Name: Avocado Sample Preparation Using the QuEChERS Method with Ammonium Formate for Pesticide Analysis
Uploaded: 2023-12-08T13:50:00
Description: Read this Scientific Article Protocol about Author Spotlight: A Matrix-Matched Calibration Approach for Mitigating Matrix Effects in Avocado Pesticide Residue Analysis at JoVE.com

We would like to thank EAN University and the University of La Laguna.

1. Preparation of the stock and working solutions
NOTE: For safety reasons, it is advisable to wear nitrile gloves, a laboratory coat, and safety glasses throughout the protocol.
<ol>
	<li>Prepare individual stock solutions of each of the 45 commercial pesticide standards (see Table of Materials) at approximately 1,000 mg/L in acetonitrile in 10 mL volumetric flasks.</li>
	<li>Combine the above individual stock solutions to prepare a 400 mg/L stock solution ...

Analyzing Pesticides in Avocado Using the QuEChERS Method and CG-MS/MS

<ol>
	<li>Raposo, F., Barcel&#243;, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Challenges+and+strategies+of+matrix+effects+using+chromatography-mass+spectrometry:+An+overview+from+research+versus+regulatory+viewpoints.">Challenges and strategies of matrix effects using chromatography-mass spectrometry: An overview from research versus regulatory viewpoints.</a> Trends Analyt Chem. 134, 116068 (2021).</li><li>Rahman, M. M., Abd El-Aty, A. M., Shim, J. H. <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> Anal Chim Acta. 801, 14-21 (2013).</li><li>Poole, C. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Matrix-induced+response+enhancement+in+pesticide+residue+analysis+by+gas+chromatography.">Matrix-induced response enhancement in pesticide residue analysis by gas chromatography.</a> J Chromatogr A. 1158 (1-2), 241-250 (2007).</li><li>Anastassiades, M., Ma&#353;tovsk&#225;, K., 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+analyte+protectants+to+improve+gas+chromatographic+analysis+of+pesticides.">Evaluation of analyte protectants to improve gas chromatographic analysis of pesticides.</a> J Chromatogr A. 1015 (1-2), 163-184 (2003).</li><li>Trufelli, H., Palma, P., Famiglini, G., Cappiello, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+overview+of+matrix+effects+in+liquid+chromatography-mass+spectrometry.">An overview of matrix effects in liquid chromatography-mass spectrometry.</a> Mass Spectrom Reviews. 30 (3), 491-509 (2011).</li><li>European Commission SANTE/11312/2021. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Guidance+document+on+analytical+quality+control+and+method+validation+procedures+for+pesticide+residues+analysis+in+food+and+feed.">Guidance document on analytical quality control and method validation procedures for pesticide residues analysis in food and feed.</a> European Commission. , (2021).</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> J Chromatogr A. 1270, 235-245 (2012).</li><li>Lehotay, S. J., Ma&#353;tovsk&#225;, K., Yun, S. 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K., Piekoszewski, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sample+preparation+and+determination+of+pesticides+in+fat-containing+foods.">Sample preparation and determination of pesticides in fat-containing foods.</a> Food Chem. 269, 527-541 (2018).</li><li>Yanty, N. A. M., Marikkar, J. M. N., Long, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+varietal+differences+on+composition+and+thermal+characteristics+of+avocado+oil.">Effect of varietal differences on composition and thermal characteristics of avocado oil.</a> J Am Oil Chem Soc. 88, 1997-2003 (2011).</li><li>Pano-Farias, N. S., Ceballos-Maga&#241;a, S. G., Muniz-Valencia, R., Gonzalez, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Validation+and+assessment+of+matrix+effect+and+uncertainty+of+a+gas+chromatography+coupled+to+mass+spectrometry+method+for+pesticides+in+papaya+and+avocado+samples.">Validation and assessment of matrix effect and uncertainty of a gas chromatography coupled to mass spectrometry method for pesticides in papaya and avocado samples.</a> J Food Drug Anal. 25 (3), 501-509 (2017).