Eluant perchloric acid

Post-column techniques tend to be more complex because additional instrumentation e.g. a pump and mixing chamber are required. However, some solutes can be made to fluoresce by simply modifying the eluant pH. This approach has been used for the analysis of quinine and rodenticides. With the former, the compound is chromatographed under basic conditions and then made fluorescent by the addition of perchloric acid after it elutes from the column. With rodenticides, chromatography under acidic conditions is needed and they are then made to fluoresce by changing the pH of the eluate to pH 11 by mixing with a methanol/ammonia solution. 

Figure 9 A synthetic mixture of water-soluble carboxylic acids separated by anion-exchange chromatography. Column 0.3 cm x 300 cm Diaoion CA 08, 16-20 p (Mitsubishi Kasei Kogyo). Eluant 200 mM HC1. Detection reaction with Fe3-benzohy-droxamic acid-dicyclohexy carbodiimide-hydroxylamine perchlorate-triethyl amine with absorbance at 536 nm. Analytes (1) aspartate, (2) gluconate, (3) glucuronate, (4) pyroglutamate, (5) lactate, (6) acetate, (7) tartrate, (8) malate, (9) citrate, (10) succinate, (11) isocitrate, (12) w-butyrate, (13) a-ketoglutarate. (Reprinted with permission from Kasai, Y., Tanimura, T., and Tamura, Z., Anal. Chem., 49, 655, 1977. 1977 Analytical Chemistry).

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