You can apply nitrogen gas at the API source by using any combination of the three gas sources: sheath gas, auxiliary gas, and (optional) sweep gas.
Sheath gas is the inner-coaxial nitrogen gas that nebulizes the sample solution into a fine mist as it exits the electrospray needle.
The heated auxiliary gas is the outer coaxial nitrogen gas that helps the sheath gas to nebulize and evaporate the sample solution by focusing the vapor plume and lowering the humidity in the API source. The auxiliary gas heats as it passes through the heater/vaporizer tube. The heater/vaporizer tube is thermally insulated from the metal electrospray needle to prevent the direct heating of the sample solution. You can control the heater/vaporizer temperature from the Tune application or the Method Editor. The temperature range is from ambient room temperature to 650 °C. For the recommended initial operating settings, see To Set the Recommended API Source Settings.
Sweep gas is the off-axis nitrogen gas that flows out from behind the optional ion sweep cone to aid in solvent declustering and adduct reduction. The optional ion sweep cone has an inlet for the sweep gas.
All analyses are analyte dependent and require separate optimization with sheath gas, sweep gas, and auxiliary gas to determine which combination yields optimum performance. Optimize with each gas independently before you perform experiments using MSn techniques and before you perform any quantitative analysis experiments.
For higher LC flow rates, apply auxiliary gas to increase the signal intensity.
When you are analyzing complex matrices such as plasma or nonvolatile salt buffers, you must use sweep gas to increase the ruggedness of the system. For full-scan MS or data-dependent scan experiments, apply sweep gas to improve the signal-to-noise ratio.