Determination of total mercury in whole blood by flow injection cold vapor atomic absorption spectrometry with room temperature digestion using tetramethylammonium hydroxide

Abstract

An improved method is described for the determination of total Hg in whole blood based on flow injection cold vapor atomic absorption spectrometry (FI-CVAAS). Aliquots of whole blood (300 µl) are diluted 1 + 1 v/v with 10% v/v tetramethylammonium hydroxide (TMAH) solution, incubated for 1 h at room temperature and then further diluted 1 + 4 v/v with 2% v/v HCl. The TMAH approach is directly compared to a previously published method that utilizes an on-line microwave-assisted heating step as part of the FI arrangement. Thus, the key issue addressed here is the elimination of the on-line microwave digestion step from the FI manifold, because of problems observed with precipitation in the reaction coil and high back pressure in FI manifold. Matrix-matched calibration standards are used and the method detection limit (3σ) is 0.2 µg l⁻¹. Method accuracy is traceable to Standard Reference Material (SRM) 966 Toxic Metals in Bovine Blood from the National Institute of Standards and Technology (NIST). Additional validation data are provided based on the analysis of whole blood materials from the New York State Department of Health's Proficiency Testing Program for Trace Elements and from the trace elements intercomparison program operated by the Institut National de Santé Publique du Québec, Canada. Accuracy (−2.5%) and precision (<6.0% repeatability and <10% intermediate precision) of the TMAH method compare favorably with values obtained for the on-line microwave method (<10.0% repeatability and <15% reproducibility), and the TMAH method is essentially free of the disadvantages associated with the latter method.