THIOUREA (NH2) 2 CS HAS THE IMPORTANT ROLE IN VARIED INDUSTRIAL PROCESS ESPECIALLY IN ELECTROREFINING PROCESS. IN CATHODIC COPPER REFINERY UNITS DIFFERENT ADDITIVES ARE INTRODUCED INTO THE ELECTROLYTIC BATH TO MAINTAIN CATHODE QUALITY REQUIREMENTS. THESE ADDITIVES, WHICH ACT MOSTLY AS INHIBITORS, ADSORB ONTO THE CATHODE SURFACE WHERE THEY TAKE PART IN THE ELECTROCHEMICAL CRYSTALLIZATION PROCESS. THIOUREA AND GELATIN ARE COMMON ORGANIC ADDITIVES USED IN MODERN TANK HOUSES TO PRODUCE SMOOTH, DENSE AND COHERENT DEPOSITS. THESE ADDITIVES INFLUENCE THE ELECTROCRYSTALLISATION OF COPPER IN VARIOUS WAYS. ACCORDINGLY THIOREA DETERMINATION IS VERY IMPORTANT. THE PRESENT WORK DESCRIBES THE APPLICATION OF ADSORPTION ABILITY OF THIOUREA ON THE SURFACE OF PLATINUM ELECTRODE FOR THIOUREA DETECTION. THE RESULTS DISPLAY THAT THIOUREA BINDS TO SURFACE AND PROVIDES A RESISTANCE AGAINST ELECTRON TRANSFER. THIS RESISTANCE IS INCREASED LINEARLY WITH THIOUREA CONCENTRATION. THE CHARGE TRANSFER RESISTANCE (RCT) WAS MEASURED WITH THE HELP OF ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY (EIS) TECHNIQUE. EXPERIMENTAL FACTORS OPTIMIZED FOR ACQUIRE THE BEST RESULTS. THE ELECTRODE RESISTANCE PROVIDED A LINEAR RESPONSE TO THE THIOUREA OVER THE CONCENTRATION RANGE OF 0.5-6 PPM WITH A STANDARD DEVIATION OF 6.5% AND DETECTION LIMIT OF 0.23 PPM.

INTRODUCTION: ELECTROCHEMICAL NOISE (EN) IS SIMULTANEOUS MEASUREMENT OF POTENTIAL AND CURRENT OF TWO IDENTICAL ELECTRODES VERSUS TIME. IN THIS REGARDS, TWO NOMINALLY IDENTICAL ELECTRODES CONNECTED BY A ZERO RESISTANCE AMMETER (ZRA) THAT CAUSES TWO ELECTRODES SENSE A SIMILAR POTENTIAL. THE POTENTIAL IS MEASURED VS. A STANDARD REFERENCE ELECTRODE OR A THIRD SIMILAR IDENTICAL ELECTRODE [1-2]...

IONOPHORE DERIVATIVE ANION RECEPTOR HAS BEEN TESTED AS ELECTRO ACTIVE MATERIAL FOR THE DEVELOPMENT OF ANION SELECTIVE ELECTRODES. THE RECEPTOR WAS INCORPORATED IN PLASTICIZED POLY (VINYL CHLORIDE) MEMBRANES OF DIFFERENT COMPOSITIONS. THE MEMBRANE THAT PROVIDED THE BEST RESPONSE AND SELECTIVITY TOWARDS NITRATE WAS SELECTED TO DEVELOP A NEW NITRATE-SELECTIVE ELECTRODE. IN THIS WORK A NEW STRATEGY FOR OPTIMIZING MEMBRANE COMPONENTS BY ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY (EIS) IS USED. THE PERFORMANCE OF THIS ELECTRODE WAS INVESTIGATED USING POTENTIOMETRIC AND EIS TECHNIQUES. THE ELECTRODE EXHIBITED A NERNSTIAN RESPONSE OVER THE NITRATE CONCENTRATION RANGE OF 1.0×10-7 TO 1.0×10-1 M WITH A SLOPE OF 59.5 MV/DECADE BY POTENTIOMETRIC TECHNIQUE. IT SHOWED GOOD SELECTIVITY TO NITRATE RELATIVE TO MANY COMMON ANIONS. WHILE USING THE EIS TECHNIQUE, THE LINEAR CONCENTRATION RANGE WAS 1.0×10-8 TO 1.0×10-1 M AND THE PH RANGE INCREASED TO 4.0-10.0. THE PROPOSED ELECTRODE WAS APPLIED TO THE DETERMINATION OF NITRATE IN WASTEWATERS.

CONDUCTIVE POLYMERS DUE TO THEIR WIDE APPLICATIONS HAVE ATTRACTED THE ATTENTION OF MANY RESEARCHERS IN RECENT YEARS [1]. ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY (EIS) IS A USEFUL TECHNIQUE FOR STUDYING THE STRUCTURE AND CONDUCTIVE PROPERTIES AT THE CONDUCTIVE POLYMERS SUCH AS POLYPYRROLE AND POLYANILINE [2]. IN THIS WORK, ELECTROCOPOLYMERIZAITON OF PYRROLE (PY) AND 2, 4- DINITROANILINE (DNA) ON COMPOSITE GRAPHITE ELECTRODE IS DONE BY CYCLIC VOLTAMMETRY (CV) METHOD IN POTENTIAL RANGE OF - 0.2 TO 1 VOLT (VS. AG/AGCL), AT A SCAN RATE 100 MVS-1 IN 1M PHOSPHORIC ACID, INCLUDING EQUAL AMOUNTS OF MOLAR CONCENTRATIONS OF POTASSIUM CHLORIDE (KCL) AND PARA TOLUENE SULFONIC ACID (PTSA) AS SUPPORT ELECTROLYTE. THESE MODIFIED COMPOSITE GRAPHITE ELECTRODE (MCGE) HAVE BEEN CHARACTERIZED USING FOURIER TRANSFORM INFRARED (FTIR), AND SCANNING ELECTRON MICROSCOPY (SEM) TECHNIQUES, RESPECTIVELY. ELECTROCHEMICAL BEHAVIOR OF POLY(PYCO- DNA)/CGE IS INVESTIGATED BY ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY (EIS) AND DIFFERENTIAL PULSE VOLTAMMETRY (DPV). EISAPPLIED TO STUDYTHE CONDUCTIVE PROPERTIES MODIFIED ELECTRODE IN 1MM IRON SOLUTION INCLUDING 1 M KCL. SEMICIRCLE DIAMETER OF THE NYQUIST DIAGRAM IS EQUAL TO THE CHARGE TRANSFER RESISTANCE (RCT) AT THE ELECTRODE SURFACE. THE NYQUIST PLOT SHOWS LESS THAN CHARGE TRANSFER RESISTANCE (RCT) OF POLY (PY-CO- DNA)/CGE COMPARE TO BARE CGE (FIG. 1). THE RESULTS SHOWED POLY (PY-CO-DNA)/CGE BE APPLIED TO THE FIELD OF ELECTRONIC AND SENSOR FABRICATION [3].