Search

Abstract: The effect of surface microstructures of microchannels on the separation efficiency in microchip electrophoresis has been studied. In order to understand the influence of the surface microstructures on the microchip electrophoresis performance, a thermostatic system was designed and fabricated for precisely control of the chip temperature since the surrounding temperature causes a significant effect on the separation efficiency. The periodically ordered microstructures (dams) of different sizes were fabricated on the microchannels by a simple printing process using different gray levels of the vector graphic software. And the influence of dam sizes in microchannels on the separation efficiency was evaluated by using the number of theoretical plates (N) and the relative resolution (Rs’). Analyzing the variations of mixing elements caused by the periodically ordered dams in the separate channel and elution time, we found that with small dam size fabricated at low gray level of ca. 30%, the resolution of dopamine and epinephrine increased slightly, while it decreased obviously with larger dam sizes especially fabricated at gray level of 50%. [Copyright &y& Elsevier]

Abstract: Generally speaking, measurement of hydroxylated radical products of salicylic acid requires a fussy separation process. In this study, we describe a simple method to electrochemically detect hydroxyl radicals ( 4-hydroxybenzoic acid (4-HBA) as the The erated by the Fenton reaction from iron (II) sulfate and hydrogen peroxide in a phosphate buffer solution. Experimental results show that our method can detect the igh sensitivity without any separation process. The differential pulse voltammetric responses show a linear dependence on the concentration of ange of 2.0×10−6 and 1.0×10−3 M with a determination limit down to 5.0×10−7 M. As a demonstration, the kinetics of the Fenton reaction was mapped by measuring the reaction product of hydroxyl radical trapped by 4-HBA. The result is in good agreement with that reported previously. All the results show that the present approach could provide a simple, inexpensive and promising method for biomedicine and iatrology. [Copyright &y& Elsevier]

Abstract: Rapid separation and determination of acetaminophen and its hydrolysate with end-channel electrochemical (EC) detection integrated on a plastified poly(ethylene terephthalate) (PET)-toner microchip capillary electrophoresis (CE) system was investigated. In this separation and detection system, a Pt ultramicroelectrode integrated on a three-dimensional adjustor was used as working electrode. Factors influencing the separation and detection were investigated and optimized. Results show that acetaminophen and p-aminophenol can be well separated within 84s with R.S.D.<1% for migration time and R.S.D.<3.6% for detection current for both analytes. Detection limits for both analytes are determined to be 5.0μM (S/N=3). This method has been successfully applied to the detection of trace p-aminophenol in paracetamol tablets. The results demonstrate that the PET-toner microchips can obtain better performance than PDMS microfluidic devices but at much lower cost. [Copyright &y& Elsevier]

Abstract: Separation and determination of dopamine and epinephrine with end-channel electrochemical (EC) detection integrated on a native printed microchip capillary electrophoresis (CE) system was investigated. Factors influencing the separation and detection were investigated and optimized. Results show manipulating EOF, which can be easily achieved by adjusting buffer pH, is a simple and effective way to achieve the baseline separation of dopamine and epinephrine in native polymeric microchips. Without surface modification of microchannel, printed microchips with advantages of low cost and easy preparation can achieve high performance like other microfluidic devices. [Copyright &y& Elsevier]