Abstract: Titania can selectively adsorb phosphopeptides. In order to obtain TiO2 with high specific surface area and improve the separation and enrichment of phosphopeptide, a SiO2@TiO2 composite was prepared by layer-by-layer selfassembly method. The specific surface area and average pore diameter of SiO2@TiO2 are 116.26 m2/g and 8.42 nm, respectively. The core-shell composite was used in the separation and enrichment of casein phosphopeptides (CPPs). The adsorption rate of CPPs was determined to be 93.0% by high performance liquid chromatography (HPLC), and the desorption rate was 81.5%. The sequence of the five phosphopeptides present in the eluent was identified as PS*H, PS*PR, S*SRS*E, PHS* and PS*SRS*EP by liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-Q-TOFMS ), respectively. The contents of CPPs in commercial CPPs product, calcium tablets and infant formula were determined by HPLC with theophylline as the internal standard, and the results showed that average recoveries of CPPS were 92.5%–95.1%. It can be concluded that the core-shell SiO2@TiO2 composite had excellent properties and allowed efficient separation and enrichment of CPPs, and the proposed method was accurate and reliable to determine CPPs in real samples.

Key words: SiO2@TiO2 composite, solid phase extraction, separation and enrichment, casein phosphate peptides