3725I-038 - 2/6 Preparative Injector, SS w/ Switch

The IDEX Rheodyne Model 3725I-038 is a PEEK manual sample injector engineered for reliable sample introduction in analytical liquid chromatography systems where metal-free flow paths and chemical compatibility are required. The injector is constructed primarily from PEEK (polyether ether ketone), providing excellent resistance to aggressive solvents while eliminating potential metal interactions with sensitive analytes.

This configuration includes the integrated position sensing switch (“I” version), allowing electronic confirmation of valve position. The switch provides feedback indicating whether the injector is in the LOAD or INJECT position, enabling synchronization with chromatography software, detectors, or data acquisition systems.

The valve features the proven Rheodyne Make-Before-Break (MBB) switching design, ensuring that mobile phase flow remains continuous as the valve rotates between positions. This prevents pressure disturbances and helps maintain stable chromatographic baselines during manual injections.

The Model 3725I-038 incorporates a front-mounted needle port for direct loop loading and is commonly supplied with a 20 µL sample loop. This design allows fast, repeatable manual injections for routine analytical workflows.

Designed for bio-compatible and corrosion-resistant chromatography systems, the valve supports operating pressures up to 4000 psi (≈275 bar) and temperatures up to 80°C, making it suitable for a wide range of analytical LC applications.

Key Features

• PEEK valve construction for metal-free chromatography
• Six-port manual injector for analytical LC systems
• Integrated position sensing switch for injection confirmation
• Front needle port for direct sample loading
• Make-Before-Break valve switching for uninterrupted mobile phase flow
• Maximum operating pressure of 4000 psi
• Maximum operating temperature of 80°C
• Supplied with standard 20 µL sample loop
• Excellent compatibility with aqueous buffers and organic solvents

Advantages of PEEK Construction

The PEEK construction of the Model 3725I-038 eliminates metal surfaces within the wetted flow path, reducing the risk of analyte adsorption or catalytic degradation. This makes the injector well suited for applications involving proteins, peptides, biomolecules, ion chromatography, and trace-metal sensitive analyses.

PEEK also provides strong resistance to common LC solvents such as acetonitrile, methanol, water, and buffered mobile phases, allowing the injector to perform reliably across a broad range of chromatographic methods.

Injection Methods

The injector supports both complete loop filling and partial loop filling injection techniques. Complete loop filling ensures highly reproducible injection volumes because the sample loop defines the injected volume, while partial loop filling allows smaller injections when limited sample volumes are available.

Maintenance and Serviceability

The valve is designed for long service life with replaceable wear components such as the rotor seal and stator face assembly. Maintenance kits are available to restore valve performance and extend operational lifetime.

Typical Applications

The Model 3725I-038 is commonly used in laboratories requiring a biocompatible manual LC injector with electronic position feedback. Typical uses include biopharmaceutical analysis, ion chromatography, environmental testing, and analytical LC research workflows.