Biomedical Engineering Reference
In-Depth Information
a
18
15
12
9
6
3
0
0
30
60
90
120
Sample Sequence No.
Neat Solutions
CS and QC
Incurred Sample
b
N
W
S
R
Fig. 18
(
a
,
top
): Gradually increasing IS responses due to increased mixing of the transferred
supernatant (100 mL) with reconstitution solution (400 m L). (
b
,
bottom
): Schematic diagram show-
ing the autosampler needle loaded a sample near the bottom of a well (96-well plate), where was
mainly reconstitution solution (deficient of the analyte and its internal standard) when homoge-
neous mixing had not been reached.
N
autosampler needle,
W
a well in a 96-well plate,
S
superna-
tant,
R
reconstitution solution. Reproduced from ref. [
36
] with permission from Elsevier
this question in most of the cases. The best approach would be to monitor IS response
variations during the analysis of incurred samples by using some predefined accep-
tance criteria, such as within ±50 % of the mean IS response of the accepted CS and
QC samples in the same run. Once variable or abnormal IS responses are observed,
each case should be evaluated or investigated when there is a pattern or trend. Based
on the outcome of the evaluation or investigation, the affected samples may be rein-
jected, reanalyzed or their results may be accepted together with some scientific proof.
The last approach would not only be preferable, i.e., saving time and cost, but it may
be also the only option in some cases. For examples, when all the samples from a
subject have consistently higher or lower IS responses than those of the CS and QC
