Nonsolvent quantitation of anionic surfactants and inorganic ingredients in laundry detergent products

Abstract

AbstractThis paper reports the development of a method for measuring alkylbenzene sulfonates and alkyl sulfates (AS) without requiring the use of chlorinated organic solvents, such as chloroform. Alkylbenzene sulfonates and AS are precipitated with calcium and then isolated by filtration. Through this filtration process, they are separated from inorganic sulfur compounds. After the precipitate is prepared, the level of sulfur is measured by inductively coupled plasma atomic emission spectrometry (ICP‐AES) to determine the total anionic surfactant level. Separately, AS are hydrolyzed in an autoclave, and the level of alkylbenzene sulfonates is then measured in the same manner. By using the autoclave, a safe and rapid hydrolysis step has been achieved. In addition to alkylbenzene sulfonates and AS, phosphate, silicate, sulfate, and zeolite can be determined with this sample preparation. This sample preparation procedure was investigated by ICP‐AES and was confirmed applicable for simultaneous measurements of alkylbenzene sulfonates, AS, phosphate, silicate, sulfate, and zeolite without using organic solvents. Relative standard deviation for the analysis is less than 1.7%, recovery is more than 99.0%, and the calibration curve gives a correlation coefficient of R=1.000. The detection limit of this method for alkylbenzene sulfonates and AS is 0.6%, for zeolite, 0.04%, for phosphate, 0.4%, for silicate, 0.1%, and for sulfate, 0.2%, by weight in product. This method is applicable to various laundry detergent products that contain the materials mentioned above and is 10 times faster than the six wet chemical methods normally used to analyze these compounds.