Liquid-phase microextraction combined with flow-injection tandem mass spectrometry Rapid screening of amphetamines from biological matrices

Liquid-Phase microextraction based on polypropylene hollow fibres was combined with flow-injection tandem mass spectrometry for rapid screening of drugs in biological matrices. Amphetamine and analogues were utilised as model compounds. These drugs were extracted from 0.5 mL samples of whole blood or urine. The samples were made alkaline with 0.5 mL of 1 M NaOH and the urine samples were diluted with 3 mL water to reduce the salt concentration. The uncharged analytes were then extracted through a hollow fibre impregnated with dihexyl ether into 25 μL of 0.01 M HCl inside the hollow fibre. Parallel extraction of 20–30 samples was performed for 15 min. After extraction 20 μL of the extract was injected directly into the flow-injection tandem mass spectrometry system. Atmospheric pressure ionisation operated in positive mode was used as ion spray. All analytes were detected simultaneously after 0.1 min, utilising a combination of selected ion monitoring mass spectrometry and selected reaction monitoring tandem mass spectrometry. Limits of detection (S/N = 5) varied between the compounds and were estimated to be 2–100 ng/mL in urine and 0.4–14 ng/mL in whole blood. Comparison of injection of pure acceptor solution with urine and whole blood extracts demonstrated the efficient sample clean-up by LPME. Ion suppression due to matrix effects was not seen, rendering LPME-FIA-APCI-MS-MS a promising alternative for rapid screening of drugs in biological matrices.