Metal-organic frameworks and β-cyclodextrin-based composite electrode for simultaneous quantification of guanine and adenine in a lab-on-valve manifold

In this work, a novel chemically modified electrode is constructed based on metal-organic frameworks and beta-cyclodextrin (Cu-3(BTC)(2)/beta-CD, BTC = benzene-1,3,5-tricarboxylate) composite material. The electrode was used for simultaneous determination of guanine and adenine in a sequential injection lab-on-valve format and exhibited sensitive responses to guanine and adenine oxidation due to the pi-pi stacking interaction of Cu-3(BTC)(2) and the inclusion behavior of beta-CD. The analytical performance was assessed with respect to the supporting electrolyte and its pH, accumulation time and accumulation potential, and the fluid flow rates. Under optimal conditions, linear calibration ranges for both guanine and adenine were from 1.0 x 10(-7) to 1.0 x 10(-5) mol L-1, and detection limits (S/N = 3) were found to be 5.2 x 10(-8) and 2.8 x 10(-8) mol L-1, respectively. The proposed sensor showed advantages of high sensitivity, simple sample preparation protocol, enhanced throughput and good reproducibility. Finally, the practical application of the proposed sensor has been performed for the determination of guanine and adenine in real samples with satisfactory results.