Flowcells
FLOWCELL TYPES
BAS makes an assortment of flowcell types for the epsilon platform. You may choose from single, dual, or quad working electrodes with radial or cross-flow patterns. The main types are shown in the following diagram. When reading the diagram, start at the top with a choice of flow pattern, then read down to see the possible combinations of auxiliary electrode, gasket, and working electrode that correspond to that flow type.
Flow Pattern |
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 Cross |
 Arc |
 Radial |
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(Includes phenolic base, arms, and reference retainer.) |
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 MF-1093 |
 MF-1087 |
 MF-1091 |
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 0.5mil MF-1044 2.0mil MF-1046 5.0mil MF-1047 |
 0.5mil MF-1067 2.0mil MF-1066 |
 0.5mil MF-1068 2.0mil MF-1069 |
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These part numbers are for glassy carbon working electrodes. Working electrodes also can be made from carbon paste, copper, gold, platinum, and silver. Many of these are available off-the-shelf, while others can be custom fabricated.
PLUMBING CONNECTIONS
Please refer to this diagram when assembling the flowcell. Bear in mind that your flowcell may differ slightly from the one pictured, depending on what configuration was purchased.
Place the thin-layer gasket over the pins of the auxiliary electrode, taking care that the cutout section matches both the flow pattern inside the cell, and the orientation of the working electrodes.
NONE OF THE TINY FLOW HOLES ON THE SURFACE OF THE AUXILIARY ELECTRODE, AND NONE OF THE ELECTRODE SURFACES ON THE FACE OF THE WORKING ELECTRODE, SHOULD BE COVERED BY THE GASKET.
Place the working electrode over the gasket, with the individual electrodes facing the gasket and the large brown circle of sealant facing out. Put the steel backing plate over the working electrode, taking care that its two pins go into the two empty holes (the other two holes are occupied by the pins of the auxiliary electrode). Attach the quick-release mechanism so its arms engage the arms of the auxiliary electrode. Tighten securely. Do not install the reference electrode at this time.
Before connecting the column to the flowcell, consider the flow direction through the cell. In the flowcell pictured above, in which the reference electrode compartment is offset to one side, that side must be the exit, because if your sample entered this way it would be diluted in the reference compartment. But for some of our other flowcells, in which the reference compartment is centered, and there's no flow through it, flow direction makes no difference.
Connect the column to the inlet of the flowcell using a fingertight plastic connector. Be sure to slide the connector back up the tubing first, so you can completely bottom out the tubing into the socket of the flowcell:
Connect the outlet of the flowcell to a waste line in the same manner.
IMPORTANT! The flowcell must not be grounded to the chassis or your detector will not work. Grounding can occur if steel tubing is used to make the connections to the flowcell. For example, the flowcell can ground to the injector if steel tubing and a metal column are used. (Steel tubing and a plastic column are all right, as are plastic tubing and a metal column.) If you must use steel, you can back the tubing out of the flowcell just enough so no contact is made -- use an ohmeter to check this.
Start the pump and allow mobile phase to flow through the cell and fill the reference electrode compartment. Stop the pump once the fluid has risen above the level of the shelf on which the o-ring will sit (you may have to block the flow of the exit tubing to get the fluid to rise this high). If there are bubbles in the well, remove the liquid with a disposable pipet and refill the well several times.
The reference electrode will be installed next. This closeup shows the reference electrode and its associated parts:
With the pump stopped, place the o-ring on its shelf. Remove the yellow rubbery coating from the tip of the reference electrode if you haven't already done so (see REFERENCE ELECTRODES.) Then insert the reference electrode into the well at a slight angle, to avoid trapping an air bubble under it. Insert fully, then mop up any liquid above the o-ring or behind the flowcell with a laboratory tissue. Screw down the locking collar finger tight.
ELECTRICAL CONNECTIONS
The three electrodes of the flowcell (working, auxiliary, and reference) are connected to the epsilon controller by the terminal ends of the cell lead(s). The connections are differentiated by color, size, and sex. The other end of the cell lead(s) is connected to the back of the epsilon controller.
WARNING: NEVER CONNECT THE CELL LEADS WHEN THE EPSILON CONTROLLER IS TURNED ON, AND NEVER TOUCH THE EXPOSED PINS OF THE CELL LEADS WHEN THE INSTRUMENT IS ON. DOING SO COULD DAMAGE THE SENSITIVE AMPLIFIERS AND VOID YOUR WARRANTY.
The black connectors with male pins are for the working electrodes. They are labeled W1-W4, and get plugged into the recessed sockets on the edges of the working electrode block. In multi-electrode systems there may be a preferred location for each electrode, so pay careful attention to the application when making these connections.
The red female connector is for the auxiliary electrode. It connects to the gold pin atop the auxiliary block.
The white female connector is for the reference electrode. It connects to the silver pin at the end of the white wire atop the reference electrode.
The grounding lug should be securely bolted to the threaded stud on the inside rear of the flowcell compartment.
