Problem: Acetonitrile costs have soared by 6 to 8 times since the summer of 2008 due to a global shortage of this key chromatography solvent. The factors contributing to the shortage are primarily related to the global economic downturn. Unlike the situation with other solvents, such as methanol, there are no facilities dedicated to the manufacture of acetonitrile. Instead, raw acetonitrile is obtained as a byproduct in the production of acrylonitrile, a plastic used in automobile components and other products. As a consequence of the collapse in the automotive industry and the associated overall reduction in demand for acrylonitrile, there has been a significant decrease in the supply of acetonitrile.

It is anticipated that the supply and pricing issues around acetonitrile could well continue, due in part to a forecast growth in global consumption of 5 percent per year over the next five years. This is based on the expected increasing use of acetonitrile in the production of engineered drugs, generic pharmaceuticals and pesticides, particularly in China and India. Consequently, many laboratories continue to seek solutions to conserve solvent usage within their chromatography protocols.

Solution: There are a number of potential strategies that can be adopted by chromatographers to alleviate the ongoing acetonitrile supply issues, such as reducing the amount used by decreasing column length, width and particle size, or by replacing it completely with an alternative solvent. However, changing HPLC methods may require protocol development and revalidation. Alternatively, to eliminate the need for time-consuming protocol development, chromatographers could simply recycle their eluent, particularly if using an isocratic solvent system.

Although solvent recycling has both economic and environmental benefits, it has previously not been extensively practiced. This is because traditional recycling systems have tended to be cumbersome, requiring frequent manual resetting to allow for baseline drift, take up valuable bench space, and can only be used to recycle a single solvent or set mixture. However, modern recycling systems such as the Thermo Scientific SRS Pro Solvent Recycling system, are now microprocessor controlled and can overcome many of these issues, helping to reduce mobile phase consumption by up to 90 percent.

The innovative SRS Pro redirects untainted mobile phase to the solvent reservoir during isocratic HPLC operation. Through the continuous monitoring of the chromatographic detector output signal, the mobile phase is only recycled to the solvent reservoir when the baseline is below a threshold value. When this value is exceeded as a peak is eluted, the tainted eluent flow is redirected to waste, accounting for the transport time from the detector to the switching valve. Once the signal returns below the threshold, the mobile phase is switched back to the reservoir.

The modern and compact design of the SRS Pro eliminates the need for a power adaptor, as the solvent saver is powered directly from the chromatography data system PC, via a USB connection. Furthermore, the easy-to-use software enables simple configuration of the system parameters and online monitoring. Additionally, the SRS Pro is designed to recycle the mobile phase only when switched on. Even in the case of a power failure, the valve is automatically positioned in the waste position to ensure that the mobile phase reservoir remains uncontaminated.

To summarize, while the shortage of acetonitrile has certainly been a key driver for the uptake of modern solvent recycling systems in chromatography laboratories, solvent recycling is not limited only to acetonitrile and can be applied to most isocratic mobile phase. Any reduction in the consumption and disposal of organic waste, leading to “greener” HPLC and reduced costs, is surely a benefit in the long run.

For more information, please visit www. thermo.com/recyclesolvent.