Abstract
A simple and express method for the quantitative determination of zopiclone in model solutions of the substance and in “Zopiclone” tablets, 7.5 mg, by the kinetic-spectrophotometric method according to 3,3’,5,5’-tetramethylbenzidine oxidation has been developed. It is based on the system of two coupled reaction: 4-methyl-1-piperazineperoxycarboxylic acid generated in zopiclone perhydrolysis reacts with the excess of hydrogen peroxide in the weak alkaline medium with formation of coloured 3,3’,5,5’-tetramethyldiphenylquinone diimine (λmax = 420 nm, рН = 8.4). The reaction is performed spectrophotometrically by measuring the rate of change of the absorbance at 420 nm. The method was used for constructing the calibration graph. The initial rate of the reaction was obtained from the linear site of the slope of the initial tangent to the absorbance-time curve. In the pH range of 8.2-8.5 the rate of the coloured product formation becomes maximum. The calibration graph for zopiclone has a linear dependence in the range of 6-36 mg/l with the limit of detection (LOD) and quantitation (LOQ) of 1.81 and 6.04 mg/l, respectively. For five determinations of 18, 24 and 30 mg/l of zopiclone RSD is 1.81, 1.46 and 1.69%, respectively. The analytical performance of the method was validated statistically with respect to LOD, LOQ, accuracy, precision and linearity for zopiclone estimation in a pure substance and the results were satisfactory. “Zopiclone” tablets compared to the reference method contain 99.83±1.19% of C17H17ClN6O3 (RSD = 0.96% , δ = -0.17%). The assay of zopiclone in the presence of its hydrolysis products without preliminary separation is an important advantage of the method.
Highlights
Zopiclone (6-(5-chloro-2-pyridyl)-6,7-dihydro-7-oxo5H-pyrrolo-[3,4-b]pyrazin-5-yl-4-methylpiperazine-1carboxylate) is an ester with similar sedative, anxiolytic, muscle relaxant, amnestic, and anticonvulsant properties to those of benzodiazepines
The reaction involved in the present study is based on the perhydrolysis reaction of zopiclone with the excess of hydrogen peroxide in the weak alkaline medium forming 4-methyl-1-piperazinepercarboxylic acid (PA)
It has been shown that hydrolytic cleavage products that are present do not interfere the zopiclone determination
Summary
Zopiclone (6-(5-chloro-2-pyridyl)-6,7-dihydro-7-oxo5H-pyrrolo-[3,4-b]pyrazin-5-yl-4-methylpiperazine-1carboxylate) is an ester with similar sedative, anxiolytic, muscle relaxant, amnestic, and anticonvulsant properties to those of benzodiazepines. The B.Ph. describes a non-aqueous titrimetric method for its determination in its bulk and liquid chromatography for tablets [4]. The aim of this work was to develop a new kinetic method of the quantitative determination of zopiclone using the indicator reaction of 3,3’,5,5’-tetramethylbenzidine (TMB) oxidation by hydrogen peroxide in the weak alkaline medium. To create and maintain the pH required 0.2 M phosphate buffer with pH 8.4 prepared according to Green was used For this purpose 12 g of NaH2PO4 was dissolved in 450 ml of DDW and 50.6 ml of 1.9 mol/l NaOH was added, pH was monitored potentiometrically. Dissolve 0.0300 g of the zopiclone substance in 96% ethanol in a 100 ml volumetric flask, dilute the solution to the volume with the same solvent and mix thoroughly. All the chemicals and reagents were of analytical grade and the solutions were freshly prepared
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
