The fabrication and evaluation of different electrode materials and electrode alignments for microchip electrophoresis with electrochemical (EC) detection is described. The influences of electrode material, both metal and carbon-based, on sensitivity and limits of detection (LOD) were examined. In addition, the effects of working electrode alignment on analytical performance (in terms of peak shape, resolution, sensitivity, and LOD) were directly compared. Using dopamine (DA), norepinephrine (NE), and catechol (CAT) as test analytes, it was found that pyrolyzed photoresist electrodes with end-channel alignment yielded the lowest limit of detection (35 nM for DA). In addition to being easier to implement, end-channel alignment also offered better analytical performance than off-channel alignment for the detection of all three analytes. In-channel electrode alignment resulted in a 3.6-fold reduction in peak skew and reduced peak tailing by a factor of 2.1 for catechol in comparison to end-channel alignment.

Traditional fabrication methods for polymer microchips, the bonding of two substrates together to form the microchip, can make the integration of carbon electrodes difficult. We have developed a simple and inexpensive method to integrate graphite/PMMA composite electrodes (GPCEs) into a PMMA substrate. These substrates can be bonded to other PMMA layers using a solvent-assisted thermal bonding method. The optimal composition of the GPCEs for electrochemical detection was determined using cyclic voltammetry with dopamine as a test analyte. Using the optimized GPCEs in an all-PMMA flow cell with flow injection analysis, it was possible to detect 50 nM dopamine under the best conditions. These electrodes were also evaluated for the detection of dopamine and catechol following separation by microchip electrophoresis (ME).

Contents 1. Introduction 2. Geneml information about electronic melts 3. Theoretical formulae for various thermal conductivity components of the melts 3.1 Molecular thermal conductivity 3.2 Thermal conductivity connected with electronic processes of heat transfer 4 . Methods of measuring the thermal conductivity of melts 5 . Thermal conductivity of molten salts 6. Thermal conductivity of metal melts 7. Thermal conductivity of molten semiconductors 8. Conclusion References 3, For the positive sign of the thermoelectric power in solid and liquid metals see [29].4, Usually the value of RH is equal to or somewhat smaller than that suggested by free electron theory. The sign of RH is always negative. 16) [60], [114], [125], and [126] quote one and the same result for Bi,Te, obtained by Fedorov in [127]. 17) Electrical conductivity for calculation was taken: for Te from [30], [76], [212]; for ZnSb from [30]; for Bi,Te, from [78], [215]; for GeTe from [207]; for SnTe [207]; for PbTe from [207]; for 80 molyo Bi,Te,-20 molyo Bi,Se, from [218]; for TlTe from [217]; for TI2Te, from [216]; for Ag,S from [2lO], [214], [221]. 18) The melts of Ag,S, GaTe, Cu,AsSe,, and Cu,SbSe, behave similarly but in a somewhat more complicated manner. 19) This figure also gives data for the melt of solid solution of 74 molyo Sb,Te,-26 molyo Bi,Te,. Due to the absence of references on electrical conductivity data it was impossible t o estimate the ratio LIL, in the melt. of the compounds investigated.

No abstract

No abstract

No abstract

No abstract

No abstract