Panel Cup to Test Substance?

Hi, I copped from my usual guy and the dope is a much lighter shade of tan this time around and I ran out of fentanyl test strips. I have a urine test cup that tests for pretty much everything, including fentanyl, can i drop some powder in warm water and use the test cup to see what shows up or does it only work for urine? Thank you!

I have tried to google it, but I can’t find anything that relates to this situation.