DETERMINATION OF TOTAL CARBON IN AIR PARTICULATE MATTERS BY THERMAL COMBUSTION ION CHROMATOGRAPHY

A new analytical procedure based on Thermal Combustion-Ion chromatogra phy was developed for an hourly determination of total carbon in air p articulate matters using equipment readily available in the chemical l aboratory. Optimised conditions were developed for both thermal combus tion (oxygen flowrate at 100 ml min(-1) for 15 minutes at 900 degrees C), sampling of carbon dioxide generated (20 ml of 50 mM KOH with 10 d rops of n-butanol as scrubbing solution) and carbonate determination b y non-suppressed ion chromatography (0.6 mM potassium hydrogen phthala te as eluent), giving a working range of 0.1 to 40 mg-C l(-1) or 20 to 800 mu g-C and a detection limit of 0.02 mg-C l(-1) or 0.4 mu g-C usi ng a 20 mi scrubbing solution and 0.2 mu g m(-3) on hourly basis with a flowrate of 33 1 min(-1). The method offers comparable analytical pe rformance and wider working range as the conventional NDIR method whic h uses dedicated equipment. The reliability of the method has been est ablished using graphite and various organic standard compounds with re sults showing satisfactory recoveries and good precision. Carbonaceous matters from the blank glass filters and the interference of other an ions had been found not to affect the validity of the results. The met hod developed has been successfully applied for field studies at two s elected sites in Hong Kong with commercial and industrial activities.