Microcolumn Electrophoresis for Electrokinetic Flow Analysis

ABSTRACT

A 2-mm i.d. and 100-mm length electrophoretic microcolumn packed with quartz microparticles was proposed in this article. To investigate the microcolumn preparation, thermal effect and electrophoretic separation, tryptophan and tyrosine were used as the target analytes, and their separation parameters were optimized, including quartz microparticle size, buffer concentration and pH, and so on. With the 2-mm i.d. fused-silica microcolumn packed with 9 µm length uniform quartz microncrystals and the electrophoretic buffer solution of 0.75 mmol/L sodium tetraborate (pH 11.0), the thermal effect of the microcolumn electrophoresis was limited satisfactorily, and underivatized tryptophan and tyrosine were separated on baseline and detected at 224 nm by an ordinary spectrophotometer. The limits of detection for tryptophan and tyrosine were 0.018 and 0.080 µmol/L, respectively. The separation efficiency of tryptophan was 4.0 × 10⁴ plates/m. The sample capacity of the electrophoretic microcolumn achieved 35 µL. Owing to low consumption of reagent solutions and organic solvents, the microcolumn electrophoresis belongs to a green analytical method. With the advantages of high detection sensitivity, large sample capacity, instrumental simplicity, and portability, it can be employed as one of the high-performance separation techniques for an in-situ and real-time electrokinetic flow analysis system. It can also be developed for preparative electrophoresis.

KEYWORDS:

• electrokinetic flow analysis
• green analytical method
• microcolumn electrophoresis
• quartz microncrystals
• quartz microparticles
• thermal effect

ACKNOWLEDGEMENT

The authors gratefully thank the Natural Science Foundation of China (No. 20675075) for the financial support to carry out this work.

Notes

^a The concentration of tryptophan and tyrosine are 0.125 mmol/L and 0.25 mmol/L. The injection volume is 1.0 µL, applied voltage is 800 V and detection wavelength is 224 nm, other conditions are the same as in Fig. 2a.

^a 9 µm quartz microncrystals packed into the electrophoretic microcolumn are prepared by hydrothermal synthesis, other conditions are the same as in Table 1.

An invited paper submitted to a special issue on Green Spectroscopy and Analytical Techniques, organized by Professor Miguel de la Guardia, of the Department of Chemistry, University of Valencia, Spain, and Professor Arabinda Kumar Das, of the Department of Chemistry, University of Burdwan, West Bengal, India.