &. #. 1. 9. 3. ;., Lehotay, S. J., Hern&#225;ndez-Borges, J., Rodr&#237;guez-Delgado, M. &. #. 1. 9. 3. ;. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Use+of+ammonium+formate+in+QuEChERS+for+high-throughput+analysis+of+pesticides+in+food+by+fast,+low-pressure+gas+chromatography+and+liquid+chromatography+tandem+mass+spectrometry.">Use of ammonium formate in QuEChERS for high-throughput analysis of pesticides in food by fast, low-pressure gas chromatography and liquid chromatography tandem mass spectrometry.</a> Journal of Chromatography A. 1358, 75-84 (2014).</li><li>Han, L., Sapozhnikova, Y., Lehotay, S. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Method+validation+for+243+pesticides+and+environmental+contaminants+in+meats+and+poultry+by+tandem+mass+spectrometry+coupled+to+low-pressure+gas+chromatography+and+ultrahigh-performance+liquid+chromatography.">Method validation for 243 pesticides and environmental contaminants in meats and poultry by tandem mass spectrometry coupled to low-pressure gas chromatography and ultrahigh-performance liquid chromatography.</a> Food Control. 66, 270-282 (2016).</li><li>Lehotay, S. J., Han, L., Sapozhnikova, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Automated+mini-column+solid-phase+extraction+clean-up+for+high-throughput+analysis+of+chemical+contaminants+in+foods+by+low-pressure+gas+chromatography-tandem+mass+spectrometry.">Automated mini-column solid-phase extraction clean-up for high-throughput analysis of chemical contaminants in foods by low-pressure gas chromatography-tandem mass spectrometry.</a> Chromatographia. 79 (17), 1113-1130 (2016).</li><li>Lehotay, S. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Possibilities+and+limitations+of+isocratic+fast+liquid+chromatography-tandem+mass+spectrometry+analysis+of+pesticide+residues+in+fruits+and+vegetables.">Possibilities and limitations of isocratic fast liquid chromatography-tandem mass spectrometry analysis of pesticide residues in fruits and vegetables.</a> Chromatographia. 82 (1), 235-250 (2019).</li><li>Han, L., Matarrita, J., Sapozhnikova, Y., Lehotay, S. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluation+of+a+recent+product+to+remove+lipids+and+other+matrix+co-extractives+in+the+analysis+of+pesticide+residues+and+environmental+contaminants+in+foods.">Evaluation of a recent product to remove lipids and other matrix co-extractives in the analysis of pesticide residues and environmental contaminants in foods.</a> Journal of Chromatography A. 1449, 17-29 (2016).</li><li>Varela-Mart&#237;nez, D. A., Gonz&#225;lez-Curbelo, M. &. #. 1. 9. 3. ;., Gonz&#225;lez-S&#225;lamo, J., Hern&#225;ndez-Borges, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+pesticides+in+cherimoya+and+gulupa+minor+tropical+fruits+using+AOAC+2007.1+and+ammonium+formate+QuEChERS+versions:+A+comparative+study.">Analysis of pesticides in cherimoya and gulupa minor tropical fruits using AOAC 2007.1 and ammonium formate QuEChERS versions: A comparative study.</a> Microchemical Journal. 157, 104950 (2020).</li><li>Gonz&#225;lez-Curbelo, M. &. #. 1. 9. 3. ;., Varela-Mart&#237;nez, D. A., Ria&#241;o-Herrera, D. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pesticide-residue+analysis+in+soils+by+the+QuEChERS+method:+A+review.">Pesticide-residue analysis in soils by the QuEChERS method: A review.</a> Molecules. 27 (13), 4323 (2022).</li><li>Anastassiades, M., Ma&#353;tovsk&#225;, K., Lehotay, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluation+of+analyte+protectants+to+improve+gas+chromatographic+analysis+of+pesticides.">Evaluation of analyte protectants to improve gas chromatographic analysis of pesticides.</a> Journal of Chromatography A. 1015 (1-2), 163-184 (2003).</li><li>Ma&#353;tovsk&#225;, K., Lehotay, S., Anastassiades, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Combination+of+analyte+protectants+to+overcome+matrix+effects+in+routine+GC+analysis+of+pesticide+residues+in+food+matrixes.">Combination of analyte protectants to overcome matrix effects in routine GC analysis of pesticide residues in food matrixes.</a> Analytical Chemistry. 77 (24), 8129-8137 (2005).</li><li>Rahman, M., Abd El-Aty, A., Shim, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Matrix+enhancement+effect:+A+blessing+or+a+curse+for+gas+chromatography?+-+A+review.">Matrix enhancement effect: A blessing or a curse for gas chromatography? - A review.</a> Analytica Chimica Acta. 801, 14-21 (2013).</li><li>Rouvire, F., Bulet&#233;, A., Cren-Oliv&#233;, C., Arnaudguilhem, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multiresidue+analysis+of+aromatic+organochlorines+in+soil+by+gas+chromatography-mass+spectrometry+and+QuEChERS+extraction+based+on+water/dichloromethane+partitioning.+Comparison+with+accelerated+solvent+extraction.">Multiresidue analysis of aromatic organochlorines in soil by gas chromatography-mass spectrometry and QuEChERS extraction based on water/dichloromethane partitioning. Comparison with accelerated solvent extraction.</a> Talanta. 93, 336-344 (2012).</li><li>Lesueur, C., Gartner, M., Mentler, A., Fuerhacker, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+four+extraction+methods+for+the+analysis+of+24+pesticides+in+soil+samples+with+gas+chromatography-mass+spectrometry+and+liquid+chromatography-ion+trap-mass+spectrometry.">Comparison of four extraction methods for the analysis of 24 pesticides in soil samples with gas chromatography-mass spectrometry and liquid chromatography-ion trap-mass spectrometry.</a> Talanta. 75 (1), 284-293 (2008).</li><li>&#208;urovi&#263;-Pej&#269;ev, R. D., Bursi&#263;, V. P., Zeremski, T. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+QuEChERS+with+traditional+sample+preparation+methods+in+the+determination+of+multiclass+pesticides+in+soil.">Comparison of QuEChERS with traditional sample preparation methods in the determination of multiclass pesticides in soil.</a> Journal of AOAC International. 102 (1), 46-51 (2019).</li><li>European Commission. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=SANTE/11312/2021.+Guidance+document+on+analytical+quality+control+and+method+validation+procedures+for+pesticide+residues+analysis+in+food+and+feed.">SANTE/11312/2021. Guidance document on analytical quality control and method validation procedures for pesticide residues analysis in food and feed.</a> European Commission. , (2021).</li></ol>

