Zirconium immobilized on gold-mercaptopropionic acid self-assembled monolayer for trace determination of phosphate in blood serum by using CV, EIS, and OSWV

Preparation, characterization, and application of a new sensor for the determination of phosphate in blood serum is described by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and osteryoung square wave voltammetry (OSWV) in the presence of an appropriate redox reaction probe. The sensor was based on ionic adsorption of phosphate on Zr(IV) immobilized on gold-mercaptopropionic acid self-assembled monolayer (Au-MPA-Zr(IV) SAM) electrode. Parameters influencing the method were optimized. A linear range calibration curve from 1.0 x 10(-7) to 1.0 x 10(-6) M PO43- with a detection limit of 5.30 x 10(-8) M and mean of relative standard deviations (R.S.D.) of 2.75% for n = 4 was observed in the best conditions by OSWV. Possible interferences from the coexisting ions were also investigated. The results demonstrated that sensor could be used for the determination of phosphate in the presence of various ions. Regeneration of the surface was carried out successfully by 5-min sonication in 0.1 M KOH solution and then 1-min incubation in 1.0 x 10(-3) M Zr(IV) with a good reproducibility, R.S.D. = 1.47% for n = 4 by OSWV. The validity of the method and applicability of the sensor were successfully tested by detection of phosphate in blood serum after deproteinization of sample without interference from sample matrix. The long-term storage stability of the electrode was studied. The experimental data is presented and discussed from which the new sensor is characterized. (C) 2008 Elsevier B.V. All rights reserved.