Validation of an Electronic VOC Sensor Against Gas Chromatography–Mass Spectrometry
Xiao Dong Zhu, Waqar Ahmed, Kamila Schmidt, Rita Elaine de Souza BARROSO, Stephen J. Fowler, Christopher F. Blanford
Abstract
Gas chromatography (GC) is a standard method to quantify volatile organic compounds (VOCs). However, this technique has high capital costs and is not suitable for real-time monitoring. Commercial metal oxide (MOX) sensors, on the other hand, are compact, cost-effective, and capable of providing real-time data to inform process control. This work used <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula>-pinene in dry argon as a model system to compare the VOC detection performance of Bosch Sensortec’s BME680 sensor against the same VOC analyzed by thermal desorption-GC–mass spectrometry (TD-GC-MS) after adsorption onto a polymeric sorbent. Electronic sensor measurements were conducted in temperature- and atmosphere-controlled environments to minimize confounding effects on the resistance response. The BME680 electronic sensors showed limits of detection (LODs) ranging from 20 to 39 parts per billion (ppb), with a linear range above 40 ppb. The GC-MS in multiple reaction monitoring (MRM) mode exhibited an LOD at (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.61~\pm ~0.33$ </tex-math></inline-formula>) ppb and a linear range from 1 to 100 ppb, equivalent to an adsorption volume of 2-<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula>L VOC gas samples at concentrations of 1–100 ppb of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula>-pinene in the gas control system. The overlapping calibration region ranges for these two methods spanned from 40 to 100 ppb. There was >30% sensor-to-sensor variability in the response from the MOX sensing components that were reduced to 5%–7% using a two-point calibration method.