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This 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. JAOCS 74, 787-792 (1997).

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This paper reports the development of a method for measuring alkyl-benzene sulfonates, alkyl sulfates, and other inorganic ingredients in laundry detergent products without requiring the use of chlorinated organic solvents such as chloroform. Zeolite is first filtered as a residue on filter paper from an aqueous detergent solution. A calcium solution is then added to the filtrate. Alkyl-benzene sulfonates, alkyl sulfates, and phosphate are precipitated as calcium salts and recovered as residues via filtration. The filters are then subjected to X-ray fluorescence spectrometry (XRF) for measuring the levels of zeolite, phosphate, and total anionic surfactant. The remaining filtrate is also subjected to XRF by using the microdroplet preparation for measuring levels of sulfate and silicate. Separately, the level of alkyl-benzene sulfonates is measured following the same XRF procedure after alkyl sulfates are hydrolyzed using an autoclave. This sample preparation procedure was investigated using XRF and was confirmed to be applicable for simultaneous measurements of alkyl-benzene sulfonates, alkyl sulfates, zeolite, phosphate, silicate, and sulfate without using any organic solvents. In the method described in this paper, interelement effects between anionic surfactants and phosphate are not negligible. Fluorescent X-rays of sulfur or phosphorus are absorbed by calcium complexes of phosphate or anionic surfactants. The slope of calibration curves varies with the levels of coexistent elements; external calibration methods cannot be employed for unknown sample matrices. However, for quality assurance purposes, this method is ideal in terms of turnaround time and laboratory hygiene.Paper no. S1101 in JSD 2, 79-83 (January 1999). KEY WORDS:Alkyl sulfate, alkyl-benzene sulfonate, laundry detergent, phosphate, silicate, sulfate, X-ray fluorescence spectrometry, zeolite.Epton (1,2) developed a two-phase titration for anionic surfactant quantitation that has now become universally accepted methodology for anionic surfactants determination. Chloroform is dictated for two-phase titration in the official methods (3-5), but recently the use of potentially hazardous organic solvents such as chloroform in the working environment is restricted by law (6). Kawauchi (7) developed an inductively coupled plasma atomic emission spectrometry (ICP-AES) method where anionic surfactants and inorganic ingredients in laundry detergent products were determined without using any organic solvents. This ICP-AES method was designed to replace the two-phase titration methodology, providing one potential solution to the issue while also reducing turnaround time without compromising data quality. This time, X-ray fluorescence spectrometry (XRF) was applied for surfactant determination to eliminate the use of organic solvent. The XRF method uses the same sample preparation procedure as the ICP method and has achieved quicker determination for the materials listed above in laundry detergent products. In this paper, the advantages and disadvantages of th...