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UNIT V pH, BUFFERS AND ISOTONIC SOLUTION

UNIT V pH, BUFFERS AND ISOTONIC SOLUTION. By: Ms. Santoshi Naik Assistant Professor Yenepoya Pharmacy College and Research Centre. Introduction. pH - represents hydrogen ion potential . It is defined as the common logarithm of the reciprocal of the hydrogen ion concentration. OR. pH.

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UNIT V pH, BUFFERS AND ISOTONIC SOLUTION

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  1. UNIT VpH, BUFFERS AND ISOTONIC SOLUTION By: Ms. Santoshi Naik Assistant Professor Yenepoya Pharmacy College and Research Centre

  2. Introduction • pH - represents hydrogen ion potential. • It is defined as the common logarithm of the reciprocal of the hydrogen ion concentration. OR pH pH [H+]

  3. Sorensen suggested simplified method of expressing hydrogen ion concentration

  4. pH DETERMINATION 1) Colorimetric method – pH paper

  5. 2) Electrometric method –pH meter

  6. Applications of Electrometric method • To find out the concentration of H+ ion. • To find out the concentration of OH- ion. • To find out the concentration of buffers to be added. • To improve the stability, solubility and purity of given solution.

  7. Buffers • Buffers are compounds or mixtures of compounds that resist changes in pH, even after the addition of small quantities of acids or alkali. • Buffers are classified as: 1) Acidic buffer –pH less than 7 • Its combination of weak acid and its salt. Eg: CH3COOH & CH3COONa. 2) Basic buffer –pH more than 7 • Its combination of weak base and its salt. Eg: NH4OH & NH4Cl.

  8. Applications of Buffers • Maintenance of life • Biochemical assay • In shampoos • In brewing industry • In textile industry • In baby lotions

  9. Buffer equation • Also referred as Henderson Haselbalch equation. • It is used to calculate the pH of the solution or to find out the concentration of H+ ions.

  10. Buffer Capacity • Is defined as the resistance offered by the buffer in the change in pH on addition of small amount of acid or base. • It is denoted by 𝛽. • Buffer capacity is also defined as the ratio of small increment caused by strong acids or strong bases causing small change in the pH on its addition. 𝛽

  11. Buffers in Pharmaceutical and Biological systems • Buffers in Pharmaceutical systems • Salicylic acid stored in glass bottles. • Ephedrine and Ephedrine HCl • Buffer system consisting of boric acid, sodium borate and NaCl.

  12. Buffers in Biological systems • In-vivo biologic buffer systems eg: blood and lacrimal fluid. • Urine

  13. Buffered Isotonic solution • Isotonic solution: refers to solutions having same osmotic pressure across a semipermeable membrane. Eg: 0.9% NaCl solution. • Hypertonic solution: refers to solution where the concentration of solutes is greater outside the cell than inside it. Eg: 2% NaCl solution. It leads to cell shrinkage or crenation. • Hypotonic solution: refers to solution where the concentration of solutes is greater inside the cell than outside it. Eg: 0.2% NaCl solution. It leads to swelling and finally hemolysis.

  14. Tonicity and Measurements of tonicity • Is the concentration of only the solutes that cannot cross the membrane since these solutes exert osmotic pressure on that membrane. • Methods: • Hemolytic method • Measurement of slight temperature differences. • Calculating tonicity using Liso values.

  15. Methods of adjusting Tonicity & pH

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