DEVELOPMENT OF AN AUTOMATIC ANALYZER FOR ORGANIC HALOGENS USING A GAS-CHROMATOGRAPHIC TECHNIQUE

The determination of organic halogens is mostly carried out by the oxy gen-flask method, while very few attempts have been reported for autom atic instrumentation of the halogen analyzer. A rapid and simple micro analyzer is therefore proposed using the gas-chromatographic technique by which chlorine, bromine and iodine are qualified and quantified, r espectively. A sample of 1 similar to 1.5 mg is weighed and ignited in stantaneously in a quartz combustion tube at 900 degrees C with a carr ier gas comprizing helium and oxygen (1 : 1) at a flow rate of 20 ml/m in. The combustion gas passes through a Teflon column at 60 degrees C packed with methylsilicone oil as a stationary phase. Halogens coming out of the column are then chemically converted to equimolar iodine by contact with silver iodide at 200 degrees C. The iodine vapor is spec trophotometrically detected in a small gas cell incorporated with a li ght source of 525 nm and a phototransistor. The retention times of the halogen peaks are 4 min for chlorine, 8 min for bromine and 35 min fo r iodine, respectively. By raising the column temperature to 80 degree s C, however, iodine comes out at 15 min. Since the detector output is proportional to the light transmittance, a computer program was made to transform the signal every one second to the absorbance scale. The integrator prints out the peak data to 5 figures.