Abstract: Nonlinear response of a pulsed flame photometric detector （PFPD） in an oxygen-bearing sample matrix limits trace sulfur analysis, particularly at low concentration levels. In this study, a gas chromatography-pulsed flame photometric detector （GC-PFPD） system integrating gas control, pulsed flame ignition, detection, and signal processing was developed for trace H₂S detection. To address oxygen-induced nonlinearity, a signal processing method was proposed based on the sulfur-specific chemiluminescence delay characteristics. This method utilizes delay-window integration to isolate sulfur signals from hydrocarbon emission interference at the ignition onset, followed by a square-root transformation to linearize the response. The performance was evaluated using nitrogen and air as carrier gases by comparing full-spectrum signal integration and delay-window integration strategies. Under nitrogen, the square root of delay-window integration exhibited excellent linearity with a coefficient of determination （R²） of 0.999 7, significantly outperforming the full-spectrum integration （R²=0.989 0）. Under air, the square root of delay-window integration maintained high linearity （R²=0.998 9）, which was also markedly superior to that of the full-spectrum integration （R²=0.914 4）, demonstrating effective suppression of the oxygen-induced matrix effect. At a concentration of 1.277 nmol/L, the sulfur peaks were temporally separated and clearly distinguished from hydrocarbon interference peaks at the initial ignition stage, yielding a signal-to-noise ratio greater than or equal to 10. Based on blank noise and the linearized response, the instrument detection limit was determined to be 0.613 nmol/L. Repeatability tests with ten consecutive measurements at 5.109 nmol/L showed a relative standard deviation of 1.38%, indicating favorable short-term stability. The developed GC-PFPD system and delay-window method achieve high-linearity and high-sensitivity detection of trace H₂S under oxygen-containing conditions without hardware modifications. This approach enhances quantitative accuracy in complex gas matrices, providing a practical solution for environmental monitoring and the development of domestic analytical instruments.

Key words: gas chromatography （GC）, pulsed flame photometric detector （PFPD）, trace-level detection, sulfides