A commercially available MIP specific for NSAIDs was used and
the procedure recommended by the supplier was adapted as indicated.
MIP cartridge was equilibrated with 1 mL acetonitrile, 1 mL
methanol and 1 mL 10 mM ammonium formate (pH 3) in water
under gravity flow. A sample volume, from 1 to 50 mL, was adjusted
to pH 3 by the addition of 100 mM ammonium formate in water
(ratio sample-buffer 10:1 v/v) and loaded through the MIP cartridge
at an approximate speed of 2 mL min−1 using a SPE vacuum manifold.
Cartridge was washed with 1 mL deionized water and 1 mL
40% (v/v) acetonitrile in water. Vacuum was applied through the
cartridge after the washing step to remove residual moisture and
dry the cartridge. Finally, NSAIDs were eluted with 1 mL methanol,
filtered using 0.22 m PTFE syringe filters, and directly analyzed by
the corresponding LC-DAD and UHPLC–MS–MS systems.
A conventional octadecyl silica C18 solid phase was also used in
a SPE procedure in order to compare the selectivity obtained by the
proposed MIPs. The employed extraction protocol for C18 supports
was based on that found in the literature