QCS-016 - Quality Operations Procedures for Pharmaceutical, API, and Biotechnology - page 83

SOP No. QCS-016.00 Effective date: mm/dd/yyyy
Approved by:

Similarly, the fact that an article has been prepared to closer tolerances than those specified in the
monograph does not constitute a basis for a claim that the article “exceeds” the pharmacopeial
requirements.

16.3.3.1 interpretation of requirements
Analytical results observed in the laboratory (or calculated from experimental measurements) are
compared with stated limits to determine whether there is conformance with compendial assay or
test requirements. The observed or calculated values usually will contain more significant figures
than there are in the stated limit, and an observed or calculated result is to be rounded off to the
number of places that are in agreement with the limit expression by the following procedure ( Note:
Limits, which are fixed numbers, are not rounded off).
When rounding off is required, consider only one digit in the decimal place to the right of the last
place in the limit expression. If this digit is <5, it is eliminated and the preceding digit is unchanged.
If this digit is >5, it is eliminated and the preceding digit is increased by 1. If this digit equals 5, it
is eliminated and the preceding digit is increased by 1.

illustration of rounding numerical values for comparison
with requirements
compendial requirement

unrounded value (%) rounded result (%) conforms

Assay limit ≥98.0% 97.96 98.0 Yes

97.92 97.9 No

97.95 98.0 Yes

101.55 101.6 No

Assay limit ≤101.5%

101.46 101.5 Yes

101.45 101.5 Yes

Limit test ≤0.02% 0.025 0.03 No

0.015 0.02 Yes

0.027 0.03 No

0.00035 0.0004 No

Limit test ≤3 ppm

0.00025 0.0003 Yes

0.00028 0.0003 Yes

16.3.3.2 significant figures
Great attention is paid to the use of significant figures in laboratory reports.
Electronic calculators are used to facilitate the computations associated with experimental num-
bers; even inexpensive calculators are designed so as to deal with, and display, numbers having 10
or more digits. This places the burden of accounting for the appropriate representation of numerical
data on the investigator.
Everyday laboratory measurements limit the number of digits that represent reality.
The concept of significant figures seeks to limit the number of digits in a quantity to those that
are justified based on its origin.
Two features play a role in the determination of significant figures:

a. Measurement

b. Computation using measured values