</li><li>Pano-Farias, N. S., Ceballos-Maga&#241;a, S. G., Jurado, J. M., Aguayo-Villarreal, I. A., Mu&#241;iz-Valencia, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analytical+method+for+pesticides+in+avocado+and+papaya+by+means+of+ultra-high+performance+liquid+chromatography+coupled+to+a+triple+quadrupole+mass+detector:+Validation+and+uncertainty+assessment.">Analytical method for pesticides in avocado and papaya by means of ultra-high performance liquid chromatography coupled to a triple quadrupole mass detector: Validation and uncertainty assessment.</a> J Food Sci. 83 (8), 2265-2272 (2018).</li><li>Pano-Farias, N. S., Ceballos-Maga&#241;a, S. G., Gonzalez, J., Jurado, J. M., Mu&#241;iz-Valencia, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Supercritical+fluid+chromatography+with+photodiode+array+detection+for+pesticide+analysis+in+papaya+and+avocado+samples.">Supercritical fluid chromatography with photodiode array detection for pesticide analysis in papaya and avocado samples.</a> J Sep Sci. 38 (7), 1240-1247 (2015).</li><li>Lozano, A., Rajski, &. #. 3. 2. 1. ;., Ucl&#233;s, S., Belmonte-Valles, N., Mezcua, M., Fern&#225;ndez-Alba, A. R. <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+zirconium+dioxide-based+sorbents+to+decrease+the+matrix+effect+in+avocado+and+almond+multiresidue+pesticide+analysis+followed+by+gas+chromatography+tandem+mass+spectrometry.">Evaluation of zirconium dioxide-based sorbents to decrease the matrix effect in avocado and almond multiresidue pesticide analysis followed by gas chromatography tandem mass spectrometry.</a> Talanta. 118, 68-83 (2014).</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> J Chromatogr A. 1449, 17-29 (2016).</li><li>Chamkasem, N., Ollis, L. W., Harmon, T., Lee, S., Mercer, G. <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+136+pesticides+in+avocado+using+a+modified+QuEChERS+method+with+LC-MS/MS+and+GC-MS/MS.">Analysis of 136 pesticides in avocado using a modified QuEChERS method with LC-MS/MS and GC-MS/MS.</a> J Agric Food Chem. 61 (10), 2315-2329 (2013).</li><li>Rajski, &. #. 3. 2. 1. ;., Lozano, A., Ucl&#233;s, A., Ferrer, C., Fern&#225;ndez-Alba, A. R. <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+high+oil+vegetal+commodities+by+using+various+multi-residue+methods+and+clean-ups+followed+by+liquid+chromatography+tandem+mass+spectrometry.">Determination of pesticide residues in high oil vegetal commodities by using various multi-residue methods and clean-ups followed by liquid chromatography tandem mass spectrometry.</a> J Chromatogr A. 1304, 109-120 (2013).</li><li>Hern&#225;ndez-Borges, J., Ravelo-P&#233;rez, L. M., Hern&#225;ndez-Su&#225;rez, E. M., Carnero, A., 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=Analysis+of+abamectin+residues+in+avocados+by+high-performance+liquid+chromatography+with+fluorescence+detection.">Analysis of abamectin residues in avocados by high-performance liquid chromatography with fluorescence detection.</a> J Chromatogr A. 1165 (1-2), 52-57 (2007).</li><li>Moreno, J. F., Li&#233;banas, F. A., Frenich, A. G., Vidal, J. M. <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+different+sample+treatments+for+determining+pesticide+residues+in+fat+vegetable+matrices+like+avocado+by+low-pressure+gas+chromatography-tandem+mass+spectrometry.">Evaluation of different sample treatments for determining pesticide residues in fat vegetable matrices like avocado by low-pressure gas chromatography-tandem mass spectrometry.</a> J Chromatogr A. 1111 (1), 97-105 (2006).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Commission+Directive+2002/63/EC+of+11+July+2002+establishing+Community+methods+of+sampling+for+the+official+control+of+pesticide+residues+in+and+on+products+of+plant+and+animal+origin+and+repealing+Directive+79/700/EEC.">Commission Directive 2002/63/EC of 11 July 2002 establishing Community methods of sampling for the official control of pesticide residues in and on products of plant and animal origin and repealing Directive 79/700/EEC.</a> Official Journal of the European Union. L187, 30-43 (2002).</li><li>. <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,+396/2005,+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, 396/2005, 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. L70, 1-16 (2005).</li><li>Gonz&#225;lez-Curbelo, M. &. #. 1. 9. 3. ;., Lehotay, S. 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=Validation+of+a+modified+QuEChERS+version+for+high-throughput+analysis+of+a+wide+range+of+pesticides+in+foods.">Validation of a modified QuEChERS version for high-throughput analysis of a wide range of pesticides in foods.