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NEN-EN 14526 specifies a method for the quantitative determination of saxitoxin (STX), decarbamoyl saxitoxin (dcSTX), neosaxitoxin (NEO), decarbamoyl neosaxitoxin (dcNEO), gonyautoxin 1 and 4 (GTX1,4; sum of isomers), gonyautoxin 2 and 3 (GTX2,3; sum of isomers), gonyautoxin 5 (GTX5 also called B1), gonyautoxin 6 (GTX6 also called B2), decarbamoyl gonyautoxin 2 and 3 (dcGTX2,3; sum of isomers), N-sulfocarbamoyl-gonyautoxin 1 and 2 (C1,2; sum of isomers) and (depending on the availability of certified reference materials (CRMs)) N-sulfocarbamoyl-gonyautoxin 3 and 4 (C3,4; sum of isomers) in (raw) mussels, oysters, scallops and clams. Laboratory experience has shown that it is also be applicable in other shellfish and cooked shellfish products. The method described was validated in an interlaboratory study and was also verified in a EURL-performance test aiming the total toxicity of the samples. Toxins which were not available in the first interlaboratory study as dcGTX2,3 and dcNEO were validated in two additional interlaboratory studies. The lowest validated levels are given in μg toxin (free base)/kg shellfish tissue and also as μmol/kg shellfish tissue and are listed in Table 1.