Poly(ethylene glycol) functionalization of monolithic poly(divinyl benzene) for improved miniaturized solid phase extraction of protein-rich samples

Non-specific protein adsorption on hydrophobic solid phase extraction (SPE) adsorbents can reduce the efficacy of purification. To improve sample clean-up, poly(divinyl benzene) (PDVB) monoliths grafted with hydrophilic polyethylene glycol methacrylate (PEGMA) were developed. Residual vinyl groups (RVGs) of the PDVB were employed as anchor points for PEGMA grafting. Two PEGMA monomers, M_n 360 and 950, were compared for graft solutions containing 5–20% monomer. Protein binding was qualitatively screened using fluorescently labeled human serum albumin (HSA) to determine optimal PEGMA concentration. The fluorescent signal of PDVB was reduced for PDVB-g-PEGMA₃₆₀ (10%) and PDVB-g-PEGMA₉₅₀ (20%). The PEGMA content (w/w%) was quantified by solid state ¹H NMR to be 29.9 ± 1.6% for PDVB-g-PEGMA₃₆₀ and 7.7 ± 1.2% for PDVB-g-PEGMA₉₅₀. To assess adsorbent performance breakthrough curves for PDVB, PDVB-g-PEGMA₃₆₀ and PDVB-g-PEGMA₉₅₀ were compared. The breakthrough volume (V_B) and shape of the curve for PDVB-g-PEGMA₉₅₀ were maintained relative to PDVB (2.3 and 2.8 mL, respectively). A reduced V_B of 0.5 mL and shallow breakthrough curve indicated PDVB-g-PEGMA₃₆₀ was not suitable for SPE. A high ibuprofen recovery of 92 ± 0.30 and 78 ± 0.93% was seen for PDVB and PDVB-g-PEGMA₉₅₀, respectively. Protein adsorption was reduced from 31 ± 2.41 to 12 ± 0.49% for PDVB and PDVB-g-PEGMA₉₅₀, respectively. SPE of ibuprofen from plasma was compared for PDVB and PDVB-g-PEGMA₉₅₀ by at-line electrospray ionization mass spectrometry (ESI-MS). PDVB-g-PEGMA₉₅₀ demonstrated a threefold increase in assay sensitivity indicating a superior analyte purification.