Nicotine determination in mushrooms by LC-MS/MS and early studies on the impact of drying on nicotine formation
Résumé
Recently a problem concerning significant amount of nicotine in dried wild mushrooms (mainly Boletus edulis from China) has been submitted to the European Commission. As a consequence the European Food Safety Authority (EFSA) has proposed temporary maximum residue levels (MRLs) of 0.036 mg kg-1 for fresh wild mushrooms and 1.17 mg kg-1 for dried wild mushrooms (2.3 mg kg-1 just for dried ceps). The EFSA also has highlighted the necessity of a monitoring and testing programme that will be launched by food business operators at the start of the forthcoming 2009 harvest season. In the present work 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, that employs an HPLC-MS-MS system and (±)-Nicotine-D4 as internal standard, has a limit of quantitation of 6 g kg-1 and 60 g kg-1 for fresh and dried product respectively. Analyses of spiked samples with different quantities of nicotine show that recovery ranges from 107 to 122% with relative standard deviation ranging from 2.9 to 10.1 %, depending on the spiking level. The combined uncertainty, calculated at low level for frozen (0.015 mg kg-1 ) and at high level for dried ( 2 mg kg-1) matrix was 13% and 10%, respectively. The application of the method to some real samples of mushrooms purchased on the market or obtained from local producers shows ranges of nicotine content of 0.01-0.04 mg kg-1 and 0.1-4.5 mg kg-1 in fresh/frozen and dried matrixes, respectively. To understand reasons of this unexpected high content of the nicotine in dried matrixes some experiments of drying mushrooms were performed in laboratory in different conditions.
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