Multi-residue analysis of pesticides in tea by online SEC-GC/MS.

A multi-residue method for the analysis of pesticides in tea was developed by online size exclusion chromatography (SEC)-GC/MS with full scan mode. The sample was fortified with chlorpyrifos-d(10) isotope internal standard and extracted by acetonitrile. After purification by primary secondary amine sorbent and solvent exchange by SEC mobile phase, the sample was detected by online SEC-GC/MS. The purification result of the online system was evaluated by comparing the correlation between Chinese cabbage and tea matrix. The factors for method optimization included sample preparation, matrix effects and the instrument parameters of each online component. Scatter plot was introduced in this study to directly illustrate the results of the condition optimization and matrix effects in the online system. For most of the pesticides, the average recoveries ranged from 70 to 130% and the RSD were below 15%. The feasibility of the application of full scan mode in multi-residue determination of trace amounts of pesticides (LODs below 0.01 mg/kg) in a complex matrix was discussed.

Development of the fingerprint for the quality of Radix Linderae through ultra-pressure liquid chromatography-photodiode array detection/electrospray ionization mass spectrometry.

An ultra-pressure LC (UPLC) method has been developed and validated for the quality evaluation of a traditional Chinese medicine (Radix Linderae) by chemical fingerprint analysis with chromatograms collected at two wavelengths (260 and 320 nm). Eleven characteristic peaks in the fingerprints were identified by comparing their retention times, UV spectra and ESI-MS/MS data with those of the reference substances or the data in the literatures. Both correlation coefficient of similarities in chromatograms and relative peak areas of common peaks were calculated for quality expression of the Radix Linderae samples collected from different areas in China. The results showed high variation of relative peak area and correlation coefficients among the samples collected from various habitats, which indicated that the quality consistency of Radix Linderae is still a problem worthy of serious concern.