Portable analytical system integrating purge and trap and microplasma optical emission spectrometry for online discriminative detection of NO.

Pollution caused by nitrogen oxides (NO, mainly NO and NO) has attracted considerable attention due to its negative implications on the environment and human health. Herein, a novel, portable, and battery-operated system integrating a purge and trap (P&T) system with a miniaturized point discharge optical emission spectrometer (μPD-OES) was developed for monitoring atmospheric NO. Among NO, NO can be selectively and directly absorbed by sodium hydroxide (NaOH) solution and converted to nitrite (NO). In contrast to NO, NO cannot be absorbed by NaOH and must be oxidized to NO by KMnO prior to its absorption. When NO and NO samplers were exposed simultaneously, NO can be calculated as the difference. The concentration of NO in the air was determined by analyzing the NO. The obtained NO solution was purged with an argon carrier gas at a rate of 400 mL min for 5 min to remove all the volatile organic compounds contained in the solution before reacting with cyclamate to generate volatile cyclohexene, which was efficiently isolated and preconcentrated by P&T. Subsequently, the cyclohexene was desorbed from the P&T unit and swept into the μPD-OES for its detection under optimized conditions. The system demonstrated a detection limit of 0.02 ppbv (0.04 μg/m) for NO, surpassing conventional methods. Precision expressed as the relative standard deviation (RSD, n = 11) was better than 3.5 %. The system was validated by analyzing two NO standard gases and fourteen ambient air samples, and the obtained analytical results demonstrated its promising potential for rapid, sensitive, and precise NO evaluation and monitoring.