手性镧系位移试剂识别-核磁共振氢谱法测定保健食品中肉碱对映体含量

Determination of carnitine enantiomers in dietary supplement by1H-nuclear magnetic resonance combined with chiral lanthanide shift reagents

目的 采用手性镧系位移试剂识别-核磁共振氢谱法(CLSR-1H qNMR)对保健食品中的肉碱对映体进行快速定性、定量分析研究。方法 样品经氘代甲醇溶解,以吡嗪为内标,经过涡旋、超声辅助萃取、离心后,取适量上层清液,加入手性镧系位移试剂Eu(thfc)3,直接对待测物进行检测。结果 左旋肉碱的质量浓度线性范围在16.3~4 800μg/mL,相关系数(r)>0.99,检出限(LOD)为24.5 mg/kg,定量限(LOQ)为73.5 mg/kg;右旋肉碱的质量浓度线性范围在10.6~530μg/mL,r>0.99,LOD为27.5 mg/kg,LOQ为82.5 mg/kg。方法的加标回收率为95.9%~114.6%,RSD(n=6)为3.31%~6.12%。对网购宣称具有减肥功效的胶囊、奶茶、咖啡粉、片剂进行检测,均未检测出右旋肉碱。结论 本方法简便、快速、灵敏,25 min内即可完成检测,能够为肉碱对映体各自含量的快速检测提供理论基础。

Objective A qualitative and quantitative method has been established to rapidly determine carnitine enantiomers in dietary supplement by1H-nuclear magnetic resonance combined with chiral lanthanide shift reagents(CLSR-1H qNMR).Methods Pyrazine acted as internal standard was added to the samples dissolved in d4-methanol. After vortexing,ultrasonic-assisted extraction and centrifugation,an appropriate amount of supernatant and chiral lanthanide shift reagent(CLSR)Eu(thfc)3were added to the NMR tube for directly determination.Results The linearity range of L-carnitine was16. 3~4 800 μg/mL with correlation coefficient(r)>0. 99. The limit of detection(LOD)was 24. 5 mg/kg,and the limit of quantification(LOQ)was 73. 5 mg/kg. While the linearity range of D-carnitine was 10. 6~530 μg/mL with r>0. 99. The LOD was 27. 5 mg/kg,and the LOQ was 82. 5 mg/kg. Recovery rates obtained from spiked samples were between 95. 9%and 114. 6% with the RSDs(n=6)of 3. 31%~6. 12%. Tests on capsules,milk tea,coffee powder and tablet from online shopping that claimed to have weight-loss effects failed to detect D-carnitine.Conclusion This method is simple,rapid and sensitive. And the sample test could be completed within 25 min,which could provide a theoretical basis for rapidly detection of carnitine enantiomers.