Development of mass spectroscopic technique for nitric acid measurements

为了准确测量硝酸，需要建立一种可靠的校准方法。为此，我们从加热到40 ℃的渗透管中产生HNO 3蒸气。然后将其与零空气混合以引入总活性氮（NOy）检测器。从NOy信号确定HNO 3混合比。此外，HNO 3的生成速率与NOy数据估计的HNO 3生成速率在10%以内。当将含有HNO 3的空气引入HNO 3测量系统的入口时，显著的滞后持续超过20分钟。当HNO_3混合比为0.1-10 ppbv的空气引入质谱系统时，观察到HNO_3信号，其与HNO_3混合比大致成正比。然而，即使在不添加HNO 3的情况下，也观察到对应于0.05- 0.1ppbv的HNO 3信号。该信号被解释为是由于HNO 3从质谱系统的壁上释放。这表明，为了以高时间分辨率测量HNO 3，抑制背景信号是重要的。

In order to measure nitric acid (HNO3) accurately, we need to establish a reliable method of calibration. For this purpose, we generated HNO3 vapor from permeation tube heated at 40 C.It was then mixed with zero air to be introduced into total reactive nitrogen (NOy) detector. HNO3 mixing ratios were determined from the NOy signals. In addition, the rate of HNO3 generation agreed with that estimated from the NOy data to within 10 %. When the air containing HNO3 was introduced into the inlet of HNO3 measuring system, significant hysterisis continued for over 20 minutes. Bu reducing the length of the inlet tube, significant improvement was observed.When air with HNO3 mixing ratios of 0.1-10 ppbv was introduced into the mass spectrometric system, HNO3 signals were observed, roughly proportional to the HNO3 mixing ratios. However, HNO3 signals corresponding to 0.05-0.1 ppbv were observed even in the case where no HNO3 was added. This signal is interpreted to be due to the release of HNO3 from the wall of the mass spectrometric system. This shows that it is important to suppress the background signals in order to measure HNO3 with high temporal resolutions.