称取5.0 g婴幼儿奶粉样品，在乙醇2 mL，水4 mL和氨水20 mL的介质中，于75℃的恒温水浴中振荡水解40 min，每间隔5 min振荡一次，水解完成后冷却至室温，并在水解混合物中加入乙醇10 mL，混匀。用体积比为1∶1的乙醚-石油醚混合液30 mL振荡提取10 min，离心5 min，收集醚层提取液，留存于烧瓶中；再用乙醚-石油醚按相同步骤重复提取2次。将所收集的醚层提取液合并旋转蒸发至干，所得残留物即为从样品提取所得脂肪总量。取此提取所得脂肪60.0 mg，溶解于异辛烷4 mL中，再加入2 mol·L^-1氢氧化钾-甲醇溶液200 μL，振荡30 s，静置至澄清，使脂肪酸甲酯化。加入硫酸氢钠1 g中和氢氧化钾，然后离心3 min。取其上层溶液按仪器工作条件进行气相色谱-质谱分析。采用高极性HP-88毛细管色谱柱，进样量为1.0 μL，从130~240℃按程序升温的条件进行分离，并引入质谱仪进行测定，质谱测定中用电子轰击（EI）离子源，和在m/z 45~450内全扫描模式进行定性和定量测定。试验中选择样品中含量较低的反式脂肪酸为分析物，并测定了相关的参数。所测定的12种反式脂肪酸甲酯分别在一定的质量浓度内与其相应的峰面积之间呈线性关系，其检出限（3S/N）为0.42~1.45 mg·L^-1。按标准加入法测得的回收率为75.5%~107%，测定值的相对标准偏差（n=5）在1.1%~8.5%之间。脂肪酸采用面积归一化法测定。按此方法分析了3种婴儿奶粉，其中饱和脂肪酸含量在50%以上，反式脂肪酸含量均小于0.5%，均符合国家标准规定。

5.0 g of the sample of infant formula milk powder, were hydrolyzed in an ammoniacal medium containing 2 mL of ethanol, 4 mL of H₂O and 20 mL of aq. ammonia at 75℃ in a constant temperature water bath for 40 min with shaking at each 5 min intervals. The mixture, after the hydrolysis was ended, was cooled to room temperature and mixed with 10 mL of ethanol. The hydrolyzed fat in the reaction mixture was then extracted with 30 mL of a mixed solvent of ether and petroleum ether with a volum ratio of 1:1 by shaking for 10 min. After centrifuging for 5 min, the upper etheric layer was collected and kept in a flask. The lower layer was extracted with the ether mixture again for 2 times in the same way described above. The upper etheric layers were collected and combined in the same flask. The combined etheric layer was then evaporated to dryness under swirling. The fatty compounds in the milk powder sample were then remained in the residue. An aliquot of 60.0 mg of the residue was taken and dissolved in 4 mL of iso-octane. Then the fatty acids in the solution were methyl-esterifred by shaking for 30 s with 200 μL of 2 mol·L^-1 potassium hydroxide in methanol. The reaction mixture was kept under steady condition until it was turned to clear and transparent state, thus to have the esterification ended. 1 g of sodium bisulfate was added to the solution for neutralization of the potassium hydroxide, and after centrifuging for 3 min, the solution of upper layer was taken for GC-MS analysis under the instrumental working condition. 1.0 μL of the solution was introduced and the GC-separation was carried out by using the highly polar HP-88 capillary chromatographic column under the mode of programmed temperature elevation from 130℃ to 240℃. In the MS analysis, the EI ionization source and whole scanning mode in the range of m/z 45 to 450 were adopted for qualitative and quantitative determinations. Twelve trans-fatty acids were used as analyte in the related tests. Linear relationships between values of peak areas measured and mass concentrations of the respective trans-fatty acid methyl ester were found in definite ranges, and the detection limits (3S/N) found were between 0.42-1.45 mg·L^-1. Recovery was tested by standard addition method, giving recoveries ranged from 75.5%-107%. Values of RSDs (n=5) found were in the range of 1.1%-8.5%. Fatty acids were determined by area normalization method. The proposed method was used to analyze 3 infant formula milk powder samples, giving contents of saturated fatty acids over 50% and of trans-fatty acids all less than 0.5%, and showing that these milk powder were in conformity to the GB standards of our country.