Determination of mercury in biological samples using solid sampling high-resolution continuum source electrothermal atomization atomic absorption spectrometry with calibration against aqueous standards

Abstract

A straightforward procedure is proposed for the determination of mercury in biological samples using solid sampling and high-resolution continuum source electrothermal atomic absorption spectrometry (HR-CS-ETAAS) in a graphite furnace with calibration against aqueous standards. Potassium permanganate was used to stabilize mercury in the aqueous standards, in order to avoid analyte losses during the drying stage. The temperature program was considerably shortened due to the elimination of the pyrolysis stage, resulting in higher analytical frequency, as a drying step with a total hold time of only 3 s was used. The elimination of the pyrolysis stage was necessary to avoid losses, most likely due to the vaporization of methyl mercury, which is highly volatile and the main mercury species in fish and other marine organisms. No chemical modifier was used for the solid samples, as it was found to delay the analyte signal, resulting in an overlap with the high continuous background absorption due to radiation scattering at particles vaporized from the sample matrix. Without a modifier the mercury signal appeared first and could be separated from the strong background absorption. Six certified reference materials (CRM) were analyzed, and good agreement was found between determined and certified values according to the t-test for a 95% confidence level. The precision, expressed as relative standard deviation (RSD), was typically around 5% except for one CRM (pig kidney), for which the RSD was 11%. The limit of detection (3s, n = 10), calculated according to the ‘zero-mass response’, was determined as 0.1 μg g−1. The method has proved to be adequate for routine monitoring purposes due to its simplicity and high sensitivity.