聚合物袋是一种应用广泛的,简单,以及用于气态样品的存储和离线分析的经济有效的方法。各种材料已被用作取样袋,所有已知的都含有杂质,成本不同,耐用性,和存储能力。在这里,我们对几种著名的袋子材料进行了比较研究,Tedlar(PVF),Kynar(PVDF),聚四氟乙烯(PTFE),和纳洛芬(PET),以及一种新材料,乙烯-乙烯基共聚物(EVOH),通常用于储存食物。我们调查了储存条件的影响,湿度,湿度袋子清洁,和光照对挥发性有机化合物浓度(丙酮,乙酸,异戊二烯,苯,柠檬烯,除其他外)在袋子中储存长达48小时的呼出人体呼吸样本中。具体来说,我们在所有材料的袋子中显示出短链脂肪酸(SCFA)的高损失(对于大多数SCFA,储存8小时后低于50%)。我们发现特德拉的样本,纳洛芬,和EVOH袋在暴露于UV辐射48小时的时间段时经历组成的变化。我们报告了所有袋中的高初始杂质水平,并且在48小时后加倍。我们将二次电喷雾电离(SESI)和质子转移反应(PTR)质谱在采样袋中储存后进行离线分析。通过呈现所有重要的m/z特征的强度变化,我们提供了对袋子内容物的时间演变的分析观点。我们还提出了一个简单的,自动化,和具有成本效益的离线样品引入系统,这使得能够将从聚合物袋收集的气体样品控制递送到质谱仪中。总的来说,我们的研究结果表明,取样袋表现出高水平的杂质,对几个环境因素敏感(例如,曝光),并为某些类别的化合物提供低回收率,例如,短链脂肪酸。
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 significantm/zfeatures. 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.