The concentration of the components in a pharmaceutical preparation is based on its quantity relative to the total quantity of the preparation .
The aim : to learn pharmacy students how to prepare pharmaceutical preparation of wanted concentration from another pharmaceutical preparation of different concentration.
Contents :
1. Dilution & concentration of liquids:
2. stock solution
3. Dilution of alcohol
4. Dilution of acids
5. Dilution of solids & semisolids
6. Trituration
7. Alligation
Dilution:
? By addition of diluents .
? By admixture with solutions or mixture of lower strength .
Concentration :
? By addition of active ingredient
? By admixture with solutions or mixture of greater strength .
? Evaporation of the diluents.
Calculating the percentage or ratio strength of the solution made by diluting or concentration a solution of given quantity & strength by equation:
1. Inverse proportion .
2. The equation: ( Q1 C1 = Q2 C2)
(1st quantity 1st concentration) = (2nd quantity 2nd concentration).
3. By determining the quantity of active constituents ( solute ) needed & then calculating the quantity of the available solution (usually concentrated or stock solution ) that will provide the needed amount of constituents.
Dilution & concentration of liquids:
Example : If 500 ml of 15% (v/v) solution of methyl salicylate in alcohol are diluted to 1500 ml . What will be the percentage strength ?
x= 5%
Or :
Q1 C1 = Q2 C2
500 ml 15%=1500 ml x %
x= 5%
Or :
500 ml of 15% (v/v) solution contains 75 ml of solute
Ex.: If 50ml of 1:20 w/v solution are diluted to 1000 ml , what is the ratio strength (w/v)?
1:20 = 5%
Or:
Or:
Q1 C1 = Q2 C2
50ml 5% = 1000ml x%
x =0.25% = 1:400
Or:
50ml of a 1:20 solution contains 2.5g of solute
Ex: How many grams of 10 (w/w) ammonia solution can be made from 1800g of 28% w/w strong ammonia solution?
Or : Q1 C1 = Q2 C2
1800 28% = x g 10%
x = 5040g
Ex: How many milliliters of a 1:5000 w/v solution of drug can be made from 125ml of a 0.2% solution ?
1:5000 = 0.02%
Or :
0.2% = 1:500
Or: