Biomedical Engineering Reference
In-Depth Information
Fig. 8
Optimization of solvent composition for maximizing absolute recovery of paclitaxel after
SPE extraction. Solvents used in the elution step were composed of 0.1 % formic acid in the indi-
cated solvent composition. (
a
) Optimization of the strong-wash solvent: triplicate SPE cartridges
were washed with a range of 55-95 % methanol; drug was eluted from all cartridges with 100%meth-
anol and (
b
) optimization of the elution solvent: triplicate SPE cartridges were washed with 5 %
methanol and eluted with methanol concentrations ranging from 60 to 100 % (Reproduced with
permission from Elsevier)
strategy, and the injection volume. The use of smaller I.D. columns and lower flow
rates can improve the sensitivity of ESI-MS/MS considerably [
3
] . However, loading
capacities are proportionally lower too [
14
]. After balancing these considerations, a
0.5 mm I.D. mLC column was selected. Sufficient mLC resolution was desirable for
two reasons. First, when minimal separation was employed, a severe ion suppres-
sion effect that originated from the sample matrix was observed. This suppression
effect severely compromised sensitivity, but could be eliminated by increasing m LC
separation. Second, it was found that the formation of both [M + Na]
+
and [M + K]
+
ions was relatively high when minimal mLC separation was used, even with the
addition of acidified 2 mM ammonium acetate-formate as a mobile phase modifier.
However, adequate chromatographic separation reduced these undesirable adduct
ions and enhanced the formation of [M + H]
+
. The most likely explanation of this
