gc-ms/ms analysis and data acquisition for assessing pesticides in avocado samples prepared by the quechers method

QuEChERS メソッドと CG-MS/MS を使用したアボカド中の農薬の分析

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.

QuEChERS 法とギ酸アンモニウムを用いた農薬分析用アボカドサンプル調製(英語)

QuEChERS 法およびガスクロマトグラフィー-タンデム質量分析によるアボカド品種中の 45 種類の農薬の測定(英語)

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.

QuEChERS メソッドで調製したアボカドサンプル中の農薬を評価するための GC-MS/MS 分析およびデータ取得(英語)

分析は、オートサンプラーに70電子ボルトの電子イオン化インターフェースを備えたトリプル四重極を備えたGC-MS/MSシステムを使用して実施します。ガス圧が正しいことを確認してください。ヘリウムは140 PSIで、アルゴンは65 PSIです。フロントパネルにあるメインGCスイッチをオンにします。そして、背面にあるMSスイッチをオンにします。GC-MS/MS システムのすべてのパラメータを制御する GCMS リアルタイム解析ソフトウェアを開きます。真空制御をクリックします。その後、ロータリーポンプ1が進み、真空システムを開始します。開始をクリックして、ターボ分子ポンプ1と2をオンにします。次に、イオン源ヒーターの開始オプションをクリックします。MS 界面温度を 250 °C、イオン源温度を 300 °Cに設定します。GCオーブンを初期温度50°Cに1分間維持します。次に、毎分25°Cの速度で摂氏180度まで上げます。その後、毎分5°Cで230°Cに温度を上げ、次に毎分25°Cで290°Cに上げます。その後、温度を摂氏290度に6分間一定に保ちます。合計解析時間は 24.6 分です。これらのシステムがすべてオンになったら、[閉じる]をクリックします。次に、分析ソフトウェアからチューニングオプションをクリックし、ピークモニタービューを選択して、質量分析計の条件の初期検証を実行します。[Acquisition] をクリックし、表示されたウィンドウで [Download Initial Parameters] をクリックします。機器がGCおよびMSの準備ができていることを確認します。データ取得には、ソフトウェアから新しいバッチファイルをクリックし、サンプル名、サンプルID、メソッドファイル、データファイル、注入量、チューニングファイルなどの情報を含むシーケンスを作成します。必要に応じて行を追加し、[保存]をクリックします。[Batch Start] をクリックして、インジェクション プロセスを開始します。スプリットリストモードで摂氏250度で注入を行い、注入量を1マイクロリットルに保ちます。注射後1分後、スプリットを開きます。.マルチプルリアクションモニタリング、またはMRMモード(トリプル四重極を搭載したMS/MSシステムで使用される標準モード)を使用して、分析対象物を分析します。データ解析のために、実行後の解析ソフトウェアを開きます。解析するインジェクションをクリックします。分析種を含むテーブル内をナビゲーションし、目的のピークを選択します。ピークまたは関心領域をクリックして、クロマトグラムを視覚化します。ピーク積分を確認し、必要に応じて手動積分を実行します。すべての分析種の面積を検証して、必要な計算と分析法評価を行います。マトリックスマッチド検量線の生成により、ほとんどの農薬の組み合わせでソフト ME に分類される 20% 未満の比較的一貫したマトリックス効果が明らかになりました。表示された図の結果は、アボカドの種類ごとに平均回収率が70〜120%の許容範囲内にある農薬の数を示しています。試験した農薬のかなりの割合が、この特定の範囲内に収まる回収率を示し、相対標準偏差値は20%未満でした

Research

JoVE Journal

Chemistry

GC-MS/MS Analysis and Data Acquisition for Assessing Pesticides in Avocado Samples Prepared by the QuEChERS Method

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 ...

化学