In this ICP-MS troubleshooting video, Mike Adams (the "Health Ranger"), founder of CWClabs.com and author of Food Forensics (http://FoodForensics.com) explains how to diagnose Pulse / Analog calibration problems and fix them.
If your resulting concentration reporting seems accurate at high ranges but is off at low ranges, you have a "pulse" tuning problem! Here's how to double check and resolve this problem.
Mike Adams is one of the world's leading food scientists and has pioneered the development of dietary formulas that block heavy metals and radioactive Cesium-137.
His lab offers commercial food testing services at http://CWClabs.com