Microplasma emission spectroscopy of carbon dioxide using the carbon monoxide Ångström system

Anders Persson,Martin Berglund

doi:10.1063/1.5134947

Abstract

The present paper describes a system and method for indirect emission spectroscopy of CO2 in the visible spectrum. This is achieved by using a microplasma spectrometer that first converts CO2 into CO and then measures emissions from the CO Ångström system (B1Σ + → A1Π) at 560 nm. The experiments were performed on gaseous samples of CO2, mixed in both N2 and air, to concentrations between 0.01% and 100%. In addition to the microplasma spectrometer, the process was monitored by mass spectrometry with a residual gas analyzer. The CO2 to CO conversion efficiency was found to be very high, reaching a maximum of 41% at close to 100% selectivity. Furthermore, the CO Ångström system was shown to facilitate excellent spectroscopic measurement of CO2 concentrations below 10%, with a linearity of R2 &gt; 0.99 and an expected limit of detection in the parts-per-thousands range. The most promising aspect of the results was that the analysis was performed on extremely small total sample amounts where the gas flow through the systems was in the 0.1 µmole/s range. Hence, the present system has the prospect of filling a void in current sensor technology, where inexpensive and easy-to-use optical systems, such as nondispersive infrared sensors, cannot handle small sample amounts, while mass spectrometers, which can handle such samples, still are expensive, complex, and bulky.

Highlights

Carbon dioxide is probably the most common sample molecule in gas spectroscopy with applications spanning from regulating ventilation systems1 and tracking industrial processes2 to environmental monitoring3 or even space science.4 The most common sensors are based on nondispersive infrared (NDIR) spectroscopy and can and accurately detect and quantify CO2 down toward a few ppm.5 More precise optical instruments based on, e.g., cavity ringdown spectroscopy6 or off-axis integrated cavity output spectroscopy7 can reduce the limit of detection orders of magnitude more. most of these sensors strive toward minimizing dead volumes, they all require fairly large total sample amounts to perform an accurate analysis
In addition to the microplasma spectrometer, the process was monitored by mass spectrometry with a residual gas analyzer
The most promising aspect of the results was that the analysis was performed on extremely small total sample amounts where the gas flow through the systems was in the 0.1 μmole/s range

Summary

Introduction

Carbon dioxide is probably the most common sample molecule in gas spectroscopy with applications spanning from regulating ventilation systems and tracking industrial processes to environmental monitoring or even space science. The most common sensors are based on nondispersive infrared (NDIR) spectroscopy and can and accurately detect and quantify CO2 down toward a few ppm. More precise optical instruments based on, e.g., cavity ringdown spectroscopy or off-axis integrated cavity output spectroscopy can reduce the limit of detection orders of magnitude more. most of these sensors strive toward minimizing dead volumes, they all require fairly large total sample amounts to perform an accurate analysis. Carbon dioxide is probably the most common sample molecule in gas spectroscopy with applications spanning from regulating ventilation systems and tracking industrial processes to environmental monitoring or even space science.. The most common sensors are based on nondispersive infrared (NDIR) spectroscopy and can and accurately detect and quantify CO2 down toward a few ppm.. More precise optical instruments based on, e.g., cavity ringdown spectroscopy or off-axis integrated cavity output spectroscopy can reduce the limit of detection orders of magnitude more. Most of these sensors strive toward minimizing dead volumes, they all require fairly large total sample amounts to perform an accurate analysis. In applications where the total sample amount is inherently limited, e.g., when analyzing single cells or rare isotopes, other methodology and technology are required.

Methods

Results

Conclusion