Can someone work in 2 departments (ex: QA laboratory & Production Laborer) and be paid dfferenteny for each deptment

I am a QA/QC chemist for a chemical manufacturer in Massachuesttes. In a better times I was able to fill in (part time) as a chemical operator in the production plant. It was the perfect 2nd job. I was paid at my chemist rate with overtime (if applicable). Now I am told that I can not work in the production plant because my hourly wage as a chemist is too much. My question is can someone work full time in one department (at one hourly rate) and work part-time in another deptment (at a different hourly rate).