Measurement of bubble velocity using Capacitively Coupled Contactless Conductivity Detection(C^4D)technique

The feasibility of applying Capacitively Coupled Contactless Conductivity Detection （C4D） technique to measurement of bubble velocity in gas-liquid two-phase flow in millimeter-scale pipe is investigated. And, a new method, which combines the C4D technique and the principle of cross-correlation velocity measurement, is proposed for the measurement of bubble velocity. This research includes two parts. First, based on the principle of C4 D, a new five-electrode C4D sensor is developed. Then, with two conductivity signals obtained by the C4D sensor, the velocity measurement of bubble is implemented according to the principle of cross-correlation. The research results indicate that the C4D technique is highly effective and anticipates a broad potential in the field of two-phase flow. Experimental results show that the five-electrode C4D sensor is suitable for measuring the velocity of single bubbles with a relative error of less than 5%.

Sensitive Determination of Five Priority Haloacetic Acids by Electromembrane Extraction with Capillary Electrophoresis

A method for sensitive determination of five priority haloacetic acids in drinking water has been developed for the first time based on electromembrane extraction(EME)prior to CZE with capacitively coupled contactless conductivity detection(CZE-C^(4)D).The target analytes were extracted from 10 mL of the sample solution(donor phase),through the supported liquid membrane(using a polypropylene membrane supporting 1-octanol),and into 10μL of 50 mmol/L NaAc solution(acceptor phase).The extracted solution was directly analyzed by CZE-C^(4)D without de-rivatization.Several factors that affect separation,detection and extraction efficiency were investigated.Under the optimum conditions,five haloacetic acids(monochloroacetic acid,dichloroacetic acid,trichloroacetic acid,mono-bromoacetic acid,and dibromoacetic acid)could be well separated from other components coexisting in water samples within 23 min,exhibiting a linear calibration over two orders of magnitude(r≥0.9943);the enrichment factors at 430-671 were obtained in a 30 min of extraction,and the limits of detection were in the range of 0.17-0.61 ng/mL.The intraday relative standard deviations for peak areas investigated at 10 ng/mL were between 1.2%and 9.7%for the combined EME-CZE-C^(4)D procedure.This approach offers an attractive alternative to the officially proposed method for purified drinking water analysis,which requires derivatization procedure prior to gas chromatography analysis.

Simple and cost-effective determination of ciprofloxacin hydrochloride by electrical micro-titration

By employing an electrical micro-titration system, in which a capacitively coupled contactless conductivity detector（C^4D） 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 of2.0–8.0 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.