Determination of total and inorganic mercury in whole blood by cold vapor inductively coupled plasma mass spectrometry (CVICP-MS) with alkaline sample preparation

Abstract

A simple method with a fast sample preparation procedure for total and inorganic mercury determinations in blood samples is proposed based on flow injection cold vapor inductively coupled plasma mass spectrometry (FI-CV ICP-MS). Aliquots of whole blood (500 µL) are diluted 1 + 1 v/v with 10.0% v/v tetramethylammonium hydroxide (TMAH) solution, incubated for 3 h at room temperature and then further diluted 1 + 4 v/v with 2.0% v/v HCl. The inorganic Hg was released by on-line addition of L-cysteine and then reduced to elemental Hg by SnCl₂. On the other hand, total mercury was determined by on-line addition of KMnO₄ and then reduced to elemental Hg by NaBH₄. Samples were calibrated against matrix-matching. The method detection limit was found to be 0.80 µg L⁻¹ and 0.08 µg L⁻¹ for inorganic and total mercury, respectively. Sample throughput is 20 samples h⁻¹. The method accuracy is traceable to Standard Reference Material (SRM) 966 Toxic Metals in Bovine Blood from the National Institute of Standards and Technology (NIST). For additional validation purposes, human whole blood samples were analyzed by the proposed method and by an established CV AAS method, with no statistical difference between the two techniques at 95% confidence level on applying the t-test.