| Chinese herbal medicines (CHMs) have been widely used as medication or dietary supplement because of mild pharmaceutical effects and minimum side effects. With the trend of'back-to-the-nature', a greater boost in the use of CHMs will be expected, with a projected $400 billion market by 2010. The commercial cultivation of CHMs receives frequent application of a large number of pesticides to prevent, repel or mitigate the effects of pest, resulting in a high risk of pesticide contamination in CHMs. Therefore it is necessary to monitor their residues in CHMs. Recently, a number of works on the determination of pesticide residue in CHMs have been published. However, most of these works are focused on organochlorine pesticides detection. The reports on multi-residue analysis in CHMs are still sparse. In this article, we systematically studied the determination methods of pesticide residues in CHMs with satisfactory results. The main results of the study are as follows:1. Gas chromatography with nitrogen phosphorus detector (GC-NPD) was applied to the simultaneous determination of 15 organophosphorus and 6 carbamate pesticides residues in Angelica sinensis. The pesticides were extracted by microwave-assisted extraction (MAE) and ultrasound-assisted extraction (UAE) techniques, respectively. The experimental variables were optimized through orthogonal array experimental design. Cleanup of extracts was performed with column chromatography using florisil and neutral aluminum as the sorbents. The determination of pesticides in the final extracts was carried out by GC-NPD. The correlation coefficients, R2, in the linear range tests were better than 0.9950. LODs varied from 0.002 to 0.015 mg/L. The average recoveries obtained from MAE and UAE were in the range of 75.1-129% and 70.6-129%, respectively, and the relative standard deviations of MAE and UAE were 3.1-10.6% and 1.0-17.8%, respectively. These results indicate that MAE and UAE techniques both show satisfactory extraction efficiency and meet the demands of residue analysis. The proposed method has been applied in the simultaneous determination of OPPs and ONPs residues in Angelica sinensis with satisfactory results.2. A reliable, rapid and nontoxic analytical method was proposed for the simultaneous determination of 16 organophosphorus pesticides (OPPs) in Chinese herbal medicines (CHMs). The pesticides were extracted by ethanol and the experimental variables such as temperature, extraction time and volume of ethanol, were optimized through orthogonal array experimental design. Cleanup of extracts was performed with dispersive-solid phase extraction using primary secondary amine (PSA) as the sorbent. The determination of pesticides in the final extracts was carried out by gas chromatography-flame photometric detection (GC-FPD). The correlation coefficients, R2, in the linear range tests were better than 0.9992. Under optimized conditions the obtained recoveries, except for isocarbophos, were in the range of 73.8-123%, with relative standard deviations equal to or lower than 15.2%, and limits of detection ranging from 0.001 to 0.009 mg/L. These results indicated that the established method was satisfactory for routine screening of pesticide residues, and not subjected to great interference from different sample matrices. The proposed procedure was successfully applied to the simultaneous determination of the pesticide residues in Radix astragali, Flos chrysanthemi, Semen armeniacae amarum and Semen sinapis samples.3. A method for the determination of 24 pesticides in Radix astragali by GC-MS was described. The sample was extracted by microwave-assisted extraction (MAE), the experimental variables were optimized through orthogonal array experimental design, and the extracts were concentrated to near dryness. n-Hexane was chosen as the dissolving solvent. Subsequently, dispersive-SPE was used for cleanup, and the type and quantity of sorbents (Al2O3, GCB, and PSA) were tested in the experiments. The best results were 150 mg PSA and 100 mg MgSO4 for cleanup. Pesticides were identified and quantified by GC-MS in SIM mode. The correlation coefficients, R2, in the linear range tests were better than 0.9971. The average recoveries for most pesticides (spiked at 0.02,0.1 and 0.2 mg/kg) ranged from 70 to 110%, the RSD was below 16.0% in most instances, and LODs varied from 0.0002 to 0.01 mg/L. The proposed method meets the requirement of pesticide residue analysis, and the method has been applied to the determination of the above pesticides in Radix astragali with satisfactory results.
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