Batch and hydrodynamic monitoring of vitamin C using novel periodate selective sensors based on a newly synthesized Ni(II)-Schiff bases complexes as a neutral receptors

A highly selective membrane electrodes based on a two newly synthesized nickel (II) Schiff bases, [NiL1] and [NiL2] where L-1 and L-2 are N,N/bis(salicylaldehyde)4,5-dimethyl-1,2-phenylenediamine (H2L1) and N,N/bis(salicylaldehyde)4,5-dichloro-1,2-phenylenediamine (H2L2) were used as a neutral carrier ionophores for static and hydrodynamic potentiometric mode of operations for the determination of periodate. Under static mode of operation, the sensors displayed a near-Nernstian slope of -66.1 +/- 0.8 and -59.9 +/- 1.1 mV decade(-1) of activity and detection limits to 5.2 x 10(-6) and 7.3 x 10(-6) mol L-1 for the sensors based on [NiL1] and [NiL2], respectively. Under hydrodynamic mode of operation (FIA), the slope of the calibration plot, limit of detection, and working linear range were -71.1 mVdecade(-1) of activity, 7.3 x 10(-6) and 1.0 x 10(-5) to 1.0 x 10(-3) mol L-1, respectively. The response time of the sensors in whole concentration ranges was very short (< 10 s). The response of the sensors was independent on the pH range of 3-8. A tubular version was further developed and coupled to a flow injection system for ascorbic acid (AA) determination in beverages and pharmaceutical preparations. This approach was achieved by selecting a 50-cm reactor and an overall flow of 3 mL min(-1), and injecting volume 100 mu L of AA standards in a 1.0 x 10(-4) mol L-1 IO4- solution. Under these conditions, a linearity range of 2-13 mu g mL(-1), with a slope of 4.97 mV (mg/L)(-1) (r(2) = 0.9995), detection limit 0.9 mg L-1 and a reproducibility of +/- 1.1 mV (n = 5) was recorded. This simple and inexpensive flow injection analysis manifold, with a good potentiometric detector, enabled the analysis of similar to 50 samples h(-1) without requiring pretreatment procedures. An average recovery of 98.8% and a mean standard deviation of 1.3% were obtained. (C) 2009 Elsevier B.V. All rights reserved.