Scientists in France have devised a way to rapidly and cheaply screen how soluble compounds are.

Chemical and biological systems often rely on a large number of parameters. Complete investigations of these parameters need time and significant amounts of product. Currently these investigations use robotic fluidic workstations, but these are expensive, and require labour and large product volumes. Alternatively, high throughput microfluidic techniques are used as they allow rapid screening, but fabrication and multiplexing are difficult.

Philippe Laval and colleagues working for a joint Rhodia-CNRS research centre have produced a chip for screening phase and solubility conditions. A series of droplets with differing compositions is produced by mixing silicone oil and aqueous phases at different rates. Ten channels containing different droplet compositions can be created in less than 20 min.

After the device is full it is rapidly cooled to induce crystallisation. Once the solutions have crystallised, a temperature gradient is applied to produce a two-dimensional array of droplets of different concentrations at different temperatures. In droplets where the temperature is higher than the solubility temperature, the crystals dissolve. In other droplets the crystals are partly solubilised, but still exist in equilibrium, producing a direct and quantitative solubility assessment.

'The microfluidic device has been developed to improve research productivity', said Laval, adding 'This low cost system, compared to robotic platforms, enables us to carry out high throughput screening of concentration vs. temperature diagrams with very little amount of products'. He continued that an additional advantage is that 'tens of experimental conditions can be tested in just a few hours'.

Vikki Chapman