Dry purge for the removal of water from the solid sorbents used to sample volatile organic compounds from the atmospheric air
Dry purge for the removal of water from the solid sorbents used to sample volatile organic compounds from the atmospheric air
复制标题
DOI：
10.1039/b004678g
复制
发表时间：
2000
期刊：
影响因子：
4.2
通讯作者：
J. Gawlowski;T. Gierczak;Elżbieta Pietruszyñska;M. Gawryś;J. Niedzielski
中科院分区：
文献类型：
--
作者：
J. Gawlowski;T. Gierczak;Elżbieta Pietruszyñska;M. Gawryś;J. Niedzielski
研究了用于挥发性有机化合物（VOC）分析的空气和水样吸附剂中水分的干式吹扫技术。作为取样模拟步骤，使固定体积的湿空气通过填充有吸附剂床的管。随后通过干燥气体吹扫进行解吸。在所有实验过程中，直接测量阱出口处气体中的水蒸气浓度。不超过300 ml的干燥气体足以完全去除Tenax、Chromosor B 106、Carbotrap B和C中的水，即使在相对湿度高达95%的大量空气中取样。吸附的水也可以有效地从碳分子筛中清除：Carbosieve S-III和Carboxen 569、1000和1001。Carboxen 1000是最简单的，Carbosieve S-III是最困难的情况，需要吹扫气体体积大约60- 100%。羧基569和1001占据中间位置。对于碳分子筛，取样管出口处的水蒸气浓度对干气体体积的依赖性是非常典型的：对应于恒定浓度的长段之后是急剧下降，直到水被完全去除。实现此任务所需的干燥气体体积取决于样品大小和相对湿度以及解吸温度。吸附剂质量的影响非常小。后一种现象是出乎意料的，但对分析实践非常重要。吸附剂质量的增加防止了弱吸附分析物的损失，而不需要诉诸于增加吹扫气体体积。通过在吹扫气体的出口通道中放置湿度传感器，可以轻松监控水解吸过程并实现自动化。
The dry purging technique used to remove water from the air and water sampling adsorbents in volatile organic compounds (VOC) analysis was investigated. As a sampling simulation step, a fixed volume of humid air was passed through the tube filled with the sorbent bed. Desorption by the dry gas purging followed. The concentration of water vapour in the gas at the outlet of the trap was directly measured in the course of all experiments. No more than 300 ml of dry gas is enough for complete removal of water from Tenax, Chromosorb 106, and Carbotraps B and C, even if large volumes of air at relative humidity as high as 95% are sampled. Adsorbed water can also be purged effectively from the carbon molecular sieves: Carbosieve S-III and Carboxen 569, 1000 and 1001. Carboxen 1000 is the easiest and Carbosieve S-III the most difficult case that requires the purging gas volume larger by about 60–100%. Carboxen 569 and 1001 occupy an intermediary position. For carbon molecular sieves the dependence of water vapour concentration at the outlet of the sampling tube on the dry gas volume is very characteristic: a long segment that corresponds to the constant concentration is followed by a sharp decrease until the water is removed completely. The volume of dry gas necessary to achieve this task depends on the sample magnitude and relative humidity and on the desorption temperature. The adsorbent mass exerts a very small effect. The latter phenomenon is unexpected but very important for analytical practice. Increase in the adsorbent mass prevents the losses of weakly adsorbed analytes without the need to resort to increasing the purging gas volume. The water desorption process can easily be monitored and automated by placing a humidity sensor in the outlet channel of the purging gas.