US HPLC six-way valve injector use and maintenance instructions

The six-way valve injector is a key component in high-performance liquid chromatography (HPLC) systems, known for its reliability and precision. It consists of two main parts: a rotating seal called the rotor and a stationary base known as the stator. Among various models, the Rheodyne six-way valve injector stands out as one of the most versatile options, widely used by leading HPLC manufacturers worldwide. How it works: When the handle is in the "Load" position, the sample is introduced into the metering loop via an injection port using a micro-syringe. Once the loop is filled, any excess sample is expelled through an overflow hole. Then, by rotating the handle to the "Inject" position, the valve connects to the mobile phase flow path. The pump then flushes the loop with the mobile phase, pushing the sample into the analytical column for separation and analysis. Despite its simple design, the six-way valve injector offers long service life, ease of use, and minimal daily maintenance. However, proper handling and regular care can significantly extend its lifespan, protect downstream equipment, and improve analytical accuracy. With correct operation, the valve can perform up to 30,000 injections without maintenance. Here are some important usage and maintenance tips: 1. Avoid leaving the handle between the "Load" and "Inject" positions. Staying in this intermediate position can cause pressure surges, potentially damaging the valve. Always rotate the handle quickly to the desired position. 2. HPLC syringes differ from those used in gas chromatography. They feature flat-tipped needles that fit tightly against the inner wall of the injector’s sealing tube, ensuring good sealing and preventing air bubbles or damage to internal components. 3. There are two common injection methods: partial volume and full-volume loading. In partial volume injection, the sample volume can be up to 75% of the loop volume. For example, a 20 µL loop can inject up to 15 µL. To ensure accuracy and reproducibility, the injected volume should be at least 3–5 times the loop volume. So, for a 20 µL loop, you should inject at least 60–100 µL of sample. A 100 µL flat-head syringe is often recommended for full-loop injection. 4. Custom quantitative loops can be made based on specific needs. While exact volume calculation isn't always necessary, consistency between calibration and sample injections is crucial. Even if the actual loop volume varies slightly (e.g., 9 µL instead of 10 µL), consistent injection volumes will help minimize errors during data processing. 5. Sample preparation is critical. The solution must be free of particles, which can clog the valve and cause wear. Always filter the sample through a 0.45 µm membrane before injection. After each run, rinse the injector thoroughly with a salt-free diluent, water, or mobile phase to prevent residue buildup, especially from buffered salts. 6. During loading, make sure to wipe the outside of the syringe needle with lint-free paper to avoid contamination. Also, perform a few rinse cycles by switching the valve between the "Load" and "Inject" positions to clean the system effectively. Proper use of the six-way valve injector ensures reliable performance, accurate results, and longer equipment life. Following these guidelines will help maintain the integrity of your HPLC system and optimize your analytical workflow.

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