Determination of sulfate in brackish waters by laser Raman spectroscopy

Abstract After recent developments in our vibrational studies, we can arrive at a new method of determining sulfate in brackish waters. This paper discusses the recent developments and applications of the new method. The first thing is the establishment of a calibration work to the sulfate solutions of different concentrations using an internal standard by laser Raman spectroscopy. The second is an application of this method to the determination of sulfate in many samples of brackish waters around an estuary. The calibration curve of sulfate ion was linear up to the concentration of 0.04 mol/dm 3 in Raman spectroscopy. Sodium chloride had no effect on this calibration curve up to the concentration of 1.0 mol/dm 3 . We then applied Raman spectroscopy to determine the sulfate concentration in brackish waters near an estuary. The concentration of sulfate in brackish waters at most of the sample points was higher in ebb tide than in flood tide except at some points. Similar tendency was found for the chloride concentration of sample solutions. The concentration ratio of sulfate to chloride was nearly equal to 0.14 at most points in the flood tide. But the ratio was found to be higher in the ebb tide.