Determination of mercury in fish muscles, fins and scales


                                        Rostislav Červenka^



The most toxic specie of mercury, methylmercury, is formed in aquatic system and is included in
food chain from bacteria to plankton and consequently to fish. Fish is the significantly source of
human methylmercury exposure. The determination of mercury and primarily methylmercury in fish
muscle is therefore important. For determination of total mercury is mostly used pyrolysis atomic
absorption spectrometry with gold amalgamation using analyser AMA 254. The widely used analytical
method for methylmercury determination is gas chromatography (GC) with element specific detection.
The analyses are based on a sequence of successive analytical steps – analyte isolation of the
sample, modification of analytes through derivatization, preconcentration, separation by
chromatography and detection by atomic fluorescence spectrometry (AFS).

For the isolation of methylmercury was used ultrasonication extraction in the presence of 25% w/v
KOH in methanol. Extraction efficiency of the total mercury was determined using the AMA 254
mercury analyser, extraction yields of methylmercury using GC-AFS. The pH value and dilution of
extract are important factors influencing derivatization process. Aqueous derivatization with
sodium tetraethylborate was performed. The procedure for the methylmercury determination was
verified by certified reference material DORM-2 analysis and real samples of fish muscle were
analyzed.

In samples of fish muscle the high content of methylmercury was determined. Therefore a analysis
method for the total mercury determination without a fish kill was searched. The mercury content in
fish scales and fins was analyzed. A treatment way of scales, homogenization and possibilities of
analysis of individual scales were investigated. For determination of approximate content of
mercury in the fish muscle, the dependence of mercury content in the fish muscles on mercury
content in the fish scales and fins was studied.