The remote, timely and in-field detection of sulfured additives in natural gas pipelines is a challenge for environmental, commercial and safety reasons. Moreover, the constant control of the level of odorants in a pipeline is required by law to prevent explosions and accidents. Currently, the detection of the most common odorants (THT = tetrahydrothiophane; TBM = tertiary butyl mercaptan) added to natural gas streams in pipelines is made in situ by using portable gas chromatography apparatuses. In this study, we report the analysis of the ultraviolet spectra obtained by a customized ultraviolet spectrophotometer, named Spectra, for the in-field detection of thiophane and tertiary butyl mercaptan. Spectra were conceived to accomplish the remote analysis of odorants in the pipelines of the natural gas stream through the adoption of technical solutions aimed to adapt a basic bench ultraviolet spectrophotometer to the in-field analysis of gases. The remotely controlled system acquires spectra continuously, performing the quantitative determination of odorants and catching systemic or accidental variations of the gaseous mixture in different sites of the pipeline. The analysis of the experimental spectra was carried out also through theoretical quantum mechanical approaches aimed to detect and to correctly assign the nature of the intrinsic electronic transitions of the two odorants, thiophane and tertiary butyl mercaptan, that cause the ultraviolet absorptions. So far, these theoretical aspects have never been studied before. The absorption maxima of thiophane and tertiary butyl mercaptan spectra were computationally simulated through the usage of selected molecular models with satisfactory results. The good matches between the experimental and theoretical datasets corroborate the reliability of the collected data. During the tests, unexpected pollutants and accidental malfunctions have been detected and also identified by Spectra, making this instrument suitable for many purposes.

中文翻译：

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EXPRESS：基于紫外可见光谱及其理论基础监测天然气管道中的四氢噻吩 (THT) 和叔丁基硫醇 (TBM) 气味

出于环境、商业和安全原因，远程、及时和现场检测天然气管道中的含硫添加剂是一项挑战。此外，法律要求不断控制管道中的气味水平，以防止爆炸和事故。目前，最常见的气味剂（THT = 四氢噻吩；TBM = 叔丁基硫醇）添加到管道中的天然气流中是通过使用便携式气相色谱仪进行原位检测的。在这项研究中，我们报告了由名为 Spectra 的定制紫外分光光度计获得的紫外光谱分析，用于现场检测噻吩和叔丁基硫醇。Spectra 旨在通过采用旨在使基本台式紫外分光光度计适用于现场气体分析的技术解决方案来完成对天然气流管道中气味物质的远程分析。远程控制系统连续获取光谱，执行气味物质的定量测定并捕获管道不同位置的气体混合物的系统或意外变化。实验光谱的分析也通过理论量子力学方法进行，旨在检测和正确分配导致紫外线吸收的两种气味剂噻吩和叔丁基硫醇的本征电子跃迁的性质。到目前为止，这些理论方面以前从未被研究过。通过使用选定的分子模型，计算模拟了噻吩和叔丁基硫醇光谱的吸收最大值，结果令人满意。实验和理论数据集之间的良好匹配证实了所收集数据的可靠性。在测试过程中，Spectra 检测并识别了意外污染物和意外故障，使该仪器适用于多种用途。