Paul Dipayan, Furgeson Amanda, Osthoff Hans D
Department of Chemistry, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada.
Rev Sci Instrum. 2009 Nov;80(11):114101. doi: 10.1063/1.3258204.
A novel measurement technique, thermal dissociation cavity ring-down spectroscopy (TD-CRDS), for rapid (1 s time resolution) and sensitive (precision approximately 100 parts per trillion by volume (10(-12); pptv)) quantification of total peroxy nitrate (SigmaPN) and total alkyl nitrate (SigmaAN) abundances in laboratory-generated gas mixtures is described. The organic nitrates are dissociated in a heated inlet to produce NO(2), whose concentration is monitored by pulsed-laser CRDS at 532 nm. Mixing ratios are determined by difference relative to a cold inlet reference channel. Conversion of laboratory-generated mixtures of AN in zero air (at an inlet temperature of 450 degrees C) is quantitative over a wide range of mixing ratios (0-100 parts per billion by volume (10(-9), ppbv)), as judged from simultaneous measurements of NO(y) using a commercial NO-O(3) chemiluminescence monitor. Conversion of PN is quantitative up to about 4 ppbv (at an inlet temperature of 250 degrees C); at higher concentrations, the measurements are affected by recombination reactions of the dissociation products. The results imply that TD-CRDS can be used as a generic detector of dilute mixtures of organic nitrates in air at near-ambient concentration levels in laboratory experiments. Potential applications of the TD-CRDS technique in the laboratory are discussed.
本文描述了一种新型测量技术——热解离腔增强吸收光谱法（TD-CRDS），用于快速（1秒时间分辨率）且灵敏地（精度约为万亿分之一体积分数（10⁻¹²；pptv））定量分析实验室生成的气体混合物中总过氧硝酸酯（ΣPN）和总烷基硝酸酯（ΣAN）的含量。有机硝酸盐在加热的进样口中解离产生NO₂，其浓度通过532nm的脉冲激光CRDS进行监测。混合比通过相对于冷进样口参考通道的差值来确定。根据使用商用NO-O₃化学发光监测仪同时测量的NO(y)判断，在零空气中（进样口温度为450℃），实验室生成的AN混合物在很宽的混合比范围（0至十亿分之一体积分数（10⁻⁹，ppbv））内的转化是定量的。PN在高达约4 ppbv（进样口温度为250℃）时的转化是定量的；在更高浓度下，测量会受到解离产物重组反应的影响。结果表明，在实验室实验中，TD-CRDS可作为近环境浓度水平下空气中有机硝酸盐稀混合物的通用检测器。讨论了TD-CRDS技术在实验室中的潜在应用。
