GLOW-DISCHARGE ATOMIC-EMISSION SPECTROMETRY FOR THE DETERMINATION OF CHLORIDES AND TOTAL ORGANOCHLORINE IN WATER SAMPLES VIA ONLINE CONTINUOUS GENERATION OF CHLORINE

A method for the determination of ultratraces of chloride in solution by glow discharge atomic emission spectrometry (GD-AES) based on the e volution of molecular chlorine from chloride in an aqueous solution is described. Chloride conversion into volatile chlorine was achieved by continuous chemical oxidation in a flow system, the chlorine then bei ng separated from the aqueous phase ria an on-line gas-liquid separato r. Radiofrequency (rf) powered GD and direct current (dc) GD sources w ere investigated comparatively, while detection was performed, both in the visible (VIS) at 479.45 nm and in the near infrared (NIR) at 837. 60 nm, using a charge-coupled-device. Discharge parameters affecting t he emission intensity of chlorine (pressure and power) were investigat ed for both discharges with helium as the plasma gas, Once these param eters had been optimized, the corresponding analytical performance cha racteristics were evaluated. Rf-GD provided better detection limits (D Ls) for chloride than the dc-GD (dc-GD, 2.5 ng ml(-1) in the VIS and 0 .5 ng ml(-1) in the NIR; rf-GD, 1.0 ng ml(-1) in the VIS and 0.14 ng m l(-1) in the NIR), Finally, the method using rf-GD-AES and detection i n the NIR was used successfully to develop a sensitive method for the determination of the adsorbable organic halogen (AOX) parameter in the wastewater from a cellulose factory in Asturias (Spain), after precon centration and combustion steps to yield chloride ions from the organo chlorides.