Kj. Schmidt et al., Quantitation of sulfur oxyanions in industrial metal refining solutions with dispersive and fourier transform raman spectroscopy, APPL SPECTR, 53(10), 1999, pp. 1206-1211
Fourier transform (FT)-Raman and dispersive, visible excitation Raman spect
ra are reported for standard solutions and highly colored industrial metal
refining solutions containing sulfur oxyanions, primarily sulfate and sulfa
mate. Good-quality spectra are obtained for both standard and industrial so
lutions. However, quantitation of both sulfur oxyanion concentrations is co
mplicated by self-absorption effects, In the FT-Raman spectra, self-absorpt
ion of the incident laser beam yields an exponential correlation between Ra
man peak intensity, directly proportional to the apparent sulfate concentra
tion, and the actual sulfate concentration, An internal standard, dispersiv
e Raman spectroscopy, and excitation at 647 nm were used in an attempt to a
pply a self-absorption correction for absorption of the incident laser beam
by ratioing the relative Raman intensities of the standard and species of
interest. This approach improves the accuracy for sulfate and sulfamate det
ermination to +/- 6.1% and +/- 3.4%, respectively. This study represents th
e most detailed characterization presented so far of the errors expected in
quantitative Raman spectroscopy of industrial solutions. These results sug
gest that Raman spectroscopy is a uniquely powerful technique for the quali
tative and quantitative characterization of industrial metal refining solut
ions.