Measurement of pH-lec-lab

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Measurement of pH :

Measurement of pH 1


Methods Colorimetric methods Titration methods pH papers Electrochemical methods

Electrochemical Method- Use of pH Meter :

Principle: When a pH glass electrode is dipped into a solution whose pH is to be measured, a potential difference is generated on the inside of the glass membrane depending on concentration of H +. The pH meter takes the input from glass electrode and from reference electrode and compares these two values to get a millivolt (mV) reading which is converted to pH units by the following guidelines. zero mV = pH 7.0 59.2 mV per unit pH change mV are positive for pH less than 7.0 mV are negative for pH greater than 7.0 Electrochemical Method- Use of pH Met er

pH Meter :

pH Meter Components of a pH Meter pH electrode : an electrode whose output voltage changes as the pH (hydrogen ion concentration) changes. A reference electrode : an electrode whose output voltage remains constant. A measuring unit: a millivolt meter with a special high resistance input circuit and ability to change electrode millivolts to readable pH units. Automatic temperature compensator (optio nal) -------------------------------------------------------------------------------------- Combined electrode: consists of a pH electrode and reference electrode built into a single body or housing . 4

Types of electrodes :

Types of electrodes


Procedure Put the pH METER on by connecting it to suitable electric line. Wait for 10 minutes. Calibrate the equipment with standard solutions with pH of 7.0, 4.0 and 10.0. Now the pH meter is ready for use Take the unknown solution and dip the combined electrode in it . Wait for 1 minute , Record the pH from display. Wash the electrode after each step.

PowerPoint Presentation:

Interpretation Reference range blood plasma 7.35-7.45 Acidosis– decrease in pH Metabolic acidosis Respiratory acidosis. Alkalosis- increase in blood pH Metabolic alkalosis; Respiratory alkalosis

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