</a> Abstracts of Papers of the American Chemical Society. 246, (2013).</li><li>Gonz&#225;lez-Curbelo, M. &. #. 1. 9. 3. ;., Lehotay, S. J., Hern&#225;ndez-Borges, J., Rodr&#237;guez Delgado, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ammonium+formate+buffer+in+QuEChERS+for+high+throughput+analysis+of+pesticides+in+food+by+fast,+low-pressure+GC-MS/MS+and+LC-MS/MS.">Ammonium formate buffer in QuEChERS for high throughput analysis of pesticides in food by fast, low-pressure GC-MS/MS and LC-MS/MS.</a> Abstracts of Papers of the American Chemical Society. 248, (2014).</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> J Chromatogr A. 1358, 75-84 (2014).</li><li>Varela-Mart&#237;nez, D. A., Gonz&#225;lez-S&#225;lamo, J., Gonz&#225;lez-Curbelo, M. &. #. 1. 9. 3. ;., Quick 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>Gonz&#225;lez-Curbelo, 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=Analysis+of+organochlorine+pesticides+in+a+soil+sample+by+a+modified+QuEChERS+approach+using+ammonium+formate.">Analysis of organochlorine pesticides in a soil sample by a modified QuEChERS approach using ammonium formate.</a> J Vis Exp. 191, e64901 (2023).</li><li>Gonz&#225;lez-Curbelo, M. &. #. 1. 9. 3. ;., Dionis-Delgado, S., Asensio-Ramos, M., 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=Pesticide+analysis+in+toasted+barley+and+chickpea+flours.">Pesticide analysis in toasted barley and chickpea flours.</a> J Sep Sci. 35 (2), 299-307 (2012).</li><li>Varela-Mart&#237;nez, D. 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The primary limitation associated with matrix-matched calibration arises from the use of blank samples as calibration standards. This leads to an augmented number of samples to be processed for analysis and an increased injection of matrix components in each analytical sequence, potentially leading to higher instrument maintenance demands. Nonetheless, this strategy is more suitable than standard addition, which would generate a much larger number of samples to be injected due to the need to perform a calibration curve f...

In chemical analysis, the matrix effect (ME) can be defined in various ways, but a widely accepted general definition is as follows: it refers to the change in the signal, particularly a change in the slope of the calibration curve when the sample matrix or portion of it is present during the analysis of a specific analyte. As a critical aspect, ME necessitates thorough investigation during the validation process of any analytical method, as it directly affects the accuracy of quantitative measurement for the target analytes1. Ideally, a sample pretreatment procedure should be selective enough to avoid extracting any components from the sample matrix. However, despite significant efforts, many of these matrix components still end up in the final determination systems in most cases. Consequently, such matrix components often compromise the recovery and precision values, introduce additional noise, and escalate the overall cost and labor involved in the method.
In gas chromatography (GC), ME arises due to the presence of active sites within the GC system, which interact with the target analytes through various mechanisms. On the one hand, the matrix constituents block or mask these active sites that would otherwise interact with the target analytes, resulting in frequent signal enhancement2. On the other hand, active sites that remain unobstructed may cause peak tailing or analyte decomposition due to strong interactions, leading to a negative ME. However, this can offer potential benefits in certain cases2. It is crucial to emphasize that achieving complete inertness in a GC system is exceedingly challenging, despite using highly inert components and proper maintenance. With continuous use, the accumulation of matrix components in the GC system becomes more pronounced, causing an increased ME. Nowadays, it is widely recognized that analytes containing oxygen, nitrogen, phosphorus, sulfur, and similar elements, exhibit a greater ME as they readily interact with these active sites. Conversely, highly stable compounds such as hydrocarbons or organohalogens do not undergo such interactions and do not show observable ME during analysis2,3.
