Table 1.

H.p.l.c. conditions for drug assays.

Drug	Mobile phase	H.p.l.c. column	Mobile phase flow rate (ml min−1)	Detector wavelength (nm)	Retention time of analyte (min)
Caffeine (internal standard)	95% Na acetate buffer (pH 4.0, 1.7 mm)/5% acetonitrile	C-18	2	276	8.5 (10.2)
Amiodarone	58% distilled water with 0.01 m NH4CIO4/42% acetronitrile (adjusted to pH 3.0 with perchloric acid)	C-8	2	242	8.75
Amitriptyline	60% distilled water with 3 mm octanesulphonic acid, and 0.5 mm NNN’N′-TMED/40% acetonitrile (adjusted to pH 2.5 with H3PO4)	C-8	2	230	7.0
Nortriptyline	As for amitriptyline				7.75
Naproxen	85% 20 mm phosphate buffer (pH 7.0)/15% acetonitrile	C-18	1.8	254	5.5
Tolbutamide	70% 10 mm Na acetate/ 30% acetonitrile (adjusted to pH 4.3 with glacial acetic acid)	C-18	2	254	6.75
Phenytoin	As for tolbutamide	C-18	2	254	5.2

C-18: Waters, Nova Pak, particle size 4 micron, 3.9 mm (id) × 150 mm C-8: Beckman Ultrasphere (Octyl), particle size 5 micron, 4.6 mm (id) × 25 cm.