Development of new analytical techniques for NOx speciation in the environment

A previously developed analysis technique capable of speciating and providing nanogram concentration determinations for several atmospheric nitrogen compounds was investigated further. This analysis system utilized glass hollow tubes, interior coated with chemisorbing compounds to preconcentrate HNO{dollar}sb3{dollar}, HNO{dollar}sb2{dollar}, NO{dollar}sb2{dollar}, and NO from a flowing sample gas stream. Chemically coated, sand-packed tubes were used to collect NH{dollar}sb4sp{lcub}+{rcub}{dollar} and NO{dollar}sb3sp{lcub}-{rcub}{dollar} plus NO{dollar}sb2sp{lcub}-{rcub}{dollar}. The preconcentrated analytes were thermally desorbed in an inert gas stream flowing into a chemiluminescence detector.; In this study, an analysis modification was developed that allows for the separation and determination of NO{dollar}sb2sp{lcub}-{rcub}{dollar} and NO{dollar}sb3sp{lcub}-{rcub}{dollar} collected on the packed and hollow tube surfaces. Glacial acetic acid fumes, when passed over the preconcentration surface, removed NO{dollar}sb2sp{lcub}-{rcub}{dollar} as gaseous HNO{dollar}sb2{dollar}, which was then chemically converted to NO for chemiluminescence detection. Collected NO{dollar}sb3sp{lcub}-{rcub}{dollar} was unaffected by the acid and was determined in a separate analysis step by thermal desorption. This analysis technique provided specific concentration information for particulate NO{dollar}sb2sp{lcub}-{rcub}{dollar} and particulate NO{dollar}sb3sp{lcub}-{rcub}{dollar} and was used to examine the effect of oxidative processes that occur on chemisorbing surfaces, in general.; The hollow- and packed-tube analysis system was also incorporated into an automatic analyzer arrangement capable of providing semi-continuous determinations for these atmospheric nitrogen compounds. This four-component, computer-controlled analyzer operated unattended for periods of up to one week. The instrument was also used to analyze for NOx components in tobacco smoke.; The automatic NOx analyzer was operated for a five-day period aboard ship in the Gulf of Mexico and for an eight-day period in Tampa, Florida, providing both remote-site and urban-site NOx diurnal variation information.; The use of acidic vanadium(III) solution was investigated for the reduction of aqueous NO{dollar}sb2sp{lcub}-{rcub}{dollar} and NO{dollar}sb3sp{lcub}-{rcub}{dollar} to NO for chemiluminescence detection. NO{dollar}sb2sp{lcub}-{rcub}{dollar} was reduced to NO in room temperature vanadium(III), while NO{dollar}sb3sp{lcub}-{rcub}{dollar} was reduced to NO in vanadium(III) solution heated to 80-90{dollar}spcirc{dollar}C. In this manner, NO{dollar}sb2sp{lcub}-{rcub}{dollar} and NO{dollar}sb3sp{lcub}-{rcub}{dollar} contained in the same sample were determined separately, using a temperature-cycling routine. The detection limit for this analysis system was 2-3 nanograms of nitrite or nitrate-nitrogen, giving a lower concentration detection limit of approximately 1 nM of nitrogen compound.