Study On Electrochemical And Photoelectrochemical Analysis Method For Detecting Trace Water In Organic Compounds

In this paper, the basic principles of electrochemical and photoelectro-chemical analysis method were reviewed in brief, and the development and application of two analytical methods were also introduced. The nature of the water, hydration and disadvantage of trace water in organic compounds were briefly expounded. Main properties and applications ruthenium complexes, especially, [Ru(1,10- phenanthroline)2(1,10-phenanthroline-5,6-dione)2+](PF6)2 (RuPhD) were reviewed in detail. Sensitivity to water-based RuPhD, the electrochemical and photoelectrochemical analysis method were developed for detecting trace water in organic compounds.The completed work in the paper is summarized as following three aspects:1. As basis of sensitivity of RuPhD to water, the electron transfer reaction on the surface of glassy carbon electrode (GCE) was investigated for the hydration reaction product of RuPhD with water in non-aqueous media. An electrochemical method for detecting trace water in organic compounds was developed based on the electrode reaction of RuPhD hydration product. In acetonitrile solution containing 0.05 mol/L tetrabutylammonium hexafluorophosphate and 1.0×10-4 mol/L RuPhD, the anodic peak currents of the differential pulse voltammetry (DPV) were proportional to water concentration in the range of 0.2%-4.76% with a linear correlation coefficient of 0.9835, and the detection limit for water was estimated to 0.03% (S/N= 3). RSD was less than 5.78%(n= 5)2. The modified electrode was prepared by electropolymerizing RuPhD on the glassy carbon electrode, and the electrode reaction was investigated after the reaction of the ruthenium complex on the electrode surface with water in non-aqueous media. The electrode was employed as working electrode of electrochemical sensor, to develop a simple and convenient method for detecting trace water in organic compounds. As basis of the selective response of the sensor, the trace water of organic compounds can be monitored by using DPV in non-aqueous medium. In the acetonitrile solution containing 0.05 mol/L tetrabutylammonium hexafluorophosphate, the anodic peak currents of the modified electrode at potential of -0.12 V wereproportional to water concentration in the range of 0.02%～5.66% with a linear correlation coefficient of 0.9994, and the detection limit for water was estimated to 0.005% (S/N= 3). The sensor was successfully applied to detect the trace water in acetonitrile, acetone,93 gasoline and diesel oil. The result showed that the relative standard deviation was less than 3.64%, and the recovery was 94.1%～105%. 3. RuPhD was electropolymerized on the surface of electrode modified by multi-walled carbon nanotubes and graphene, and the prepared electrode was employed as working electrode of photoelectrochemical sensor, to develop an analytical method for detecting trace water in organic compounds based on the photoelectrochemical effect after the reaction of RuPhD with water. Under the optimum conditions, the photocurrents of the sensor were proportional to water concentration in the range of 0.10%～1.00% with a linear correlation coefficient of 0.9994, and the detection limit for water was estimated to 0.016%(S/N= 3), RSD was less than 2.47%(n= 5).