CAPILLARY BATCH INJECTION-ANALYSIS AND CAPILLARY-FLOW INJECTION-ANALYSIS WITH ELECTROCHEMICAL DETECTION - A COMPARATIVE-STUDY OF BOTH METHODS

Capillary batch injection analysis (CBIA) and capillary flow injection analysis (CFIA) in combination with electrochemical detection as well as optical detection methods were studied and compared with respect t o their performance. Despite the differences in technical equipment bo th techniques share the same idea of reproducible transport and washou t of nanolitre samples over sensing surfaces. Thus the same electroche mical flow cell can be used for both CBIA and CFIA. The amperometric a nd potentiometric CBIA responses were studied under various experiment al conditions in order to optimise the CBIA set-up. In particular, the density of the sample solution relative to that of the cell electroly te had a remarkable effect on the hydrodynamic characteristics of CBIA . Dispersion in CFIA was investigated using on column UV-detection for electroosmotic flow (EOF) conditions as well as for gravity flow cond itions. It is demonstrated for a 75 mu m capillary that the relative b and broadening of the sample plug under gravity flow is only about twi ce as large as under EOF. Furthermore, dispersion in a system that inv olves a chemical reaction between the sample and the carrier solution, namely CrO72- and Fe2+ has been investigated by amperometric detectio n and exploited for the determination of dichromate microsamples.