SFC/SFE

Supercritical Fluid Technology

Over the years, JASCO has responded to the growing emphasis on reducing chemical waste by offering an alternative to traditional HPLC with a full line of “green” SFC/SFE products. The reduction in the use of organic solvents has cost, health, and safety benefits as well as faster, cleaner sample recovery during experimental procedures. These advantages are a result of supercritical fluids liquid-like densities offering higher solubility and increased column loading. The low viscosity and high diffusion of supercritical fluids enable faster separations and extractions.

The JASCO Advantage

• JASCO’s modular SFC/SFE platforms have been optimized and refined over the last 20 years to provide reliable, worry-free performance for a wide variety of applications.
• The patented JASCO back-pressure regulator employs a high-speed switching valve to ensure that a constant back pressure is maintained at all times, regardless of the flow rate. Most other systems use a restriction device which is flow dependent and hence is unable to provide the essential constant pressure conditions. The JASCO design has the additional benefit of very low dead volume (below 10 μL) which prevents fractions from remixing. It also presents a significant reduction in any precipitation buildup in the flow line.
• JASCO offers a wide range of detectors with high pressure cells – UV, Diode Array (real-time collection of 3-D spectra and chromatograms), and the only CD detector available for SFC.
• Our analytical SFC/SFE systems can be converted easily to HPLC.
• JASCO’s modifier delivery pumps guarantee stable delivery performance even at high flow rates.
• JASCO offers a truly modular system – from a simple extractor to a complex multi-instrument system that shares the same basic components.
• JASCO SFC systems are compatible with most Mass Spectrometers and offer direct control in both Excalibur and Analyst software.
• JASCO provides professional, fast and courteous support on all of our products. We have service centers strategically located throughout the U.S. to ensure the highest level of customer satisfaction. Our scheduled and on-site training classes are available for advanced application training.

Supercritical Fluid Chromatograpy & extraction

First discovered in 1879, supercritical fluids have been used for extraction applications since the 1950’s. The 1980’s saw an increase in their use as mobile phase for analytical separations. The work was mainly capillary scale (GC type) work, but some packed column (LC type) applications were developed. Since then, the expected growth in the technique has not taken place but the availability of new programmable pumps and an electronic back pressure regulator opens the door for future development.
The benefits of using supercritical fluids are their liquid-like densities offering higher solubility and increased column loading. They have low viscosity and are highly diffuse enabling faster separation and extraction. The reduction in the use of organic solvents has cost, health, and safety benefits as well as faster (cleaner) sample recovery during experimental procedures.

The Benefits of Electronic Back Pressure Regulation

A supercritical fluid chromatography system differs from other chromatographic systems (eg. Liquid-LC Gas-GC) by the inclusion of a back pressure regulating device. This device maintains the system pressure (from delivery pump through to detector) above the critical pressure (Pc) of the fluid used. The main pressure drop in the system takes place in the back pressure device. In HPLC and GC, the pressure gradually drops to atmospheric pressure as the mobile phase passes through the column. Thermostatting of the SFC system is also necessary in order to keep the temperature above the critical temperature (Tc) of the fluid being used as mobile phase. The supercritical fluid offers increased solvating power and the maintenance of experimental conditions ensures improvement in chromatographic separations. There are two types of back pressure device currently used in SFC:
1. Simple restrictor
2. Mechanical or electronic feedback regulator

The simple restrictor consists of a length of capillary tubing having an appropriate internal diameter for the required pressure and flow rate used in the system. This device which is easy to make, is used mainly for open tubular or packed capillary column work. However, in order to change the system pressure the flow rate also has to be changed, because the pressure is built up only by the flow resistance of the restrictor.
The mechanical or electrical feedback device is used for conventional size packed columns. This regulator consists of a pressure sensing device and a needle valve. It controls the back pressure independently of the mass flow rate of the fluid. This device is more convenient than the simple restrictor for the precise examination of retention behavior in SFC. However, conventional back-pressure regulators suffer the disadvantage of a large dead volume, ranging from a few milliliters to tens of milliliters. These large volumes do not allow changes in pressure to take place fast enough for pressure programming to be performed. Successful fractionation of solutes is also less likely due to the large dead volume of the regulator. In order for the system to control the pressure independently of the mass flow rate, the regulator must have a low dead volume, less than 10 microliters.

SFC/SFE PU-1580-CO₂ Pump and BP-1580-81 Back Pressure Regulator

JASCO has solved this problem by developing a pressure regulating system which operates on different principals from conventional regulators.The system is comprised of a regulative valve, pressure transducer, and control electronics. The regulating valve consists of a needle which is driven by a solenoid and a valve seat. In general this type of valve controls the flow resistance by changing the gap between the valve needle and seat. The new valve is based on high speed switching of the fluid flow by periodically opening and closing the flow path. It eliminates the possibility of blocking the valve flow path.
Precipitated solutes and dry ice originated from carbon dioxide are trapped and forced to pass through the valve. A glass collection reservoir connected to the outlet port of the regulating valve allows fractionation of system eluent. When a measured pressure is lower than a reference signal, the output of the comparator turns the solenoid drive current on to close the drive flow. When the measured pressure is higher than the control signal the output switches off the current allowing the fluid to pass through the valve. In this way the control
electronics and hydraulics cause the valve to periodically open and close.

This new back pressure regulator offers greater experimental flexibility by enabling super critical conditions to be maintained independently of mass flow rate.
Fractionation is made easier by utilizing the collection facility at
the outlet of the regulator, and simplifies preparative scale chromatography.