Separation Of Inorganic Ions And Carbohydrates By Chip Electrophoresis With Coupled Conductivity Detection

Conductivity detection is one of electrochemical detection methods commonly used in chip electrophoresis, The circuit used in contactless conductivity detection system is often complicated, while electric coupling effect in normal contact conductivity detection system may cause electrolysis and electrode polarization. The aforementioned problems are well settled by conductivity detection based on electric coupling effect in chip electrophoresis system. Separation of small ions and carbohydrates was studied with this detection method using glass and polymer chips with double T structure.In the first chapter, chip materials, detection method and the characteristic of micro-fluidics were reviewed, the developments and applications of the contact conductivity and contactless conductivity were introduced. The principle of coupled conductivity detection was described in detail.In the second chapter, to increase the separation efficiency of small ions in a short separation channel (<5 cm), the electro osmosis flow (EOF) was controlled or reversed by cetyltrimethylammonium bromide (CTAB); the security of the coupled conductivity detection system in term of high voltage was improved by using an updated signal acquisition system. The chips of different substrates and electrode materials were investigated. Up to five anions and cations were well separated and detected, and the migration time reproducibility were 1.5% and 1.0% respectively for the cations and anions, with a detection limit down to 5μmol/L. The applicability of the system was well demonstrated by the separation of cations (K+, Ca2+, Mg2+) commonly existed in tap water that was 20 times diluted before test.In the third chapter, sucrose and glucose were successfully separated and detected with the system in boric acid buffer without any labeling. For the first time, system peaks without sample injection were reported, systematic investigations were made and the possible reasons were discussed. The experiments indicated that the coupling conductivity detection chip electrophoresis system can be used both for small ions and carbohydrates, which simple, reliable and portable. This system could be found wide applications in field analysis.