A new method was established for the direct, rapid and quantitative analysis of pesticide residues, dimethoate chlorothalonil and malathion by low temperature plasma ( LTP) ionization miniature ion trap mass spectrometer. The LTP ionization probe and sample inlet of ion trap mass spectrometry were enclosed in a metal cavity. With non-contact heating, the samples placed on the sample platform were desorbed into gaseous phase and ionized by LTP ionization probe. The results showed that closed ionization had an edge over the opened ionization. The quantitative analysis of 3 pesticides within the range of 0. 5-10 mg/L was realized by optimizing heating time and flow rate of air, and the relative standard deviations of signal intensity is less than 11%. LODs of pesticide, which were obtained within 5 s, were as low as several hundred pictograms. The results showed that the method could be used for the analysis of pesticide residue on green and organic fruits or vegetables.

Objective To establish an analytical method combining gas chromatography-tandem mass spectrometry(GC-MS)and liquid chromatography-tandem mass spectrometry(LC-MS)to detect diazepam residue in bait nest materials and fish samples,and improve the pretreatment steps of samples to make the experimental results accurate and the sample processing convenient and fast.Methods Taking diazepam as the research object,samples were extracted with methanol and dichloromethane/n-hexane as solvents according to the type,and the supernatant was taken for detection after centrifugation.Results The diazepam standard sample showed a good linear relationship in the range of 10～10 000 ng/mL.The retention times in methanol and mixed solvent were 13.54 min and 13.83 min,respectively,and the correlation coefficients were 0.998 and 0.999,respectively;The limit of detection(LOD)of using methanol as extraction solvent was 2 ppb,and limit of quantification(LOQ)was 6 ppb.The LOD of using mixed solvents was 5 ppb,and the LOQ was 15 ppb.When the sample is a bait nest material,the GC-MS spectrum was clear and standard,and the peak shape was sharp and prominent;When the sample is biological specimen,the GC-MS spectra are disturbed by matrix,while the LC-MS data is more accurate and faster.Conclusion It is more appropriate to use GC-MS to determine the content of bait nest materialsamples,and it is more accurate to LC-MS to determine the content of fish samples due to the complexity of the organism.