# Forming Homogeneous Three-Dimensional Structures from Discrete Silica Microspheres Using Sub/Supercritical Water

## TL;DR

A new method uses sub/supercritical water to create uniform silica structures with potential applications in high-pressure scenarios.

## Contribution

A novel method integrating dissolution and coalescence in sub/supercritical water to form uniform silica structures.

## Key findings

- The method produces permeable columns with high efficiency and varying sizes.
- Bridged-microsphere monolithic columns outperformed traditional packed columns in tests.

## Abstract

A novel technique
for producing highly uniform structures from
silica microspheres has been developed and tested. It is based on
exploiting the temperature- and pressure-dependent solvent properties
of sub/supercritical water toward silicon dioxide. The initial concept
aimed to create a “hybrid” capillary chromatographic
column on the border between a packed and a monolithic column that
would combine the benefits of both. The resultant method that integrates
dissolution and coalescence in a continuous process enabled the production
of a range of permeable columns with high efficiency and varying sizes.
Their internal structures were examined using scanning electron microscopy
and characterized using microHPLC chromatography. The structures produced
using this method may have diverse applications beyond the scope of
analytical chemistry. They prove useful in scenarios where high pressure
is necessary because of the high hydraulic resistance of small particles
and/or the passing medium with a high flow rate. A simple test of
a bridged-microsphere monolithic column and a discrete microsphere-packed
column, both after chemical modification to the C18 stationary phase,
indicated superior performance of the new type of monolithic columns.