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Chemistry LibreTexts

11. Sample Injection

The following describes the process for using pressure to inject a sample plug into the separation capillary. The process of sample injection should be practiced with non-critical samples until a high level of consistency is obtained. Inconsistant sample injection makes quantitative analysis impossible.

  1. Make sure the black control switch located on the three-way valve is pointed towards the solenoid. In this position, pressure is only introduced via the electronically actuated solenoid valve. Adjust the injection pressure with the black control valve on the regulator to the desired pressure.
  2. Turn on the timer box. Adjust the injection time using the gears located underneath the injection time display window.
  3. Replace the anode buffer vial with the sample vial containing the sample needing to be analyzed. It is important that the sample vial is fully screwed into the sample vial holder; otherwise a partial injection may result. Close the anode reservoir box lid.
  4. Inject a sample by actuating the timer box. There should be a click followed by the sound of pressurized gas entering the sample vial and then another click. During the injection, monitor the pressure gauge to make sure that the injection pressure remains steady (changes not to exceed 0.2psi)
  5. Turn off the timer box and replace the sample vial with the anode buffer vial. Close the anode reservoir box lid. If a partial injection occurs, the sample plug needs to be removed from the capillary by a pressurized flush.
  6. Replace the sample vial with the anode buffer vial. Close the lid of the interlock box.
  7. Silmultaneous turn on the high voltage power supply and click start on IGOR Pro. If you cannot do this comfortably, click start on IGOR Pro first, and then turn on the power supply and hit the Event button on the lower right corner of the UV-vis detector. This will produce a small peak (~ 0.2) on the graph which will mark the actual start time of the separation.