Cross Interference Characteristics of Photoacoustic Spectroscopy Multi-gas Analyzer

A photoacoustic spectroscopy multi-gas detection system based on infrared heat radiation light source was developed. The broadband mid-infrared thermals radiation source and band-pass filter were used to generate the photoacoustic excitation light. Combined with a small-volume non-resonant photoacoustic cell, the time-sharing measurement of multi-component gas concentration was realized. The parameters of the mid-infrared bandpass filter were determined by analyzing the main factors of cross-interference among multi-component gases and the infrared absorption spectrum of target gases. To determine the quantitative relationship of cross interference among the gases to be measured, the photoacoustic spectrometer system was calibrated by using the standard gas, and a humidifier was used to analyze the interference from water vapor. The experimental results showed that the interference levels of C2H2 to CH4 and CH4 to C2H6 reached 10.49 mu V/(mu L/L) and 18.66 mu V/(mu L/L) respectively, and the interference between other hydrocarbon gases can be ignored. The responsiveness of CO2 to CO, CH4, C2H2 and C2H4 interference was 1.615 mu V/(mu L/L), 0.055 mu V/(mu L/L), 0.130 mu V/(mu L/L)and 0.016 mu V/(mu L/L), respectively. In addition, water vapor will cause certain interference to C2H2, CH4, C2H6, C2H4, CO and CO2, and the responsiveness of the interference was 0.591 mu V/(mu L/L), 0.421 mu V/(mu L/L), 0.071 mu V/(mu L/L), 0.007 mu V/(mu L/L), 0.051 mu V/(mu L/L) and 0.055 mu V/(mu L/L). The experimental results indicated that there was a high level of interference when detecting CH4 in C2H2 background, C2H6 in CH4 background, CO in CO2 background, and other target gases in high concentration water vapor background, which should be considered in the measurement process.