Advannces in ion chromatograpy for environmental applications

Ion chromatography (IC) is a widely used analytical tool for the determination of many ionic species. Applications of ion chromatography extend over a wide range of chemical analyses. Introduction of eluent suppression in the mid-1970s extended the boundaries of conductometric detection into trace analysis. Current state-of-the-art IC systems require only water to operate, exhibit excellent reliabilities, and provide the ability of sample preconcentration and simultaneous multiple ion measurement, making them attractive for atmospheric analysis.

Atmospheric particulate matter (PM) contains many inorganic and organic soluble ions. A number of those are weak acid anions that are largely undetectable in suppressed ion chromatography. An improved method that uses sequential suppressed and unsuppressed IC for the sensitive detection of both common anions and very weak acid anions has been investigated. After suppressed conductometric detection, the effluent is passed into a membrane device where KOH is passively introduced into the eluent stream using Donnan forbidden leakage.

High temporal resolution measurement of atmospheric gases and constituents of atmospheric particulate matter (PM) is important to understand the chemistry and sources of atmospheric pollution. New continuous collection devices coupled with IC systems for fully automated measurement of soluble inorganic gases and soluble ionic constituents of atmospheric PM have been developed. Soluble gas collection is accomplished with a parallel plate wet denuder (PPWD).

For particle collection, an automated alternating filter-based system was initially developed. This system uses two glass-fiber filters that alternate between sampling, and washing and drying. More recently, a continuous soluble particle collector (PC) of simpler design has been developed; this device does not use steam. Preceded by a denuder and interfaced with an ion chromatograph, this compact collector permits automated collection and continuous extraction of soluble anions and ammonium ion in atmospheric particulate matter. The systems have been deployed in a number of major field studies held in urban and suburban locations in the United States.