Department of Chemistry and Applied Biosciences, Swiss Federal Institute of Technology, Zürich, Switzerland.
Department of Mechanical and Process Engineering, Swiss Federal Institute of Technology, Zürich, Switzerland.
J Breath Res. 2024 Aug 13;18(4). doi: 10.1088/1752-7163/ad6a31.
Polymeric bags are a widely applied, simple, and cost-effective method for the storage and offline analysis of gaseous samples. Various materials have been used as sampling bags, all known to contain impurities and differing in their cost, durability, and storage capabilities. Herein, we present a comparative study of several well-known bag materials, Tedlar (PVF), Kynar (PVDF), Teflon (PTFE), and Nalophan (PET), as well as a new material, ethylene vinyl copolymer (EVOH), commonly used for storing food. We investigated the influences of storage conditions, humidity, bag cleaning, and light exposure on volatile organic compound concentration (acetone, acetic acid, isoprene, benzene, limonene, among others) in samples of exhaled human breath stored in bags for up to 48 h. Specifically, we show high losses of short-chain fatty acids (SCFAs) in bags of all materials (for most SCFAs, less than 50% after 8 h of storage). We found that samples in Tedlar, Nalophan, and EVOH bags undergo changes in composition when exposed to UV radiation over a period of 48 h. We report high initial impurity levels in all the bags and their doubling after a period of 48 h. We compare secondary electrospray ionization and proton transfer reaction mass spectrometry in the context of offline analysis after storage in sampling bags. We provide an analytical perspective on the temporal evolution of bag contents by presenting the intensity changes of all significant/features. We also present a simple, automated, and cost-effective offline sample introduction system, which enables controlled delivery of collected gaseous samples from polymeric bags into the mass spectrometer. Overall, our findings suggest that sampling bags exhibit high levels of impurities, are sensitive to several environmental factors (e.g. light exposure), and provide low recoveries for some classes of compounds, e.g. SCFAs.
聚合物袋是一种广泛应用的、简单且具有成本效益的气体样品储存和离线分析方法。各种材料都被用作采样袋，这些材料都已知含有杂质，并且在成本、耐用性和储存能力方面存在差异。在此，我们对几种知名的袋材料进行了比较研究，包括聚偏二氟乙烯（PVF）、聚偏二氟乙烯（PVDF）、聚四氟乙烯（PTFE）和聚萘二甲酸乙二醇酯（PET），以及一种常用于储存食品的新材料——乙烯-乙烯醇共聚物（EVOH）。我们研究了储存条件、湿度、袋清洗和光照对储存于袋中长达 48 小时的呼出人体呼吸样本中挥发性有机化合物浓度（丙酮、乙酸、异戊二烯、苯、柠檬烯等）的影响。具体而言，我们发现所有材料的袋中短链脂肪酸（SCFA）的损失都很高（在 8 小时储存后，大多数 SCFA 的含量不到 50%）。我们发现，在 Tedlar、Nalophan 和 EVOH 袋中，暴露在紫外线下超过 48 小时后，样品的成分会发生变化。我们报告说，所有袋子的初始杂质水平都很高，48 小时后会翻倍。我们在离线分析中比较了二次电喷雾电离和质子转移反应质谱，离线分析是在储存在采样袋中后进行的。我们通过展示所有显著/特征的强度变化，提供了一个关于袋内物质随时间演变的分析视角。我们还提出了一种简单、自动化且具有成本效益的离线样品引入系统，该系统能够控制从聚合物袋中收集的气态样品输送到质谱仪中。总的来说，我们的研究结果表明，采样袋杂质含量高，对多种环境因素（如光照）敏感，并且对某些化合物（如 SCFA）的回收率低。
