Successive detection of benzoic acid and total parabens in foodstuffs using mercaptosuccinic acid capped cadmium telluride quantum dots

Abstract

An approach for the determination of benzoic acid (BA) and total paraben content using mercaptosuccinic acid capped CdTe quantum dots (MSA-CdTe QDs) as an optical probe is presented. The levels of these preservatives in the samples of liquid foodstuff could be determined by both visible and fluorescent detection methods. For the analysis of paraben content, sample hydrolysis under alkaline conditions was required in order to obtain p-hydroxybenzoic acid (PHBA) prior to the addition of MSA-CdTe QDs. Both BA and PHBA could be quantified by their quenching of QD fluorescence, owing to the formation of hydrogen bonds between the carboxylic acid groups of the MSA-CdTe QDs and the analytes. Reverse-phase C18 solid phase extraction cartridge was exploited to reduce sample loss and organic solvent consumption in the sample preparation steps. The developed approach was successfully applied for the determination of the BA and total paraben content found in orange juice, soft drink, energy drink, beer, coconut milk, and fish sauce, giving a limit of detection of 0.3 mg/L for BA analysis, and 0.1 mg/L for PHBA (hydrolyzed form of parabens) analysis, with a linearity range from 1.0 mg/L to 500.0 mg/L. Since the concentrations of most preservatives added to products are controlled and regulated by raw, therefore, quality control is necessary to monitor the levels of these agents in products to better ensure the safety of customers.