Determination of arsenic based on quenching of CdS quantum dots fluorescence using the gas-diffusion flow injection method

A sequential injection analysis system for determination of arsenic based on hydride generation and fluorescence quenching of mercaptoacetic acid capped cadmium sulfide quantum dots (CdS–MAA QDs) is described. The generated arsine diffused across the PTFE membrane in a gas-diffusion unit and subsequently interacted with CdS–MAA QDs. The parameters affecting the arsine generation and the fluorescence quenching of QDs were studied. Under the optimum conditions, it was observed that a increase in the concentration of As(III) corresponded well to a decrease in fluorescence intensity according to the Stern–Volmer relationship. The extent of quenching was dependent on the concentration of arsenic in the range of 0.08–3.20 mmol L−1, with the detection limit of 0.07 mg L−1. The precision (%RSD) from eight replicates of the determination of As(III) 1.0 mg L−1 was found to be 1.4%. The proposed method was applied to the determination of arsenic in ground water samples with satisfactory recoveries.