Ruiz-Bevia Francisco, Fernandez-Torres Maria J, Blasco-Alemany Maria P
Chemical Engineering Department, University of Alicante, Carretera San Vicente del Raspeig, San Vicente del Raspeig, Alicante, Spain.
Anal Chim Acta. 2009 Jan 26;632(2):304-14. doi: 10.1016/j.aca.2008.11.022. Epub 2008 Nov 18.
Purge-and-trap gas chromatography-mass spectrometry (PT-GC-MS) has become an accepted method for the analysis of trihalomethanes (THMs) in water. The purge-and-trap technique is based on an efficient transfer of volatile organic compounds from the liquid (contained in the purge chamber) to the gaseous phase by bubbling with an inert gas. The aim of this work was to study the purge system's efficiency by means of several consecutive purge cycles lasting 11 min each of the same liquid sample. The concentration range chosen of THMs was very wide [5-200 microg L(-1)]. The inert gas flow rate was 40 mL min(-1), and experiments were performed at temperatures of 25, 35 and 50 degrees C. Bromoform (CHBr(3)), the least volatile compound, needed 19 cycles to be purged quantitatively at a concentration of 200 microg L(-1) and only 7 cycles at 5 microg L(-1) for a 25 mL sample at 25 degrees C. Chloroform (CHCl(3)), the most volatile compound, required 4 cycles to be fully extracted at 200 microg L(-1) and 2 at 5 microg L(-1). Finally, Novak's theoretical model, based on the distribution constant between gas and liquid phases, was used to correlate the THMs purging extraction data.
吹扫捕集气相色谱 - 质谱联用（PT - GC - MS）已成为分析水中三卤甲烷（THMs）的一种公认方法。吹扫捕集技术基于通过用惰性气体鼓泡，将挥发性有机化合物从液体（包含在吹扫室中）高效转移到气相。这项工作的目的是通过对同一液体样品进行几个连续的吹扫循环（每个循环持续11分钟）来研究吹扫系统的效率。所选择的三卤甲烷浓度范围非常宽[5 - 200微克/升（-1）]。惰性气体流速为40毫升/分钟（-1），实验在25、35和50摄氏度的温度下进行。对于25毫升样品，在25摄氏度下，挥发性最小的化合物溴仿（CHBr(3)），在浓度为200微克/升（-1）时需要19个循环才能定量吹扫，而在5微克/升（-1）时仅需7个循环。挥发性最大的化合物氯仿（CHCl(3)），在200微克/升（-1）时需要4个循环才能完全萃取，在5微克/升（-1）时需要2个循环。最后，基于气液相之间分配常数的诺瓦克理论模型被用于关联三卤甲烷吹扫萃取数据。
