Determinação sensível e seletiva de formaldeído em amostras de alimentos após derivatização química

Formaldehyde is classified as carcinogenic agent 1. According to the World Health Organization (WHO)the acceptable daily intake of formaldehyde is 0.15 mg perkg body weight per day 2. Several methods were reported forformaldehyde determination in different samples, such as air, food, water and wood based on chromatographic separations3. However, these procedures present low analytical frequency and high reagents consumption. An alternative to chromatographic methods is based on the reaction between formaldehyde and acetyl acetone (2,4-pentadione) in the presence of ammonium acetate buffer (Nash reagent), leading to the formation of 3,5–diacetyl-1,4-dihydrolutidine (DDL), which can be monitored by spectrophotometry 4. This work shows for the first time the electrochemical determinationof formaldehydeafter chemical derivatization using the Nash reagent, with measurements carried out by square-wave voltammetryusing a glassy-carbon electrode.The electrochemical behavior of DDL was obtained by cyclic voltammograms (0 to 1.6V) inammonium acetate medium(pH = 5.5). The results show a single oxidation peak of DDL at the potential 0.8 V,while formaldehyde and the reagents are not electroactive,showing that this derivatization can be used to formaldehyde determination indirectly and selectively. This reaction at room temperature is slow, takingca. 200 min to achievethe chemical equilibrium, however, heating at 80°C wasused for 10 min to make the reaction faster and leading to a higher analytical frequency. Under the optimized conditions, the present procedure shows LOD, linear range and relative standard deviation(n=20) of 65 μgL-1, 0.4-40mgL-1and 0.7%,respectively. The procedure was applied for the analysis of shimeji and shiitakeafter the distillation of formaldehyde.The concentration of formaldehyde in the food samples was compared by spectrophotometric determination. The results obtained by the proposed method were in agreement asindicated by thet-test in a confidence level of 95%. The results indicatethe successful development of a selective and sensitive method, which is simpler, faster and generates reduced waste in comparison with chromatographic methods for the determination of formaldehydein food samples.