Applications of capillary electrophoresis with contactless conductivity detection

This thesis focuses on the application of capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C4D) in the enantiomeric separation of non-UV active pharmaceutical chemicals and fast detection of non-UV active species in clinical samples. First CE-C4D was successfully applied to the direct enantiomeric separation of five basic drugs and nine amino acids. Derivatization of the compounds or the addition of a visualization agent as for indirect optical detection schemes was not needed. Non-charged chiral selectors were employed, hydroxypropylated cyclodextrin (CD) for the more lipophilic basic drugs and 18-crown-6-tetracarboxylic acid (18C6H4) for the amino acids. Concurrent chiral separation of UV and non-UV active amino acids has been realized. Secondly, CE-C4D was used for the determination of different organic amines. Direct enantiomeric separation of 1-phenylethylamine and 1-cyclohexylethylamine was obtained with unprecedented high resolution by using a combination of dimethyl-beta-cyclodextrin and the chiral crown ether 18C6H4 as selectors. Then the enantiomeric separation of various amines was investigated, the use of contactless conductivity detection for the determination of different species in capillary electrophoresis was successfully demonstrated. The species tested included short chained aliphatic primary, secondary and tertiary amines, branched alipahtic amines, diamines, hydroxyl-substituted amines as well as species incorporating aromatic and non-aromatic cyclic moieties. The determination of the enantiomers of these amines which otherwise can only be achieved with difficulty was possible by using a combination of dimethyl-beta-CD and the chiral crown ether (+)-(18-crown-6)-2, 3, 11, 12-tetracarboxylic acid (18C6H4) as selectors. Thirdly the CE-C4D has also successfully been explored in the separation of diastereomers and enantiomers of various dipeptides, tripeptides and tetrapeptides composed of non-UV active amino acids. These peptides are essential compounds in biological systems as well as important chiral building blocks in pharmaceutical drugs. At last, the determination of gamma-hydroxybutyrate (GHB) with CE-C4D, which is a recently introduced party drug and difficult to be analyzed by on-site screening, was developed. The procedure can be used for the detection of GHB in urine and serum samples.