GC Determination of Trace Amounts of Formaldehyde in Beer with Pre-Derivatization

Formaldehyde in beer was derivatized with 2,4-dinitrophenylhydrazine (2,4-DNPH) in dil.H2SO4 and the derivative was extracted ultrasonically with cyclohexane for 3 times.One μL of the extract was teken for GC determination with ECD detector.Working condition of the gas chromatograph was given in detail.Linear relationship between the values of integral of peak area and concentration of formaldehyde (essentially its derivative) was obtained as shown by the linear regression equation of y=85 380 x+344 7 (r=0.999 9),corresponding to the linearity range of 0.05-0.8 mg·L-1,with a detection limit of 0.01 mg·L-1.Tests for precision and recovery were performed,giving values of RSD′s (n=5) less than 0.3%,and of recovery in the range from 99.8%-100.2%.