THE ACCURATE DETERMINATION OF ACIDITY CONSTANT VALUES IS OFTEN REQUIRED IN VARIOUS CHEMICAL AND BIOCHEMICAL AREAS. THESE ARE OF VITAL IMPORTANCE IN UNDERSTANDING THE DISTRIBUTION, TRANSPORT BEHAVIOR, BINDING TO RECEPTORS AND MECHANISM OF ACTION OF CERTAIN PHARMACEUTICAL PREPARATION [1]. THE ACIDITY CONSTANTS OF ORGANIC REAGENTS PLAY A VERY FUNDAMENTAL ROLE IN MANY ANALYTICAL PROCEDURES SUCH AS ACID–BASE TITRATION, SOLVENT EXTRACTION AND COMPLEX FORMATION. POTENTIOMETRIC, SPECTROPHOTOMETRIC, CONDUCTOMETRIC AND SPECTROSCOPIC ARE CONVENTIONAL METHODS FOR DETERMINATION OF ACIDITY CONSTANTS OF ORGANIC COMPOUNDS [2].

A GRAPHENE MODIFIED CARBON PASTE ELECTRODE (GR-CPE) WAS USED FOR DETERMINATION OF DIAZABICYCLO OCTANE, DABCO, AT PH=10.5 OF PHOSPHATE BUFFER SOLUTIONS (PBS). THE CHARACTERIZATION OF THE BARE AND MODIFIED ELECTRODES WAS PERFORMED BY ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY (EIS). DENSITY FUNCTIONAL THEORY (DFT) METHOD AT B3LYP/6-311++G** LEVEL OF THEORY WAS USED TO CALCULATE THE PKA VALUE OF DABCO. ...

RANK ANNIHILATION FACTOR ANALYSIS (RAFA) WAS A MEANS EMPLOYED IN ORDER TO DETERMINE SPECTROPHOTOMETRICALLY THE ACIDITY CONSTANT OF CINNAMIC ACID IN WATER AT 25°C AND AN IONIC STRENGTH OF 0.1 M. A GENERAL METHOD IN RANK ANNIHILATION FACTOR ANALYSIS (RAFA) IS ANNIHILATION OF THE CONTRIBUTION OF ONE CHEMICAL COMPONENT FROM THE ORIGINAL DATA MATRIX. ...

IN THIS STUDY, THE ACIDITY CONSTANTS OF AURIN IN BINARY MIXTURES OF METHANOL-WATER AT 25OC AND AN IONIC STRENGTH OF 0.1 M HAVE BEEN DETERMINED BY SPECTROPHOTOMETRIC AND POTENTIOMETRIC METHODS...

A SIGNIFICANT PARAMETER FOR UNDERSTANDING AND QUANTIFYING CHEMICAL PHENOMENA REACTION RATES, BIOLOGICAL ACTIVITY, BIOLOGICAL UPTAKE, BIOLOGICAL TRANSPORT AND ENVIRONMENTAL FATE [1] CAN BE DISSOCIATION CONSTANTS. IN ORDER TO THE DETERMINATION OF DISSOCIATION CONSTANTS, SEVERAL PROCEDURES SUCH AS POTENTIOMETRIC TITRATION, SPECTROPHOTOMETRIC DETERMINATION AND CONDUCTOMETRY, HAVE BEEN REPORTED [2, 3]. ...

DISSOCIATION CONSTANTS (I.E. PKA VALUES) CAN BE A KEY PARAMETER FOR UNDERSTANDING AND QUANTIFYING CHEMICAL PHENOMENA SUCH AS REACTION RATES, BIOLOGICAL ACTIVITY, BIOLOGICAL UPTAKE, BIOLOGICAL TRANSPORT, AND ENVIRONMENTAL FATE. NUMEROUS ANALYTICAL PROCEDURES INCLUDING POTENTIOMETRIC, SPECTROPHOTOMETRIC, CONDUCTOMETRIC AND SPECTROSCOPIC HAVE BEEN REPORTED FOR THE DETERMINATION OF ACIDITY CONSTANTS OF ORGANIC COMPOUNDS.THE SCANOMETRY TECHNIQUE HAS BEEN INTRODUCED RECENTLY. IN THIS METHOD COMMERCIALLY AVAILABLE FLATBED-SCANNERS FOR OBTAINING THE IMAGES OF COLOR SOLUTIONS WAS USED. THE OBTAINED IMAGES HAVE BEEN TRANSFERRED TO COMPUTER FOR ANALYZING AND DETERMINING THE INTENSITY OF COLOR SOLUTIONS. THE METHOD IS BASED ON THE REACTION IN SOLUTION PHASE, IN PLEXIGLASÒ CELLS. THE SOLUTION WAS SCANNED AND FINALLY THE RGB (RED, GREEN AND BLUE) COLOR MODEL WAS USED IN COLOR MONITOR. WE USED FOR DETERMINATION OF THE ACIDITY CONSTANT, P K A, OF METHYL RED INDICATOR, AT FIRST TIME. THE COMPARISON BETWEEN THE CURRENT AND TRADITIONAL UV-VIS SPECTROPHOTOMETRY METHODS WAS STUDIED AND THE RESULTS REVEALED SIMILAR TRENDS IN BOTH METHODS.FOR EVALUATIONPKA OF THE INDICATOR USING SPECTROPHOTOMETRIC DATA WAS DOWN BY THE HYPSPEC PROGRAM.THE CALCULATED PKA VALUES OF THE CITED INDICATOR BY SCANOMETRY AND SPECTROPHOTOMETRIC METHODS ARE3.22 AND 3.29 RESPECTIVELY. THE CORRESPONDING DISTRIBUTION DIAGRAMS WERE DEPICTED BY HYSS2009 PROGRAM AS A NEW VERSION OF THE OLDER ONE.

INTRODUCTION: ACIDITY CONSTANTS, OR PKA VALUES, ARE ONE OF THE MOST IMPORTANT CHEMICAL PROPERTIES WHICH ARE VERY USEFUL FOR UNDERSTANDING MANY FUNDAMENTAL REACTIONS IN CHEMISTRY AND BIOCHEMISTRY. ...

INTRODUCTION: NOWADAYS CYCLODEXTRINS KNOWN AS THE MOST SUCCESSFUL GROUP OF MACROCYCLIC COMPOUNDS WITHIN THE FIELD OF SUPRAMOLECULAR CHEMISTRY. THEY HAVE A UNIQUE ABILITY TO FORM INCLUSION COMPLEXES WITH WIDE VARIETY OF MOLECULES. THE COMPLEXATION OF THE GUEST MOLECULE CAN EFFECTIVELY CHANGE ITS CHEMICAL OR PHYSICAL PROPERTIES [1]. PHENYLEPHRINE (PEP) IS A SELECTIVE A1-ADRENERGIC RECEPTOR AGONIST USED PRIMARILY AS A DECONGESTANT, AS AN AGENT TO DILATE THE PUPIL, AND TO INCREASE BLOOD PRESSURE. PEP IS USED AS A DECONGESTANT SOLD AS AN ORAL MEDICINE, AS A NASAL SPRAY, OR AS EYE DROPS [2]. IN THIS WORK THE ACID-BASE EQUILIBRIUM OF PEP IS STUDIED IN THE ABSENCE AND PRESENCE OF B-CYCLODEXTRIN (B -CD).