| Ginkgo leaves are valuable because they contain biologically active, pharmaceutically valuable flavonoid glycosides and ginkgolides. Ginkgo leaf extracts can improve cerebrovascular circulation, accelerate vasodilatation, and inhibit the congregation of platelets. Consequently, Ginkgo leaf extracts are thought to be a remedy for angina, myocardial infarction, and thrombus. Ginkgo leaf has been popularly used as an herbal medicine in many countries, including the United States, Germany, the United Kingdom, and France. Because of its potential health benefits, ginkgo is a valuable crop. Pesticides are used on ginkgo to protect the plants from damage and infestation by insects and pathogens. Organophosphorus, organochlorine, and pyrethroid insecticides are three classes of insecticides commonly used in agriculture. Pesticide residue caused serious pollution and was a serious health risk. In recent years, it is on the increase that the number of test items of which the ginkgo leaves for import and export should be tested of governments, making more strict standards and lower MRL continuously, so exports of ginkgo leaves of our country are facing more and more technical barriers.This is the first attempt to use GC/MS to determine the concentrations of 81 pesticides with different physiochemical properties on ginkgo leaves. The work first aimed to develop a rapid and accurate method to determine the presence and concentrations of organophosphorus, organochlorine, and pyrethrins pesticides; the second aim was to evaluate the application of GC/MS and the QuEChERS sample preparation method for the analysis of pesticide residues on ginkgo leaves. The main results were as follows:1. We optimized the chromatogram and MS condition, chose the suitable chromatographic column, temperature programming and selected ions, and then successfully established a GC-MS detection method for the target. The suitable chromatogram and MS condition was that DB-5MS capillary column and the oven temperature was started at 40°C and held for 1 min; was increased to 130°C at a rate of 40°C/min, to 250°C at a rate of 5°C /min, and to 300°C at a rate of 10°C/min; and was held at 300°C for 5 min. And the selected ions used for identification and quantitation were shown in Table 1. In this chromatogram and MS condition, 81 pesticides were separated well and correlation coefficients were greater than 0.99 for concentrations from 0.02 to 0.4 mg/mL for most pesticides.2. Analysis of residues of 81 pesticides on ginkgo leaves using SPE sample preparation and gas chromatography-mass spectrometry. Extraction solvent, the dosage of extraction solvent, sorbent, elution solvent and the dosage of elution solvent were optimized. And the determinated SPE sample preparation method was that the sample was extracted with 30mL acetonitrile: toluene (3:1, v/v) for 12min, then was purified by Carb/NH2 column and eluted by 30mL acetonitrile: toluene (3:1, v/v), and the elution solvent was evaporated to dryness before dilution in 1mL toluene and was injected into the GC-MS system. The majority of the pesticides (74-93%) gave satisfactory recoveries (ranging from 70 to 110%), less than 3% of the substances showed recoveries lower than 70% and RSDs 20% were obtained for samples fortified at 0.02, 0.05, and 0.1 mg/kg (n = 5).3. Analysis of residues of 81 pesticides on ginkgo leaves using GPC sample preparation and gas chromatography-mass spectrometry. Through optimized, the determinated GPC sample preparation method was that the sample was extracted with 30mL acetonitrile: toluene (3:1, v/v) for 12min, then was evaporated to dryness before dilution in 3mL ethyl acetate: hexamethylene (1:1, v/v) and purified by 200mg GCB, the dilution solvent was injected into GPC and collection time was 16min-33min, and collection solvent was evaporated to dryness before dilution in 1mL toluene and was injected into the GC-MS system. 62-74% of the pesticides gave satisfactory recoveries (ranging from 70 to 110%), less than 16% of the substances showed recoveries lower than 70% and RSDs 20% were obtained for samples fortified at 0.02, 0.05, and 0.1 mg/kg (n = 5).4. Analysis of residues of 81 pesticides on ginkgo leaves using QuEChERS sample preparation and gas chromatography-mass spectrometry. Five sorbents (graphitized carbon black, primary secondary amine, amino, alumina, and Florisil) and two solvents (toluene and hexane) were optimized for the cleanup procedure. The determinated QuEChERS sample preparation method was that the sample was extracted with 20mL acetonitrile for 30min, then was centrifuged for 10min, and 10mL aliquot extraction solvent was evaporated to dryness before dilution in toluene and purified by 50 mg GBC, 50 mg PSA, then upper layer solvent was injected into the GC-MS system. A majority of the pesticides (86–94%) gave satisfactory recoveries (from 70 to 110%), and 1–6% of the substances gave recoveries higher than 110% of the spiked concentration (n = 5) at 0.02, 0.05, and 0.1 mg/kg. Less than 5% of the substances showed recoveries lower than 70%. The method was proven to be repeatable with RSDs lower than 20%. The LOD and LOQ ranged from 0.05 to 17.6 and 0.16 to 58.8 mg/kg, respectively. The proposed method allows the simultaneous analyses of a large number of pesticides with good recoveries, low detection limits, and high throughput.
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