1.1Impurity introduction
There is no precise definition for "impurity, " because of the apparent negativity
attached to this word in the pharmaceutical sciences. Webster's dictionary defines
impurity as something that is impure or makes something else impure A better definition
of an impure substance may be as follows: a substance of interest mixed or impregnated
with an extraneous or usually inferior substance. A simple definition for an impurity,
is, any material that aft arts the purity of the material of interest, viz., active ingredient or
drug substance. The impurities are not necessarily always inferior. From the standpoint of
its usage, the drug substance is compromised in terms of purity even if it contains another
material with superior pharmacological or toxicological properties. At first pass this may
not be readily clear, however, on further thought, it would become apparent that if we are
to ensure that an accurate amount of the drug substance is being administered to the
patient, then we must assess its purity independently from the extraneous materials.