Determination of formaldehyde in beer based on cloud point extraction using 2,4-dinitrophenylhydrazine as derivative reagent

A cloud point extraction method was developed for extraction of formaldehyde in beer prior to high performance liquid chromatography analysis. The formaldehyde was taken into complex with 2,4-dinitrophenylhydrazine in aqueous nonionic surfactant Triton X-114 medium and concentrated in the surfactant-rich phase by bringing the solution to the temperature of 60 °C. Under optimal conditions, the limit of detection of formaldehyde is 0.7 ng mL−1. The intra- and inter-day precisions expressed as relative standard deviations are 4.2% and 5.5%, respectively. The proposed method was successfully applied for determination of formaldehyde in various beer samples. The contents of formaldehyde in these samples are in the range of 172–385 ng mL−1. The results were in agreement with those obtained by the state standard method (steam-distillation and spectrophotometry analysis) used in China. The developed method was demonstrated to be rapid and sensitive for extraction and determination of formaldehyde in beer.