Methods of adjusting isotonicity

• Methods of adjusting isotonicity of a solution is essential in pharmaceutical and medical applications to prevent cellular damage or discomfort.
• The goal is to match the osmotic pressure of the solution to physiological fluids, such as blood or tears (~290 mOsmol/kg).

Class I Method (Cryoscopic Method):

Based on Freezing Point Depression:

• Uses the formula:
  • $ΔT=K_f×m$
• Where:
  • ΔT = change in freezing point
  • Kf = cryoscopic constant
  • m = molality of solute
• Adjust the molality to achieve the desired change in freezing point, which corresponds to isotonicity.

Class II Method (Osmotic Pressure Method):

Based on Osmotic Pressure:

• Formula:
  • $π= i ×M ×R ×T$
• Where:
  • π = osmotic pressure
  • i = van’t Hoff factor (number of particles)
  • M = molarity
  • R = ideal gas constant
  • T = temperature (Kelvin)
• Adjust solute concentration to match the osmotic pressure of an isotonic solution.

White-Vincent Methods of adjusting isotonicity:

Based on Isotonic Equivalents:

• Formula:
  • $IE=w/MW×i$
  • Where:
    • IE = isotonic equivalent
    • w = weight of solute (g)
    • MW = molecular weight of solute
    • i = van’t Hoff factor
  • Calculate isotonic equivalents for all solutes and determine the amount of isotonicity-adjusting substance needed.

Sprowls Methods of adjusting isotonicity:

Based on Equivalent Weights:

• Formula: $EW=M/100×φ$
• Where:
  • EW = equivalent weight
  • M = molecular weight of solute
  • φ = osmotic coefficient
• Determine the total equivalent weight of solutes and adjust accordingly to achieve isotonicity.

Thank you for reading from Firsthope's notes, don't forget to check YouTube videos!