Food Composition and Methods Development Lab, Agricultural Research Service, Beltsville Human Nutrition Research Center, USDA , 10300 Baltimore Avenue, Building 161, Beltsville, Maryland 20705, United States.
Anal Chem. 2017 Oct 3;89(19):10537-10546. doi: 10.1021/acs.analchem.7b02753. Epub 2017 Sep 18.
Online two-dimensional (2D) comprehensive liquid chromatography (LC × LC) has become increasingly popular. Most LC × LC separations employ one or more detectors at the outlet of the second dimension, D, with very short runs to avoid undersampling. We used six detectors, including dual parallel mass spectrometry (LC1MS2), for detection of the first dimension, D. We made an argentation (silver-ion) UHPLC column from a strong cation exchange column for D, coupled with UV and LC1MS2 detection. LC1MS2 in D combined with LC1MS2 in D, plus five other detectors, constituted LC2MS4 in a comprehensive LC1MS2 × LC1MS2 2D-LC separation. Electrospray ionization (ESI) high resolution accurate mass (HRAM) mass spectrometry (MS) and atmospheric pressure chemical ionization (APCI) MS were used in parallel for D detection, while atmospheric pressure photoionization (APPI) MS and ESI-MS were used for detection of D. The LC1MS2 used for D allowed quantification of triacylglycerol (TAG) molecular species of Parinari curatellifolia and other seed oils, while the D allowed isomers of TAG containing 18:3 fatty acyl chains as well as TAG regioisomers to be separated and identified. The LC1MS2 in D allowed identification of oxo-TAG species by HRAM MS and quantification of 806.3 ± 1.3 and 1101 ± 22 μg/g of α- and γ- tocopherols, respectively, in P. curatellifolia by APCI-MS. It is now feasible to use silver-ion UHPLC as the D separation in LC × LC and to use multiple mass spectrometers across both dimensions to perform conventional quantitative analysis and to take advantage of the newest LC × LC separation technology to identify isomers that are otherwise difficult to separate.
在线二维（2D）全面液相色谱（LC×LC）已经变得越来越流行。大多数 LC×LC 分离在第二维（D）的出口处使用一个或多个检测器，运行时间非常短，以避免欠采样。我们在 D 中使用了包括双平行质谱（LC1MS2）在内的六个检测器进行检测。我们用一个强阳离子交换柱制作了一个银离子（silver-ion）UHPLC 柱用于 D，与 UV 和 LC1MS2 检测结合使用。D 中的 LC1MS2 与 D 中的 LC1MS2 以及其他五个检测器结合，构成了 LC2MS4 全面 LC1MS2×LC1MS2 2D-LC 分离。电喷雾电离（ESI）高分辨率精确质量（HRAM）质谱（MS）和大气压化学电离（APCI）MS 用于 D 的平行检测，而大气压光电离（APPI）MS 和 ESI-MS 则用于 D 的检测。D 中的 LC1MS2 允许定量 Parinari curatellifolia 和其他种子油的三酰基甘油（TAG）分子种类，而 D 则允许分离和鉴定含 18:3 脂肪酸链的 TAG 异构体以及 TAG 区域异构体。D 中的 LC1MS2 通过 HRAM MS 鉴定了氧化 TAG 种类，并通过 APCI-MS 定量鉴定了 P. curatellifolia 中的α-和γ-生育酚分别为 806.3±1.3 和 1101±22μg/g。现在可以在 LC×LC 中使用银离子 UHPLC 作为 D 分离，并在两个维度上使用多个质谱仪进行常规定量分析，并利用最新的 LC×LC 分离技术来鉴定否则难以分离的异构体。
