Fig. 5From: High concentrations of illicit stimulants and cutting agents cause false positives on fentanyl test stripsDevelopment time for fentanyl test strip control and test bars: FTS were tested in DI water and 1 mg/mL fentanyl standard. Photographs were taken every 5 s of test strips up to 420 s. The integrated intensities of the control and test bars were analyzed using ImageJBack to article page