How to detect cuts: if you intend to use a synthetic psychoactive substance, first you need to check it using a test kit. Most popular drug testing kits are colorimetric reagents, simple spot-tests which produce different color reactions with different compounds. It’s the same kind of tests as used by police. To detect fentanyl or it’s analogues it’s recommended to use fentanyl test strips.
How to test fentanyl: if you intend to use an opioid, first you need to check it using a test kit to rule out presence of dangerous adulterants such as fentanyl. Fentanyl can be even 100 times more potent than morphine, and therefore is easy to accidentaly overdose on. Fentanyl can be mixed in any kind of sample and can’t be identified by appearance. To detect fentanyl or analogs it’s recommended to use fentanyl test strips.