... extraction cartridges are com-mercially available ( GL-SPE Vacuum Manifold, GL Sciences, Tokyo, Japan and some man-ufacturers in USA); it enables the attachment of 12 cartridges, and the simultaneous ... Morphine and its analogues 8) Matsubara K, Fukushima S, Akane A et al. (1992) Increased urinary morphine, codeine and tetrahydropapavero-line in Parkinsonian patient undergoing L-3,4-dihydroxyphenylalanine ... analysisReagents and their preparation• Standard solutions of morphine for a calibration curve (2, 6 and 20 µg/mL): see “Reagents and their preparation”, above of GC and GC/MS analysis section.•...