Diatom biosilica for liquid chromatography

Abstract

This work presents, for the first time, the preparation method and subsequent use of biosilica in column liquid chromatography in reverse-phase mode. Diatom biosilica consists of the siliceous exoskeletons (frustules) of unicellular algae. Controlled cultivation of Pseudostaurosira trainorii diatoms resulted in frustules with an average diameter of approximately 4 µm, sidewall thickness of 1 µm, and a bottom thickness of 110–150 nm. These frustules contained pores (holes) with diameters ranging from 150 to 300 nm. XRD measurements revealed an opal A silica structure, with some lamellar features, and the material was characterized by a surface area of 21.1 m²/g.

The raw material required careful preparation to remove residual organics by heating it. Following this, the surface was modified with octadecyldimethylchlorosilane to create a reverse-phase chromatographic adsorbent. The resulting columns demonstrated good chromatographic performance, with a theoretical plate number (N) of 22,000 plates for alkylbenzenes on a 160 mm long column, and permeability (K_F) of 5.33 × 10⁻¹⁵ m².

The prepared material exhibited lower hydrophobicity compared to the commercially available HALO C18 stationary phase, which can be attributed to its lower surface area and high number of silanol groups. As a result, only partial separation of six polyaromatic hydrocarbons was achieved due to excessive tailing. However, five anti-inflammatory drugs and two veterinary antibiotics were successfully separated.