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

介绍了一种用于城市大气中自动醛监测系统的方法。扩散塔由聚四氟乙烯(PPTFE)多孔管(长25 cm，直径4 mm，表面孔隙率77%)集中放置在直径为6.6 mm的玻璃套内，用于收集气体甲醛和CH3CHO。样品空气以0.2L/min的速度送入PPTFE管内。自动化系统使用扩散洗涤器连接到高效液相色谱仪(DS-HPLC)。空气采样后，将捕集液移入混合室，用光纤传感器调节至2ml的恒定体积，然后用自动进样器将样品液进样到岛津LC-10A。然后，样品溶液中的醛-DNPH衍生物被分离，并在360 nm处进行紫外检测。色谱柱为Shim-pack VP-ODS柱，流动相为乙酸乙酯/水(40/60v/v)，流速为0.2ml/ﾟ。在样品分析过程中，扩散洗涤器被一种新的捕集溶液清洗，为下一次采样做好准备。上述所有操作均由序列编程器(muFA20，横河电气公司)控制。周期性地控制所有电磁阀、泵和高效液相，然后在60min内自动进行醛的测量。对于12L空气采样量，DS-HPLC法对甲醛和甲烷的检出限分别为0.1ppbv。因此，所研制的DS-HPLC系统适用于城市大气中甲醛和甲烷的测定。

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.