Chemistry Reference
In-Depth Information
Quality Control Samples:
Samples run to make sure the instrument has been
properly calibrated or standardized. Quality control samples are also often
used to provide an in-process assurance of the test's performance during
use.
Quantitation Limit (QL or LOQ):
The lowest concentration of an analyte in a
sample that can be determined (quantitated) with acceptable precision and
accuracy under the stated operational conditions of the method.
Range:
The interval between the upper and lower levels of analyte (inclusive) that
have been demonstrated to be determined with a suitable level of precision,
accuracy, and linearity using the method as written.
Reanalyze:
Repeating the analysis or performing different analyses on the original
sample preparation, reference standards, or reagents.
Recovery:
Extraction efficiency generally reported as a percentage of the known
amount of an analyte.
Repeatability:
Precision results of the method operating over a short time interval
under the same conditions (inter-assay precision). Generally, the criteria of
concern in USP procedures.
Reproducibility:
Precision results of collaborative studies between laboratories.
Resample:
To obtain a new sample aliquot from the original test substance source.
The sample is used for retesting and should be taken from the same homo-
geneous material that yielded the out-of-specification (OOS) result.
Resolution (R
S
):
The separation of two chromatographic peaks that takes into
account the retention times and peak widths. Calculated by the equation:
r
S
= 2(tr
2
- tr
1
)/(w
b1
+ w
b2
), or by
=
α−
α+
A value of 1.0 is considered to be the minimum for a separation to occur,
values of 1.5 or better for good quantitation, and values of 2.0 or higher for
robustness or disparate levels such as those found in impurity profiles.
Retest:
Repeating the analytical procedure on a resampled aliquot.
See
Resample.
Robustness:
The capacity of a method to remain unaffected by small,
deliberate
variations in method parameters; a measure of the reliability of a method.
Often used to set the system suitability parameters of a method.
Signature (signed):
The record of the individual who performed a particular action
or review. This record can be initials, full handwritten signature, personal
seal, or authenticated and secure electronic signature.
Specification:
A list of tests, references to analytical procedures, and appropriate
acceptance criteria for the test described.
Specificity:
Specificity is the ability to measure accurately and specifically the ana-
lyte of interest in the presence of other components that may be expected to
be present in the sample matrix.
Stability:
Degree or rate of degradation of an analyte in a given matrix under spe-
cific conditions over a given time interval.
Stability Indicating Method (SIM):
A validated, quantitative analytical procedure
used to accurately, precisely, and selectively detect a decrease in the amount
N
1
k
Rs
4
k
1
