Introduction

Headspace gas chromatography–mass spectrometry (HS-GC–MS) is widely considered the gold standard of quantitative fecal VOC analysis. However, guidelines providing general recommendations for bioanalytical method application in research and clinical setting are lacking.

Objectives

To propose an evidence-based research protocol for fecal VOC analysis by HS-GC–MS, based on extensive testing of instrumental and sampling conditions on detection and quantification limits, linearity, accuracy and repeatability of VOC outcome.

Methods

The influence of the following variables were assessed: addition of different salt solutions, injection temperature, injection speed, injection volume, septum use, use of calibration curves and fecal sample mass. Ultimately, the optimal sample preparation was assessed using fecal samples from healthy preterm infants. Fecal VOC analysis in this specific population has potential as diagnostic biomarkers, but available amount of feces is limited here, so optimization of VOC extraction is of importance.

Results

We demonstrated that addition of lithium chloride enhanced the release of polar compounds (e.g. small alcohols) into the headspace. Second, a linear relationship between injection volume, speed and temperature, and fecal sample mass on the abundance of VOC was demonstrated. Furthermore, the use of a septum preserved 90% of the non-polar compounds. By application of optimal instrumental and sampling conditions, a maximum of 320 unique compounds consisting of 14 different chemical classes could be detected.

Conclusions

These findings may contribute to standardized analysis of fecal VOC by HS-GC–MS, facilitating future application of fecal VOC in clinical practice.

中文翻译：

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通过气相色谱-质谱法分析粪便挥发性有机化合物的优化样品制备

介绍

顶空气相色谱-质谱 (HS-GC-MS) 被广泛认为是定量粪便 VOC 分析的金标准。然而，缺乏为研究和临床环境中的生物分析方法应用提供一般建议的指南。

目标

基于对仪器和采样条件对 VOC 结果的检测和定量限、线性度、准确性和可重复性的广泛测试，提出了一种基于证据的 HS-GC-MS 分析粪便 VOC 的研究方案。

方法

评估了以下变量的影响：添加不同的盐溶液、注射温度、注射速度、注射体积、隔膜使用、校准曲线的使用和粪便样品质量。最终，使用健康早产儿的粪便样品评估了最佳样品制备方法。该特定人群的粪便 VOC 分析具有作为诊断生物标志物的潜力，但此处可用的粪便量有限，因此优化 VOC 提取非常重要。

结果

我们证明了氯化锂的添加增强了极性化合物（例如小醇）向顶部空间的释放。其次，证明了注射体积、速度和温度以及粪便样品质量与 VOC 丰度之间的线性关系。此外，使用隔膜保留了 90% 的非极性化合物。通过应用最佳仪器和采样条件，最多可以检测到 320 种独特的化合物，包括 14 种不同的化学类别。

结论

这些发现可能有助于 HS-GC-MS 对粪便 VOC 的标准化分析，促进粪便 VOC 在临床实践中的应用。