Surface molecularly imprinted silica for selective solid-phase extraction of biochanin A, daidzein and genistein from urine samples

• Selective molecularly imprinted silica polymer (SiO2MIP) for extraction of biochanin A, daidzein and genistein was synthesized.
• The structural differences between imprinted and non-imprinted polymers were observed.
• The selective sorption of BCA and its analogues toward imprinted polymer was obtained.
• The results show potential ability of synthesized polymer in analysis of phytoestrogens in urine samples.

Selective molecularly imprinted silica polymer (SiO2MIP) for extraction of biochanin A, daidzein and genistein was synthesized using the surface molecular imprinting technique with the silica gel as a support. Biochanin A (BCA) was used as a template, 3-aminopropyltriethoxysilane (APTES) as a functional monomer, and tetraethoxysilicane (TEOS) as a cross-linker. Non-imprinted polymer with the sol–gel process (SiO2NIP) was also prepared for comparison. The synthesized polymers were characterized by Fourier transform infrared spectrometry (FTIR), scanning electron microscopy (SEM) and a standard Brunauer-Emett-Teller (BET) and Barret–Joyner–Halenda (BJH) analysis. The obtained results indicated the structural differences between imprinted and non-imprinted polymers. Finally, the SiO2MIP and SiO2NIP were adopted as the adsorbents of solid phase extraction for isolation and preconcentration of biochanin A and its structural analogues–daidzein and genistein from aqueous and urine samples. The performance analysis revealed that SiO2MIP displayed better affinity to the three investigated isoflavones compared with SiO2NIP. The recoveries of spiked samples for studied analytes ranged from 65.7% to 102.6% for molecularly imprinted silica polymer and 8.9–16.0% for non-imprinted sorbents.