Determination of formaldehyde in air by flow injection using pararosaniline and spectrophotometric detection

Abstract

Two flow injection (Fl) methods, conventional and stopped-flow, are described for the determination of formaldehyde based on its reaction with pararosaniline in the presence of sulphite ion followed by spectrophotometric detection at 570 nm. The calibration graphs are linear over the ranges 2.0–50 and 0.2–10 µg ml–1 of formaldehyde for conventional and stopped-flow Fl, respectively. The coefficient of variation was 6.3% at the 0.6 µg ml–1 level in the stopped-flow mode, the detection limit being 0.1 µg ml–1 of formaldehyde. Sampling rates of 41 and 18 samples h–1 were achieved in the conventional and stopped-flow modes, respectively, this being a major advantage of these methods. The effect of several organic and inorganic species was studied and only low relative molecular mass aldehydes were found to interfere. The stopped-flow method was applied to the determination of formaldehyde in air in work environments and its accuracy was confirmed by comparing the results with those obtained using the standard chromotropic acid method.