Page 20 - Pharmaceutical Analytical Chemistry III
P. 20
The Effect of Determinate Errors Upon Analytical Results
Proportional Errors:
They increase or decrease in proportional to the size of the sample
taken for analysis.
• – Absolute error varies with size of sample.
• – Relative error is constant
Example: Presence of given proportion of interfering impurity in
sample, the amount of an interferent increases with the size of
the sample.
The determination of Cu2+ iodometrically, if the sample contain
Fe3+ impurity, the error will be proportional to the sample size as
the impurity will increase by the sample size.
