Determination of total carbon in air particulate matters by thermal combustion-ion chromatography

Abstract

A new analytical procedure based on Thermal Combustion-Ion chromatography was developed for an hourly determination of total carbon in air particulate matters using equipment readily available in the chemical laboratory. Optimised conditions were developed for both thermal combustion (oxygen flowrate at 100 ml min-1 for 15 minutes at 900°C), sampling of carbon dioxide generated (20 ml of 50 mM KOH with 10 drops of n-butanol as scrubbing solution) and carbonate determination by non-suppressed ion chromatography (0.6 mM potassium hydrogen phthalate as eluent), giving a working range of 0.1 to 40 mg-C 1-1 or 20 to 800 μg-C and a detection limit of 0.02 mg-C 1-1 or 0.4 μg-C using a 20 ml scrubbing solution and 0.2 μg m-3 on hourly basis with a flowrate of 33 1 min-1. The method offers comparable analytical performance and wider working range as the conventional NDIR method which uses dedicated equipment. The reliability of the method has been established using graphite and various organic standard compounds with results showing satisfactory recoveries and good precision. Carbonaceous matters from the blank glass filters and the interference of other anions had been found not to affect the validity of the results. The method developed has been successfully applied for field studies at two selected sites in Hong Kong with commercial and industrial activities.