HPLC Method for Determining the Formaldehyde Content of Beer

Controlling the content of formaldehyde in beer is very important because of formaldehyde's toxicity. Nevertheless, accurate determination of its content in beer is difficult because of its low concentration in beer and reversible combination with sulfite. A selective and sensitive HPLC method for the determination of formaldehyde in beer, based on the derivatization of formaldehyde and 2,4-dinitrophenylhydrazine (DNPH), is described. Sample pretreatment was as follows: extraction of formaldehyde from beer through steam distillation of a beer sample preceded by adding 20 mL of phosphoric acid (concentration, 200 g/L) into 20 mL of beer and collection of 100 mL of distillate; mixing of 0.5 mL of the distillate and 1 mL of DNPH (concentration,1 g/L) in a 5-mL tube; and derivatizing for 20 min at 60 degrees C. After derivatization, separation of the derivate was achieved using a C18 column (4 x 250 mm, 5 mu m) and isocratic elution with 45% acetonitrile. This whole method enabled formaldehyde in beer to be determined with recoveries close to 100%, a repeatability error of less than 1%, and a limit of detection (LOD) of less than 3 mu g/L. The overall method was successfully applied to the determination of formaldehyde in marketplace beers. The results showed that the concentration of formaldehyde in Chinese beers ranged from 0.062 to 0.453 mg/L, and the average content of formaldehyde in these beers was 0.134 mg/L.