Flow Injection-Spectrophotometric Determination of Micro-amounts of Formaldehyde in Foodstuffs

In an alkaline solution of 0.4 mol·L-1 KOH,formaldehyde was reacted with phloroglucinol to form an unstable orange colored product with absorption maxima at 474 nm.The above mentioned reaction was used in the rapid determination of micro-amounts of formaldehyde in foodstuffs and by the use of flow-injection technique,the course of the color reaction was controlled strictly and the absorbance of the colored product was measured timely.Linear relationship between the absorbance and concentration of formaldehyde was kept within 10 mg·L-1.At the sampling frequency of 35 sample per hour,the detection limit was found to be 0.023 mg·L-1.Precision of the method was tested at the concentration level of 7 mg·L-1 for 11 determinations,value of RSD obtained was 0.29%.Formaldehyde in the foodstuff sample was separated by steam distillation from a H3PO4 solution and the distillate was absorbed in dil.KOH solution.