Modified pararosaniline method for the determination of formaldehyde in air

A modified pararosaniline colorimetric method for more precise determination of formaldehyde in aqueous solution is described. Unlike earlier methods, the use of hazardous mercury reagent is not required. The optimization of reagent concentrations, the effect of varying temperature, and potentially interfering compounds are reported. Comparative data on the analysis of aqueous formaldehyde solutions shows that the modified pararosaniline method is more sensitive, more reproducible, and easier to use than the widely accepted chromotropic acid method. The slopes of the calibration lines are 0.533 AU mL ..mu..g/sup -1/ (absorbance units per (microgram per milliliter)) for the pararosaniline and 0.233 AU mL ..mu..g/sup -1/ for chromotropic acid. Both methods were used to determine indoor formaldehyde levels in two energy-efficient homes, and the findings are compared.