Impulse-response functions of low-through detectors based on the membrane-stabilised liquid-liquid interface Part II. Experimental verification

✍ Scribed by Stefan Wilke

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 704 KB
• Volume: 295
• Category: Article
• ISSN: 0003-2670
• DOI: 10.1016/0003-2670(94)80347-1

✦ Synopsis

The impulse-response functions of an amperometric and potentiometric flow-through detector based on the membrane stabilised water-nitrobenxene interface have been determined by measuring the response to a short concentration pulse which was generated by a flow-injection system. The response time determining diffusion layer was represented by a cellulose membrane separating the flowing aqueous solution and the ion-sensing stationary organic phase. The shape of the experimentally obtained signal-time responses was found to be in excellent agreement with the theoretical curves calculated by the models derived recently. As expected from the theory, the response in amperometry was found to be faster than in potentiometry. Diffusion coefficients of the species in the membrane were determined by fitting the parameters of the model to the measured curve. The following values were calculated from the amperometric response (in lo-" m2/s): 7.3 (thiocyanate), 8.6 (iodide) and 1.7 (dodecylsulfate). From the dimensions of the flow system, the width of the exciting concentration pulse was estimated to be less than 0.02dZ/D,.

It has been proved by numerical simulations, that the shape of the detector signal is almost identical with the impulse-response function itself under this condition.