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A gas chromatography-tandem mass spectrometry based method has been developed for multi-determination of 18 polychlorinated biphenyls (including 7 indicator PCBs, and 12 coplanar PCBs) in the meat, head, shell and egg of Macrobrachium nipponense. 20 g homogenized samples are extracted by the mixture solution of V (dichloromethane) : V (hexane) = (1 : 1). Then concentrated sulfuric acid is used for the digestion of organic matter. Thereafter, the extracts are cleaned up through SPE florisil column and make it ready for analysis. GC-MS/MS technique was used for the analysis. In terms of the GC part, column HP-5 (30 m × 0.32 mm, 0.32 μm) is used for the separation of 18 PCBs through temperature programming. For the tandem mass spectrometry condition, multiple reaction monitoring (MRM) model with positive electron impact ion source (EI+) is chosen for the qualification and quantification. The results reveal that in the spiked levels of 50, 400 and 1 000 ng/kg, the average recoveries ranged from 72% to 109% for all the 18 PCBs in each part of M. nipponense. The relative standard deviations is below 10%, the limits of detection of this method is 0.10-10 ng/kg. This method has good precision and accuracy. The pretreatment method is simple and fast. Thus this method can be used in the determination of the above mentioned 18 PCBs in M. nipponense. Testing of the actual samples from a farm in Nanjing, only some PCBs is checked out. [ABSTRACT FROM AUTHOR]

Fate of carbendazim residue during the beer brewing process was determined by the high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The simultaneous determination of carbendazim in different samples (barley, malt, spent grain, agreement wort, finalize wort and beer) were developed. For barley, malt and spent grain samples, the QuEChERS method was used for the pretreatment. 6 g MgSO4 and 1.5 g NaAc were used for the extraction, and 150 mg of MgSO4, 50 mg C18 and 50 mg PSA were used for the purification. Agreement wort, finalize wort and beer samples were directly diluted with deionized water and then purified with C18 solid phase extraction column. The main results are presented as followed: The mean recoveries varied from 72% to 99% and the relative standard deviations (RSD) was less than 9%. The limit of quantitation was 0.01 mg/kg. The residues of carbendazim is 1.99 mg/kg in barley, 2.71 mg/kg in malt, 0.41 mg/kg in spent grain, 1.37 mg/kg in agreement wort, 1.34 mg/kg in finalize wort and 0.12 mg/kg in beer. During saccharification, boiling and fermentation processes, the residue of carbendazim has been reduced with the processing factor 0.51, 0.98 and 0.089, respectively. The removal efficiency of fermentation was the highest. [ABSTRACT FROM AUTHOR]