Rheodyne Alltech EV550-104-AL SelectPRO HPLC Column Selector 6-Column No AC

Rheodyne Alltech EV550-104-AL SelectPRO HPLC Column Selector 6-Column No AC Adapter

The Rheodyne Alltech EV550-104-AL is a SelectPRO Laboratory Fluid Processor Column Selector — an automated valve-switching instrument designed to route mobile phase flow through multiple HPLC columns without manual reconnection. The unit supports up to six column positions and can be operated locally from the front panel or remotely via the rear D-sub interface. It is manufactured by Rheodyne (now part of IDEX Health & Science) and was sold under the Alltech brand. Made in the USA.

Specifications & What's Included

• Manufacturer: Rheodyne (marketed by Alltech as SelectPRO)
• Model: EV550-104-AL
• Series: SelectPRO Laboratory Fluid Processor
• Part Number (rear panel): 5123088
• Column positions: Up to 6 (configurable; schematic shows 6-column and 3-column modes)
• Central valve rotor: Color-coded IN, OUT, and positions 1–6
• Internal valve banks: Two column-position banks visible in photos
• Control modes: Local (front panel) and Remote (rear connector)
• Front panel: Digital position display, Up/Down selection buttons, Local/Remote indicator LEDs
• Rear I/O connector: 25-pin D-sub (DB25) for remote control and I/O
• Power input: 24V DC, 1.7A (rear-panel DC jack)
• Country of manufacture: USA
• Form factor: Freestanding cylindrical benchtop unit with carry straps
• AC adapter: Not included (24V DC, 1.7A adapter required)
• Cosmetic condition: Slight crack on upper right front case near top panel seam (see photos)

Applications

The SelectPRO EV550 series is used in high-performance liquid chromatography (HPLC) laboratories to automate column switching — allowing a single HPLC system to cycle through multiple analytical columns sequentially or on demand without operator intervention. This capability is commonly used in method development workflows, where multiple stationary phases need to be evaluated, and in high-throughput environments where continuous analysis across columns improves system uptime. The Rheodyne valve-based architecture provides low dead volume switching, which is critical for maintaining chromatographic separation integrity. Remote control via the D-sub interface allows the selector to be integrated into automated HPLC systems and controlled by a workstation or HPLC controller. Rheodyne (founded in the 1970s and long headquartered in Rohnert Park, California) has been a leading manufacturer of HPLC injection valves and fluid-path components; the SelectPRO series represents their approach to modular, multi-column automated fluid management for analytical labs.