Determination of alkylbenzenesulfonate using a tristimulus colorimeter and polyurethane foam as an adsorbent.

Abstract

A simple solid-phase colorimetry for the determination of alkylbenzenesulfonate (ABS) has been proposed. Methylene Blue (MB) reacts with ABS to produce an ion-associate, which is adsorbed onto a flexible polyurethane foam (PUF, polyether type; density, 20 kg/m3; hardness, 11.5 kgf). The color intensity of the foam-adsorbed MB-ABS complex was proportional to the ABS concentration, and thus the concentration of ABS could be determined by both visual and tristimulus methods. The recommended procedure is as follows. Five ml of 1M acetate buffer solution (pH 5.0) and 10 ml of 1.0×10-3 M MB were added to a 200 ml sample solution containing less than 0.8 ppm of ABS. A chip of PUF (2×2×2 cm) was put into the solution and stirred with a magnetic stirrer for 15 minutes. The chip taken up from the solution was rinsed with distilled water to remove any excess MB. The color intensity was measured by tristimulus colorimetry with a calibration curve, together with a visual measurement, followed by the standard series method. The proposed methods were applied to the determination of ABS in pond and river-water samples.