Department of Chemistry and Biochemistry, The University of Texas at Arlington, Arlington, TX 76019, USA.
Department of Chemistry and Biochemistry, The University of Texas at Arlington, Arlington, TX 76019, USA.
J Chromatogr A. 2018 Nov 2;1574:1-8. doi: 10.1016/j.chroma.2018.09.002. Epub 2018 Sep 1.
In some cases, trace component analysis only requires a sensitive and high-resolution mass spectrometer. However, enantiomers must be completely separated to be differentiated with a mass spectrometer, which is highly dependent on the stationary-mobile phase composition. In case of a challenging chiral separation, instead of trying new columns for screening purpose, resolution enhancement techniques could be used to resolve partially overlapping peaks. A well-known enhancement method is the power law, which increases the linear dynamic range of each analyte and reduces excessive noise. In many cases, the peak noise can decrease significantly by applying the power law. However, the main drawback is that this approach changes relative peak areas and heights of each peak in a non-linear fashion which limits its use for quantitative purposes. In this study, a normalized power law was utilized for extracting correct area information. It is a simple (5 step) protocol that only requires Microsoft Excel, and results in enhanced visualization of trace components, especially in low signal/noise environments, and makes integration convenient and reproducible. Several difficult chiral trace component analyses were investigated, including applications pertaining to ultrafast high-throughput chromatography, enantiopurity, and peak purity analysis. For complicated cases with multiple overlapped peaks of different resolutions, a segmented normalized power law was utilized. A trace component coeluting near a dead volume peak and a trace enantiomeric component in the tail of the corresponding enantiomeric peak were virtually enhanced. As an additional tool, first and second derivatives were utilized to identify if an enantiomeric impurity is coeluting with the dominant enantiomer under overload conditions. Idiosyncrasies of the derivative test are discussed. This study shows how these simple approaches can be used for accurate quantitation, specifically for trace enantiomeric components.
在某些情况下，痕量组分分析只需要一台灵敏且分辨率高的质谱仪。然而，为了用质谱仪进行区分，对映异构体必须完全分离，这高度依赖于固定相-流动相的组成。在面临具有挑战性的手性分离时，与其尝试筛选新的色谱柱，不如使用分辨率增强技术来解决部分重叠的峰。一种众所周知的增强方法是幂律法，它可以提高每个分析物的线性动态范围并减少过度噪声。在许多情况下，通过应用幂律可以显著降低峰噪声。然而，主要的缺点是这种方法以非线性方式改变每个峰的相对峰面积和高度，限制了其用于定量目的。在本研究中，使用归一化幂律法来提取正确的面积信息。这是一种简单的（5 步）方法，仅需要 Microsoft Excel，并且可以增强痕量组分的可视化效果，尤其是在低信号/噪声环境下，并且使积分变得方便且可重现。研究了几个困难的痕量手性组分分析，包括与超快高通量色谱、对映体纯度和峰纯度分析相关的应用。对于具有不同分辨率的多个重叠峰的复杂情况，使用分段归一化幂律法。可以实际增强靠近死体积峰共流出的痕量组分和相应对映体峰尾部的痕量对映体组分。作为附加工具，还使用一阶和二阶导数来确定在过载条件下对映体杂质是否与主导对映体共流出。讨论了导数测试的特点。本研究展示了这些简单方法如何用于准确的定量，特别是痕量对映体组分的定量。
