Study On The Applications Of Capillary Electrophoresis- Capacitively Coupled Contactless Conductivity Detection Combined With Preliminary Enrichment

1. PrefaceCapillary electrophoresis (CE) is one of the most widely used and rapidly developed analytical techniques in recent years. Compared with HPLC, CE has many advantages, including rapid analysis speed, automation, good reproducibility, and low cost, etc. Furthermore, CE can also provide higher separation efficiency and detection sensitivity even for very small sample volume. This work mainly introduces the basic principles and research progresses of capillary electrophoresis, capacitively coupled contactless conductivity detection (C4D) and sample enrichment technologies. This paper intends to explore its analyses and applications in noninvasive biological samples and drinking water by combining the high separation efficiency of CE with the universal detection technique of C4D and the online enrichment technology of FASI or electromembrane microextraction (EME) technology. The proposed methods can provide direct determination of analytes without need of derivatization, which greatly shortens the analysis time, improves the separation efficiency, and therefore the analytical system is simple and environmental-friendly.2. Field amplified sample of saliva inorganic ions followed by capillary zone electrophoresis with capacitively coupled contactless conductivity detectionA capillary electrophoresis approach with capacitively coupled contactless conductivity detection method has been developed for the determination of inorganic metabolites (thiocyanate, nitrite and nitrate) in human saliva. Field amplified sample injection, as a simple sample stacking technique, was used in conjunction for online preconcentration of above inorganic anions. A selective separation for the target anions from other coexisting constituents present in saliva could be obtained within 14 min in a 10 mmol/L His-90 mmol/L HAc buffer (pH 3.70) at the separation voltage; of-18 kV. The limits of detection and limits of quantification of the three analytes were within the range of 3.1～4.9 ng/mL (S/N=3) and 10～16 ng/mL (S/N=10), respectively. The average recovery data were in the range of 81～108% at three different concentrations. This method provides a simple, rapid and direct approach for metabolite analyses of nitric oxide and cyanide based on noninvasive saliva sample, which presents a potential fast screening tool for clinical test.3. Electromembrane extraction of bromate in drinking water ions by capillary electrophoresis coupled with contactless conductivity detectionA capillary electrophoresis approach with capacitively coupled contactless conductivity detection method has been developed for the determination of bromate in drinking water, which is the primary disinfection by-product of ozonation, and the detection sensitivity has been significantly improved based on electromembrane extraction (EME). A selective separation for the target anions from other coexisting constituents present in drinking water could be obtained within 8 min in a 300 mmol/L HAc buffer at the separation voltage of-18 kV. The limits of detection of the bromate was 0.12 ng/mL (S/N=3). The average recovery data were in the range of 85-98% at three different concentrations. This method provides a simple, rapid and direct approach for the analysis of bromate in drinking water, which presents a potential new method for detection of bromate.