A batch and cloud point extraction kinetic spectrophotometric method for determining trace and ultra trace amounts of Benzodiazepine drugs (Clonazepam and Nitrazepam) in pure and pharmaceutical preparations

Utilizing the batch Diazotization coupling reaction and the cloud point extraction kinetic spectrophotometric method, trace and Ultra trace amounts from reducing Nitrazepam and Clonazepam were evaluated by way of using 2,5-dimethoxyaniline as a new Chromogenic reagent to give colored products (red) in acidic medium which have a maximum absorption at 500 and 502 nm, respectively. In the work, the analytical data of batch and cloud point for Nitrazepam and Clonazepam depended on initial rate and fixation time. This involved concentrations of (0,3-9), (0.05-1.2), (0.5-10) and (0.025-1) µg mL⁻¹, as well as molar absorptivity of (3.8×10⁴), (3.1×10⁵) (3.39×10⁴) and (3.47×10⁵) L mol⁻¹ cm⁻¹. According to our results, Sandall’s sensitivity were (0.0074), (0.0009), (0.0092) and (0.0009) µg cm⁻², while detection limits were (0.055) and (0.069) µg mL⁻¹, (8.4) and (8.5) ng mL⁻¹. In addition, the measurements enrichment factors were (33.33) and (50), while preconcentration factors were (8) and (9.9), respectively. The reaction of Nitrazepam and Clonazepam with 2,5-dimethoxyaniline were a pseudo first order according to kinetic studies. The proposed methods are not affected by existence of excipients so the methods can be applied successfully for determination of Nitrazepam and Clonazepam in pharmaceutical preparations.