DESIGN AND OPTIMIZATION OF A NOVEL TYPE NITROGEN-PHOSPHORUS DETECTOR FOR CAPILLARY GAS-CHROMATOGRAPHY

The design and optimization of a novel type alkali flame ionization de tector (AFID) for capillary gas chromatoraphy is presented. The design differs in that the alkali salt is continuously introduced, as a solu tion in water, into the detector by means of a liquid chromatographic syringe pump. This design permits continuous refreshment of the enhanc ement source and circumvents the need of source replacement, thereby e liminating detector response fatigue over time. Modification of an exi sting nitrogen-phosphorus detector (NPD) to allow direct introduction of the alkali salt into the detector will be described. Next, importan t operational parameters such as the location of introduction, type an d concentration of the salt and the flow of the various detector gasse s are optimized experimentally with regard to detector sensitivity, se lectivity, minimum detectability and noise level. Moreover the lineari ty, reproducibility and stability of the detector are evaluated. It wi ll be shown that the new detector design exhibits excellent response c haracteristics for phosphorus compounds which are comparable to or bet ter than those observed with commercially available AFIDs or NPDs. Fin ally, the performance of the detector will be demonstrated by two envi ronmental applications.