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Four commercially available fish fillets were freeze-dried, homogenized, and analyzed tor mercury by the Texas A&M Trace Element Research Laboratory and the Utah Public Health Laboratory (UPHL) utilizing thermal decomposition/amalgamation atomic absorption spectrophotometry. Two-way analysis of variance detected bias in the data between the two laboratories. Some of the bias could be attributed to different calibration curve quantitation and near detection limit quantitation, albeit causal explanations could be confounded with other effects. Knowledge of analytical bias will aid interpretation of interlaboratory data. The swordfish mercury content, as determined by both laboratories, was about 1 ppm, while mercury content found in the Atlantic salmon was about 0.021 ppm. For the Alaskan halibut, the Texas A&M measured a mercury concentration of 0.155 ppm, while the UPHL measured a mercury concentration of 0.181 ppm for the same fish. The Texas A&M determined that the Canadian-raised salmon contained about 0.019 ppm of mercury, while the UPHL determined a mercury content of about 0.025 ppm for the same fish. The mercury found within the fish fillets did not exceed nationwide mercury mean values determined by the U.S. Food and Drug Administration. [ABSTRACT FROM AUTHOR]

The analytical method for determining the concentration of mercury in fish by thermal decomposition, amalgamation/atomic absorption spectrophotometry was thoroughly studied. Specific issues addressed were accurate modeling of instrumental response, the use of quartz and nickel boats, carryover effects, software limitations, and troubleshooting. The DMA-80 Direct Mercury Analyzer instrument was calibrated using a total of 22 points, and the resultant curves statistically analyzed. At minimum, second-order polynomials were required to adequately model the data. TORT-2 standard reference material was analyzed in both quartz and nickel boats and found to give equivalent performance in both types of vessels and well within the 95% confidence interval. DOLT-3 standard reference material also yielded values well within the 95% confidence interval, but the DORM-2 standard reference material did not. Carryover effects were found to be minimal with a new catalyst tube but increased with catalyst age. Blanks should be run after the analysis of high mercury content samples; however, when the catalyst has aged, two blanks are required to reduce apparent mercury signals to nominal blank values. Comparable results between thermal decomposition, amalgamation/atomic absorption spectrophotometry and cold-vapor atomic absorption spectrophotometry were demonstrated. The feasibility of using this instrument to analyze hair was also explored and found to be suitable. Software problems and limitations have been noted when attempting to implement a high-throughput methodology. Instrumental drift was found to be minimal when operated over long periods. Blank values can provide important diagnostic indicators. [ABSTRACT FROM AUTHOR]