Specifications      Operation      Troubleshooting

Specifications:

Does the Pressure Injection Cell require electrical power?

No.  The liquid sample is forced through the capillary using pressurized gas typically supplied by a tank.

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Operation:

How much pressure is required? 

Loading samples into a capillary for mass spectroscopy typically requires 100 to 400 psi.  Packing capillary columns typically requires 500 to 1000 psi.

How long does packing a column take? 

Packing a 20 cm column typically takes a few hours.  When you are finished packing the column, turn off the pressure at the gas tank and let the column sit overnight so that the pressure in the cell leaks out through the packing.  This avoids pull back of the packing media.

How can you determine the approximate flow rate through a capillary?

If the solution is flowing only through an otherwise empty capillary tube, the flow rate is straightforward to calculate.  However, a frit or a packed capillary typically causes much more flow resistance, so it is best to measure the flow rate with a test solution.

To measure the flow rate, run a test solution through a sample capillary and at the outlet place a calibrated micropipette.  The solution should wick up the micropipette on its own so you don't need any special fittings to seal them together.  For example, Drummond and other brands of micropipettes, available from most laboratory product suppliers, come in 1, 2, 3, 4, 5, 10, 20, ... µl volumes.  Using a stopwatch, measure how long it takes from when the solution starts to exit the capillary and begins filling the micropipette until the micropipette is filled. 

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Troubleshooting

Gas leaks through the top-to-base interface of the pressure injection cell.   The three bolts might not be fully tightened or the O-ring might be nicked or dirty or missing.  If the O-ring is dirty, wash it off with a soap and water and return it to its groove.  Contact us for a replacement O-ring.

Gas leaks around the capillary. The ferrule should be replaced.    

You do not see sample traveling through the capillary after a few minutes. Check that the gas tank is supplying the desired pressure (typically on the order of several hundred psi) and that the 3-way valve knob is pointing toward the pressurized gas line.

The media pulls back when you release the pressure. 

When you are finished packing the column, turn off the pressure at the gas tank and let the column sit overnight so that the pressure in the cell leaks out through the packing.  This avoids pull back of the packing media.

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