Evaluation and validation of detection limits for trace gas detection based on infrared spectroscopy

Abstract

Fourier Transform Infrared Spectroscopy (FTIR) technology is widely used due to its advantage of simultaneous multicomponent measurement. However, the scientific evaluation of its true Limit of Detection (LOD) has lacked systematic research. This study established an infrared spectroscopic gas detection system based on a multiple-reflection long-path absorption cell and conducted research on LOD evaluation methods for three gases: methane, carbon monoxide, and ammonia. By combining theoretical simulations from the HITRAN database with actual measured spectra, characteristic absorption bands that are free from interference by background water vapor and carbon dioxide were optimally selected. Independent sample injection tests were performed under identical system conditions, and the detection limit was calculated using a statistical standard deviation model. This study verified that the evaluation model based on continuous multiple injections and the standard deviation method can objectively and realistically reflect the instrument's ultimate detection capability, providing a rigorous methodological basis for the quantitative analysis of multi-component gases in complex working conditions.