Application of open tubular capillary columns coated with zirconium phosphonate for enrichment of phosphopeptides

A new approach utilizing open tubular capillary columns coated with zirconium phosphonate (ZrP-OTCC) for enrichment of phosphopeptides is described. The experimental conditions: interior diameter, length of capillary and flow rate was optimized using tryptic digest of α-casein (a phosphoprotein) as a model sample. The ZrP-OTCC was demonstrated to tolerate urea, sodium dodecyl sulphate (SDS), and NaCl. Further experimental results show that the ZrP-OTCC can trap the phosphopeptides even at the concentration of α-casein as low as 10−8 M. This column has also been successfully coupled online with nano-liquid chromatography for enrichment and then separation of phosphopeptides from a complex sample, and finally analyzed the phosphopeptides by mass spectrometry (MS).