Lestremau F, Desauziers V, Fanlo J L
Laboratoire Genie de l'Environnement Industriel, Ecole des Mines d'Alès, France.
Analyst. 2001 Nov;126(11):1969-73. doi: 10.1039/b105099k.
Solid-phase micro extraction (SPME) is a promising technique for fast and low cost trace analysis. However, some limitations of the technique were encountered when using a PDMS (polydimethylsiloxane)/Carboxen fibre for sampling a mixture of volatile aliphatic amines in air. On the GC chromatogram, two supplementary peaks were noticed in addition to the analyte peaks, thus limiting qualitative and quantitative analysis in this particular case. This paper presents the investigations to identify the artefacts and determine the origin of their formation. First, GC-MS identification, by both electron impact and chemical ionisation modes, demonstrated that the two artefacts were unsaturated amines assumed to be formed by a dehydrogenation reaction of the target amines. This reaction was found to occur during thermal desorption of analytes in the GC injection port and to be catalysed by temperature and by metals consisting of the inox (stainless-steel) needle of the SPME device. It was also demonstrated that artefact formation was not significant when using PDMS or PDMS/divinylbenzene fibres. This difference with PDMS/Carboxen fibre can be explained by the high desorption temperature required for this fibre. Moreover, the microporosity of Carboxen induces a longer desorption time which increases the contact between analytes and inox and thereby enhances artefact formation.
固相微萃取（SPME）是一种用于快速、低成本痕量分析的有前景的技术。然而，当使用聚二甲基硅氧烷（PDMS）/碳分子筛纤维在空气中采集挥发性脂肪胺混合物时，该技术存在一些局限性。在气相色谱图上，除了分析物峰外，还发现了两个额外的峰，从而限制了在这种特定情况下的定性和定量分析。本文介绍了为识别这些假象并确定其形成原因所进行的研究。首先，通过电子轰击和化学电离模式的气相色谱-质谱联用鉴定表明，这两种假象是不饱和胺，推测是由目标胺的脱氢反应形成的。发现该反应在气相色谱进样口中分析物的热解吸过程中发生，并由温度和SPME装置的不锈钢针中的金属催化。还证明，使用PDMS或PDMS/二乙烯基苯纤维时，假象的形成并不显著。与PDMS/碳分子筛纤维的这种差异可以通过该纤维所需的高解吸温度来解释。此外，碳分子筛的微孔性导致解吸时间延长，这增加了分析物与不锈钢的接触，从而增强了假象的形成。
