高效液相色谱-二极管阵列检测法测定小麦粉及面粉改良剂中福美双
摘要
<p id=C2>Thiram is an important dithiocarbamate (DTC) fungicide. In the United States and the European Union, the limit range of thiram is 0.1-15 mg/kg in fruits and vegetables, but there is no specific limit for grains. The maximum residue limit (MRL) for wheat is 1 mg/kg (calculated as carbon disulfide, CS<sub>2</sub>) in the National Food Safety Standard (GB 2763-2019). At present, the relevant regulation methods in China are targeted at the detection of dithiocarbamates and are incapable of detecting thiram specifically. CS<sub>2</sub> is produced by the reaction of dithiocarbamate and acid, and it is then determined by spectrophotometry or GC; this renders the quantification of dithiocarbamate indirect. HPLC and HPLC-MS/MS methods are also reported for the detection of thiram. Most of the literature focuses on the determination of thiram in vegetables, fruits, soil, etc. In these methods, thiram is converted into dimethyldithiocarbamate (DMD) anions in an alkaline buffer solution, and DMD can be determined by HPLC-UV or LC-MS. However, ziram can also be converted into the DMD anion under alkaline conditions. Therefore, thiram cannot be distinguished from ziram, and this may produce false-positive results. Research has shown that in the presence of sulfite, thiram is converted into a DMD-sulfite adduct, which can be a marker for the selective determination of thiram. Furthermore, thiram can be directly detected by HPLC and HPLC-MS/MS after extraction with dichloromethane, chloroform, hexane, cyclohexane, ethyl acetate, or methanol and clean-up by solid phase extraction in vegetables and fruits. However, until now, few studies have reported the determination of thiram in wheat flour and flour improvers. Therefore, it is of great importance to develop a method for thiram in wheat flour. In this study, an analytical method based on HPLC-DAD was developed for the determination of thiram in wheat flour and flour improvers. The wheat flour and flour improver samples w