Aquametry is the analytical process of measuring the amount of water present in a product. It is commonly known as Karl Fischer titration which uses a Karl Fischer reagent to determine water content amperometrically. The water content of pharmaceutical products and materials is important to measure as water can be present as a solvent, absorbed water, or water of crystallization. The properties and stability of products are affected by their water content. Karl Fischer titration is a popular method for precise water determination and has applications in analyzing soils, foods, and other materials.

1. Aquametry
Abdullah Al Noman
Daffodil International
University.
Bangladesh.

2. Aquametry
AQUAMETRY AQUA- means water METRY- means measurement
Aquametry is a analytical process to measure the water present in any
product.
Determining micro quantities of water by the use of Karl Fischer Reagent by
the application of current is known as aquametry. It is also been known as
amperometry.

3. Importance of water determination
Quantitative determination of water is important because many drugs contain
water:
As a solvent
As absorbed water
As water of crystallization
As an adulterant
Physical properties of a drug or a raw material are modified by its water content.
Pharmaceutical procedures of granulation, tablet formation & coating operations
are affected by water content.

4. Methods of Water Determination
Methods of Water determination can be of
two types
1. Thermal Methods:
Loss on drying
Azeotropic Distillation Method
2. Chemical Methods:
Karl Fischer Titration

5. Importance of aquametry
1.Quantitative Determination of Water in pharmaceutical products is
important.because H2O may be present in the products as – Solvent Absorbed
water. water of Crystallization
2.This is important, because – Physical properties of a drug or raw material is
modified by the presence of H2O
3. Physical stability of the product may be hampered in presence of water.
So , we should determine whether it possesses water or not.
4. Water content of drugs may also be important for other reasons i.e- when
crude drugs

6. The principle of Karl Fischer titration
Fundamental Reaction
The fundamental principle behind the Karl Fischer Titration is based on the Bunsen
reaction between iodine and sulphur dioxide in an aqueous medium shown below:
I2+ SO2+2H2O → 2HI+ H2SO4
Karl Fischer discovered that this reaction could be modified to be used for the
determination of water in a non-aqueous system containing an excess of
sulphurdioxide. He used a primary alcohol (methanol) as the solvent, and a base
(pyridine) as the buffering agent. So the reaction changed into
py. I2+ py ·SO2+H2O+ py → 2py ·HI+ py ·SO3

7. Preparation of Karl Fischer titration
Into a glass- stoppered flask (about 750 ml capacity) anhydrous methanol (400
ml,containing not more than .03% water ) is placed and pure dry pyridine(80 g)
is taken.
Flask is immersed in a freezing mixture and slowly sulphur dioxide is passed
into the cold solution , with continuous agitation, until the increase in weight is
20 g .
Finally iodine is added (45 g) , and shaked well to dissolve and the mixture is
allowed to stand for 24 hr before use.

8. Advantages of Karl Fischer Titration
Karl Fischer Titration Method is very popular for a large practical advantage which
it holds over other moisture determination technique,
These includes
Easy Sample Preparation
High Accuracy and Precision
Independence of presence any volatile materials
Nearly Unlimited Measuring Range
Short Analysis Duration
Small Sample Quantities required
Suitability for analysing-
Solids
Liquids
Gases

9. Application
Soil quality: The appearance of large information banks on soil properties in
Europe was provoked by necessity of increasing of agricultural production
economics, i.e. the commercial price of soil as the production medium.
Quality of food materials and products: Moisture content affects food quality,
i.e. texture, taste, appearance and stability of foods depends on the amount of
water they contain. A knowledge of the moisture content is often necessary to
predict the behavior of foods during processing, e.g. mixing, drying,
transportation, flow through a pipe or packaging, storage stability or shelf-life