Determination of selected nickel isotopes in biological samples by inductively coupled plasma mass spectrometry with isotope dilution

Abstract

The bis-(1-pyrrolidinecarbodithioato) nickel(II) complex was extracted from acid-digested samples of blood, urine and faeces into 4-methylpentan-2-one. The organic extracts were evaporated to dryness and dissolved in 2.8% v/v HNO₃ prior to analysis by inductively coupled plasma mass spectrometry (ICP-MS). The extraction procedure freed m/z 60, 61 and 62 from polyatomic interferences, allowing ⁶¹Ni and ⁶²Ni to be used for combined isotope dilution (ID) and tracer studies. Satisfactory recovery was obtained for naturally abundant Ni added to serum (97.1 ± 1.9%) and urine samples (100.8 ± 2.8%) using ID with ⁶²Ni. Average recovery of ⁶²Ni added to plasma, serum, red blood cells, faeces and urine, determined using ID-ICP-MS with ⁶¹Ni, was 99.8 ± 3.2%.