Fentanyl Test Strips used to detect the presence of fentanyl in other substances. Accurate for detecting fentanyl in liquid, pills and powder substances. These test strips are designed and tested to detect trace amounts of fentanyl up to 20 ng/mL in pills, powders, urine, and residue. Designed for simplicity, our fentanyl test kits come with fentanyl test strips a 10 mg micro scoop for accurate measurements, and easy to follow instructions.