Nicotine determination in mushrooms by LC-MS/MS with preliminary studies on the impact of drying on nicotine formation

摘要

A problem concerning significant amounts of nicotine in dried wild mushrooms (mainly Boletus edulis from China) has been reported to the European Commission. As a consequence, the European Food Safety Authority (EFSA) proposed temporary maximum residue levels (MRLs) of 0.036 mg kg~(-1) for fresh wild mushrooms and 1.17mgkg~(-1) for dried wild mushrooms (2.3mgkg~(-1) for dried ceps only). The EFSA also highlighted the necessity for a monitoring and testing programme to be launched by food business operators at the start of the 2009 harvest season. In the present study, a quick and sensitive analytical method for routine analysis of nicotine in fresh and dried mushrooms was developed and validated by a single-laboratory procedure. The method, which employs an LC-MS/MS system and (±)-nicotine-d_4 as internal standard, has a limit of quantification of 6 and 60 μgkg~(-1) for fresh and dried product, respectively. Analyses of samples spiked with different levels of nicotine showed recoveries ranging from 107 to 122%, with relative standard deviations of 2.9-10.1% depending on the spiking level. The combined uncertainties, calculated at a low level for frozen (0.015 mg kg~(-1)) and a high level for the dried (2mgkg~(-1)) matrix, were 13 and 10%, respectively. Application of the method to real samples of mushrooms purchased on the market or obtained from local producers showed nicotine levels ranging 0.01-0.04 and 0.1-4.5 mg kg~(-1) in fresh/frozen and dried matrices, respectively. To establish reasons for the unexpectedly high levels of the nicotine in dried matrices, preliminary laboratory experiments involving drying mushrooms were performed under various conditions.