Analysis of Inorganic Builders in Detergent Powders by Laser Raman Spectrometry

Abstract

The analysis of inorganic builders in detergent powders was studied by means of laser Raman spectrometry after the extraction with 95% ethanol. The Raman spectra of aqueous solutions of typical inorganic builders, that is, sodium tripolyphosphate (Na5P3O10), sodium pyrophosphate (Na4P2O7), sodium carbonate, and sodium sulfate, were measured. The characteristic peaks of each compound were located at 1090 cm-1, 1065 cm-1, 1020 cm', and 978 cm-1, respectively. We found that each component was able to be readily detected from Raman spectra of mixtures of four compounds. The Raman spectra were applied to the analysis of some commercial detergent powders and it was clarified that builders of each of the samples can be readily identified by the characteristic peaks mentioned above. The determination of Na5P3O10, Na4P2O7, Na2CO3, and Na2SO4 in the detergent powders were made by using sodium formate as an internal standard. It was shown that the analytical curve for each component exhibits a good linearity, and quantity of each of the builders in commercial detergent powders can be determined with good precision.