Repeatability and validity of a fluorimetric HPLC method in the quantification of yessotoxin in blue mussels (Mytilus edulis) related to the mouse bioassay

Repeatability and validity of a fluorimetric HPLC method in quantification of yessotoxin (YTX) in mussels related to the mouse bioassay was studied. B lue mussels (Mytilus edulis) from the Sognefjord, Norway were sampled from March to November, 1997, and October to December, 1998. A total of 75 sampl es were analysed for YTX by HPLC using 4-[2-(6,7-dimethoxy-4-methyl-3-oxo-3 , 4-dihydroquinoxalinyl) ethyl]-1,2,4-triazoline-3, 5-dione (DMEQ-TAD) as a fluorimetric derivatization agent. Among these, 28 of the samples were ana lysed by HPLC in duplicate. All samples were analysed by the mouse bioassay using both chloroform and ether in the final step of extraction. The dupli cate measurements using HPLC was found equal and the method repeatable (p < 0.05). The absolute difference between the two measurements was found to i ncrease with increasing level of measurements. This significant positive co rrelation (p < 0.05) was mainly due to concentrations of YTX higher than 20 0 mug/100 g mussel meat. However the precision of the results obtained was not found to be less in the upper level than in the lower level. Based on t he internal correlation analysis including the mouse bioassay and the HPLC method a cut-off value of less than or equal to 10 mug YTX/5 g digestive gl and was found preferable. The mouse bioassay of ether extracts often failed to detect high levels of YTX, and as demonstrated by the low K-values, the agreement between the mouse bioassay of ether extracts and the HPLC method was very weak. The HPLC method was found to give repeatable results and th ereby found to be reliable. Consequently, the HPLC method seems to the meth od of choice for detection and quantification of YTX in mussels when compar ed with the mouse bioassay. (C) 2001 Elsevier Science Ltd. All rights reser ved.