Computerized data acquisition and analysis applied to chemiluminescence detection of nitric oxide in headspace gas

Nitric oxide (NO) is an important messenger molecule which is implicated in an ever increasing number of physiological, pharmacological, and pathological processes. Quantitative and qualitative analysis of NO has been hindered by its extremely short half-life in biological systems, and thus there is a keen interest in developing accurate techniques to measure NO. We have employed a modification of the chemiluminescence NO detection technique used by J.F. Brien et al. (J Pharmacol Methods 1991;25:19-27) to measure the photo-induced release of NO from several structurally unrelated drugs including streptozotocin (STZ) and sodium nitroprusside (SNP). We were unable to calibrate the instrument by measuring peak heights from an attached chart recorder in response to increasing amounts of injected nitric oxide. The extremely fast rise times of peaks from the chemiluminescence detector exceeded the capacity of the pen-servomotor mechanism of the chart recorder to accurately measure nitric oxide response curves. We, therefore, digitized the detector's output with an analog-to-digital convertor board connected to an IBM PC. The signal was acquired and analyzed by a program called NOXIDE. Using the NOXIDE program we were able to accurately measure both the peak height and total integrated area of each peak and show that the area, but not peak height, correlates extremely well (r = 0.9991) with standard injections of 20.0-750.0 pmol NO.