By employing an electrical micro-titration system, in which a capacitively coupled contactless conductivity detector (C 4 D) was used to monitor the reaction process in real time, herein a novel method for determining ciprofloxacin hydrochloride (CIPHCl) was developed for the first time. Mode 1: Standard CIPHCl solutions at different concentrations were loaded into reaction cells, respectively, and were titrated with standard Ag + . Upon the titration, the formation of a precipitate alters the number of ions in the solution, raising the change of conductivity, which was monitored by a special C 4 D to construct a titration curve. The endpoint of the titration was located from the peak of the curve. Between the elapsed time and the initial concentration of titrand, a linear relationship was established over the range of 2.0–8.0 mmol/L. Mode 2: Standard Fe 3+ took the place of Ag + , and was used as titrant to recognize ciprofloxacin contributed to the formation of complexation, which also resulting a change of solution conductivity. Under optimized conditions, a working range of 1.0–5.0 mmol/L CIPHCl was found. Because the reaction solutions were isolated from the working electrodes, this pioneer work shows significant simplicity and cost-effectiveness, by eliminating the requirements for detector exchange/renewal between different measurements, and by involving no auxiliary chemicals. Both of the two approaches were applied successfully to determine CIPHCl in tablet samples. And the results were in good agreement with those obtained by reference method.
Herein, an approach for versatile titration by monitoring the chemical reaction process with a developed capacitively coupled contactless conductivity detector (C 4 D) was developed. A disposable glass reaction cell, in which sub-milliliter titrand was loaded, was inserted into the working head stage of the C 4 D. Upon addition of titrant, the ionic strength and/or mobility of components in the solution changed, causing consequently change of conductivity. The C 4 D monitored the change in real time. A V-shaped titration curve was gained, allowing an easy identification of the endpoint. Between the elapsed time and the initial concentration of titrand, linear relationships were found for classical acid-base, precipitation, complexation and redox reaction over certain ranges, enabling the establishment of quantitative determinations. The new approach had a few charming advantages (e.g. simplicity and cost effectiveness) over contact electrochemical methods because that the solution was isolated from the working electrodes. Therefore, a development of versatile and multifunctional platform for micro-titrations is promising.
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