Paper-based electrochemiluminescence device for the rapid estimation of trimethylamine in fish via the quenching effect of thioglycolic acid-capped cadmium selenide quantum dots.

A paper-based electrochemiluminescence device (µPAD-ECL) for the estimation of trimethylamine (TMA) concentration in fish was developed using tris(2,2'-bipyridyl)ruthenium(II) complex coupled with water soluble thioglycolic acid-capped CdSe quantum dots on the inkjet-printed paper-based device. The quenching effect of tertiary amines on the ECL intensity was found to be sensitive and concentration dependent. This effect allows the measurement of TMA at low concentrations. Under the optimal conditions, the linear concentration range was exhibited from 1 × 10-12 to 1 × 10-7 M and a detection limit of 2.09 × 10-13 M, with relative standard deviation of 1.97 %. The applicability of µPAD-ECL is demonstrated by the rapid estimation of trimethylamine concentration in fish tissue, and could be used as a method for screening the total amount of tertiary amines in fishery products in remote communities. The results obtained using the paper-based devices agreed well with those obtained applying high performance liquid chromatography with benzoyl derivatization, at a confidence level of 95%.

Enhanced electrogenerated chemiluminescence of tris(2,2'-bipyridyl)ruthenium(II) system by l-cysteine-capped CdTe quantum dots and its application for the determination of nitrofuran antibiotics.

This paper reports a new approach to enhance the electrogenerated chemiluminescence (ECL) of the tris(2,2'-bipyridyl)ruthenium(II) (Ru(bpy)3(2+)) system using resonance energy transfer with l-cysteine-capped cadmium telluride quantum dots (CdTe-QDs) in aqueous solution. The oxidative peak signal of Ru(bpy)3(2+) occurred at a voltage of 1.10V when the potential was cycled between 0.4 and 1.6V using cyclic voltammetry with a carbon screen-printed electrode (SPE) in a 0.11M phosphate buffer at pH 7.50. The l-cysteine-capped CdTe-QDs were synthesized and added into the solution of Ru(bpy)3(2+) to magnify the ECL signal. The ECL emission signal was investigated and the extreme enhancement of the ECL intensity was achieved due to the energy transfer by the l-cysteine-capped CdTe-QDs. It was found that the induced ECL from the Ru(bpy)3(2+) CdTe-QDs system was inhibited by the presence of selected nitrofurans. This quenching effect of nitrofuran antibiotics on the anodic ECL of Ru(bpy)3(2+) CdTe-QDs was found to be selective and concentration dependent and was observed to have a linear relationship over the concentration range 10-100×10(-6)M. The detection limits were found to be 0.40, 0.73 and 0.60µM for furaltadone (FTD), furazolidone (FZD) and nitrofurantoin (NFT). In addition, the proposed ECL method was successfully applied to detect the total residuals of selected nitrofuran residues in animal feed samples with satisfactory results.