I am trying to measure Ca in seawater samples and when using 44Ca in He mode, concentrations are consistently ~11% higher than what is expected from our standards. Additionally 44Ca in He mode is about 11% higher than 44Ca in no gas mode and 48Ca in He mode. This is consistent for every sample/standard such that if I multiply concentrations measured from 44Ca by 0.89 then they are about what they should be. He flow rate is 5 ml/min and energy discrimination is 5V. Samples are diluted 100x in 2% nitric and so plasma mode is in low matrix. Is this some sort of ArHe interference or something else? Just wondering how to fix this, thank you!