Development of Automatic and Countinuous Measurement Equipment for Monitoring of Aldehydes and Carboxylic Acids in the Urban Atmosphere

点击翻译按钮获取中文摘要

This study describes the methodolgy developed for monitoring system for automatic aldehydes in the urban atmosphere by using a diffusion scrubber connected to HPLC.The diffusion scrubber consists of a porous polytetrafluoroethylene (PPTFE) tube (25cm length, 4mm i.d.size, 77% surface porosity) concentrically disposed within a glass jacket of 6.6mm i.d.for collection of gaseous HCHO and CH_3CHO.A trapping solution (66ppmDNPH/3%H_3PO_4/ACN) was introduced gravitatively into annular space of diffusion scrubber. And a sample air was drawn into PPTFE tube at a rate of 0.2l/min. The automated system used diffusion scrubber connected to a high performance liquid chromatqgraph (DS-HPLC). After the air sampling, the trapping solution was moved into a mixing chamber and adjusted to constant volume of 2ml by an optical fiber sensor, and then the sample solution was injected into HPLC (Shimazu LC-10A) by an autoinjector. Then, aldehyde-DNPH derivatives in the sample solution were separated and determine by UV detector set at 360nm. The separation column used was a ODS (Shim-pack VP-ODS) heated at 40ﾟC and the mobile phase was used acetnitrite/water (40/60 v/v) at flow rate of 0.2ml/min. During the sample analysis, the diffusion scrubber was cleaned with a new trapping solution and got ready for the next sampling. All operations mentioned above were controlled by a sequence prograrnmer (muFA20, Yokogawa electric Co.) governing all the electromagnetic valves, pumps and HPLC periodically, then aldehydes measurement was performed automatically within 60 min. The detection limits of HCHO and CH_3CHO by DS-HPLC were 0.1 ppbv, respectively, for 12l of air sampling volume. Therefore, the developed DS-HPLC system is suitable for the measurement of HCHO and CH_3CHO in the urban atmosphere.