采用单因素试验和正交试验优化硫酸催化反应条件,以气相色谱-质谱法测定人血浆样品中37种脂肪酸含量。样品于4℃融化,分取100 μL,加入500 μL含0.4 mol·L^-1氢氧化钾的甲醇溶液,涡旋30 s,室温放置10 min。加入2 mL正己烷,离心5 min,在上清液中加入含7%(体积分数)硫酸(催化剂)的甲醇溶液1 mL,吹氮至干,加入200 μL水,于65℃反应20 min。冷却至室温,加入2 mL正己烷,分取上层清液注入附氢火焰离子化检测器的气相色谱仪,目标物经Rt-2560色谱柱固定后在程序升温条件下分离,以配电子轰击离子源的质谱仪检测。结果显示:影响脂肪酸测定的催化反应因素分别为反应温度、硫酸体积分数、反应时间,其中反应温度具有显著性影响(P≤0.05);37种脂肪酸可在78 min内完成色谱分离,其质量浓度均在0.1~50 mg·L^-1内与其对应的峰面积呈线性关系,检出限(3S/N)为0.003 0~0.411 0 mg·L^-1;对质控样品进行3个浓度水平(1,5,10 mg·L^-1)的加标回收试验,回收率为80.0%~118%。对质控样品重复测定5次和连续测定5 d,所得测定值的相对标准偏差分别为0.27%~6.2%(日内精密度试验)和0.91%~8.7%(日间精密度试验)。方法用于分析云南4个特有少数民族人群1 913个血浆样品,发现肥胖组脂肪酸总含量高于正常组,且脂肪酸种类及含量在各民族血浆间分布存在差异。

Single-factor and orthogonal experiments were used to optimize the catalytic reaction conditions of H₂SO₄, and the 37 fatty acids in the human plasma samples were determined by gas chromatography-mass spectrometry. The samples were thawed at 4℃, and an aliquot (100 μL) of the sample was added to 500 μL of CH₃OH solution containing 0.4 mol·L^-1 KOH. The mixture was vortexed for 30 s, and settled at room temperature for 10 min. n-Hexane of 2 mL was added, and the mixture was vortexed for 5 min. CH₃OH solution (1 mL) containing 7% (volume fraction) H₂SO₄ was added into the supernatant, and the mixed solution was blown to dry by N₂. After adding 200 μL of H₂O to promote reaction at 65℃ for 20 min, the solution was cooled down to room temperature, and mixed with 2 mL of n-hexane. The supernatant was introduced into gas chromatograph with flame ionization detector, and the targets were separated on Rt-2560 column with temperature program and detected with mass spectrometer equipped with electron impact ion source. It was shown that the catalytic reaction factors affecting the fatty acid determination were reaction temperature, volume fraction of H₂SO₄, reaction time, in which the reaction temperature had a significant effect (P ≤ 0.05). The 37 fatty acids could be separated by chromatography within 78 min, and linear relationships between values of peak area and mass concentration were found in the same range of 0.1-50 mg·L^-1, with detection limits (3S/N) of 0.003 0-0.411 0 mg·L^-1. Recovery tests were made on quality control samples at three concentration levels (1, 5, 10 mg·L^-1) by standard addition method, giving recoveries in the range of 80.0%-118%. Five repeated determinations and 5 d continuous determinations were made on quality control samples, and RSDs of the determined values for the inter-day and intra-day precision tests were found in the ranges of 0.27%-6.2% and 0.91%-8.7%. The proposed method was applied to the analysis of 1 913 plasma samples in 4 peculiar ethnic minorities in Yunnan, and it was found that the total content of fatty acids was higher in obese group compared to the healthy control group, and there were differences in the distribution of fatty acids in the plasma of the 4 ethnic minorities.