OBJECTIVE or GOAL
Tune the optimal position of the iKey and verify that it is not charging/arcing. (A spray position close to the cone might seem to provide high sensitivity in the short term, but when the emitter tip or the cone are charging, the emitter tip suffers 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, 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 a large amount of aqueous mobile phase. Or, for example, if you have a known component that is difficult to ionize or is in very low concentration in your sample, use the composition on that spot.
- Optimize the source parameters (keep in mind that a capillary voltage of 3.8 kV is very common for the iKey) and optimize the X, Y, and Z positions for maximum sensitivity. Once you have optimized the spray position, flush the infusion key to wash solution and remove it.
- Place your 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 tune page. You should have a complete black screen with no sparks. If you see a lightning show or a white light at the emitter tip, the tip is charging. If you see white sparks near the cone or an entire lightning line, there is charging as well. In that case you must move the iKey further away form the cone to create a stable spray for the long term.
- If the entire screen stays black, there is no charging at initial conditions. However, you should check 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 50:50, for example, and later to final conditions, to determine that there is truly no charging.