Abstract
A spectrophotometric flow injection method is proposed for the determination of formaldehyde (HCHO) in wastewater. The condensation of HCHO with hydroxylamine sulfate produces formaldoxime. In this reaction hydroxylamine decreases in proportion to the concentration of HCHO. Residual hydroxylamine reduces the iron(III)-1,10-phenanthroline (phen) complex to a red iron(II)-phen complex (λmax = 510 nm). Therefore, the decrease in hydroxylamine can be monitored by measuring the decrease in the absorbance at 510 nm. Consequently, HCHO can be determined indirectly. A standard/sample solution containing HCHO is injected into a water carrier solution so that a negative FIA peak can be obtained. Under the optimized experimental conditions, HCHO in an aqueous solution was determined over the concentration range of 0.25∼1.0 mg L−1. The limit of detection (S/N = 3) was 20 μg L−1 HCHO. The relative standard deviation values (n = 4) were 2.03, 0.80 and 0.27% for the responses at 0.25, 0.50 and 1.00 mg L−1. The sampling throughput was 15 samples h−1. Analytical results for 5 wastewater samples were obtained with no significant difference between the proposed method and an official method.
