Center for Environmental Standards and Measurement, Health and Environmental Risk Division, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan.
Anal Chem. 2023 May 23;95(20):7855-7862. doi: 10.1021/acs.analchem.2c05639. Epub 2023 May 8.
A fresh dual presaturation (pre-SAT) method was developed to quantify analytes accurately near the suppressed water signal in H NMR spectra obtained from HO-rich samples. The method includes an extra dummy pre-SAT with a suitable offset for each analyte signal in addition to the water pre-SAT. The residual HOD signal at 4.66 ppm was observed using DO solutions containing l-phenylalanine (Phe) or l-valine (Val) and an internal standard of 3-(trimethylsilyl)-1-propanesulfonic acid- sodium salt (DSS-). When the HOD signal was suppressed using the conventional single pre-SAT method, the measured concentration of Phe from the NCH signal at 3.89 ppm decreased by a maximum of 48%, whereas the dual pre-SAT method gave a reduction in the Phe concentration measured from the NCH signal of less than 3%. The proposed dual pre-SAT method achieved accurate quantification of glycine (Gly) and maleic acid (MA) in a 10 vol % DO/HO solution. The measured concentrations of Gly of 513.5 ± 8.9 mg kg and MA of 512.2 ± 10.3 mg kg corresponded to sample preparation values of Gly of 502.9 ± 1.7 mg kg and MA of 506.7 ± 2.9 mg kg (the number after "±" indicates the expanded uncertainty ( = 2)).
一种新的双预饱和（pre-SAT）方法被开发出来，用于准确地量化 HO 丰富样品的 H NMR 谱中靠近被抑制水信号的分析物。该方法包括除了水预 SAT 之外，为每个分析物信号添加一个合适偏移量的额外虚拟预 SAT。在含有 l-苯丙氨酸（Phe）或 l-缬氨酸（Val）和 3-（三甲基硅基）-1-丙磺酸-钠盐（DSS-）内标的 DO 溶液中观察到 4.66 ppm 处的残留 HOD 信号。当使用常规的单预 SAT 方法抑制 HOD 信号时，从 3.89 ppm 的 NCH 信号测量的 Phe 的浓度最大降低了 48%，而双预 SAT 方法从 NCH 信号测量的 Phe 浓度降低了不到 3%。所提出的双预 SAT 方法实现了在 10 体积% DO/HO 溶液中甘氨酸（Gly）和马来酸（MA）的准确定量。测量的 Gly 浓度为 513.5 ± 8.9 mg kg，MA 浓度为 512.2 ± 10.3 mg kg，对应于 Gly 的样品制备值为 502.9 ± 1.7 mg kg，MA 的样品制备值为 506.7 ± 2.9 mg kg（“±”后面的数字表示扩展不确定度（ = 2））。
