Zhongguo shipin weisheng zazhi (Nov 2023)
Determination of glutamine enantiomers in functional foods by a water-soluble lanthanide shift reagent-identified method based on the 1H-qNMR technique
Abstract
ObjectiveThis study aimed to achieve rapid qualitative and quantitative analysis of the respective contents of glutamine （Gln） enantiomers in functional foods by establishing a water-soluble lanthanide shift reagent-identified method based on the 1H-qNMR technique.MethodsThe internal standard disodium terephthalate was added to the samples dissolved in ultrapure water. After vertexing and centrifuging， an appropriate amount of supernatant was taken into the NMR tube with deuterium water as a field-locking solvent and the water-soluble lanthanide shift reagent samarium （Ⅲ）-propylenediaminetetraacetate as the chiral selector. The 1H-NMR spectrum was collected by a 600 MHz nuclear magnetic resonance spectrometer for the direct determination of the contents of Gln enantiomers in functional foods.ResultsThe Gln enantiomers and DT quantitative peaks were well-separated. The mass concentration of D- and L-glutamine has a good linearity in the range of 100.0-2 000.0 µg/mL with R2>0.99. The limit of detection was 30.0 µg/mL， and the limit of quantification was 100.0 µg/mL. The average recovery rates obtained from standard addition methods were between 94.27% and 116.07% with the relative standard deviations （n=6） being 0.18%-1.84%.ConclusionThis method offers high recovery， good repeatability， and a simple pretreatment process， and the sample test can be completed within 15 min. The testing of different dosage forms of functional foods purchased from the supermarket platform revealed that the enantiomeric purity of Gln in the samples was ≥99%. No significant difference was observed between this method and high-performance liquid chromatography （P>0.05） in the determination of total Gln. The method can provide a practical technique for the rapid detection of the contents of glutamine enantiomers.
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