Response Surface Methodology in Spectrophotometric Determination of Formaldehyde Using Ch romotropic Acid

Formaldehyde in small quantities is commonly analyzed by spectrophotometric methods. One of the most-commonly used spectrophotometric techniques for this purpose is based on the reaction with chromotropic acid. Because of its simplicity, sensitivity, selectivity and its low cost, it is still widely used. Investigations for replacing the concentrated sulfuric acid with other acids or using more dilute solutions of sulfuric acid have been performed. Herein, spectrophotometric determination of formaldehyde by chromotropic acid in the sulfuric acid medium is explored and modified by response surface methodology. The reaction was monitored by measuring the absorbance of the product at 574 nm. The factors affecting the response, i.e. concentration of sulfuric acid and concentration of chromotropic acid, were explored and optimized using response surface methodology. The calibration curve was linear in the range of 0.03-7.00 mg l-1 with detection limit of 0.005 mg l-1. The method was found to be sensitive, selective and was applied to determine the formaldehyde in toothpaste, clothing softener and acetic acid samples with satisfactory results.