Indirect Determination of Formaldehyde in Food by AAS

A method for indirect determination of formaldehyde in food by AAS was proposed in this paper. Formaldehyde was reacted with Fehling′s solution (an alkaline solution containing Cu2+ ion and sodium potassium tartrate) in a boiling water bath for 30 min to give Cu2O precipitate; or with Tollen′s solution (an ammoniacal solution of Ag+ ion) in a water bath at 50 ℃ for 15 min to give elementary silver. The precipitate obtained was dissolved in 6 mol·L-1 HCl (for Cu2O) or 6 mol·L-1 HNO3 (for Ag), and determined by AAS. The amounts of Cu or Ag found were converted into contents of formaldehyde. Linear relationships between values of absorbance and mass concentration of Cu and Ag were obtained in ranges within 7.000 and 6.000 mg·L-1 respectively. Tests for accuracy were made by addition of standard solution to sample solutions at the concentration level of 1.000 mg·L-1 and analyzed by the proposed method, values of recovery found were in ranges of 99.6%-101% for Cu and 81.9%-84.2% for Ag.