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

Abstract

A highly selective membrane electrodes based on a two newly synthesized nickel (II) Schiff bases, [NiL 1] and [NiL 2] where L 1 and L 2 are N,N/bis(salicylaldehyde)4,5-dimethyl-1,2-phenylenediamine (H 2L 1) and N,N/bis(salicylaldehyde)4,5-dichloro-1,2-phenylenediamine (H 2L 2) 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 × 10 −6 and 7.3 × 10 −6 mol L −1 for the sensors based on [NiL 1] and [NiL 2], 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 × 10 −6 and 1.0 × 10 −5 to 1.0 × 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 μL of AA standards in a 1.0 × 10 −4 mol L −1 IO 4 − solution. Under these conditions, a linearity range of 2–13 μg 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 ∼50 samples h −1 without requiring pretreatment procedures. An average recovery of 98.8% and a mean standard deviation of 1.3% were obtained.