PCP-Molarities and chemical concentrations

What is Concentration?

Concentration refers to the ratio of the amount of the ingredient to  the amount of product.

What are the different ways concentration can be expressed?

It can be expressed in a number of different ways:

1.Quantity per volume

2.Percentage concentrations

3.Ratios

Parts

What is the Quantity per volume expression and Describe ?

•A quantity per volume expression gives the amount or weight of a drug (either in moles or grams) in a volume of solution.

•It is also referred to as an amount strength.

•For example, a 9 g/L solution of sodium chloride means that 9 grams of sodium chloride are dissolved in 1 litre of solution.

Example calculation - Quantity per volume 

500mg= 0.5g

200ml – 0.2 L

0.5/0.2= 2.5g/L

What is percentage concentrations and describe it?

•Percentages are used to express the amount of liquid or solid active ingredient in a defined amount of liquid or solid product.

•There are four commonly used percentage terms:

1.% w/w (percentage weight in weight)

2.% w/v (percentage weight in volume)

3.% v/v (percentage volume in volume)

% v/w (percentage volume in weight)

What is % w/w?

•Weight of a solid active ingredient in 100 g of a solid product.

•For example, 1% w/w denotes that 1 g of active ingredient is contained in 100 g of the final solid product.

How much active ingredient have we got in …

What is % w/v ?

Weight of a solid active ingredient in 100 mL of a liquid product.

For example, a 2% w/v means there is 2 g of drug in 100 mL of the final liquid solution

What is the % v/v ?

•Volume of liquid active ingredient in 100 mL of a liquid product.

•For example, a 30% v/v denotes there is 30 mL of drug in 100 mL of final liquid solution.

What is % v/w?

•Amount of liquid drug in millilitres in 100 g of solid product.

•For example, 40% v/w means there is 40 mL of drug in 100 g of solid product.

Example calculation- using %w/v

1.25g in 100ml 

1.25/100 × 540 = 6.75g

Example calc - % w/w

3g per 100g

find in 1 g then multiply up : 3/100 × 25 = 0.75g

What is a Ratio concentrations and describe them ?

•Ratios are used to express the amount of one pharmaceutical ingredient relative to the amount of another.

•There are two phrases used for ratios that are similar but would yield different amounts…

• to (1:10 1 drug 10 parts X ) -total added together

• in ( 1 in 10 1 part drug ,9 parts X) -total 10 (stated)

Example calculations- to ratio

1ml of drug in 20ml in solvent 

21 ml  total 

250/21 = 11.9ml

What is parts of concentration (ppm) and describe it ?

•Parts per million (ppm) is used for concentrations where the ratio of active ingredient to product is very small.

•It is equivalent to a ratio of p in 1,000,000.

•1 ppm w/v = 1 g in 1,000,000 ml

Example calculation- ppm

0.45g in 1,000,000ml  of drug

450mg in 1,000,000ml

 1mg :1000000/450 =

 222ml = 2.22l

How to convert between concentrations- ratio general method ?

step 1- write out information

step 2- convert units to g

step 3 - find what is in 1 g

step 4 write in a ratio

EXAMPLE : ratio - concentration conversion calculation

Ratio concentration-

1. 10mg in 5 ml

2. 0.01g in 5ml

3. In 1g:

5/0.01=500ml

4 . RATIO- 1 in 500

How to convert between concentrations - percentage general method?

step 1- write out information

step 2 - convert any units 

step 3 - find what is in 100ml 

step 4 - write as a percentage 

EXAMPLE- percentage ratio calculation

1. 10mg in 5 ml

2. 0.01g per 5ml

3. 100ml – 20x0.01= 0.2 g

4. 0.2%

What is molarity ?

•Molarity is the measure of the number of moles of a substance dissolved in litres of a solution.

What is Molarity equation?

Molarity (mol/L) = number of moles / volume (L)