Determination of copper in biodiesel samples using CdTe-GSH quantum dots as photoluminescence probes

Abstract

The use of glutathione-capped CdTe quantum dots is proposed for the determination of copper in biodiesel samples. The developed method was based on proportional quenching of photoluminescence intensity of the nanocrystals with the copper concentration. Three different sizes of CdTe quantum dots (QDs) were prepared and modified in aqueous dispersion by glutathione (GSH), and their interactions with copper were investigated. As a result of the interaction, the CdTe-GSH QDS photoluminescence intensity decreased linearly in the presence of Cu(II) in the range of concentration from 2.2 to 30.0μgL−1. The maximum photoluminescence intensity was obtained at pH6.5, with excitation and emission wavelengths at 400 and 532nm, respectively. The detection limit was 0.67μgL−1, and the precision expressed as relative standard deviation (RSD%, n=10) was 1.0% for a sample with a copper concentration of 5.0μgL−1. Accuracy was assessed by means of addition and recovery experiments carried out in biodiesel samples, with results ranging from 98.4% to 102.5%. The proposed method can be regarded as an efficient and expeditious alternative for copper determination in biodiesel, after extraction employing ultrasound-assisted sample treatment, as confirmed by the good correlation between the obtained results and those provided by graphite furnace atomic absorption spectrometry, after acid digestion.