This is short note for the quick revision of the chapter-1 of D.Pharm or any other pharmacy course syllabus. It includes -accuracy, precision and significant figures. -Impurities (definition, sources and effects) - Limit test (definition) -Limit test for chlorides -Limit test for sulphates.

1. Accuracy, Precision and significant figures
Prepared By – Kartik Tiwari (Lecturer)
Hygia College of Pharmacy, Lucknow (U.P)
Content as Per D. Pharm Syllabus
Accuracy Precision Significant figures
Accuracy is the closeness of
agreement between a measured
value and a true or accepted value
(measurement error reveals the
amount of inaccuracy).
Accuracy =
Observed value
Exact value
* 100
Precision is a measure of the degree
of consistency and agreement among
independent measurements of the
same quantity (also the reliability or
reproducibilityof the result).
Significant figures are the digits of value
which carry meaning towards the
resolution of the measurement. Significant
figures are the number of digits necessary
to express the result of a measurement
compatible with the measured precision.
Impurities
Any unwanted foreign - matter present in a
compound which are differ from the actual
molecular formula.
Impurities:
Sourcesof impurities
1. During manufacturing.
 From Raw materials
 Reagents used in the manufacturing process
 Solvent used in the manufacturing process
 Reaction equipment
 ManufacturingHazards
2. During purification and processing.
 Reagent used to remove other impurities
 Solvents used in the process of purification
 Contamination due to vessels and equipment(
filters, centrifuges, dryers etc.) used for purification
3. During storage.
 Errors in packaging materials
 Faulty packaging process
 Microbialcontamination
Impurities could make the original substance incompatible and
speed up the deterioration of the substance. Some
contaminants actively participate in the chemical process,
altering the chemical properties of original substances.
The impurities effect on
 Potency
 Self life of drug
 Therapeutic value
It occurs due to
 Oxidation of the drug
 Temperature
 Humidity
Effects of impurities
Limit test is defined as quantitative or semi- quantitative test
designed to be identifies and control small quantities of
impurity which is likely to be present in the substance.
Limit test includes chloride, sulphate, iron, heavy metals and
Arsenic.
Limit Test:
Limit Test (Principle, Chemical reaction, Procedure and Observation)
LIMIT TEST FOR CHLORIDES LIMIT TEST FOR SULPHATES
Principle: It is based upon the chemical reaction between
silver nitrate and soluble chloride to obtained silver chloride
in the presence of nitric acid. The test solution becomes
turbid due to the silver chloride that is produced when dilute
nitric acid is present.
Procedure:
Observation: Turbidity of the test solution should be less
than standard solution.
Principle: The limit test of sulphate is based on the chemical
reactions between barium chloride and soluble sulphate in
the presence of acetic acid.
Procedure:
Observation: Turbidity of the test solution should be less
than standard solution.
Test solution Standard solution
1. Specific weight of compound is
dissolved in water or solution is
prepared as directed in the
pharmacopoeia and transfer to
nessler cylinder
2. Add 0.15 ml of 5M acetic acid
3. Add 2.5 ml of barium sulphate
4. Add sufficient distilled water to
Produce 50 ml.
1. Mix 15 ml of sulphate standard
solution and 15 ml of distilled
water in a nessler cylinder.
2. Add 0.15 ml of 5M acetic acid
3. Add 2.5 ml of barium sulphate
4. Add sufficient distilled water to
Produce 50 ml.
Test solution Standard solution
1. Specific amount of compound
dissolve in a distilled water and
solution is prepared according to
Pharmacopoeia and transfer to
nessler cylinder.
2. Add 1ml of dil. HNO3
3. Dilute to 50 ml of water
4. Add 1ml of AgNO3
1. Take 10 ml of chloride standard
solution (25ppm Cl) and 5 ml of
water.
2. Add 1ml of dil. HNO3
3. Dilute to 50 ml of water
4. Add 1ml of AgNO3