电子电离质谱碎裂和检测北极沉积物中 2,6,10,14-四甲基-7-(3-甲基戊-4-烯基)-十五-5-烯的自动氧化产物。

Electron ionization mass spectrometric fragmentation and detection of autoxidation products of 2,6,10,14-tetramethyl-7-(3-methylpent-4-enyl)-pentadec-5-ene in Arctic sediments.

机构信息

Aix Marseille Univ, Université de Toulon, CNRS, IRD, MIO UM 110, 13288, Marseille France.

Biogeochemistry Research Centre, School of Geography, Earth and Environmental Sciences, University of Plymouth, Drake Circus, Plymouth, PL4 8AA, UK.

出版信息

Rapid Commun Mass Spectrom. 2020 Aug 15;34(15):e8816. doi: 10.1002/rcm.8816.

DOI:10.1002/rcm.8816

PMID:32315098

Abstract

RATIONALE

Some highly branched isoprenoid (HBI) alkenes are commonly used as proxies for palaeoceanographic reconstructions. However, there is a need to identify compounds that are sufficiently stable and abundant to be used as tracers of HBI oxidation in sediments. 2,6,10,14-Tetramethyl-7-(3-methylpent-4-enyl)-pentadec-5(Z/E)-en-4-ols resulting from 2,6,10,14-tetramethyl-7-(3-methylpent-4-enyl)-pentadec-5-ene appear to be useful for this purpose.

METHODS

Comparison of electron ionization (EI) mass spectra and retention times with those of standards allowed formal identification of autoxidation products of 2,6,10,14-tetramethyl-7-(3-methylpent-4-enyl)-pentadec-5-ene. EI-MS fragmentations of TMS ethers of the main oxidation products (2,6,10,14-tetramethyl-7-(3-methylpent-4-enyl)-pentadec-5(Z/E)-en-4-ols) were deduced by gas chromatography/electron ionization mass spectrometry (GC/EI-MS), low-energy collision-induced dissociation tandem mass spectrometry (CID-MS/MS) and accurate mass measurements. These compounds were then quantified in Arctic sediment samples in MS/MS multiple reaction monitoring (MRM) mode using transitions based on the main fragmentation pathways elucidated.

RESULTS

2,6,10,14-Tetramethyl-7-(3-methylpent-4-enyl)-pentadec-5(Z/E)-en-4-ols were identified after autoxidation of the HBI alkene 2,6,10,14-tetramethyl-7-(3-methylpent-4-enyl)-pentadec-5-ene. Low-energy CID-MS/MS analyses and accurate mass measurements allowed the EI-MS fragmentation pathways of their trimethylsilyl (TMS) derivatives to be elucidated. Some specific fragment ions and chromatographic retention times were also useful for further characterization. As an application of some of the described fragmentations, TMS derivatives of these metabolites were characterized and quantified in MRM mode in Arctic sediments.

CONCLUSIONS

Due to their production in high proportions during autoxidation of their parent HBI diene, their apparent stability in sediments, and their specific EIMS fragmentations, (Z and E)-2,6,10,14-tetramethyl-7-(3-methylpent-4-enyl)-pentadec-5-en-4-ol TMS derivatives appeared to be useful tracers of HBI autoxidation in sediments.

摘要

原理

一些高度支链异戊二烯（HBI）烯烃通常被用作古海洋重建的示踪剂。然而，需要识别足够稳定和丰富的化合物，作为沉积物中 HBI 氧化的示踪剂。2,6,10,14-四甲基-7-(3-甲基戊-4-烯基）-十五-5(Z/E）-烯-4-醇是 2,6,10,14-四甲基-7-(3-甲基戊-4-烯基）-十五-5-烯的自氧化产物，似乎可用作此目的。

方法

通过与标准品的电子电离（EI）质谱和保留时间进行比较，可正式鉴定 2,6,10,14-四甲基-7-(3-甲基戊-4-烯基）-十五-5-烯的自动氧化产物。通过气相色谱/电子电离质谱（GC/EI-MS）、低能碰撞诱导解离串联质谱（CID-MS/MS）和精确质量测量，推导出主要氧化产物（2,6,10,14-四甲基-7-(3-甲基戊-4-烯基）-十五-5(Z/E）-烯-4-醇）的 TMS 醚的 EI-MS 碎裂。然后，使用从主要裂解途径中阐明的跃迁，在 MS/MS 多重反应监测（MRM）模式下，在北极沉积物样品中定量这些化合物。

结果

在 HBI 烯烃 2,6,10,14-四甲基-7-(3-甲基戊-4-烯基）-十五-5-烯自动氧化后，鉴定出 2,6,10,14-四甲基-7-(3-甲基戊-4-烯基）-十五-5(Z/E）-烯-4-醇。低能 CID-MS/MS 分析和精确质量测量允许阐明其三甲基硅（TMS）衍生物的 EI-MS 裂解途径。一些特定的碎片离子和色谱保留时间也有助于进一步表征。作为一些描述的裂解的应用，以 MRM 模式在北极沉积物中对这些代谢物的 TMS 衍生物进行了表征和定量。