Luminescence method for the determination of lorazepam in tablets

New terbium complex of 7-chloro-5-(2-chlorophenyl)-3-hydroxy-1,2-dihydro-3H- 1,4-benzdiazepin-2-one (lorazepam, L), which is highly luminescent and do not require luminescence enhancers, is reported. The luminescence intensity of the Tb-L complex was enhanced by the addition of Tergitol 7 in water solution. The Tb-L-Tergitol 7 complex with a components ratio 1:1:2 was proposed to be used as the analytical form for the luminescence determination of drug--lorazepam. The calibration curve is linear in the 0.05-20.0 pg/mL range of lorazepam (LOD is 0.016 microg/mL). This method was applied for the determination of lorazepam in dosage form--tablets "Apo-lorazepam"--2.5 mg.