Overall, ME cannot be fully eliminated, leading to the development of several strategies for compensation or correction when complete removal of matrix components is not feasible. Among these strategies, the utilization of deuterated internal standards (ISs), analyte protectants, matrix-matched calibration, the standard addition method, or the modification of injection techniques have been documented in scientific literature1,2,4,5. The SANTE/11312/2021 guidelines have also recommended these strategies6.
Regarding the application of matrix-matched calibration to compensate for MEs, sample sequences in practical situations encompass diverse types of foods or various samples from the same commodity. In this case, the assumption is made that employing any sample from the same commodity will effectively compensate for ME in all samples. However, there is a lack of sufficient studies in the existing literature that specifically investigate this issue7.
The multiresidue determination of pesticides in matrices containing an appreciable percentage of fat and pigments constitutes a challenging task. The considerable amount of coextracted material can significantly affect the extraction efficiency and interfere with the subsequent chromatographic determination, potentially damaging the column, source, and detector, and resulting in significant MEs8,9,10. Consequently, the analysis of pesticides at trace levels in such matrices necessitates a significant reduction of matrix components before analysis while ensuring high recovery values7. Obtaining high recovery values is crucial to ensure that pesticide analyses remain reliable, accurate, and compliant with regulatory standards. This is vital for ensuring food safety, environmental protection, and informed decision-making in agriculture and related fields.
Avocado is a fruit of high commercial value cultivated in tropical and Mediterranean climates worldwide and widely consumed both in its regions of origin and in the numerous export markets. From the analytical point of view, avocado is a complex matrix containing a significant number of fatty acids (i.e., oleic, palmitic, and linoleic), similar to nuts, a significant pigment content, as in green leaves, as well as sugars and organic acids, similar to those found in other fruits11. Due to its fatty nature, special attention must be given when employing any analytical method for analysis. While pesticide residue analysis has been conducted on avocados using GC-MS in some instances8,12,13,14,15,16,17,18,19,20, it has been relatively less frequent compared to other matrices. In most cases, a version of the Quick-Easy-Cheap-Effective-Rugged-Safe (QuEChERS) method has been applied8,12,13,14,15,16,17,18. None of these studies have investigated the consistency of MEs among different avocado varieties.
Therefore, the aim of this work was to study the consistency of MEs and recovery values for 45 representative pesticides across different varieties of avocado (i.e., Criollo, Hass, and Lorena) using the QuEChERS method with ammonium formate and GC-MS/MS. To the best of our knowledge, this is the first time that this type of study has been conducted on such fatty matrix samples.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>3-Ethoxy-1,2-propanediol</td>
