ABSTRACT
Orthophosphate is an essential macronutrient in natural water that controls primary production and strongly influences the global ocean carbon cycle. Electrochemical determination of orthophosphate is highly recommended because electrochemistry provides the simplest means of determination. Here the determination of orthophosphate based on the formation of a phosphomolybdate complex is reported. Mixed-valent molybdenum oxide (MoxOy) was prepared by cyclic voltammetry on poly-1,2-diaminoanthraquinone (1,2-DAAQ), which was performed by cyclic voltammetry on the surface of a glassy carbon electrode under pre-optimized conditions for the thickness of the modified electrode layers. The proposed modified electrode was used for square-wave voltammetry of orthophosphate ions under pre-optimized square-wave parameters (i.e., frequency and amplitude) in strongly acidic medium (pH < 1). The linear range was 0.05-4 µM with a limit of quantification (LOD) of 0.0093 µM with no effect on two peaks due to cross interference from silicate. Furthermore, MoxOy/PDAAQ shows good reproducibility with a relative standard deviation (RSD) of 2.17% for the peak at 0.035 V and 3.56% for the peak at 0.2 V. Real seawater samples were also analyzed for PO43- analysis by UV spectrophotometry and the results were compared with the measurement results of our proposed electrode, with good recoveries obtained.
ABSTRACT
A glassy carbon (GC) electrode was modified with poly(1,8-diaminonaphthalene) (p-1,8-DAN) that was coated with silver nanoparticles (Ag NPs) (size: 10.0-60.0 nm by TEM) by electrodeposition process using cyclic voltammetry (CV) technique. The resulting nanocomposite was characterized by FE-SEM, AFM, EDX, XPS, TEM and XRD. The surface area and the electrochemical characteristics of the electrode were investigated by CV and square wave voltammetry (SWV) techniques, and the probe preparation conditions were optimized. The electrode was used for individual and simultaneous determination of the heavy metal ions cadmium(II) (Cd2+), lead(II) (Pb2+) and copper(II) (Cu2+) in water samples by square wave anodic stripping voltammetry (ASV) using scan rate 0.005 V. s-1. The probe showed well separated anodic stripping peaks for Cd2+, Pb2+, and Cu2+. Attractive features of the method include (a) peak voltages of -1.02, -0.78 and - 0.32 V (vs. Ag/AgCl) for the three ions, and (b) low limits of detection (19, 30 and 6 ng.L-1, respectively. The electrode can also detect zinc(II) (Zn2+) and mercury(II) (Hg2+), typically at -1.36 V and + 0.9, respectively. Graphical abstract Schematic presentation of simultaneous electrochemical determination of Pb2+, Cd2+, and Cu2+ at a poly(1,8-diaminonaphthalene)-modified glassy carbon electrode coated with silver nanoparticles.
