SmartSPE is Chromatography!

Optimized outcomes require accurate flow.
SPE flow-driven pneumatically or by vacuum can not achieve and maintain optimum flow.

Use of chromatographic SmartSPE knowledge. Cation exchange of basic drugs in blood (always mixed mode, 50 μm particles). Flow chosen depends on chemistry performed! Optimum flow for ITSP cation exchange load and elute = 1.2 μl/s. Solvent wash steps have a different optimum flow! Solvent wash step at 1.2 μl/s (SCX) removes < 90% of phospholipids and fatty acids. Solvent was step at 5 μl/s (RP) removes > 99% of phospholipids and fatty acids. With 1.2 μl/s solvent wash, phospholipids are observable by - ion full scan LC/MS & not observable with 5 μl/s solvent wash!