Determination of 266 pesticide residues in apple juice by matrix solid-phase dispersion and gas chromatography–mass selective detection
A macro matrix solid-phase dispersion (MSPD) method was developed to extract 266 pesticides from apple juice samples prior to gas chromatography–mass selective detection (GC–MSD) determination. A 10 g samples was mixed with 20 g diatomaceous earth. The mixture was transferred into a glass column. Pesticide residues were leached with a 160mL hexane–dichloromethane (1:1) at 5 mL/min. Two hundred and sixty-six pesticides were divided into three groups and detected by GC–MSD under selective ion monitoring. The proposed method takes advantage of both liquid–liquid extraction and conventional MSPD methods. Application was illustrated by the analysis of 236 apple juice samples produced in Shaanxi province China mainland this year.
1. Introduction Pesticide is a term used for a broad range of chemicals, synthetic or natural, that serve to control insects, fungi, bacteria, weeds, nematodes, rodents and other pests. Since the eraof synthetic organic pesticides began around 1940, pesticideshave been providing enormous benefits for increasing agriculturalproduction and quality ue to the fact that pests anddiseases damage up to one-third of rops whether in growingor in harvesting or in storage. However, most pesticides ail in natural degradation. The rapidly growing use of pesticides,often accompanied insufficient technical research radvice, and has unfortunately generated many environmentalproblems. As a result, human beings are exposed indirectlyunder pesticides, which are usually in small amount of certainfoodstuff. the most important aspects in minimizing potential hazards to human health. In 2002, a research program named Pivotal Technology of Food Safety was launched by the Ministry of Science and Technology in China, with two basic objectives, namely, to establish a technological regulation system on food safety, and to research on the multi-residual analysis approach for pesticides and veterinary medicines, antibiotics and synthetic hormones in foodstuff. The goal of our research team is to develop a multi-residual analytical method for pesticides in apple juice, because China mainland is one of the largest producers of fruit juices, and several pesticides, such as acepmate, were once found in U.S. in apple juice exported by China. The benefit of multi-residual method is evident, for it allows more pesticides to be analyzed at one time with less resource and time consumption. Numerous analytical methods for determining pesticides residues in various fruits and fruit juices have been published [1–8]. The ones most frequently used are gas chromatography
with electron-capture (ECD), nitrogen–phosphorus (NPD),flame photometric detection (FPD), mass spectrometric detection(MSD) and high performance liquid chromatography(HPLC) with diode-array detection (DAD) and fluorescencedetection. Before the residues were determined,samples required extraction and purification, and in this respectliquid–liquid extraction (LLE) [9], solid-phase extraction (SPE) [10], accelerated solvent extraction (ASE) [11],gel permeation chromatography (GPC) [12] and matrix solidphasedispersion (MSPD) [13] served as common methods.MSPD is a sample pretreatment technique based on SPE,thus, with much easier application than that of SPE, MSPD also helps prevent emulsion from happening in liquid distribution, reduce the volume of organic solvents and acceleratethe analysis, as SPE does. MSPD was first applied to extractand purify drug residues in animal tissue samples [14], andin recent years its application became popular in pesticidedetection and has been introduced to multi-residual analysis[13–21] on pesticides in vegetal samples such as fruits,vegetables, fruit juices, etc.In previous paper [22] we established a rapid and reliablemulti-residual method based on MSPD for determiningin apple juice the residues of 106 pesticides widely used inagricultural production. Some experimental parameters were optimized, for example, the pesticide-to-matrix ratio, composition of organic solvent, elution volume, elution rate, etc.By taking these measures we have reached an optimum experimentalcondition, which determines the ratio at 2:1, thehexane–dichloromethane solution volume (1:1) at 160mLand the flow rate at 5 mL/min.In this paper we will elaborate on the development of themulti-residual method. Two hundred and sixty-six pesticideswere divided into three groups, prepared by the same MSPDprocedure, and detected by gas hromatography–mass selecteddetection under selective ion monitoring (SIM). Theanalysis required three separate injections to cover all of thepesticides. The accuracy, precision, limits of detection, and linearity of the method were verified according to ResiduesAnalysis Quality Control Guide (RAQCG) [23] as constitutedby the General Administration of Quality Supervision,Inspection and Quarantine of the People’s Republic of China.
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