ABSTRACT
Novel methods for the determination of inorganic oxyanions by electrospray (ES) ionization mass spectrometry have been developed using dehydration reactions between oxyanions and carboxylic acids at the ES interface. Twelve oxyanions (VO3 (-) , CrO4 (2-) , MoO4 (2-) , WO4 (2-) , BO3 (3-) , SiO3 (2-) , SiO4 (4-) , AsO4 (4-) , AsO2 (-) , SeO4 (2-) , SeO3 (2-) and NO2 (-) ), out of 16 tested, reacted with at least one of four aminopolycarboxylic acids, i.e. iminodiacetic acid (IDA), nitrilotriacetic acid (NTA), trans-1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid and triethylenetetramine-N,N,N',Nâ³,N'â³,N'â³-hexaacetic acid, at the ES interface to produce the dehydration products that gave intense mass ion responses, sufficient for trace analysis. As examples, trace determinations of Cr(VI) and silica in water samples were achieved after online ion exchange chromatography, where the dehydration product of CrO4 (2-) and NTA (m/z 290) and that of SiO4 (4-) and IDA (m/z 192) were measured. The limits of detection of the respective methods were 17 nM (0.83 ng Cr/ml) for Cr(VI) and 0.17 µM (4.8 ng Si/mL) for SiO4 (4-) .
ABSTRACT
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.
ABSTRACT
Determination methods of halide ions (X(-) = F(-), Cl(-), Br(-) and I(-)) by electrospray ionization mass spectrometry (ESIMS) were developed, where negative ions of the ternary complexes of group-13 elements, nitrilotriacetic acid (NTA), and halides were measured. In particular, these halides were simultaneously determined by measuring [InX(nta)](-), and the limits of detection (LODs) were 1.1 µmol dm(-3) for F(-), 0.32 µmol dm(-3) for Cl(-), 3.8 nmol dm(-3) for Br(-), and 1.6 nmol dm(-3) for I(-), respectively. This approach was extended to the determination of CN(-), where the ternary complex of Cu(II), CN(-) and 4-(2-pyridylazo)resorcinol (PAR), i.e., [(63)Cu(II)(CN)(par)](-) (m/z 302) was measured. The LOD for CN(-) was 20 nmol dm(-3).
