Solventless determination of total anionic surfactants in waters using polyurethane foam as support and analysis of digital images

• A solventless method was developed for the determination of total anionic surfactants.
• Polyurethane foam replaced chloroform in the procedure.
• Analysis of digital images were employed in the detection process.
• The proposed method showed no difference from standard method.

This work reports the development of a novel green analytical procedure for the determination of total anionic surfactants in waters. The method was based on the replacement of CHCl3 by polyurethane foam (PUF) for the extraction of an ionic-pair formed between methylene blue (MB+) and anionic surfactants. Besides, colored species retained on PUF were measured directly on the foam surface by treating digital images recorded with a scanner. Several parameters that could affect the performance of the method were evaluated. At optimum conditions, the concentration of MB+ used was 1.7 × 10− 5 mol L− 1, PUF mass was 50 mg and shaking time was 15 min. Collection parameters related to the analysis of digital images presented no significant influence on the method. The application of the proposed method in the analysis of river waters was only possible after adjustment of the ionic strength and pH of the standard solutions and samples with a 0.01 mol L− 1 phosphate buffer solution with pH 7.5. The limit of quantification was 0.14 mg L− 1, enough to attend the Brazilian legislation regarding the maximum concentration permitted of total anionic surfactant in surface waters. The developed method was compared with a standard method and presented no significant difference at 95% confidence level.