Fluorescently labeled carbohydrates released from glycoproteins were separated using a commercially available microfluidic chip electrophoresis system. While the instrumentation was primarily designed for DNA analysis it was found that the application base can be easily expanded using the development software provided by the manufacturer. The carbohydrates were released by enzymatic digestion (PNGase F) from glycoproteins present in human plasma after boronic acid - lectin affinity enrichment. After fluorescent labeling with 8-aminopyrene-1,3,6-trisulfonic acid the carbohydrates were separated based on capillary gel electrophoresis mechanism and detected by a fluorescence detector using a blue (470 nm) LED. The separation was completed in 40 s in a microfluidic channel of 14 mm length. Glucose ladder carbohydrate oligomers differing by one glucose unit were baseline separated up to a 20-mer with the main limitation being the detection sensitivity. As expected, the observed resolution in these experiments did not approach that of standard CE with 20 times longer separation distance; however, the chip-based analysis excelled in the speed of the separation. Similar electrophoretic profiles of glycans released from plasma glycoproteins were obtained using a standard CE equipment with 35 cm separation length and microfluidic chips with a separation distance of only 14 mm.

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Introduction of a sample into the separation column (microchip channel) in capillary zone electrophoresis (microchip electrophoresis) will cause a disturbance in the originally uniform composition of the background electrolyte. The disturbance, a system zone, can move in some electrolyte systems along the separation channel and, on reaching the position of the detector, cause a system peak. As shown by the linear theory of electromigration based on linearized continuity equations formulated in matrix form, the mobility of the system zone--the system eigenmobility--can be obtained as the eigenvalue of the matrix. Progress in the theory of electromigration allows us to predict the existence and mobilities of the system zones, even in very complex electrolyte systems consisting of several multivalent weak electrolytes, or in micellar systems (systems with SDS micelles) used for protein sizing in microchips. The theory is implemented in PeakMaster software, which is available as freeware (www.natur.cuni.cz/gas). The linearized theory also predicts background electrolytes having no stationary injection zone (water zone, water gap, water dip, EO zone) or unstable electrolyte systems exhibiting oscillations and creating periodic structures. The oscillating systems have complex system eigenmobilities (eigenvalues of the matrix are complex). This paper reviews the theoretical background of the system peaks (system eigenpeaks) and gives practical hints for their prediction and for preparing background electrolytes not perturbed by the occurrence of system peaks and by excessive peak broadening.

ITP with indirect fluorescence detection (IFD) was introduced three decades ago. Despite this fact, the method has never become widely adopted. The main aim of this work was to utilize the ITP-IFD for the separation of carboxylic acids by using a commercially available, portable, microfluidic chip electrophoresis system. On the 16.8-mm effective length separation channel, a maximum of eight carboxylic acids could be separated, with LOD values in a range from 0.12 to 0.4 mM. The commercial chips used for all experiments have multichannel structures important for analysis of more than one sample per a chip in case of standard use. This multichannel structure was used to investigate the possibility of multiple sample loading for ITP separation. Application of ITP-IFD was investigated for analysis of benzoate in diet soft drinks and the results were in good agreement with results of a CE method.