Physical Pharmacy

SOLUBILIZATIONSOLUBILIZATIONBy

Abdul-Wahhab KhedrDemonstrator of Pharmaceutics & Industrial

Pharmacy

Definition:Definition:

• SolubilizationSolubilization is the process of bringing into solution substances which are insoluble or sparingly soluble in water.

• Methods of Solubilization:1) The use of mixed solvents (blending and Co-solvency).2) The use of surface active agents (Micelle formation).3) The use of hydrotropic salts e.g. iodine and potassium

iodide.4) Complex formation e.g. caffeine and barbiturate.

Determination of Solubility of Benzoic acidDetermination of Solubility of Benzoic acid

• Procedure:Procedure:1. In a glass bottle, add 0.5 gm benzoic acid & 20 ml

distilled water.2. Shake for 10 min and set aside for another 10 min.3. Filter the contents of the bottle, take 10 ml of the

filterate and titrate with 0.1 N NaOH using Ph.Ph. as indicator (3-5 dps).

4. The End Point is determined by the appearance of the first permanent faint pink colour.

5. Repeat the above steps using surfactant solutions (1%, 3%, 5%, 7%) instead of distilled water and determine the end points.

E.P = Volume of titrant used

0.5 gm benzoic acid

20 ml dist. Water or sample soln

Shake for 10 minSet aside for 10 min

10 ml of filterate

3 dps Ph.Ph

0.1 N NaOH

ProcedureProcedure

Filter

Calculation of SolubilityCalculation of Solubility

)/(10

1000.lub lg

FPEilitySo

Factor (F): is the amount of benzoic acid (in grams) neutralized by 1 ml of titrant (0.1 N NaOH).

Calculation of Factor (F):Calculation of Factor (F):

+ NaOH + H2O

1 mole benzoic acid ≡ 1 mole NaOH 122 gm ≡ 1000 ml 1 M NaOH 122 gm ≡ 1000 ml 1 N NaOH 122 /10 ≡ 1000 ml 0.1 N NaOH F ≡ 1 ml 0.1 N NaOH

0122.0100010

122

F

Calculation of SolubilityCalculation of Solubility

)/(10

10000122.0.lub lg

PEilitySo

Results:Results:

Surfactant ConcnE.PSolubility (g/l)

1%

3%

5%

7%

Then draw the relationship between surfactant concn (on x-axis) and solubility (on y-axis).