A laser-photolysis fragment-fluorescence (LPFF) method for the detection of gaseous nitric acid in ambient air

Abstract

The development and first tests of a novel method for the direct, sensitive, selective, and fast detection of gaseous nitric acid in air are described. The detection method is based on the laser-photolysis fragment-fluorescence (LPFF) method using 193 nm (ArF) laser light. The photolysis process yielding OH fluorescence has been thoroughly investigated. Up to now, the method has been found to be practically free of interferences. The mixing ratio for nitric acid is measured on-line with a detection limit of about 0.1 ppbv for an accumulation time of the signal of 10-t5 min. A number of tests and field measurements were performed to demonstrate the feasibility and limits of the described detection method.

Measurement of gaseous HNO3 over the Atlantic Ocean

“…This trend was observed during this journey on a number of days but the substantial variability of the HNO~ mixing ratio and the insufficient detection limit prevents giving a clear, statistically significant diurnal cycle. Similar diurnal cycles were also noticed before (Warneck, 1988;Papenbrock and Stuhl, 1990b) for land-based measurements. Because of low NO2 concentrations, the formation by the reaction OH + NO 2 appears to be too slow to explain the increased mixing ratio of HNO 3 during the day.…”

“…The total dwell time of the sample in all these tubes is estimated to be about 2 s. Because of technical reasons (very large mass flows through the vacuum cleaner, flow rate not accurately known), the calibration was not performed at the inlet of the sampling system, but the calibration mixture was introduced at the needle valve position. In recent tests, it was shown that it didn't matter whether the calibration was performed at the sampling position at the separator or at the adjustable needle valve (Papenbrock and Stuhl, 1990b). This instant and direct calibration was performed twice a day.…”

Atmospheric measurements of gas-phase HNO<sub>3</sub> and SO<sub>2</sub> using chemical ionization mass spectrometry during the MINATROC field campaign 2000 on Monte Cimone

“…Intercomparison campaigns using different experimental methods for measuring gaseous HNO 3 , including the filter-pack method, denuder-tube technique and tunable-diode-laser absorption method have found only relatively poor agreement between the different techniques even at relatively high HNO 3 levels and demonstrated that none of the techniques was capable of measuring HNO 3 below 100 pptv for integration times of less than 10 min (Gregory et al, 1990). Further methods, the mist chamber method of Talbot et al (1990) and the laserphotolysis fragment-fluorescence method of Papenbrock and Stuhl (1990), reported detection limits of 10 and 100 pptv, respectively, for an integration time of 10 min. Recently novel HNO 3 measurement techniques, based on chemical ionization mass spectrometry (CIMS), have been developed to overcome the drawbacks of the other techniques Schneider et al, 1998;Huey et al, 1996;Mauldin et al, 1998;Miller et al, 2000;Furutani et al, 2002).…”

Development and characterization of a fast measurement system for gas‐phase nitric acid with a chemical ionization mass spectrometer in the marine boundary layer

“…It was pointed out that they suffered interference or artifacts [ Hering et al , 1988; Fehsenfeld et al , 1998] and low time resolution. Even for the recently developed mist chamber [ Talbot et al , 1990], diffusion scrubber [ Komazaki et al , 2001], and laser‐photolysis fragment‐fluorescence methods [ Papenbrock and Stuhl , 1990], >10 min is needed to reach the lower detection limit of 10 pptv. It is also gradually recognized that the specific sticky character of HNO 3 molecules makes it difficult to reliably quantify the HNO 3 concentration [ Crosley , 1996; Parrish and Fehsenfeld , 2000].…”