			<td>Sigma Aldrich</td>
			<td>260428-1G</td>
			<td></td>
		</tr>
		<tr>
			<td>Acetonitrile</td>
			<td>Merk</td>
			<td>1006652500</td>
			<td></td>
		</tr>
		<tr>
			<td>Ammonium formate</td>
			<td>Sigma Aldrich</td>
			<td>156264-1KG</td>
			<td></td>
		</tr>
		<tr>
			<td>AOAC 20i/s autosampler</td>
			<td>Shimadzu</td>
			<td>221-723115-58</td>
			<td></td>
		</tr>
		<tr>
			<td>Automatic shaker MX-T6-PRO</td>
			<td>SCILOGEX</td>
			<td>8.23222E+11</td>
			<td></td>
		</tr>
		<tr>
			<td>Balance</td>
			<td>OHAUS</td>
			<td>PA224</td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge tubes, 15 mL</td>
			<td>Nest</td>
			<td>601002</td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge tubes, 2 mL</td>
			<td>Eppendorf</td>
			<td>4610-1815</td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge tubes, 50 mL</td>
			<td>Nest</td>
			<td>602002</td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge Z206A</td>
			<td>MERMLE</td>
			<td>6019500118</td>
			<td></td>
		</tr>
		<tr>
			<td>Choper 2L</td>
			<td>Oster</td>
			<td>2114111</td>
			<td></td>
		</tr>
		<tr>
			<td>Column SH-Rxi-5sil MS, 30 m x 0.25 mm, 0.25 &#181;m</td>
			<td>Shimadzu</td>
			<td>221-75954-30</td>
			<td>MS GC column&#160;</td>
		</tr>
		<tr>
			<td>Dispensette 5-50 mL</td>
			<td>BRAND</td>
			<td>4600361</td>
			<td></td>
		</tr>
		<tr>
			<td>DSC-18</td>
			<td>Sigma Aldrich</td>
			<td>52600-U</td>
			<td></td>
		</tr>
		<tr>
			<td>D-Sorbitol</td>
			<td>Sigma Aldrich</td>
			<td>240850-5G</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethyl acetate</td>
			<td>Merk</td>
			<td>1313181212</td>
			<td></td>
		</tr>
		<tr>
			<td>GCMS-TQ8040&#160;</td>
			<td>Shimadzu</td>
			<td>211552</td>
			<td></td>
		</tr>
		<tr>
			<td>Graphitized carbon black</td>
			<td>Sigma Aldrich</td>
			<td>57210-U</td>
			<td></td>
		</tr>
		<tr>
			<td>Injection syringe</td>
			<td>Shimadzu</td>
			<td>LC2213461800</td>
			<td></td>
		</tr>
		<tr>
			<td>L-Gulonic acid &#947;-lactone</td>
			<td>Sigma Aldrich</td>
			<td>310301-5G</td>
			<td></td>
		</tr>
		<tr>
			<td>Linner splitless</td>
			<td>Shimadzu</td>
			<td>221-4887-02</td>
			<td></td>
		</tr>
		<tr>
			<td>Magnesium sulfate anhydrus</td>
			<td>Sigma Aldrich</td>
			<td>M7506-2KG</td>
			<td></td>
		</tr>
		<tr>
			<td>Methanol</td>
			<td>Panreac</td>
			<td>131091.12.12</td>
			<td></td>
		</tr>
		<tr>
			<td>Milli-Q ultrapure (type 1) water</td>
			<td>Millipore</td>
			<td>F4H4783518</td>
			<td></td>
		</tr>
		<tr>
			<td>Pipette tips 10 - 100 &#181;L</td>
			<td>Biologix</td>
			<td>200010</td>
			<td></td>
		</tr>
		<tr>
			<td>Pipette tips 100 - 1000 &#181;L</td>
			<td>Brand</td>
			<td>541287</td>
			<td></td>
		</tr>
		<tr>
			<td>Pipette tips 20 - 200 &#181;L</td>
			<td>Brand</td>
			<td>732028</td>
			<td></td>
		</tr>
		<tr>
			<td>Pipettes Pasteur</td>
			<td>NORMAX</td>
			<td>5426023</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>SCILOGEX</td>
			<td>7.12111E+11</td>
			<td></td>
		</tr>
		<tr>
			<td>Primary-secondary amine</td>
			<td>Sigma Aldrich</td>
			<td>52738-U</td>
			<td></td>
		</tr>
		<tr>
			<td>Shikimic acid</td>
			<td>Sigma Aldrich</td>
			<td>S5375-1G</td>
			<td></td>
