Chemistry Reference
In-Depth Information
D e ad Volu me:
The volume (V
d
) of the chromatographic system not including the
column packing. Includes the column interstitial volume and extra col-
umn volume contributed by the injector, detector, tubing, and connections.
Determined by injecting an inert compound (e.g., acetone).
Design Qualification (DQ):
DQ ensures that an instrument is designed and pro-
duced in a validated environment according to good laboratory practices
(GLPs), current good manufacturing practices (cGMPs), and/or ISO 9000
standards.
Detection Limit (DL or LOD):
Characteristic of limit tests, the DL is defined as
the lowest concentration of an analyte in a sample that can be detected, not
quantitated. It is a limit test that specifies whether or not an analyte is above
or below a certain value.
Documentation:
The organized collection of written or electronic records that
describes the structure, purpose, operation, maintenance, and data require-
ments for systems, instruments, or tests. Includes manuals, procedures,
specifications, operating records, final reports, data, etc.
Efficiency:
The number of theoretical plates (N) in a chromatographic separation.
There are several ways to calculate N; one common way is N = 16(t
R
- t
0
)
2
,
where t
R
is the retention time and t
0
is the retention time of an unretained
peak.
See also
H E T P.
Error:
Any deviation of the observed value from the true value.
External Standard:
The analyte itself, in high chemical purity, which is not added
to the actual samples, but is used to generate an external standard calibra-
tion plot then used to quantitate the analyte in a sample matrix. In order to
successfully utilize the external standard method, it is demonstrated, in a
reproducible manner, the recovery efficiency of the analyte in the actual
sample matrix. Recovery is evaluated by spiking a placebo of the sample
matrix with the external standard and showing how much has been recov-
ered. It can then be assumed that the recovery of the same analyte in an
actual sample will have the same recovery efficiency.
F Test:
A variance ratio test that describes if two independent estimates of variance
can reasonably be accepted as being two estimates of the variance of a
single, normally distributed sample.
Good Laboratory Practices (GLP):
The organizational process and the conditions
under which laboratory studies are planned, performed, monitored, recorded,
and reported. See, for example, 21 Code of Federal Regulations (CFR) part 58.
Gradient Elution:
Increasing mobile-phase strength versus time in a chromato-
graphic run. Gradients can be continuous or stepwise.
HETP:
Height equivalent to a theoretical plate, a measure of a chromatographic
column's efficiency (N). HETP = L/N, where L is the column length and N
is the number of theoretical plates.
Identification:
Ensuring the identity of an analyte.
Impurity:
Any component present in the intermediate or API that is not the desired
ent it y.
Impurity Profile:
A description of the identified and unidentified impurities present
in an API.