I have no conflicts of interest to disclose.

The original9 and the two official versions13,14 of the QuEChERS method use magnesium sulfate together with sodium chloride, acetate, or citrate salts to promote acetonitrile/water mixture separation during extraction. However, these salts tend to be deposited as solids on the surfaces in the mass spectrometry (MS) source, which causes the need for increased maintenance of liquid chromatography (LC)-MS-based methods. In terms of overcoming...

The need to increase food production has led to the intensive and widespread use of pesticides worldwide over the last few decades. Pesticides are applied to the crops to protect them from pests and increase crop yields, but their residues usually end up in the soil environment, especially in agricultural areas1. Furthermore, some pesticides, such as organochlorine pesticides (OCPs), have a very stable structure, so their residues do not decompose easily and persist in the soil for a long time2. Generally, the soil has a high capacity to accumulate pesticide residues, especially when it has a high content of organic matter3. As a result, the soil is one of the environmental compartments most contaminated by pesticide residues. As an example, one of the complete studies to date found that 83% of 317 agricultural soils from across the European Union were contaminated with one or more pesticide residues4. 
Soil pollution by pesticide residues may affect non-target species, soil function, and consumer health through the food chain because of the high toxicity of the residues5,6. Consequently, the evaluation of pesticide residues in soils is essential to assess their potential negative effects on the environment and human health, particularly in developing countries due to a lack of strict regulations on the use of pesticides7. This makes pesticide multi-residue analysis increasingly important. However, the rapid and accurate analysis of pesticide residues in soils is a difficult challenge due to the large number of interfering substances, as well as the low concentration level and the diverse physicochemical properties of these analytes4. 
Of all the pesticide residue analysis methods, the QuEChERS method has become the quickest, easiest, cheapest, most effective, robust, and safest option8. The QuEChERS method involves two steps. In the first step, a microscale extraction based on partitioning via salting-out between an aqueous and an acetonitrile layer is performed. In the second step, a cleaning process is carried out employing a dispersive solid phase extraction (dSPE); this technique uses small amounts of several combinations of porous sorbents to remove matrix-interfering components and overcomes the disadvantages of conventional SPE9. Hence, the QuEChERS is an environmentally friendly approach with little solvent/chemical going to waste that provides very accurate results and minimizes potential sources of random and systematic errors. In fact, it has been successfully applied for the high-throughput routine analysis of hundreds of pesticides, with strong applicability in almost all types of environmental, agri-food, and biological samples8,10. This work aims to apply and validate a new modification of the QuEChERS method that was previously developed and coupled to GC-MS to analyze OCPs in agricultural soil.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>15 mL disposable glass conical centrifuge tubes</td>
			<td>PYREX</td>
			<td>99502-15</td>
			<td></td>
		</tr>
		<tr>
			<td>2 mL centrifuge tubes</td>
			<td>Eppendorf</td>
			<td>30120094</td>
			<td></td>
		</tr>
		<tr>
			<td>50 mL centrifuge tubes with screw caps</td>
			<td>VWR</td>
			<td>21008-169</td>
			<td></td>
		</tr>
		<tr>
			<td>5977B mass-selective detector</td>
			<td>Agilent Technologies</td>
			<td>1617R019</td>
			<td></td>
		</tr>
		<tr>
			<td>7820A gas chromatography system</td>
			<td>Agilent Technologies</td>
			<td>16162016</td>
			<td></td>
		</tr>
		<tr>
			<td>Acetone</td>
			<td>Supelco</td>
			<td>1006582500</td>
			<td></td>
		</tr>
		<tr>
			<td>Acetonitrile</td>
			<td>VWR</td>
			<td>83642320</td>
			<td></td>
		</tr>
		<tr>
			<td>Ammonium formate</td>