		</tr>
		<tr>
			<td>Syringe Filter PTFE/L 25 mm, 0.45 &#181;m</td>
			<td>NORMAX</td>
			<td>FE2545I</td>
			<td></td>
		</tr>
		<tr>
			<td>Triphenyl phosphate (QC)</td>
			<td>Sigma Aldrich</td>
			<td>241288-50G</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>Z-SEP+</td>
			<td>Sigma Aldrich</td>
			<td>55299-U</td>
			<td>zirconium oxide-based sorbent</td>
		</tr>
		<tr>
			<td>Pesticides</td>
			<td></td>
			<td></td>
			<td>CAS registry number</td>
		</tr>
		<tr>
			<td>4,4&#180;-DDD</td>
			<td>Sigma Aldrich</td>
			<td>35486-250MG</td>
			<td>72-54-8</td>
		</tr>
		<tr>
			<td>4,4&#180;-DDE</td>
			<td>Sigma Aldrich</td>
			<td>35487-100MG</td>
			<td>72-55-9</td>
		</tr>
		<tr>
			<td>4,4&#180;-DDT</td>
			<td>Sigma Aldrich</td>
			<td>31041-100MG</td>
			<td>50-29-3</td>
		</tr>
		<tr>
			<td>Alachlor</td>
			<td>Sigma Aldrich</td>
			<td>45316-250MG</td>
			<td>15972-60-8</td>
		</tr>
		<tr>
			<td>Aldrin</td>
			<td>Sigma Aldrich</td>
			<td>36666-25MG</td>
			<td>309-00-2</td>
		</tr>
		<tr>
			<td>Atrazine</td>
			<td>Sigma Aldrich</td>
			<td>45330-250MG-R</td>
			<td>1912-24-9</td>
		</tr>
		<tr>
			<td>Atrazine-d5 (IS)</td>
			<td>Sigma Aldrich</td>
			<td>34053-10MG-R</td>
			<td>163165-75-1</td>
		</tr>
		<tr>
			<td>Buprofezin</td>
			<td>Sigma Aldrich</td>
			<td>37886-100MG</td>
			<td>69327-76-0</td>
		</tr>
		<tr>
			<td>Carbofuran</td>
			<td>Sigma Aldrich</td>
			<td>32056-250-MG</td>
			<td>1563-66-2</td>
		</tr>
		<tr>
			<td>Chlorpropham</td>
			<td>Sigma Aldrich</td>
			<td>45393-250MG</td>
			<td>101-21-3</td>
		</tr>
		<tr>
			<td>Chlorpyrifos</td>
			<td>Sigma Aldrich</td>
			<td>45395-100MG</td>
			<td>2921-88-2</td>
		</tr>
		<tr>
			<td>Chlorpyrifos-methyl</td>
			<td>Sigma Aldrich</td>
			<td>45396-250MG</td>
			<td>5598-13-0</td>
		</tr>
		<tr>
			<td>Deltamethrin</td>
			<td>Sigma Aldrich</td>
			<td>45423-250MG</td>
			<td>52918-63-5</td>
		</tr>
		<tr>
			<td>Dichloran</td>
			<td>Sigma Aldrich</td>
			<td>45435-250MG</td>
			<td>99-30-9</td>
		</tr>
		<tr>
			<td>Dichlorvos</td>
			<td>Sigma Aldrich</td>
			<td>45441-250MG</td>
			<td>62-73-7</td>
		</tr>
		<tr>
			<td>Dieldrin</td>
			<td>Sigma Aldrich</td>
			<td>33491-100MG-R</td>
			<td>60-57-1</td>
		</tr>
		<tr>
			<td>Diphenylamine</td>
			<td>Sigma Aldrich</td>
			<td>45456-250MG</td>
			<td>122-39--4</td>
		</tr>
		<tr>
			<td>Endosulfan A</td>
			<td>Sigma Aldrich</td>
			<td>32015-250MG</td>
			<td>115-29-7</td>
		</tr>
		<tr>
			<td>Endrin</td>
			<td>Sigma Aldrich</td>
			<td>32014-250MG</td>
			<td>72-20-8</td>
		</tr>
		<tr>
			<td>EPN</td>
			<td>Sigma Aldrich</td>
			<td>36503-100MG</td>
			<td>2104-64-5</td>
		</tr>
		<tr>
			<td>Esfenvalerate</td>
			<td>Sigma Aldrich</td>
			<td>46277-100MG</td>
			<td>66230-04-4</td>
		</tr>
		<tr>
			<td>Ethion</td>
			<td>Sigma Aldrich</td>
			<td>45477-250MG</td>
			<td>563-12-2</td>
		</tr>
		<tr>
			<td>Fenamiphos</td>
			<td>Sigma Aldrich</td>
			<td>45483-250MG</td>
			<td>22224-92-6</td>
		</tr>
		<tr>
			<td>Fenitrothion</td>
			<td>Sigma Aldrich</td>
			<td>45487-250MG</td>
			<td>122-14-5</td>
		</tr>
		<tr>
			<td>Fenthion</td>
			<td>Sigma Aldrich</td>
			<td>36552-250MG</td>
			<td>55-38-9</td>
		</tr>
		<tr>
			<td>Fenvalerate</td>
