Fourier transform infrared analysis of gas composition in low-volume light bulbs

Fourier transform infrared spectroscopy has been used for in situ analysis of HBr, CH3Br, and CO within light bulbs at different stages of burning time. The interference fringes originated in the quartz walls of the bulbs have been eliminated by different methods. The NIPALS procedure yielded higher S/N ratio than the fringe-elimination method applied. The CO and HBr showed time-dependent concentration changes during the burning period. The maximum CO concentration (approximately 6 ppm) was detected after 30-50 s of burning time, and then it practically burned out after 5 h. The HBr concentration increased in the first 3 min of burning, and then its concentration stabilized at a 10-15 ppm level. After 5 s of illumination, the CH3Br concentration became undetectable.