Spectrophotometric method for the assessment of formaldehyde in environmental and food samples

A simple, sensitive, and reliable spectrophotometric method was developed for the determination of formaldehyde in drinking water and milk samples using pararosaniline as a colorimetric reagent. Under optimized conditions, formaldehyde reacts to form a reddish-purple quinonoid complex with maximum absorption at 541 nm. Key analytical parameters, including pH, reaction time, and reagent volume, were optimized for maximum sensitivity and precision. The method exhibited excellent linearity (0.05–5 mg L⁻¹, r² = 0.998) with detection and quantification limits of 10 µg·L⁻¹ and 35 µg·L⁻¹, respectively. High precision was confirmed by an RSD of 0.94 % for 1 mg·L⁻¹ formaldehyde. Application to real samples, including metropolitan and bottled water as well as commercial milk products from local markets in Saudi Arabia, revealed formaldehyde concentrations between 1.4 ± 0.02 and 9.6 ± 0.15 µg·L⁻¹. Recovery studies (95–104 %) validated the method's accuracy. The proposed approach provides a practical tool for routine formaldehyde monitoring in environmental and food samples.