			<td>Sigma Aldrich</td>
			<td>45495-250MG</td>
			<td>51630-58-1</td>
		</tr>
		<tr>
			<td>HCB</td>
			<td>Sigma Aldrich</td>
			<td>45522-250MG</td>
			<td>118-74-1</td>
		</tr>
		<tr>
			<td>Iprodione</td>
			<td>Sigma Aldrich</td>
			<td>36132-100MG</td>
			<td>36734-19-7</td>
		</tr>
		<tr>
			<td>Lindane</td>
			<td>Sigma Aldrich</td>
			<td>45548-250MG</td>
			<td>58-89-9</td>
		</tr>
		<tr>
			<td>Malathion</td>
			<td>Sigma Aldrich</td>
			<td>36143-100MG</td>
			<td>121-75-5</td>
		</tr>
		<tr>
			<td>Metalaxyl</td>
			<td>Sigma Aldrich</td>
			<td>32012-100MG</td>
			<td>57837-19-1</td>
		</tr>
		<tr>
			<td>Methidathion</td>
			<td>Sigma Aldrich</td>
			<td>36158-100MG</td>
			<td>950-37-8</td>
		</tr>
		<tr>
			<td>Myclobutanil</td>
			<td>Sigma Aldrich</td>
			<td>34360-100MG</td>
			<td>88671-89-0</td>
		</tr>
		<tr>
			<td>Oxyfluorfen</td>
			<td>Sigma Aldrich</td>
			<td>35031-100MG</td>
			<td>42874-03-3</td>
		</tr>
		<tr>
			<td>Parathion-methyl</td>
			<td>Sigma Aldrich</td>
			<td>36187-100MG</td>
			<td>298-00-0</td>
		</tr>
		<tr>
			<td>Penconazol</td>
			<td>Sigma Aldrich</td>
			<td>36189-100MG</td>
			<td>66246-88-6</td>
		</tr>
		<tr>
			<td>Pirimiphos-methyl</td>
			<td>Sigma Aldrich</td>
			<td>32058-250MG</td>
			<td>29232-93-7</td>
		</tr>
		<tr>
			<td>Propiconazole</td>
			<td>Sigma Aldrich</td>
			<td>45642-250MG</td>
			<td>60207-90-1</td>
		</tr>
		<tr>
			<td>Propoxur</td>
			<td>Sigma Aldrich</td>
			<td>45644-250MG</td>
			<td>114-26-1</td>
		</tr>
		<tr>
			<td>Propyzamide</td>
			<td>Sigma Aldrich</td>
			<td>45645-250MG</td>
			<td>23850-58-5</td>
		</tr>
		<tr>
			<td>Pyriproxifen</td>
			<td>Sigma Aldrich</td>
			<td>34174-100MG</td>
			<td>95737-68-1</td>
		</tr>
		<tr>
			<td>Tolclofos-methyl</td>
			<td>Sigma Aldrich</td>
			<td>31209-250MG</td>
			<td>5701804-9</td>
		</tr>
		<tr>
			<td>Triadimefon</td>
			<td>Sigma Aldrich</td>
			<td>45693-250MG</td>
			<td>43121-43-3</td>
		</tr>
		<tr>
			<td>Triflumizole</td>
			<td>Sigma Aldrich</td>
			<td>32611-100MG</td>
			<td>68694-11-1</td>
		</tr>
		<tr>
			<td>&#945;-HCH</td>
			<td>Sigma Aldrich</td>
			<td>33377-50MG</td>
			<td>319-86-8</td>
		</tr>
		<tr>
			<td>&#946;-HCH</td>
			<td>Sigma Aldrich</td>
			<td>33376-100MG</td>
			<td>319-85-7</td>
		</tr>
	</tbody>
</table>

determination of 45 pesticides in avocado varieties by the quechers method and gas chromatography-tandem mass spectrometry

Gas chromatography (GC) tandem mass spectrometry (MS/MS) stands as a preeminent analytical instrument extensively employed for the surveillance of pesticide residues in food. Nevertheless, these methods are vulnerable to matrix effects (MEs), which can potentially affect accurate quantification depending on the specific combination of analyte and matrix. Among the various strategies to mitigate MEs, matrix-matched calibration represents the prevailing approach in pesticide residue applications due to its cost-effectiveness and straightforward implementation. In this study, a total of 45 representative pesticides were analyzed in three different varieties of avocado (i.e., Criollo, Hass, and Lorena) using the Quick-Easy-Cheap-Effective-Rugged-Safe (QuEChERS) method with ammonium formate and GC-MS/MS. 
