Abstract. The measurement of volatile organic compounds (VOCs) can be influenced by ozone (O₃), resulting in sampling artifacts that corrupt the data obtained. Published literature reports both, positive (false enhancements of signal) and negative (loss of signal) artifacts in VOC data due to ozonolysis occurring in the sample gas. To assure good data quality it is essential to be aware of such artifact inducing processes, characterize them and try to minimize the impact with a suitable sampling setup. Here we present results from experiments with a sodium thiosulfate ozone scrubber (Na₂S₂O₃), which is a cost effective and easily applied option for O₃ scavenging during gas phase sampling. Simultaneous measurement of selected organic trace gases using gas chromatography- and proton transfer reaction-mass spectrometry was performed at different ozone levels (0–1 ppm) and different relative humidities (0–80 %). In this way both tropospheric and stratospheric conditions were examined. The measured data show that several carbonyl compounds including acetaldehyde, acetone and propanal show artificial signal enhancement when ozone is present at higher concentrations (>150 ppb) in dry air, while analytes with double bonds like isoprene (measured with GC-MS) and terpenes show lower signals due to reaction with ozone. Both effects can be eliminated or in the case of sesquiterpenes substantially reduced by using Na₂S₂O₃ impregnated quartz filters in the inlet line. With the chosen scrubbing material, relative humidity (RH) substantially improves the scrubbing efficiency. Under surface conditions between 50–80 % RH, the filter allows accurate measurement of all species examined.

中文翻译：

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臭氧和湿度对使用和不使用 Na2S2O3 臭氧洗涤器的 PTR-MS 和 GC-MS VOC 测量的影响

摘要。挥发性有机化合物 (VOC) 的测量可能会受到臭氧 (O ₃ ) 的影响，从而导致采样伪影破坏所获得的数据。已发表的文献报道了由于样气中发生的臭氧分解，VOC 数据中存在正（信号的错误增强）和负（信号丢失）伪影。为确保良好的数据质量，必须了解此类伪影诱导过程，对其进行表征，并尝试使用合适的采样设置将影响降至最低。在这里，我们展示了硫代硫酸钠臭氧洗涤器 (Na ₂ S ₂ O ₃ ) 的实验结果，这是一种成本效益高且易于应用的 O _3选项气相采样期间的清除。在不同的臭氧水平 (0–1 ppm) 和不同的相对湿度 (0–80 %) 下，使用气相色谱法和质子转移反应质谱法同时测量选定的有机痕量气体。以这种方式检查了对流层和平流层条件。测量数据表明，当臭氧在干燥空气中以较高浓度 (>150 ppb) 存在时，包括乙醛、丙酮和丙醛在内的几种羰基化合物显示出人工信号增强，而具有双键的分析物如异戊二烯（用 GC-MS 测量）和萜烯由于与臭氧反应而显示较低的信号。_{通过使用 Na 2} S ₂ O ₃可以消除这两种影响，或者在倍半萜的情况下显着降低入口管线中的浸渍石英过滤器。使用所选的洗涤材料，相对湿度 (RH) 显着提高了洗涤效率。在 50–80% RH 的表面条件下，过滤器可以准确测量所有检查的物种。