Sample Cleanup by Solid-Phase Extraction/Pipet-Tip Chromatography

Abstract

Sample cleanup by solid-phase extraction can be achieved with the use of a ZipTip see (Note 1), which is a miniature reverse-phase column packed into a 10 gmL pipet tip with a micro volume (approx 0.5 gmL) bed of reversed-phase, ion exchange, or affinity chromatography medium fixed at its end without dead volume. It is ideal for concen- trating, desalting, fractionating, and enriching 1 to 100 gmL of protein, peptide, or oligo- nucleotide samples prior to analysis. ZipTipgm-C₁₈ contains a micro bed of resin that allows final elution volumes as low as 0.5 gmL. It is intended for purifying and concen- trating femtomoles to picomoles of protein, peptide, or oligonucleotide samples prior to analysis, providing better data quality. The sample is aspirated and dispensed through ZipTip to bind, wash, and elute. Recovered samples are contaminant free and eluted in 0.5–4 gmL for direct transfer to a mass spectrometer matrix-assisted laser desorption/ ionization (MALDI) target or vial. Complex peptide and protein mixtures can be par- tially fractionated to enrich hydrophilic and hydrophobic components by eluting with an acetonitrile step gradient. The separation of different-sized fragments not only sim- plifies spectra but also minimizes peak suppression of larger fragments.