Effective reduction of polyatomic interferences produced by high chloride and carbon concentrations in determination of Cr(vi) by FPLC-ICP-MS

Abstract

Determination of Cr(VI) in aqueous samples including carbonate matrix solutions was performed by fast protein liquid chromatography (FPLC) coupled to inductively coupled plasma mass spectrometry (ICP-MS). NaCl was used for separation of Cr species representing a high burden of total dissolved solids for plasma. In addition, detection of Cr species in the NaCl and carbonate matrix was severely compromised also by chlorine and carbon polyatomic interferences at m/z 52 and 53. The influence of high amounts of chloride and carbonate ions on detection of Cr species was investigated using ICP-MS with a High Matrix Introduction (HMI) system, which reduced the sample aerosol transport and enabled direct analysis of separated Cr species in the presence of up to 4% NaCl. The potential of Helium Collision mode (He mode) and High Energy Collision Mode (HECM) to reduce polyatomic interferences from chlorine and carbon on m/z 52 and 53 was also evaluated. It was experimentally proven that for efficient removal of chlorine and carbon polyatomic interferences HECM instead of commonly used He mode should be applied. By applying HMI and HECM, determination of Cr(VI) in carbonate buffer matrices using NaCl as eluent is possible, following the most abundant Cr 52 and 53 isotopes. Despite the use of HMI and HECM, which significantly reduce the analyte transport to plasma and detector, low LODs were obtained for Cr(VI): 0.01 ng mL−1 at m/z 50, 0.06 ng mL−1 at m/z 52 and 0.02 ng mL−1 at m/z 53. The repeatability of the measurement (5 ng Cr(VI) mL−1) was better than ±1.5%. The simple solution of efficient lowering of the blank at low pH arising from a stainless steel injection needle was also demonstrated by the use of the reverse injection of samples.