DESIGN AND PERFORMANCE OF A NEW CONTINUOUS-FLOW SAMPLE-INTRODUCTION SYSTEM FOR FLAME INFRARED-EMISSION SPECTROMETRY - APPLICATIONS IN PROCESS ANALYSIS, FLOW-INJECTION ANALYSIS, AND ION-EXCHANGE HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

A new sample introduction system for the analysis of continuously flow ing liquid streams by flame infrared-emission (FIRE) spectrometry has been developed. The system uses a specially designed purge cell to str ip dissolved CO2 from solution into a hydrogen ps stream that serves a s the fuel for a hydrogen/air flame. Vibrationally excited CO2 molecul es present in the flame are monitored with a simple infrared filter (4 .4 mum) photometer. The new system can be used to introduce analytes a s a continuous liquid stream (process analysis mode) or on a discrete basis by sample injection (flow injection analysis mode). The key to t he success of the method is the new purge-cell design. The small inter nal volume of the cell minimizes problems associated with purge-cell c lean-out and produces sharp, reproducible signals. Spent analytical so lution is continuously drained from the cell, making cell disconnectio n and cleaning between samples unnecessary. Under the conditions emplo yed in this study, samples could be analyzed at a maximum rate of appr oximately 60/h. The new sample introduction system was successfully te sted in both a process analysis- and a flow injection analysis mode fo r the determination of total inorganic carbon in Waco tap water. For t he first time, flame infrared-emission spectrometry was successfully e xtended to non-volatile organic compounds by using chemical pretreatme nt with peroxydisulfate in the presence of silver ion to convert the a nalytes into dissolved carbon dioxide, prior to purging and detection by the FIRE radiometer. A test of the peroxydisulfate/Ag+ reaction usi ng six organic acids and five sugars indicated that all 11 compounds w ere oxidized to nearly the same extent. Finally, the new sample introd uction system was used in conjunction with a simple filter FIRE radiom eter as a detection system in ion-exchange high-performance liquid chr omatography. Ion-exchange chromatograms are shown for two aqueous mixt ures, one containing six organic acids and the second containing six m ono-, di-, and trisaccharides.