Determination of chromium(III), chromium(VI) and total chromium in chromate and trivalent chromium conversion coatings by electrospray ionization mass spectrometry

Developed were the determination methods of CrVI and CrIII by electrospray ionization mass spectrometry, where HCrO4− (m/z 117) and [CrIII(cydta)]− (m/z 394) were measured, respectively. Moreover, total Cr was also determined by measuring [CrIII(cydta)]− after reduction of CrVI with ascorbic acid. Here, cydta denotes trans-1,2-diaminocyclohexane-N,N,N′,N′-tetraacetic acid. The detection limits were ca. 13 nmol/dm3 for CrVI and 56 nmol/dm3 for CrIII and total Cr. The proposed methods were applied to analyze chromate and trivalent chromium conversion coatings and gave consistent results with those obtained by a diphenylcarbazide spectrophotometric method for CrVI and ICP-AES for total Cr.