The sensitive and selective determination of separated compounds in effluents from liquid chromatographic columns can be carried out by continuously adding a suitable colorimetric agent to the column effluent and continuously monitoring the absorbance of the reaction mixture. However, a considerable amount of additional broadening of the chromatographic peaks may occur in these systems, especially if slower reactions make it necessary for longer residence times to be used in the reactors. It is shown how this additional broadening can be reduced to an acceptable level by using packed reactors. Some general characteristics of these reactors are discussed and rules for the optimal design are given. A method is described for the determination of hydroperoxides in reaction mixtures from the oxidation of hydrocarbons. Separations are carried out by adsorption chromatography. In an on-line packed reactor, iodine is formed by hydroperoxides in an acidic solution of sodium iodide, and the absorbance of the reaction mixture is measured at 362 nm. A delay time of 1.5 min at a temperature of 70° in the reactor involved a standard deviation of the residence time distribution of less than 1 sec. Nanogram amounts of hydroperoxides can be determined by means of this colorimetric detector.
Deelder, R. S., Kroll, M., & van den Berg, J. H. M. (1976). Determination of trace amounts of hydroperoxides by column liquid chromatography and colorimetric detection. Journal of Chromatography, 125, 307-314. https://doi.org/10.1016/S0021-9673(00)93827-5