Improved Mass Accuracy and Isotope Confirmation through Alignment of Ultrahigh-Resolution Mass Spectra of Complex Natural Mixtures.,Analytical Chemistry

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Improved Mass Accuracy and Isotope Confirmation through Alignment of Ultrahigh-Resolution Mass Spectra of Complex Natural Mixtures.
Analytical Chemistry ( IF 6.7 ) Pub Date : 2020-01-13 , DOI: 10.1021/acs.analchem.9b04234
Julian Merder ₁ , Jan A Freund ₁ , Ulrike Feudel ₁ , Jutta Niggemann ₁ , Gabriel Singer _{2,

3} , Thorsten Dittmar _{1,

4}

Affiliation

Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) is one of the state-of-the-art methods to analyze complex natural organic mixtures. The precision of detected masses is crucial for molecular formula attribution. Random errors can be reduced by averaging multiple measurements of the same mass, but because of limited availability of ultrahigh-resolution mass spectrometers, most studies cannot afford analyzing each sample multiple times. Here we show that random errors can be eliminated also by averaging mass spectral data from independent environmental samples. By averaging the spectra of 30 samples analyzed on our 15 T instrument we reach a mass precision comparable to a single spectrum of a 21 T instrument. We also show that it is possible to accurately and reproducibly determine isotope ratios with FT-ICR-MS. Intensity ratios of isotopologues were improved to a degree that measured deviations were within the range of natural isotope fractionation effects. In analogy to δ13C in environmental studies, we propose Δ13C as an analytical measure for isotope ratio deviances instead of widely employed C deviances. In conclusion, here we present a simple tool, extensible to Orbitrap-based mass spectrometers, for postdetection data processing that significantly improves mass accuracy and the precision of intensity ratios of isotopologues at no extra cost.

中文翻译：

通过对复杂天然混合物的超高分辨率质谱进行比对，提高了质量准确度和同位素确定性。

傅里叶变换离子回旋共振质谱（FT-ICR-MS）是分析复杂的天然有机混合物的最新方法之一。检测质量的精度对于分子式归属至关重要。可以通过对相同质量的多次测量取平均值来减少随机误差，但是由于超高分辨率质谱仪的可用性有限，因此大多数研究无法承受多次分析每个样品的费用。在这里，我们显示出可以通过平均独立环境样本的质谱数据来消除随机误差。通过在我们的15 T仪器上分析的30个样品的光谱进行平均，我们可以达到与21 T仪器的单光谱相当的质量精度。我们还表明，使用FT-ICR-MS可以准确，可重复地确定同位素比。同位素同位素的强度比提高到一定程度，以使测得的偏差在自然同位素分馏作用范围内。与环境研究中的δ13C相似，我们建议使用Δ13C作为同位素比率偏差的一种分析手段，而不是广泛使用的C偏差。总之，在这里，我们提供了一种可扩展到基于Orbitrap的质谱仪的简单工具，用于后检测数据处理，无需额外费用即可显着提高质量精度和同位素同位素强度比的精度。

更新日期：2020-01-14

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