Postcolumn labeling

Honda, S., Kakehi, K., Fujikawa, K., Oka, Y., and Takahashi, M. 1988. Mechanism of the reaction of reducing carbohydrates with 2-cyanoacetamide, used for postcolumn labeling in high performance liquid chromatography for photometric, fluorimetric and electrochemical detection. Carbohydr. Res. 183 59-69. 

Postcolumn labeling requires a more complex microdevice than the simple crossed-tee design. Direct incorporation of the fluorescent label into the run buffer would eliminate this problem, but would have to not interfere with the separations. This was shown by Jin et al., who carried out protein/SDS size-... 

Liu Y, Foote RS, Jacobson SC, Ramsey RS, Ramsey JM. Electrophoretic separation of proteins on a microchip with noncovalent, postcolumn labeling. Anal Chem 2000 72 4608-4613. 

Jin LJ, Giordano BC, Landers JP. Dynamic labeling during capillary or microchip electrophoresis for laser-induced fluorescence detection of protein-SDS complexes without pre- or postcolumn labeling. Anal Chem 2001 73 4994-4999. 

Postcolumn labeling is a characteristic feature of carbohydrate analysis in which no direct physical methods are available for sensitive detection. Many labeling methods have hitherto been developed. The methods with phenol in sulfuric acid [16], orcinol in sulfuric acid [17], anthrone in sulfuric acid [18], tetrazolium blue in alkali [19], copper(II)-2-2 -bicin-chonitate [20], and 2-cyanoacetamide [21] are used for photometric detection. The methods with 2-cyanoacetamide [6], ethylenediamine [22], ethanolamine [23], taurine [24], and arginine [25] are used for fluorimetric detection. Some labeling methods for electrochemical detection were reported by Honda and Suzuki in 1984 [26,27],... 

While one of the limitations of LIF detection is that few target molecules exhibit native fluorescence, especially biologically relevant proteins and DNA of clinical interest, several different labeling approaches both on- and off-chip have been demonstrated. For the former, the microchip fabrication steps provide the ability to incorporate additional structures into the design, in many cases without adding more steps (or cost) to the fabrication process. Examples include the additional channels and reaction chambers used to perform both precolumn" and postcolumn" labeling of amino acids. 

Postcolumn labeling is a characteristic feature of carbohydrate analysis in which no direct physical methods are available for sensitive detection. Many labeling methods have hitherto been developed. The methods with phenol in... 

Honda, S. Konishi, T. Suzuki, S. Takahashi, M. Kakehi, 20. K. Ganno, S. Automated analysis of hexosamines by high-petfonnance liquid chromatography with photometric and fluorimetric postcolumn labeling using 2-cyanoacetamide. 21. Anal. Biochem. 1983,134,483. 

Sensitive monitoring of hexosamines in high-performance liquid chromatography by fluorimetric postcolumn labelling using the 2,4-pentanedione-fomialdehyde system. 22. J. Chromatogr. 1983,281, 340. 

HPLC determination This technique has been widely used, since, in general, it is less sensitive than the microbiological method. The various isomers of vitamin B12 (cyanocobalamins) can be analyzed by reversed-phase HPLC. Pre- and postcolumn labeling, column switching, and solid-phase extraction (SPE) may be used (Iwase and Ono, 1997). 

Siehen, V. J. Backhouse, C. J. Rapid on-chip postcolumn labeling and high-resolution separations of DNA. Electrophoresis 2005, 26, 4729 742. 

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