Spectrophotometic determination of Lorazepam in pharmaceutical tablets using batch and reverse flow injection methods

A reverse flow injection analysis (RFIA) spectrophotometric method have been developed and compared with batch method for the determination of lorazepam (LOR) at the microgram level in pure and pharmaceutical dosage forms. The methods are based on the reaction of LOR with 3-methyl-2-benzothiazolinone hydrazone hydrochloride (MBTH) in the presence of ferric chloride in aqueous medium. The water soluble green color product was measured at λmax 659 nm. Under the optimum conditions, linearity was observed from 2 to 40 and 25 to 400 µg/mL LOR with detection limits of 0.61 and 2.29 µg/mL LOR by batch and RFIA procedures respectively. All the chemical and physical parameters related with reverse flow system were carefully considered and both methods were successfully applied for the determination of LOR in its dosage forms. These simple and high throughput methods could be utilized for pharmaceutical analysis of LOR