concentration and dilution
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:
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 solution3. Dilution of alcohol4. Dilution of acids5. Dilution of solids & semisolids6. Trituration 7. AlligationDilution:? 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 C250ml 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 C21800 28% = x g 10%x = 5040gEx: 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:
Stock solution :
Stock solution are concentrated solution of active ( e.g. drug ) or inactive ( e.g. colorant ) substances & are used by pharmacists as a convenience to prepare solution of lesser concentration (strong solutions from which weaker once may be made conveniently ) .
Examples :
How many milliliters of a 1:400 w/v stock solution should be used to make 4L of a 1:2000 w/v solution ?
4L=4000ml
1:400=0.25%
1:2000=0.05%
Or
Or 4000 ml of 1:2000 w/v solution requires 2g of active constituent ;
Or: Q1 C1 = Q2 C2
4000ml x 0.25%= x x 0.05%
x =800 ml
Ex: How milliliters of a 1:50 stock solution of phenylephrine HCl should be used in compounding the following prescription ?
Rx: Phenylephrine HCl 0.25%
Rose water ad 30 ml
Sig. for the nose.
1:50 = 2 %
Or :30g x 0.0025=0.075 g of Phenylephrine HCl needed
1:50 means 1g in 50ml of stock solution
Calculation of active constituent:
Ex: 500 ml of 15% v/v solution in alcohol are diluted to 1500ml . What will be the % v/v?
Q1 x %1 = Q2 x % 2
500 x 15 % = 1500 x % after dilution
or 1500 ml 15%
500 ml x %
x =5 % v/v
Ex: How many grams of 10% w/w Ammonium can be made from 1800 g , 28% w/w Ammonium ?
1800 g x 28 % = x g x 10 %