			<td>VWR</td>
			<td>21254260</td>
			<td></td>
		</tr>
		<tr>
			<td>Automatic shaker KS 3000 i control</td>
			<td>IKA</td>
			<td>3940000</td>
			<td></td>
		</tr>
		<tr>
			<td>Balance</td>
			<td>Sartorius Lab Instruments Gmbh &#38; Co</td>
			<td>ENTRIS224I-1S</td>
			<td></td>
		</tr>
		<tr>
			<td>Bondesil-C18, 40 &#181;m</td>
			<td>Agilent Technologies</td>
			<td>12213012</td>
			<td></td>
		</tr>
		<tr>
			<td>Bondesil-PSA, 40 &#181;m</td>
			<td>Agilent Technologies</td>
			<td>12213024</td>
			<td></td>
		</tr>
		<tr>
			<td>Cyclohexane</td>
			<td>VWR</td>
			<td>85385320</td>
			<td></td>
		</tr>
		<tr>
			<td>EPA TCL pesticides mix</td>
			<td>Sigma Aldrich</td>
			<td>48913</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethyl acetate</td>
			<td>Supelco</td>
			<td>1036492500</td>
			<td></td>
		</tr>
		<tr>
			<td>G4567A automatic sampler</td>
			<td>Agilent Technologies</td>
			<td>19490057</td>
			<td></td>
		</tr>
		<tr>
			<td>HP-5ms Ultra Inert (5%-phenyl)-methylpolysiloxane 30 m x 250 &#181;m x 0.25 &#181;m column</td>
			<td>Agilent Technologies</td>
			<td>19091S-433UI</td>
			<td></td>
		</tr>
		<tr>
			<td>Magnesium sulfate monohydrate</td>
			<td>Sigma Aldrich</td>
			<td>434183-1KG</td>
			<td></td>
		</tr>
		<tr>
			<td>Mega Star 3.R centrifuge</td>
			<td>VWR</td>
			<td>521-1752</td>
			<td></td>
		</tr>
		<tr>
			<td>Milli-Q gradient A10</td>
			<td>Millipore</td>
			<td>RR400Q101</td>
			<td></td>
		</tr>
		<tr>
			<td>p,p&#39;-DDE-d8</td>
			<td>Dr Ehrenstorfer</td>
			<td>DRE-XA12041100AC</td>
			<td></td>
		</tr>
		<tr>
			<td>Pipette tips 2 - 200 &#181;L</td>
			<td>BRAND</td>
			<td>732008</td>
			<td></td>
		</tr>
		<tr>
			<td>Pipette tips 5 mL</td>
			<td>BRAND</td>
			<td>702595</td>
			<td></td>
		</tr>
		<tr>
			<td>Pipette tips 50 - 1000 uL</td>
			<td>BRAND</td>
			<td>732012</td>
			<td></td>
		</tr>
		<tr>
			<td>Pippette Transferpette S variabel 10 - 100 &#181;L</td>
			<td>BRAND</td>
			<td>704774</td>
			<td></td>
		</tr>
		<tr>
			<td>Pippette Transferpette S variabel 100 - 1000 &#181;L</td>
			<td>BRAND</td>
			<td>704780</td>
			<td></td>
		</tr>
		<tr>
			<td>Pippette Transferpette S variabel 20 - 200 &#181;L</td>
			<td>BRAND</td>
			<td>704778</td>
			<td></td>
		</tr>
		<tr>
			<td>Pippette Transferpette S variabel 500 - 5000 &#181;L</td>
			<td>BRAND</td>
			<td>704782</td>
			<td></td>
		</tr>
		<tr>
			<td>Vials with fused-in insert</td>
			<td>Sigma Aldrich</td>
			<td>29398-U</td>
			<td></td>
		</tr>
		<tr>
			<td>OCPs</td>
			<td></td>
			<td>CAS registry number</td>
			<td></td>
		</tr>
		<tr>
			<td>&#945;-BHC</td>
			<td></td>
			<td>319-84-6</td>
			<td></td>
		</tr>
		<tr>
			<td>&#946;-BHC</td>
			<td></td>
			<td>319-85-7</td>
			<td></td>
		</tr>
		<tr>
			<td>Lindane</td>
			<td></td>
			<td>58-89-9</td>
			<td></td>
		</tr>
		<tr>
			<td>&#948;-BHC</td>
			<td></td>
			<td>319-86-8</td>
			<td></td>
		</tr>
		<tr>
			<td>Heptachlor</td>
			<td></td>
			<td>76-44-8</td>
			<td></td>
		</tr>
		<tr>
			<td>Aldrin</td>
			<td></td>
			<td>309-00-2</td>
			<td></td>
		</tr>
		<tr>
			<td>Heptachlor epoxide</td>
			<td></td>
			<td>1024-57-3</td>
			<td></td>
		</tr>
		<tr>
			<td>&#945;-Endosulfan</td>
			<td></td>
			<td>959-98-8</td>
			<td></td>
		</tr>
		<tr>
			<td>4,4&#39;-DDE-d8 (IS)</td>
			<td></td>
			<td>93952-19-3</td>
			<td></td>
		</tr>
		<tr>
			<td>4,4&#39;-DDE</td>
			<td></td>
			<td>72-55-9</td>
			<td></td>
		</tr>
		<tr>
			<td>Dieldrin</td>
			<td></td>
			<td>60-57-1</td>
			<td></td>
		</tr>
		<tr>
			<td>Endrin</td>
			<td></td>
			<td>72-20-8</td>
			<td></td>
		</tr>
		<tr>
			<td>&#946;-Endosulfan</td>
			<td></td>
			<td>33213-65-9</td>
			<td></td>
		</tr>
		<tr>
			<td>4,4&#39;-DDD</td>
			<td></td>
			<td>72-54-8</td>
			<td></td>
		</tr>
		<tr>
			<td>Endosulfan sulfate</td>
			<td></td>
			<td>1031-07-8</td>
			<td></td>
		</tr>
		<tr>
			<td>4,4&#39;-DDT</td>
			<td></td>
			<td>50-29-3</td>
			<td></td>
		</tr>
		<tr>
			<td>Endrin ketone</td>
			<td></td>
			<td>53494-70-5</td>
			<td></td>
		</tr>
		<tr>
			<td>Methoxychlor</td>
			<td></td>
			<td>72-43-5</td>
			<td></td>
		</tr>
	</tbody>
</table>

analysis of organochlorine pesticides in a soil sample by a modified quechers approach using ammonium formate

Currently, the QuEChERS method represents the most widely used sample preparation protocol worldwide for analyzing pesticide residues in a broad variety of matrices both in official and non-official laboratories. The QuEChERS method using ammonium formate has previously proven to be advantageous compared to the original and the two official versions. On the one hand, the simple addition of 0.5 g of ammonium formate per gram of sample is sufficient to induce phase separation and achieve good analytical performance. On the other hand, ammonium formate reduces the need for maintenance in routine analyses. Here, a modified QuEChERS method using ammonium formate was applied for the simultaneous analysis of organochlorine pesticide (OCP) residues in agricultural soil. Specifically, 10 g of the sample was hydrated with 10 mL of water and then extracted with 10 mL of acetonitrile. Next, phase separation was carried out using 5 g of ammonium formate. After centrifugation, the supernatant was subjected to a dispersive solid-phase extraction clean-up step with anhydrous magnesium sulfate, primary-secondary amine, and octadecylsilane. Gas chromatography-mass spectrometry was used as the analytical technique. The QuEChERS method using ammonium formate is demonstrated as a successful alternative for extracting OCP residues from a soil sample.

The full validation of the analytical method was performed in terms of linearity, matrix effects, recovery, and repeatability.
Matrix-matched calibration curves with spiked blank samples at six concentration levels (5 &#181;g/kg, 10 &#181;g/kg, 50 &#181;g/kg, 100 &#181;g/kg, 200 &#181;g/kg, and 400 &#181;g/kg) were used for the linearity assessment. The determination coefficients (R2) were higher than or equal to 0.99 for all the OCPs. The lowest calibration level (LCL) was set at 5...

Watch this Scientific Journal Video about Analysis of Organochlorine Pesticides in a Soil Sample by a Modified QuEChERS Approach Using Ammonium Formate at JoVE.com

Analysis of Organochlorine Pesticides in a Soil Sample by a Modified QuEChERS Approach Using Ammonium Formate

The present protocol describes the utilization of ammonium formate for phase partitioning in QuEChERS, together with gas chromatography-mass spectrometry, to successfully determine organochlorine pesticide residues in a soil sample.

Currently, the QuEChERS method represents the most widely used sample preparation protocol worldwide for analyzing pesticide residues in a broad variety ...

The QuEChERS method using ammonium formate is a successful alternative to the original, as well as the two official versions for extracting organochlorine pesticides from soil samples. The addition of just 0.5 grams of ammonium formate per gram of sample is sufficient to induce phase separation between the water and acetonitrile layers and achieve good analytical performance. To begin the sample preparation, weigh 10 grams of the soil sample in a 50-milliliter centrifuge tube.Add 50 microliters of the internal standard, or IS, solution, having a concentration of 20 milligrams per liter, to the soil sample to obtain 100 micrograms of IS per kilogram of soil. Add 10 milliliters of water, and shake the tube using an automated shaker at 10 g for five minutes. Then, add 10 milliliters of acetonitrile, and shake the tube at 10 g for five minutes.Next, add five grams of ammonium formate, and shake the tube vigorously by hand for one minute before centrifuging it at 1800 g for five minutes. For cleanup, by dispersive solid-phase extraction, transfer one milliliter of the acetonitrile extract into the centrifuge tube containing anhydrous magnesium sulfate, primary secondary amine, and octadecylsilane. Vortex the tube for 30 seconds, and centrifuge it at 1800 g for five minutes.After centrifugation, transfer 200 microliters of the extract to an appropriately labeled autosampler vial, fitted with a 300-milliliter fused insert, and perform an instrumental analysis using a GC/MS system. Inject 1.5 microliters of the sample in a GC/MS system with a single quadrupole mass spectrometer using an autosampler at 280 degrees Celsius in the splitless mode. The matrix effect distributions for the organochlorine pesticides, or OCPs, studied showed both positive matrix effect percentages corresponding to a signal enhancement, as well as negative percentages corresponding to signal suppression.Values ranging between minus 20 to 20%indicated a soft matrix effect, while those between minus 20 to minus 50%and between 20 to 50%corresponded to a medium matrix effect. A strong matrix effect was indicated by percentage values higher than 50 or lower than minus 50. Evaluating the overall recovery for all the pesticides at different spiking levels revealed that most of the studied OCPs had average recovery percentages of 70 to 120%and relative standard deviation, or RSD, values lower than 20%However, heptachlor, endrin, and beta-endosulfan possessed slightly higher average recoveries.This alternative may be used for the analysis of pesticides by LC-MS, which would be even more interesting since ammonium formate is an aid for ionization in positive electrospray ionization.

analysis-organochlorine-pesticides-soil-sample-modified-quechers

Research

JoVE Journal

Chemistry

2.8K Views.  Universidad EAN. The QuEChERS method using ammonium formate is a successful alternative to the original, as well as the two official versions for extracting organochlorine pesticides from soil samples. The addition of just 0.5 grams of ammonium formate per gram of sample is sufficient to induce phase separation between the water and acetonitrile layers and achieve good analytical performance. To begin the sample preparation, weigh 10 grams of the soil sample in a 50-milliliter centrifuge tube.Add 50 mi...