Comparison of Total Mercury Determinations of Fish Fillet Homogenates by Thermal Decomposition, Amalgamation, and Atomic Absorption Spectrophotometry versus Cold Vapor Atomic Absorption Spectrophotometry

Two of the primary methods for total mercury concentration determination in fish tissue are Cold Vapor Atomic Absorption Spectrophotometry (CVAAS) (i.e., EPA Methods 245.6 and 7471A), and Thermal Decomposition, Amalgamation, and Atomic Absorption Spectrophotometry (TDAAAS) (i.e., EPA Method 7473). This paper compares these two methods for 15 fish tissue homogenates. Eight laboratories that routinely conduct total mercury analyses in fish tissues participated in the study. Each laboratory was provided identical subsamples from the 15 fish tissue homogenates (in duplicate), for their usual total mercury analysis procedures. Four laboratories used TDAAAS, while the other four laboratories used CVAAS. In general, both methods had very good intra-laboratory and intra-method precision. The TDAAAS results were significantly higher (18.3%) than the CVAAS. Previous test of mercury recovery from spiked samples found the TDAAAS method to recover 104% while the CVAAS recovered 88% (Cizdziel et al., 2002). Given the large number of historical CVAAS determinations, it is suggested that total mercury by CVAAS be multiplied by 1.183 to approximate a TDAAAS equivalent or 0.817 in the other direction.