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From injection to peak recycling - KNAUER valves

Valves are ubiquitous in all liquid chromatography 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 selection, sample injection, column selection, and fractionation as well as any switching task. KNAUER valves are designed for a wide range of chromatographic and dosing applications. Flexibility is provided by choice of different materials and sizes as well as drivers for various software packages. Valves are driven either manually or automatically through a valve drive.

Valves according to function

  • Manual valves
  • Two-position valves
  • Multiposition valves
  • Manual valves

    Hand-operated valves are mainly used for sample introduction and other applications involving 2-position valve types. The KNAUER manual valves share the same precision-engineered valve heads like the electrically driven models.

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  • Two-position valves

    The most common application of two-position valves is the usage as inection system. Normally, a 6 port valve with a sample loop is used for this purpose and the two valve positions are named LOAD and INJECT. However, 6 and 8 port two-position valves can also be used for column switching, high-thorughput sample injection or backflushing.

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  • Multiposition valves

    Multiposition valves are suited for applications like column switching or fraction collection. If the central port is employed as outlet, these valves can also be used to select between additional eluents or buffers, expanding the number of selectable solvents of a pump.

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State-of-the-art materials and production technology

Based on decades of know-how and our latest research, the AZURA V 4.1 valves with associated actuator represent the most powerful valve generation in KNAUER's history. Technological progress can be seen, for example, in the new high-pressure valves.

A special DLC coating (diamond-like carbon) offers a significantly lower coefficient of friction and enables a long service life and chemical resistance. Ultra-fine bores ensure a low dead volume. In combination with the rotor seal made of a pressure-resistant polyimide, these new valves are suitable for pressures up to 1200 bar(~17,400 psi).

With the range of valves offered by KNAUER, numerous switching tasks in 1/16 or 1/8 inch are possible, including biocompatible applications. Since KNAUER controls the entire production chain from development to production, valves can also be produced to customer specifications.

One Valve Drive for all applications 

This fully automatic valve drive saves you time in the lab 

The Valve Unifier is a smart valve drive with RFID technology (Radio-frequency identification). It features automatic valve recognition and adjusts torque and switching speed specifically for each valve. Therefore, only one valve drive is needed regardless of the valve from analytical to preparative scale. 

Each valve head is equipped with an RFID tag that stores all relevant data. This data is read wirelessly by the VU 4.1 valve drive and the switching parameters are automatically adjusted.
For example, a 1/8 inch valve with 2 mm bores, due to its size, requires a higher torque than a 1/16 inch valve with 0.3 mm bores.

With older valve actuators, these different requirements were not taken into account, just the number of connections and the mode – e.g. two or multiple positions – could be selected. Therefore, the switching parameters for a 6-way two-position valve were always the same, regardless whether a 1/8 inch or a 1/16 inch valve was mounted. As a result, especially small diameter valves were switched more slowly by the actuator than the valves would have been able to because the actuator torque had to be optimized for the harder-to-switch 1/8 inch valves. Automated valve detection via the RFID tag ensures that switching speed and torque are always optimally adjusted to ensure the best performance of each valve. For example, 1/16 inch systems benefit from a significantly reduced pressure increase during switching.

More advantages of the AZURA valve drive:

- Time savings during setup
- Exclusion of misconfiguration by the user
- GLP data such as number of switching operations are monitored for easier planning of maintenance to minimize wear-related downtime

The valve drive works as stand-alone device thanks to an integrated display but can also be controlled via our supported software. Due to various interfaces and the small footprint the valve drive AZURA VU 4.1 can easily be used to upgrade an existing system.

HPLC valves for sample injection

The injection of samples into the system is the most common application of switching valves. Whether operated manually by a lever or automated by an electric actuator, the valve in the injection position directs the fluid flow through a sample loop previously filled in the loading position. At the same time, the chromatography data system receives a signal about the switching. After this injection of the sample or completion of the chromatography run, the valve is switched back to the loading position and the sample loop can be filled with sample again.

The valve type usually used for this task is a 6-port 2-position valve (also referred to as 6-port 3-channel valve) such as our AZURA V 4.1 Ultra High Pressure Valve. The same valve can also be used to switch between two columns, if both have to be used frequently and a laborious column change is to be avoided.

End- cut valve switching configuration

The so-called "end-cut" configuration can drastically reduce separation time and protects the main column.

It is particularly suitable for separation tasks in which unwanted components that are strongly-retained on the column prolong the run. An individual precolumn, which is usually just a shorter version of the analysis column, retains the slower-eluting components (position A). As soon as the components of interest have reached the main separation column, the valve is switched and the precolumn is backflushed via a secondary pump. The main column is flushed directly by the eluent (position B).

Valve accessories

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