A portable, high-speed, vacuum-outlet GC vapor analyzer employing air as carrier gas and surface acoustic wave detection.
A portable, high-speed, vacuum-outlet GC vapor analyzer employing air as carrier gas and surface acoustic wave detection.
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DOI：
10.1021/ac0103726
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发表时间：
2001-09
影响因子：
7.4
通讯作者：
J. Whiting;C. Lu;E. Zellers;R. Sacks
中科院分区：
文献类型：
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作者：
J. Whiting;C. Lu;E. Zellers;R. Sacks
在出口压力高达0.8大气压下，使用低死体积聚合物涂层表面声波（SAW）检测器，以大气压空气为载气的出口GC。系统出口压力从0.1大气压增加到0.8大气压，导致检测器灵敏度成比例增加，柱效显著增加。后一种效应是由于最佳载气速度在空气中比在更常规的载气如氦气或氢气中低，这是由于蒸汽在空气中的二元扩散系数较小。一个12米长，0.25毫米内径。由4.5-M二甲基聚硅氧烷和7.5-M三氟丙基甲基聚硅氧烷组成的串联柱系综，在0.5大气压的出口压力下操作，对于3分钟等温分析提供高达4 × 10（4）的理论塔板和65的峰容量（分辨率，1.5）。在30摄氏度下，在该时间范围内分离蒸气压为8.6至76托的蒸气混合物。SAW检测器池的内部体积< 2微升，允许使用更高的柱出口压力，同时死区时间最小。传感器响应与溶质质量在至少2-3个十年内呈线性关系，并为测试的蒸汽提供20-50 ng的检测限。大气压力空气作为载气，适度的工作压力，和SAW传感器检测的组合非常适合现场仪器，因为它消除了对支持气体的需要，允许使用更小，低功率的泵，并提供了广泛的蒸汽分析物的灵敏度。
Vacuum-outlet GC with atmospheric-pressure air as the carrier gas is implemented at outlet pressures up to 0.8 atm using a low-dead-volume polymer-coated surface acoustic wave (SAW) detector. Increases in the system outlet pressure from 0.1 to 0.8 atm lead to proportional increases in detector sensitivity and significant increases in column efficiency. The latter effect arises from the fact that optimal carrier gas velocities are lower in air than in more conventional carrier gases such as helium or hydrogen due to the smaller binary diffusion coefficients of vapors in air. A 12-m-long, 0.25-mm-i.d. tandem column ensemble consisting of 4.5-m dimethyl polysiloxane and 7.5-m trifluoropropylmethyl polysiloxane operated at an outlet pressure of 0.5 atm provides up to 4 x 10(4) theoretical plates and a peak capacity of 65 (resolution, 1.5) for a 3-min isothermal analysis. At 30 degrees C, mixtures of vapors ranging in vapor pressure from 8.6 to 76 Torr are separated in this time frame. The SAW detector cell has an internal volume of < 2 microL, which allows the use of higher column outlet pressures with minimal dead time. The sensor response is linear with solute mass over at least 2-3 decades and provides detection limits of 20-50 ng for the vapors tested. The combination of atmospheric-pressure air as carrier gas, modest operating pressures, and SAW sensor detection is well-suited for field instrumentation since it eliminates the need for support gases, permits smaller, low-power pumps to be used, and provides sensitivity to a wide range of vapor analytes.