Enhanced chemiluminescence of carminic acid-permanganate by CdS quantum dots and its application for sensitive quenchometric flow injection assays of cloxacillin

Abstract

A novel chemiluminescence (CL) system is introduced based on the oxidation of carminic acid by KMnO4 in acidic conditions. CdS quantum dots (QDs) were synthesized using a facile hydrothermal method which efficiently enhanced the intensity of the CL system. A possible mechanism for the proposed system is presented using the kinetic curves, CL spectra, photoluminescence (PL), and ultraviolet–visible (UV–Vis) analysis. The emission intensity of the KMnO4–carminic acid–CdS QDs system was quenched in the presence of a trace level of cloxacillin. Based on this quenching effect, a novel and sensitive flow injection CL method was developed for determining cloxacillin concentrations. At optimal experimental conditions, the decreased CL intensity had a good linear relation with the cloxacillin concentration in the range of 0.008 to 22.0mgL−1. The detection limit (3σ) was 5.8µgL−1. The precision of the method was calculated by analyzing samples containing 4.0mgL−1 of cloxacillin (n=11), and the relative standard deviations (RSD%) were 2.08%. The feasibility of the method is also demonstrated for determining cloxacillin concentrations in environmental water samples and a pharmaceutical formulation.