Bio-Rad BioLogic DuoFlow pH Monitor User Manual

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The BioLogic pH monitor is an in-line electrode and flow cell that provides direct monitoring of pH conditions during
a sample run. It provides real-time monitoring of buffer pH and is designed for flow through pH recordings. The pH
monitor is available as an option to the BioLogic DuoFlow systems and is compatible with the discontinued
BioLogic HR systems. The monitor ships with all Maximizer systems.

The monitor is supplied with a tubing kit that includes installed ¼ -28 fittings. When used with either a DuoFlow or
HR system the pH monitor connects via the Signal Import Module (SIM). When a Maximizer is installed with the
DuoFlow Workstation the monitor connects directly to the system via a BNC port on the Maximizer.

The pH electrode is a sealed Calomel combination electrode consisting of a pH and a reference electrode built into
a single body. The sealed reference design eliminates the need to add electrolyte solutions and minimizes
reference dry out. The pH electrode is fully compatible with buffers (such as Tris) that may not be compatible with
Ag/AgCl containing electrodes. The pH Monitor is designed for use in chromatography applications at flow rates up
to 80 ml/min and a flow cell pressure less than 75 psi.

The flow cell is made of PEEK and has a swept volume of approximately 80ul when the pH electrode is inserted.

These instructions cover the installation, calibration, and maintenance of the pH electrode and flow cell. Be sure to
keep this information with your BioLogic DuoFlow or HR instruction manual for future reference.

Installation Instructions

Figure 1. pH Electrode and Flow Cell

The flow cell and pH electrode should be plumbed downstream of any backpressure device or detector. The pH
Monitor has a maximum pressure rating of 75 psi.

DuoFlow pH Monitor

Catalog Number 760-2040

Instructions for first time use

During shipment, the air bubble in the electrode’s stem may have moved into the bulb area. If bubbles are seen in
the bulb area, hold the electrode by its top cap and shake downwards, as is done with a clinical thermometer.

Do not expose the electrode to extreme pH solutions for prolonged periods of time, doing so will severely shorten
the lifespan of the electrode.

Before you install the pH electrode in the flow cell hydrate the pH bulb and reference junction by removing the
electrode protector boot and immersing the lower end of the electrode into distilled water or a pH 4.0 buffer for 30
minutes.

Assembling and Installing your pH Monitor

The flow cell is equipped with a mounting bracket for easy attachment to any system. The tilt of the flow cell
inhibits bubble formation.

1. Mount the flow cell to the DuoFlow rack using the mounting bracket. If a UV detector and Conductivity monitor
are being used we recommend attaching them to this same bracket.

2. Plumb the flow cell from its inlet (lower port) to the Conductivity monitor using the orange (0.02” ID) PEEK
tubing supplied with the pH monitor. Connect the outlet port to your fraction collector. Both ports are threaded
for use with ¼-28 fittings. If you anticipate high flow rates that create high backpressure, install the green
(0.03” ID) PEEK tubing.

3. Ensure that the black o-ring is in the flow cell and the red o-ring is on the lower half of the pH electrode.

4. Insert the pH electrode into the top of the flow cell and hand tighten the nut until some
resistance is encountered. Do not over tighten.

5. Attach the BNC connector from the pH electrode to the Maximizer or SIM, see figures 2 and 3.

Plumb the flow cell downstream of any backpressure device since the pH probe has a maximum pressure
rating of 75 psi.

Figure 2. pH Monitor connected via SIM module for BioLogic DuoFlow without a Maximizer system

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SIGNAL IMPORT MODULE

FRONT VIEW

pH ELECTRODE

pH FLOW CELL

pH MONITOR

REAR VIEW

TO BIOLOGIC CONTROLLER
(HR OR DUO FLOW)
OR
USB BITBUS COMMUNICATOR