Figure 4: Mass spectra of a urine sample, spiked with a mixture of p-chloroamphetamine, ketamine and 3,4-MDMA (concentration level of each, 1.0 μg/mL, respectively). The spiked urine sample was made alkaline by the addition of 1g of potassium carbonate and was then shaken for 1 min. Following this, the PP hollow fiber was used for microextraction (extraction period, 30 min). A mass spectrum was obtained for the microextraction process followed by the beveled end hollow fiber method.