Abstract: Potassium permanganate is a powerful oxidizing agent widely used in chemiluminescence generated from acidic solutions. It has been used for the chemiluminometric assay of a plethora of compounds such as morphine, various anaesthetics and catecholamines. Typical examples of permanganate chemiluminescence are shown in Table 1. The presence of adjacent hydroxyl groups on the benzene ring is usually an indication that the reaction of the compound with permanganate might be chemiluminogenic. Further investigations of permanganate chemiluminescence revealed the production of radiation from eugenol, isoeugenol and caffeic acids (as expected from the structure of the molecules) and also from cimetidine (which was an unexpected observation).

Abstract: A flow-injection ultrafiltration sampling chemiluminescence system for on-line determination of cimetidine-bovine serum albumin (BSA) interaction is proposed in this paper. Cimetidine can be oxidized by N-bromosuccinimide (NBS) and sensitized by fluorescein to produce high chemiluminescence emission in basic media. The concentration of cimetidine is linear with the CL intensity in the range 3 x 10^-7 - 1 x 10^-4 mol L-1 with a detection limit of 1 x 10^-7 mol L-1 (3σ). The drug and protein were mixed in different molar ratios in 0.067 mol L-1 phosphate buffer, pH 7.4, and incubated at 37°C in a water bath. The ultrafiltration probe was utilized to sample the mixed solution at a flow rate of 5 µL min-1. The data obtained by the proposed ultrafiltration flow-injection chemiluminescence method was analyzed with Scrathard analysis and a Klotz plot. The estimated association constant (K) and the number of the binding site (n) on one molecule of BSA by Scrathard analysis and Klotz plot were 3.15 x 10^4 L mol-1 and 0.95, 3.25 x 10^4 L mol-1 and 0.92, respectively. The proposed system proved that flow-injection chemiluminescence analysis coupled with on-line ultrafiltration sampling is a simple and reliable technique for the study of drug-protein interaction.