SEMI-MICROCOLUMN HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

Attempts to miniaturize columns for liquid chromatography (LC) have be en reported since the late 70's. A series of advantages were repeatedl y claimed in the use of microcolumns, whose inner diameters were less than 1 mm. However, several requirements and limitations have kept mic rocolumn LC within a very limited area of applications. On the contrar y, semi-microcolumn LC (inner diameter: 1 similar to 2 mm) has been wi dely accepted in academia and industry, possessing both advantages sho wn by microcolumn LC and the reliability of conventional LC. Although certain modifications, such as miniaturizing dead volumes of component s, are required in instrumental arrangements, it became possible to ea sily obtain highly efficient separation with a semi-microcolumn, even under isocratic conditions. The benefits of semi-microcolumn LC seem m ost pronouncing when a column-switching system is arranged. A tremendo us concentrating effect could be earned by first injecting a sample so lution into a short conventional-bore precolumn, and then transferring an analyte-containing fraction to a semi-microcolumn connected into a detector. This analytical format was applied to the analysis of vario us substances contained in biological liquids at very low concentratio ns. The later sections of the article discuss some of these applicatio ns, including forensic analysis and diagnosis in clinical chemistry.