Typek Rafal, Dybowski Michal P, Dawidowicz Andrzej L
Department of Chromatography, Institute of Chemical Sciences, Faculty of Chemistry, Maria Curie Sklodowska University in Lublin, 20-031, Lublin, Poland.
Forensic Toxicol. 2025 Sep 13. doi: 10.1007/s11419-025-00738-z.
The aim of this work is to investigate whether precyclization of γ-hydroxybutyric acid (GABA) allows for increasing its gas chromatography (GC) signal, and if so, is it a more effective way to increase the signal of this compound than its silylation or methylation?
Gas chromatography-mass spectrometry (GC-MS) and GC with flame ionization detection (GC-FID) response to GHBA before and after silylation, methylation, and cyclization were compared. The impact of injector temperature on GHBA and γ-butyrolactone (GBL) signals was assessed. Fourier transformed infra-red spectroscopy was used to examine the formation of macromolecular derivatives in the injector.
GHBA shows a lower GC signal than GBL due to partial polycondensation into a non-volatile polyester in the injector. Validation data were established for GHBA after each derivatization. Silylation and methylation reduced the limit of detection (LOD) by approximately 1.5- and 1.3-fold, respectively, whereas pre-cyclization led to at least a 4.6-fold decrease in LOD.
The present study elucidates the reasons behind the low GHBA signal observed in GC analysis and, consequently, supports the recommendation to perform pre-cyclization of this compound prior to analysis. Furthermore, the findings demonstrate that although signal enhancement of GHBA can be achieved through silylation or methylation, the most substantial increase is observed following its cyclization during sample preparation. The proposed in this paper cyclization procedure is both remarkably simple and highly effective, allowing for reliable quantification of this hydroxycarboxylic acid in a variety of matrices, including plasma, urine, wine, beer, and orange juice.
本研究旨在探究γ-羟基丁酸（GABA）的预环化是否能增强其气相色谱（GC）信号，若能增强，与硅烷化或甲基化相比，它是否是增强该化合物信号的更有效方法？
比较了硅烷化、甲基化和环化前后气相色谱-质谱联用（GC-MS）以及带火焰离子化检测的气相色谱（GC-FID）对γ-羟基丁酸（GHBA）的响应。评估了进样口温度对GHBA和γ-丁内酯（GBL）信号的影响。采用傅里叶变换红外光谱法检测进样口中大分子衍生物的形成。
由于在进样口中部分缩聚形成了非挥发性聚酯，GHBA的GC信号低于GBL。每种衍生化后均建立了GHBA的验证数据。硅烷化和甲基化分别使检测限（LOD）降低了约1.5倍和1.3倍，而预环化导致LOD至少降低了4.6倍。
本研究阐明了GC分析中观察到的GHBA信号较低的原因，因此支持在分析前对该化合物进行预环化的建议。此外，研究结果表明，虽然通过硅烷化或甲基化可以实现GHBA信号增强，但在样品制备过程中环化后信号增强最为显著。本文提出的环化程序既非常简单又高效，能够可靠地定量分析包括血浆、尿液、葡萄酒、啤酒和橙汁在内的多种基质中的这种羟基羧酸。
