One-step preparation of phosphate-rich carbonaceous spheres via a hydrothermal approach for phosphopeptide analysis

Carbonaceous materials with different morphologies are attracting more and more attention in many fields due to their excellent performance. Various methods have been developed to prepare carbonaceous materials with different functions. In this work, we developed a “green” strategy to prepare phosphate-rich carbonaceous spheres via a one-step mild hydrothermal carbonization (HTC) process using glucose and vinylphosphonic acid (VPA) as precursors. Water was the sole solvent employed in this synthesis process, which is environmentally friendly. To augment the content of phosphate groups on the surfaces of carbonaceous spheres, water-soluble 4,4′-azobis(4-cyanovaleric acid) was added to the HTC system as a thermal initiator. The size of the obtained carbonaceous spheres could reach 1–8 μm. Following chelation with titanium ions (Ti4+), the carbonaceous spheres were applied as an immobilized metal affinity chromatography (IMAC) material; the Ti4+ content of carbonaceous spheres reached 2.685% (wt%). This synthetic process for Ti4+-IMAC carbonaceous spheres was facile and time-saving, avoiding the tedious and complex process for traditional Ti4+-IMAC materials. Furthermore, the Ti4+-IMAC carbonaceous spheres exhibited satisfactory enrichment ability for phosphopeptides in the digest of β-casein and could enrich the low-abundance phosphopeptides in human serum, indicating a great potential use in phosphopeptide analysis.