1. Laboratory of Food Analysis, Dept. of Bioanalysis, Faculty of Pharmaceutical Sciences; Ghent Univ.; Ghent Belgium
2. Dept. of Food Safety; National Inst. of Public Health and the Environment; Bilthoven The Netherlands
3. Inst. of Apicultural Research, Chinese Acad. of Agricultural Sciences, Key Laboratory of Bee Products for Quality and Safety Control, Laboratory of Risk Assessment for Quality and Safety of Bee Products; Bee Product Quality Supervision and Testing Center; Ministry of Agriculture Beijing 100093 People's Republic of China