Rapid sub-ppm hydrogen (H₂) detection using automated loop-injection quadrupole mass spectrometry

Rapid and reliable detection of hydrogen is essential for safety monitoring in hydrogen production, storage, and transportation systems. Existing sensor and instrument-based methods-including optical techniques, gas chromatography, and conventional QMS systems-are constrained by slow response, limited selectivity, high detection limits, and an inability to directly detect hydrogen due to its weak infrared absorption, making them unsuitable for rapid and reliable trace-level monitoring. In this study, an automated loop-injection quadrupole mass spectrometry (ALI-QMS) method was developed for rapid quantitative detection of trace hydrogen. The system integrates an automated loop-injection module with a heated quartz inert capillary (120 °C) and bypass pumping configuration, enabling fast sample transfer with a delivery time below 0.3 s. Using dynamically diluted certified reference materials, a linear calibration (R² = 0.9999) was obtained over the concentration range of 2.07-199.35 μmol mol^-1 hydrogen (H₂) in nitrogen. The method enables automated measurements with a 30 s analytical cycle while consuming only 10 mL of sample gas and maintaining stable performance under varying pressure conditions representative of pipelines and gas cylinders. The developed system achieved a detection limit of 0.62 μmol mol^-1, a response time of 0.67 s, and excellent repeatability (0.27 % RSD). Accuracy evaluation using certified reference materials showed relative biases within ±5 %. These results demonstrate that the proposed approach provides a rapid and sensitive method for quantitative hydrogen monitoring, with strong potential for real-time hydrogen leak detection in industrial systems and confined environments.