Addition of tertiary amines in the semiquantitative, multi-element inductively coupled plasma mass spectrometric analysis of biological materials

Abstract

A semiquantitative inductively coupled plasma mass spectrometric (ICP-MS) analysis protocol for biological materials was developed to include water-soluble tertiary amines with microwave heated sample preparation. Certified reference materials digested with HNO₃, H₂O₂ and HF required addition of H₃BO₃ and a solution of tertiary amines (CFA-C reagent) to dissolve insoluble fluorides and neutralize free fluorides. Commercial semiquantitative analysis software that evaluates the entire m/z range and includes pre-programmed corrections for spectroscopic interferences was applied to investigate matrix interferences resulting from 10% tertiary amines and chlorides (added as 1% HCl). Measurement parameters including m/z range, spectrometer sensitivity and number of elements in the external calibration were evaluated. The accuracy of the semiquantitative analysis improved when the standard solution was matrix matched; interference-free isotopes were selected for some elements instead of scanning the whole m/z range, and additional elements with m/z values of under 80 were included for updating the instrument pre-calibration response factor. This semiquantitative analysis approach can be applied successfully for the multi-element analysis of biological materials when optimum instrumental conditions are employed. Thirty-eight elements were determined in six certified reference materials and food samples with a precision of 1–20% and accuracy of 1–50%. The determinations of Al, K, Na and Si were unreliable.