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 Cr(VI) and Cr(III) by electrospray ionization mass spectrometry, where HCrO(4)(-) (m/z 117) and [Cr(III)(cydta)](-) (m/z 394) were measured, respectively. Moreover, total Cr was also determined by measuring [Cr(III)(cydta)](-) after reduction of Cr(VI) with ascorbic acid. Here, cydta denotes trans-1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid. The detection limits were ca. 13 nmol/dm(3) for Cr(VI) and 56 nmol/dm(3) for Cr(III) 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 Cr(VI) and ICP-AES for total Cr.