Precision blending in gradient elution

Buffer solutions are stored in tanks and delivered to the chromatography column based on a preset conductivity profile specific to an elution process.

Eluents delivered from various buffer tanks are blended to create the desired conductivity profile over time. While the buffer mixture is out of specification during changes from one setpoint to the next, it is sent to waste until the conductivity reaches the desired profile setpoint.

One method to achieve the proper blend is using an on/off valve with a timer so that the correct amount of eluent is added, delivering rough precision. Another method is to use a flow control valve which can be more precise.

Equilibar back pressure regulator as a flow control valve

The Equilibar FD sanitary back pressure regulator can be configured as an advanced flow control valve, delivering precise blending for sensitive processes. The Equilibar FD advanced flow control valve (FCV) can maintain consistent flow over a wide range of flow rates (turndown ratio of 100:1), and responds immediately to changes in setpoint or upstream conditions. How it works. 

Equilibar FCVs may be used in fine blending for inline conditioning and gradient elution. The fast response of the FD flow control valve controls the process quickly and can deliver cost savings due to less waste.

The illustration below is one example of how the process may be set up. Depending on the delivery process, pump type, and process requirements, the piping configuration can be determined with help from an Equilibar application engineer. In some cases, with a positive displacement pump for instance, a recirculation loop back to the buffer tank may be required. In other cases, with the use of a centrifugal pump, a recirculation loop may not be required. Contact us to discuss your application.

Advantages of the Equilibar design are its small footprint, its high turndown ratio, and excellent response and precision. The electro-pneumatic pilot regulator can be located at the process control system, a distance from the FD valve, for a simple footprint.

Contact an Equilibar application engineer to discuss your application today.