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In this work, we developed an efficient electrochemical exfoliation strategy for the preparation of graphene (eGr) nanosheets. Newly designed nanosheets-like eGr/GCE electrode possessed large specific surface area, low defect and good electrical conductivity, which facilitates the preconcentration of Kinetin (KT) onto the electrode surface. It exhibits a linear range extending from 0.5 to 100 µM and the lowest detection limit at 0.15 µM. The KT oxidation on eGr is an adsorption-controlled process, which involves a total of 4 H+ and 4 e− in the transferring processes. Moreover, there were no significant interfering substances among inorganics (NO3−, Cu2+, K+, PO43−, SO42−, Na+, Cl−), quercetin, rutin, luteolin, luteoloside, naphthylacetic acid, 2,4-dichlorophenoxyacetic acid and indole-3-acetic acid. The recoveries are in the range of 89.6–117.43% with a relative and deviation (RSD) < 4% (n = 3) for KT detection in lettuce. [ABSTRACT FROM AUTHOR]

In the present work, a sensitive, facile and disposable sensing platform for trace analysis of heavy metal ions was developed at the Bi modified graphene-poly(sodium 4-styrenesulfonate) composite film screen printed electrode (GR/PSS/Bi/SPE). The GR/PSS/Bi/SPE improved sensitivity and linearity due to the functionalization of graphene with negatively charged PSS providing more absorbing sites. The detection limit of the GR/PSS/Bi/SPE is found to be 0.042 µg L−1 for Cd2+ and 0.089 µg L−1 for Pb2+ with linear responses of Cd2+ and Pb2+ in the range of 0.5-120 µg L−1. Finally, the practical application was confirmed in real water with satisfactory results. [ABSTRACT FROM AUTHOR]

Abstract: In this report, a voltammetric sensor for simultaneous determination of hydroquinone (HQ) and catechol (CC) was developed at a glassy carbon electrode modified with graphene (GR/GCE). The separation of oxidation and reduction peak (ΔE) is decreased from 281 to 31mV for HQ and from 250 to 26mV for CC at GR/GCE, respectively. Separation of the oxidation peak potentials for HQ and CC was about 112mV in 0.10M acetate buffer solution (pH 4.5), and the anodic currents for the oxidation of both HQ and CC are greatly increased at GR/GCE, which makes it suitable for simultaneous determination of these compounds. Under the optimized condition, the anodic peak current of HQ is linear with the concentration of HQ from 1×10−6 to 5×10−5 M in the presence of 5×10−5 M CC. A detection limit of 1.5×10−8 M (S/N =3) can be achieved. At the same time, the anodic current of CC is linear with the concentration of CC from 1×10−6 to 5×10−5 M with a detection limit of 1.0×10−8 M (S/N =3) in the presence of 5×10−5 M HQ. The proposed sensor was successfully applied to the simultaneous determination of HQ and CC in tap water, and the results are satisfactory. [ABSTRACT FROM AUTHOR]