Chemistry Reference
In-Depth Information
C*D
B*D
B*C
A*D
A*C
A*B
D
C
B
A
-0.070
-0.060
-0.050
-0.040
-0.030
-0.020
-0.010
0.000
0.010
Effects
0.020
0.030
0.040
0.050
0.060
0.070
0.080
FIgure 5.5
Example effects plot. Factor effects can be either positive or negative. The
magnitude of the bar is an indication of the magnitude of the effect.
experimental design used for the study; all the graphs used to evaluate the data, and
tables of information, including the factors evaluated and the levels; and the statisti-
cal analysis of the responses. The factor limits, and any system suitability specifica-
tions arrived at, should also be tabulated. A precautionary statement should also be
included for any analytical conditions that must be suitably controlled for measure-
ments that are susceptible to variations in the procedure.
5.6 system suItAbIlIty tests
System suitability tests are an integral part of chromatographic methods used to
verify that the resolution and reproducibility of, for example, a chromatographic
system, are adequate for the analysis to be performed [17]. System suitability tests
are based on the concept that the equipment, electronics, analytical operations, and
samples constitute an integral system that can be evaluated as a whole.
System suitability is defined as the checking of a system to ensure system perfor-
mance before or during the analysis of unknowns. Parameters such as plate count,
tailing factor, resolution, reproducibility (%RSD retention time and area for repeti-
tive injections), and signal-to-noise (S/N) are determined and compared against the
specifications set for the method. These parameters are measured during the analy-
sis of a system suitability “sample,” which is a mixture of main components and
expected by-products. Specifications for the accuracy of recovery between two stan-
dard preparations are also commonly used; the second, separately prepared accu-
racy standard is often referred to as a “check standard.” Table 5.4 lists the terms
to be measured and their recommended limits obtained from the analysis of the
system suitability standard [18]. In most cases today, chromatography data system
(CDS) software can calculate system suitability parameters to provide a review of
the separation and to summarize data. Results stored in a relational database can be
compared and summarized on a peak-by-peak or system-by-system basis to provide
the feedback necessary to determine system performance for troubleshooting. CDS
system suitability results can also be used interactively in some systems to prevent
analysis of unknown samples following a failed system suitability specification.
