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Description:
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Ion chromatography (IC ) is presently the preeminent technique for ionic analysis in atmospheric measurements . High temporal resolution measurement of atmospheric gases and constituents of particulate matter (PM ) is important to understand the chemistry and sources of atmospheric pollution . The application of hollow and filament -filled single asymmetric membrane fibers , consisting of a thin silicone layer on a tubular microporous support for removing CO2 in suppressed ion chromatography effluents is described . With appropriate choice of the removal device and operating conditions , CO2 can be essentially quantitatively (99+ % ) removed . This device further reduces the background conductivity from carbonate -based eluents after suppression . In hydroxide eluent chromatography , the device largely removes the response from CO2 present in the samples ; this greatly aids atmospheric trace gas analysis by IC .
A low -pressure (400 psi ) , fully automated , semi -continuous Gas Particle Ion Chromatography (GPIC ) system has been developed . Soluble gas collection is accomplished with a parallel plate wet denuder (PPWD ) . A hydrophobic filter based continuous particle collector (PC ) collects and continuously extracts the soluble component in atmospheric particulate matter . Two conductivity detectors are used for anion signals and ammonium , respectively . This instrument measures three most important constituents , ammonium , sulfate and nitrate in fine particulate matter (PM2 .5 ) as well as soluble acidic and basic gases like HNO3 , SO2 and NH3 .
A second Gas Particle Ion Chromatograph (GPIC ) was developed . This compact instrument also measures soluble ionogenic gases and ionic constituents in PM2 .5 . A closed liquid flow path membrane denuder collects soluble gases and a continuously wetted hydrophilic filter -based particle collector collects the particles . A single , multi -port , syringe pump handles all the liquid aspiration and dispensation . Preceded by the sampling devices , the sample processing part interfaced with an ion chromatograph permits automated collection and measurements of collected samples . A single conductivity detector is used to measure not only anions but also ammonium . The flow configuration results in an ammonium peak before anion peaks in the chromatogram . The system measures ammonia , organic acids (such as acetic , formic and oxalic acids ) , HCl , HONO , SO2 , HNO3 , and the corresponding ions in the aerosol phase . |