a Institute of Food Chemistry , University of Hohenheim , Stuttgart , Germany.
Food Addit Contam Part A Chem Anal Control Expo Risk Assess. 2013;30(11):1909-17. doi: 10.1080/19440049.2013.833669. Epub 2013 Sep 26.
Thiram belongs to the most important class of dithiocarbamate (DTC) fungicides including dimethyldithiocarbamates (DMDs), ethylenebis(dithiocarbamtes) (EBDs) and propylenebis(dithiocarbamates) (PBDs). During the surface extraction of fruit and vegetables for the LC-MS determination of residues of DMDs, EBDs and PBDs, thiram is reduced by the penicillamine buffer to the DMD anion, thus resulting in false-positive findings of DMD fungicides like ziram. Therefore, an alkaline sulfite buffer was applied for surface extraction, quantitatively transforming thiram into the DMD anion and a stable DMD-sulfite adduct that was used as a selective marker for thiram. Separation was performed isocratically on a ZIC-pHILIC column with acetonitrile-10 mM ammonium hydroxide solution (85/15). Mass selective detection was carried out on a single-quadrupole mass spectrometer coupled to an electrospray ionisation interface operating in negative mode. Using d12-thiram as the internal standard, recoveries of 80-108% were obtained from apples, tomatoes, grapes and sweet peppers, spiked in the range of 0.02-1 mg kg(-1). Limits of detection and quantification were 0.6 and 2 µg kg(-1), respectively.
代森锰锌属于最重要的一类二硫代氨基甲酸盐（DTC）杀菌剂，包括二甲基二硫代氨基甲酸盐（DMDs）、乙撑双二硫代氨基甲酸盐（EBDs）和丙撑双二硫代氨基甲酸盐（PBDs）。在采用 LC-MS 法测定 DMDs、EBDs 和 PBDs 残留量对水果蔬菜进行表面提取时，代森锰锌被半胱氨酸缓冲液还原为 DMD 阴离子，从而导致假性阳性检测出唑菌胺酯等 DMD 杀菌剂。因此，采用碱性亚硫酸盐缓冲液进行表面提取，可将代森锰锌定量转化为 DMD 阴离子和稳定的 DMD-亚硫酸盐加合物，将其作为代森锰锌的选择性标记物。采用乙腈-10 mM 氨水溶液（85/15）等度洗脱，在 ZIC-pHILIC 柱上进行分离。采用电喷雾电离接口在负离子模式下，使用单四极杆质谱仪进行质量选择检测。以 d12-代森锰锌作为内标，从苹果、番茄、葡萄和甜椒中添加 0.02-1 mg/kg 的范围内，回收率为 80-108%。检测限和定量限分别为 0.6 和 2 µg/kg。
