Study On Applications Of Microchip Electrophoresis Coupled With Laser-Induced Fluorescence Detection In Food Analysis

Capillary electrophoresis on microchips is an emerging new technology that promises to lead the next revolution in chemical analysis. It has the potential to simultaneously assay hundreds of samples in a matter of minutes or less. Microchips typically consume only picoliters of samples. These samples may potentially be prepared on-board for a complete integration of sample preparation and analysis functions. These features make microchips an attractive technology for the next generation of capillary electrophoresis instrumentation.The details are listed below:Part1Rapid Determination of Amino Acids in Milk by Microchip Electrophoresis Coupled with Laser-induced Fluorescence DetectionA simple and sensitive method for determination of amino acids in milk by microchip electrophoresis (MCE) coupled with laser-induced fluorescence (LIF) detection was developed. Seven kinds of standard amino acids were derivated with sulfoindocyanine succinimidyl ester (Cy5) and then perfectly measured by MCE-LIF within150s. The parameters of MCE separation were carefully investigated to obtain the optimal conditions:100mM sodium borate solution (pH10.0) as running buffer,0.8kV as injection voltage,22kV as separation voltage etc. The linear range of the standard amino acid solutions was from0.01μM to1.0μM and the detection limit was as low as about1.0μM. This MCE-LIF method was applied to the measurements of amino acids in actual milk samples and satisfactory experimental results were achieved.Part2Rapid Separation of Probiotics in Mixed Samples Using Microchip Electrophoresis with Laser-Induced Fluorescence DetectionMicrochip electrophoresis (MCE) coupled with laser-induced fluorescence detection (LIF) was developed for rapid separation of four kinds of probiotics including Bifidobacterium. Lactobacillus casei, Lactobacillus acidophilus and Enterococccus faecalis. All bacteria were quick separated within150s in the background electrolyte containing4.0mM tris(hydroxymethyl) amminomethane (TRIS)-4.0mM boric acid-0.09mM ethylenediamine tetraacetate (EDTA)(TBE) buffer (pH8.5) and0.025%(v/v) polyethylene oxide (PEO). The concentration of PEO, pH of running buffer, sample preparation and growth of bacteria were key factors for MCE separation and carefully investigated in this experiment.Part3Ultrasensitive Detection of Bacteria by Microchip Electrophoresis Based on Multiple-Concentration Approaches Combining Chitosan Sweeping, Field-Amplified Sample Stacking, and Reversed-Field StackingIn this paper we describe an on-chip multiple-concentration method combining chitosan (CS) sweeping, reversed-field stacking, and fieldamplified sample stacking for highly efficient detection of bacteria. Escherichia coli was selected as a model bacterium to investigate the efficiency of this multiple-concentration method. CS was the most suitable sweeping agent for microchip electrophoresis, replacing the usually used cetyltrimethylammonium bromide for capillary electrophoresis. The additive taurine had a synergistic effect by enhancing the interaction between CS and the surface of the bacteria, thus improving the analysis sensitivity. All steps of the concentration method and related mechanisms are described and discussed in detail. A concentration enhancement factor of approximately6000was obtained using this concentration method under optimal conditions as compared to using no concentration step, and the detection limit of E. coli was145CFU/mL. The multiple-concentration methodology was also applied for the quantification of bacteria in surface water, and satisfactory results were achieved. The application of this methodology showed that the concentration enhancement of bacteria clearly conferred advantageous sensitivity, speed, and sample volume compared to established methods.