For this purpose, 5 g of the avocado sample was extracted with 10 mL of acetonitrile, and then 2.5 g of ammonium formate was added to induce phase separation. Subsequently, the supernatant underwent a cleanup process via dispersive solid-phase extraction employing 150 mg of anhydrous MgSO4, 50 mg of primary-secondary amine, 50 mg of octadecylsilane, 10 mg of graphitized carbon black, and 60 mg of a zirconium oxide-based sorbent (Z-Sep+). The GC-MS/MS analysis was successfully performed in less than 25 min. Rigorous validation experiments were carried out to assess the performance of the method. The examination of a matrix-matched calibration curve for each variety of avocado revealed that the ME remained relatively consistent and less than 20% (considered as a soft ME) for most pesticide/variety combinations. Furthermore, the method&#180;s limits of quantification were lower than 5 &#181;g/kg for all three varieties. Finally, the recovery values for most pesticides fell within the acceptable range of 70-120%, with relative standard deviation values below 20%.

Avocado Sample Preparation Using the QuEChERS Method with Ammonium Formate for Pesticide Analysis

Determination of 45 Pesticides in Avocado Varieties by the QuEChERS Method and Gas Chromatography-Tandem Mass Spectrometry

Comprehensive validation of the analytical method was conducted according to SANTE/11312/2021 guidelines6, encompassing assessments of linearity, ME, recovery, and repeatability.
For the linearity assessment, matrix-matched calibration curves were constructed using spiked blank samples at multiple concentration levels (ranging from 5 to 600 &#181;g/kg). The determination coefficients (R2) for most of the selected pesticides were found to be higher than or equ...

Read this Scientific Article Protocol about Author Spotlight: A Matrix-Matched Calibration Approach for Mitigating Matrix Effects in Avocado Pesticide Residue Analysis at JoVE.com

The present protocol describes the analysis of multiclass pesticide residues in avocado varieties using the Quick-Easy-Cheap-Effective-Rugged-Safe (QuEChERS) method with ammonium formate, followed by gas chromatography-tandem mass spectrometry.

Gas chromatography (GC) tandem mass spectrometry (MS/MS) stands as a preeminent analytical instrument extensively employed for the surveillance of ...

To begin the sample preparation using the QuEChERS method, weigh five grams of an avocado sample of interest in a 50 milliliter centrifuge tube. Add 50 microliters of the procedural internal standard or P-IS solution to the tube. Add 10 milliliters of aceto nitrile to the centrifuge tube and shake the tube at 70 RPM for five minutes.Then add 2.5 grams of ammonium formate to it and shake the tube again at 70 RPM for five minutes. Subsequently, centrifuge the tube at 1, 800 G for five minutes. Next, in a two milliliter centrifuge tube, take the appropriate amounts of the reagents displayed on the screen.Then add one milliliter of the extract into the tube for purification using dispersive solid phase extraction. Vortex the tube for 30 seconds before centrifuging it at 1, 800 G for five minutes. Transfer 200 microliters of the purified extract to an auto-sampler vial, and add 20 microliters of the analyte protectant solution, followed by adding 50 microliters of a pre-prepared triphenyl phosphate solution.Finally, perform instrumental analysis using a GC-MS/MS system.