Abstract
The chromotropic acid method is used extensively for the measurement of low levels of formaldehyde in occupational and community environments. However, this procedure is not accepted universally as a standard method, and needs to be evaluated more thoroughly. Due to the deficiencies in knowledge regarding sample stability, a preliminary stability comparision of standard formaldehyde solutions in aqueous media was performed. Possible storage options of ambient, refrigeration and freezing conditions were investigated. In an attempt to detect any similarities or differences in stability between laboratory-prepared solution standards and field samples of formaldehyde, a side-by-side study was conducted. It was observed that both water-impinged solutions and laboratory-prepared aqueous formaldehyde solutions degraded rapidly upon ambient and refrigerated storage. One percent sodium bisulfite solution as the collection medium for formaldehyde provided good solution stability for ambient and refrigerated samples, with less satisfactory effect on frozen samples. The effect of the addition of methanol as a possible stabilizer for refrigerated, water-impinged formaldehyde samples was also investigated. The results indicated that although the stabilizer did enhance stability, it caused an unexplained increase in solution absorbance, most probably related to a pertubation of formaldehyde solution equilibria.