1. 1. PH AND BUFFERS Speaker : Manish Verma B.Sc. MLT 1st year
2. 2. INTRODUCTION ph p means Puissance d and H mean Hydrogen. It is the French word, which means strength/ power of hydrogen. It was introduced by Sorenson in 1909. Definition : It is defined as the negative log of the hydrogen ion concentration: pH = -log [H+]
3. 3. CONT pH is a unit of measure which describes the degree of acidity or alkalinity (basic) of a solution. It is measured on a scale of 0 to 14. Low pH values correspond to high concentrations of H+ and high pH values correspond to low concentrations of H+.
4. 4. PH VALUE The pH value of a substance is directly related to the ratio of the hydrogen ion and hydroxyl ion concentrations. If the H+ concentration is higher than OH- the material is acidic. If the OH- concentration is higher than H+ the material is basic. 7 is neutral, < is acidic, >7 is basic
5. 5. THE PH SCALE The pH scale corresponds to the concentration of hydrogen ions. If you take the exponent of the H3O+ concentrations and remove the negative sign you have the pH of the solution. For example pure water H+ ion concentration is 1 x 10^-7 M, therefore the pH would then be 7.
6. 6. MEASUREMENT OF PH The pH can be measured by: ph strips Ph indicators Ph meter
7. 7. PH STRIPS pH strips are pieces of paper that change color depending on the pH the acidity or alkalinity of a liquid. pH strips are Brownish yellow in colour (Whatman filter); by this method approx value is obtained, which are less accurate
8. 8. CONT.. They are used for urine sample and not for blood or plasma as : (1) They are affected by oxidized and reduced agents (2) They are also affected by concentration of proteins and salts
9. 9. PH INDICATORS Definition: Indicators are the organic compounds of natural or synthetic origin whose colour is dependent on pH. The pH indicators are either weak acids or weak bases having different colours in undissocisted and dissociated forms: HIn