oil contamination

Sources of Potassium in lubricating oil : - Coolant inhibitor.
Fly Ash.
Paper Mill Dust.
Road Dust.
Granite.

Potassium (K): - Method - D 5185, Unit : - mg/kg Source : - Additives / Dirt

You should send your lab a virgin oil sample; then you can eliminate the possible cause of the virgin oil containing any potassium.
If there is potassium in that sample and the manufactures guarantees that there is not, then you should ask the lab for the calibration record.
Most companies fail to test there virgin oils, this information is vital in diagnosing any problems found in results, you need to eliminate the possibility of the virgin containing Potassium, you then need to eliminate the possibility of incorrect calibrations, then look at further testing to find the cause of this potassium ingress.

Thanks for info. Lab was contacted. They are having problems with potassium contamination of oil samples.

Sounds right - K is not a contaminant metal I've historically associated with turbines. In fluid lubes, the first place it takes us is coolant as noted above, usally with some Na & and maybe Mg. Is there glycol-based coolant in use? If not, it may have more to do with the lab than what's gooing on at your site. It could be carry-over. If memory serves, AA was more prone to carry-over than ICP.