Sensitive spectrophotometric determination of formaldehyde by inhibition of the malachite green-sulfite reaction

A simple, sensitive, and selective method for rapid determination of ultratrace quantities of formaldehyde based on its inhibitory effect on the malachite green-sulfite reaction is described. The reaction is monitored spectrophotometrically by measuring the decrease in absorbance at 613 nm at a fixed time of 61 s. The method allows the determination of formaldehyde in the range 14-700 ng/ml. The limit of detection was 7 ng/ml and the relative standard deviation for 10 determinations of 140 ng/ml formaldehyde was 1.2%. The method is applied to the determination of formaldehyde in chemical industrial wastewater and phenol formaldehyde resin. (C) 1999 Academic Press.