The Analysis of Trace and Ultra-Trace Mercury in Fish Tissue

Why Analyse Fish Tissue?
The predominant source of human exposure to mercury, via the diet, is fish and seafood. Such a foodstuff is subject to European Commission Regulation (EC) # 1881/2006 that sets maximum concentration limits of mercury to ensure food safety. Lower and higher order fish have maximum allowable concentrations of 0.5 and 1.0 mg/Kg (wet weight) respectively. Many laboratories require the capability to measure mercury at 100 times lower than these levels to ensure confident quantification. CETAC (UK) have recently launched the CETAC Quicktrace M-7600 Cold Vapour Generation Atomic Absorption Spectrophotometer (CVAAS) Mercury Analyser that provides high through-put and accurate determination of mercury from a method detection limit (MDL) of 1 ng/L.

Experimental
Tissues of lower and higher order fish were obtained for analysis and NIST 1946 – Lake Superior Fish Tissue was studied to ensure quality control. Analyses were performed using the M-7600 and were validated against analyses using the CETAC Quicktrace M-8000 Cold Vapour Generation Atomic Fluorescence Spectrophotometer (CVAFS) in non-gold trap mode. Tissue samples were digested (via exposure to HNO3, H2SO4, KMnO4, K2S2O8, HCL and heat) prior to analysis.

Results
MDLs of 1 and 3 ng/L were established for the M-7600 and M-8000 respectively as well as accuracy recoveries of 89 % and 87 % for NIST 1946 (within the ± 20 % required by European Commission Directive 2001/22/EC), confirming instrument sensitivity and stability. Matrix spike analysis of NIST 1946 yielded measurement recoveries of 102 % for both instruments. The measurement of mercury in the fish tissues studied was between 0.03 and 1.10 mg/Kg (as shown in Figure 1), well within the analytical capability of both instruments.

Conclusion
The CETAC Quicktrace M-7600 Mercury Analyser offers robust and accurate measurement of mercury at ultra-trace and trace levels.