A RAPID FORMALDEHYDE ASSAY USING PURPALD REAGENT - APPLICATION UNDER PERIODATION CONDITIONS

Measurement of formaldehyde is encountered in a broad range of applica tions including the wine and alcohol industry and environmental pollut ion surveillance. In carbohydrate structural chemistry, frequent use i s made of formaldehyde by periodate oxidation of terminal vicinal diol s. Popular methods for the detection of formaldehyde use reagents such as chromotropic acid (4,5-dihydroxynaphthalene-2,7-disulfonic acid) o r acetylacetone. The chromotropic acid method requires heating of the sample under strongly acidic conditions, which is undesirable in many applications. The acetylacetone method yields a yellow color product, and is less specific and sensitive (Mimura et al., J. Hyg. Chem. 22, 3 9-41, 1976). The reaction of formaldehyde with Purpald (4-amino-3-hydr azino-5-mercapto-1,2,4-triazole) works under alkaline conditions at ro om temperature, and the sensitivity is superior to other methods. The color development by this reagent, however, requires oxidation of the adduct with hydrogen peroxide, air oxygen, or dilute periodate. We fou nd that low levels of periodate, commonly used to oxidize specifically terminal vicinal diols to yield formaldehyde, are compatible with col or development with the Purpald reagent. We have investigated the cond itions required for use of the Purpald reagent, especially in conjunct ion with periodate oxidation reactions. We have used the assay either in test tubes or with microplates, attaining sensitivity of as little as 1 nmol formaldehyde. (C) 1906 Academic Press, Inc.