OBJECTIVE or GOAL
This procedure describes how to tune the optimal position of the iKey and to verify that it is not charging / arcing. A spray position close to the cone might seem to provide a high sensitivity on the short term, however when the emitter tip or the cone are charging then the emitter tip will get irreversible damage, leading to spray instability.
- Place the infusion key in the ionKey source enclosure
- Infuse a component that resembles the type of molecules that you want to analyze (e.g. use a chemical small molecule standard or use GluFib if you are doing proteomics). Infuse in a mixture of mobile phase A and mobile phase B
- Make the infusion composition in such a way that it resembles the most challenging conditions of your analysis. For example if you have very early eluters then make a mixture with a lot of mobile phase A and only a small amount of B as it is a bigger challenge to get a good stable spray with large amount of aqueous mobile phase. Or if you e.g. have a known component that is difficult to ionize or in the very low concentration in your sample then use the composition on that spot.
- Optimize the source parameters, keep in mind that a capillary voltage of 3.8 kV is really common for the iKey and optimize the X, Y and Z position for maximum sensitivity. Once you have optimized the spray position then flush the infusion key to wash solution and remove it.
- Place you analytical iKey in the source enclosure.
- Start the mobile phase flow at initial conditions and check that the spray looks stable using the camera. Now switch off the Source LED in the tunepage. You should have a complete black screen with no sparks. If you see a lightning show or a white light at the emitter tip then the tip is charging. In case you see white sparks near the cone or an entire lighting line then there is charging as well. In that case you have to move the iKey further away form the cone to have a stable spray on the long term.
- In case the entire screen stays black then there is no charging at initial conditions. However, there should be checked for charging over the entire course of the gradient so either run a full gradient and watch the camera with the source LED off. Or switch the flow to e.g. 50:50 and later to final condition to judge that there is really no charging.