Valves: Multitalents for Chromatography
Valves are ubiquitous in all liquid chromatographic applications. They act like a switch and can control the flow path of the chromatography system in various ways.
Therefore, valves are indispensable for eluent and column selection, sample injection, fractionation as well as any switching task. Since valves can also direct flows outside of an HPLC, they are widely used in dosing applications in the chemical industry. With Knauer valves the user is flexible concerning the choice of different materials and sizes, as well as drivers for various software packages. The valves are driven either manually or actuated by a new universal valve drive.
Valves with two positions can be either used for sample injection or for more complex switching tasks. In the first position of the valve, the sample is loaded into the sample loop while in the second position, the sample is injected onto the column. Such valves are the most cost-effective alternative to autosamplers for sample introduction. Backflushing or bypassing the column and selecting between two columns can also be achieved by 2-position valves. Multiposition valves serve for quite different functions. These valves, which can connect multiple ports to a common port are the simplest, yet very effective option for fraction collecting. They can also be used for improvement of the purification by solvent and peak recycling. In case of peak recycling, eluting substances are reinjected onto the column as many times as required. As a consequence, incompletely separated peaks can be isolated from each other. Besides that, multiposition valves are useful for screening, up-scaling or selection of multiple columns, eluents, or samples. Depending on the application, material is a central issue. Diamond coated stainless steel provides great durability at high pressures up to 17 500 psi (1200 bar) making the valves perfect for UHPLC applications.
An optional metal-free design for biocompatible work supports all FPLC applications like purification of proteins, nucleotides and peptides. Inner diameters up to 1/8th inch allow preparative HPLC applications for flow rates up to 1000 mL/min.
The new Azura valve drive “Valve Unifier VU 4.1” recognizes all Knauer valves via RFID. This feature allows the automatic configuration of the drive when valves are changed by the user. Through its intelligent design and compact dimensions the valve drive fits into every HPLC-system. The optional display makes operation extremely easy and user-friendly. A low switching time reduces pressure spikes to a minimum. Sophisticated rotor seal materials and design ensure high durability, guaranteeing 50.000 switching cycles. The “Valve Unifier” can be used either as a standalone module or integrated into the multifunctional Azura assistant. The assistant is a customizable combination module which integrates up to three devices in one. It saves space and can handle a large variety of tasks in a compact solution, such as column switching using two valves. The valve drive can be controlled with OpenLAB CDS EZChrom Edition, ClarityChrom, and PurityChrom software, as well as from the Azura Mobile Control (stand-alone operation). Control is possible via LAN or through analog input/output, allowing this valve drive to be integrated into almost any LC system or customized solution (OEM-solution).
For further information: http://www.knauer.net/en/products/valves