Speciation of Chromium(vi) and Chromium(iii) Using Pneumatically Assisted Electrospray Mass Spectrometry

Abstract

Mass spectra can be obtained from aqueous solutions containing both Cr ³⁺ and Cr ₂ O ₇ ^2- as negative ions under the same spray conditions. An excess of HCl is used so that Cr ³⁺ sprays as an anionic chloro complex. Moderately energetic collision conditions produce CrO ₃ ^- from Cr ^VI and CrOCl ₂ ^- from Cr ^III . Detection limits are 100 and 60 ppb for Cr ^III and Cr ^VI , respectively. Reasonable calibration curves are provided by plotting the ratio of the analyte signal to that for ³⁷ Cl ^- .