Pyrrolizidine alkaloids in honey: risk analysis by gas chromatography-mass spectrometry

Recently, contamination of honey with pyrrolizidine alkaloids (PA) has been reported as potential health risk. Therefore, it was of interest to develop a reliable tool for selective and quantitative determination of PA in honey. Sample preparation of the novel method comprises strong cation exchange SPE (SCX-SPE), followed by two reduction steps using zinc and LiAlH(4), as well as subsequent silylation. During this procedure the separated PA are converted into the necin backbone, the common structural feature of PA toxicity, which is analyzed by GC-MS in the SIM mode. The procedure was validated using PA from extracts of Senecio vernalis as well as authentic PA standards including their corresponding N-oxides. The PA content of honey samples was quantified with heliotrine as internal standard. The method was applied to generate a dataset in order to evaluate the potential risk of PA contamination especially for retail honeys available on the German/European market. No selection criteria in terms of floral or geographical origin were applied on the samples before analysis. In total, 216 commercially available floral honey samples were analyzed. Among them 19 samples contained PA, in the range of 0.019-0.120 microg/g, calculated as retronecine equivalents. The reported method facilitates the selective determination of PA without the need to identify each individual PA independently. The PA contamination of honey is expressed in terms of a single sum parameter and no background information such as foraged plants and pollen analysis is necessary. The LOQ is 0.01 ppm with a S/N of 7:1.