Cotton swabs supported in-situ assay for quaternary ammonium compounds residues in effluents and surfaces

Cellulose paper and cotton swabs have been tested as sampling, reaction and measurement media for quaternary ammonium compounds (QACs) using the reagent Chromo Azurol S in the presence of aluminum cations (CAS-Al). On the basis of the results obtained a new method is proposed for the analysis of QACs in water samples which only entails the successive immersion of swabs into 1 mL of the samples, 1 mL of a solution of CAS-Al for the formation of a ternary blue complex, and 1 mL of water to remove the excess of reagent. The method can be used for the visual on site detection of QACs in effluents, as well as for their quantification within the 3.62-36.2 mg/L range through the direct measurement of the reflectance diffuse of the cotton tips. The proposed approach has been validated for the identification and quantification of QACs in water, and applied to effluents generated by the dairy industry. Moreover, the proposed methodology can be also adapted to the on-site detection of residues of QACs in surfaces at sub mu g/cm(2) levels. (C) 2017 Elsevier Ltd. All rights reserved.