保健食品经浓硝酸-过氧化氢(10+3)混合溶液微波消解后,加入盐酸(1+99)溶液使维生素B12中的钴离子完全离解出来,再用石墨炉原子吸收光谱法测定钴离子,据此间接测定保健食品样品中维生素B12的含量.对仪器的工作条件测定波长、灯电流、载气流量作了详述,还对各种对测定有影响的因素,包括盐酸浓度、基体改进剂的种类、石墨炉的工作条件、共存离子的干扰等也作了试验并予以优化选择.维生素B12的质量分数在0.31~4.6 mg·kg-1范围内与吸光度内呈线性关系.方法检出限(3S/N)为0.093 mg·kg-1,在1.0,2.0,4.0 μg·L-1的标准加入水平下进行了回收试验和精密度试验,所得回收率在96.9%~105.0%之间.测定值的相对标准偏差(n=7)小于2.1%.

A method for indirect determination of Vit B12 in health-care food by GFAAS was studied and reported in this paper.The sample was digested with mixed solution of conc.HNO3 and H2O2 (10+3) with microwave digestor,and Co2+ was dissociated completely by addition of HCl (1+99).Vit B12 was determined indirectly by GFAAS determination of content of cobalt in the sample.The working conditions of the instrument,including detection wavelength,lamp current,rate of carrier gas were described in detail.Influential factors,including the concentration of acid ,kinds of matrix modifier,the working condition of graphite furnace,and interferences of coexisting ions were studied and optimized.Linear relationship between values of absorbance and Vit B12 concentration ranged in 0.31-4.6 mg·kg-1 was obtained.Detection limit (3S/N) of the method was 0.093 mg·kg-1.Tests for recovery and precision were made by addition of 1.0,2.0,3.0 μg·L-1 of standard cobalt solution to 3 different health-care food samples,and determined by the proposed method,values of recovery in the range of 96.9%-105.0% and values of RSD′s (n=7) less than 2.1% were obtained.