以2,4-二硝基苯肼作衍生试剂,在稀硫酸溶液中使啤酒样品中的痕量甲醛衍生化,然后用环己烷超声萃取所生成的衍生物先后3次,分取萃取液1 μL进行气相色谱测定,采用电子捕获检测器,对气相色谱仪的工作条件作了详述.由线性回归方程y=85 380 x+3 447(r=0.999 9)所示峰面积的积分值与甲醛(实质上为其衍生物)浓度值之间呈线性关系,其相应的线性范围为0.05~0.8 mg·L-1,检出限为0.01 mg·L-1,在分析啤酒实样的同时对方法的精密度和回收率做了试验,测得其相对标准偏差(n=5)小于0.3%,回收率在99.8%~100.2%之间.

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%.