Analysis of the 1,4-benzodiazepines by methods based on hydrolysis

Vibrational spectroscopy investigation using ab initio and DFT vibrational analysis of 7-chloro-2-methylamino-5-phenyl-3H-1,4-benzodiazepine-4-oxide

The FT-IR and FT-Raman spectrum of 7-chloro-2-methylamino-5-phenyl-3H-1, 4-benzodiazepine-4-oxide (7CMP4BO) has been recorded in the region 4000-400 and 4000-100 cm(-1) respectively. The optimized geometry, Thermodynamic properties, NBO, Molecular Electrostatic Potentials, PES, frequency and intensity of the vibrational bands of 7CMP4BO were obtained by the ab initio HF and density functional theory (DFT), B3LYP/6-31G (d,p) basis set. The molecule orbital contributions were studied by using the total (TDOS), partial (PDOS), and overlap population (OPDOS) density of states. The harmonic vibrational frequencies were calculated and the scaled values have been compared with experimental FT-IR and FT-Raman spectra. A detailed interpretation of the vibrational spectra of this compound has been made on the basis of the calculated potential energy distribution (PED). The linear polarizability (α) and the first order hyperpolarizability (β) values of the investigated molecule have been computed using DFT quantum mechanical calculations. The observed and the calculated frequencies are found to be in good agreement. The experimental spectra also coincide satisfactorily with those of theoretically calculated values.

Simultaneous Determination of Clidinium Bromide and Chlordiazepoxide in Combined Dosage Forms by High-Performance Liquid Chromatography

A sensitive and precise RP-HPLC method has been developed for the simultaneous estimation of clidinium bromide (CDB) and chlordiazepoxide (CDZ) in pure and pharmaceutical formulations. The separation was achieved on a Nucleodur C₈ (250 × 4.6 mm i.d., 5 μm particle size) column at 25°C. CH₃CN-MeOH-NH₄OAc 0.1M (30 : 40 : 30, v/v/v) was used as the mobile phase at a flow rate of 1.0 mL min⁻¹ and detector wavelength at 218 nm. Almotriptan (ALT) was used as internal standard. The validation of the proposed method was carried out for linearity, accuracy, precision, LOD, LOQ, and robustness. The method showed good linearity in the ranges of 2.5–300.0 and 3.0–500.0 μg mL⁻¹ for CDB and CDZ, respectively. The percentage recovery obtained for CDB and CDZ was 100.40–103.38 and 99.98–105.59%, respectively. LOD and LOQ were 0.088 and 0.294 μg mL⁻¹ for CDB and 0.121 and 0.403 μg mL⁻¹ for CDZ, respectively. The proposed method was successfully applied to the determination of CDB and CDZ in combined dosage forms and the results tallied well with the label claim.

Applying cloud point extraction technique for the extraction of oxazepam from human urine as a colour or fluorescent derivative prior to spectroscopic analysis methods

Two new methods based on cloud point extraction (CPE) technique were developed and optimized for the extraction and preconcentration of oxazepam from human urine, as an azo or fluorescent derivative. The first method is a spectrophotometric one, which is based on the acid hydrolysis of the oxazepam to a benzophenone, diazotization of the benzophenone, and then the coupling with oxine to form an azo dye. The second method is a spectrofluorimetric one, which involves reduction of the target compound using Zn°/HCl at room temperature with the formation of a highly fluorescent derivative. The main factors affecting the chemical reactions and CPE were investigated and optimized systematically. Under optimum experimental conditions, the calibration graphs were linear in the range of 0.1 to 1.5 (0.05 to 2.0) µg/ml with correlation coefficients of 0.9989 (0.9985), for the CPE-spectrophotometric (CPE-spectrofluorimetric) method. The limit of detection was found to be 0.034 (0.018) µg/ml and the relative standard deviation was calculated to be 1.35 (2.52)%. Recoveries in the spiked samples ranged from 87 to 94%. Finally, the proposed methods were applied to the determination of oxazepam in human urine.

Voltammetric behavior and quantification of the sedative-hypnotic drug chlordiazepoxide in bulk form, pharmaceutical formulation and human serum at a mercury electrode

Chlordiazepoxide is a sedative-hypnotic drug widely employed as a transquilizer and anti-depressant. Its electrochemical behavior in Britton-Robinson (B-R) buffers of pH 2-11 at a mercury electrode has been investigated using dc-polarography, cyclic voltammetry and controlled-potential coulometry. Polarograms of the drug in B-R buffers of pH 2-10 exhibited three 2-electron waves, while at pH>10, only a single 4-electron wave was observed. The first, second, and third waves in buffers of pH<or=10 may be attributed to the reduction of N-oxide, C=N and C=N centers, respectively. The single wave (pH>10) may be due to the reduction of both the N-oxide and C=N centers in a one step. The shift of the E(1/2,) values to more negative potentials upon the increase of pH indicated the involvement of protons in the electrode reaction and that the proton-transfer reaction precedes the electrode process proper. The estimated data indicated that, one proton and two electrons are participated in the rate-determining step of each of the reduced centers. The general sequence of chlordiazepoxide reduction processes via each of its reactant centers may be expressed as: H(+), e, e, H(+)((fast)).Based on the interfacial adsorptive character of the drug onto the mercury electrode, a validated direct square-wave adsorptive cathodic stripping (SWAdCS) voltammetric procedure has been described for the trace determination of the drug in bulk form, tablets and human serum. The procedure did not require sample pretreatment or time-consuming extraction or evaporation steps prior to the assay of the drug. The optimized operational conditions of the proposed procedure have been found to be: accumulation potential E(acc.)=-0.9 V, accumulation time t(acc.)=30s, pulse-amplitude=50 mV, scan increment=10 mV and frequency=120 Hz. The proposed procedure is much more simple, fast, sensitive, costly low and achieved much more lower limits of detection (LOD) (4.4 x 10(-10)M and 6.6 x 10(-10)M) and limits of quantitation (LOQ) (1.5 x 10(-9)M and 2.2 x 10(-9)M), respectively in pharmaceutical formulation and spiked human serum, compared to previously reported methods.

Chromatographic separation of 2,3-benzodiazepines

A review of chromatographic methods for the determination of 2,3-benzodiazepines (2,3-BZs) is presented. The determinations are performed to investigate the presence of potential impurities in drug substances and to study their pharmacokinetic profile in biological samples, either in animals or in humans. Several methods dealt with a pretreatment of samples, i.e., liquid-liquid extraction by using a variety of solvents, solid-phase extraction, direct injection of specimens into the chromatographic apparatus. Different chromatographic techniques have been used. High-performance liquid chromatography allows optimal sensitivity and specificity by using ultraviolet or diode array detection methods. Gas chromatography-mass spectrometry and gas chromatography with nitrogen-phosphorous or electron-capture detectors have been also reported. Suitable methods for the separation of enantiomers of 2,3-BZs have been described. Thin-layer chromatography has been shown to be capable to isolate analytes from biological samples as urine or faeces. The reported chromatographic techniques are currently applied to define the metabolic pathways of 2,3-BZs in experimental and clinical studies.

Simultaneous determination of chlordiazepoxide and clidinium bromide in pharmaceutical formulations by derivative spectrophotometry

A direct and simple first derivative spectrophotometric method has been developed for the simultaneous determination of clidinium bromide and chlordiazepoxide in pharmaceutical formulations. Acetonitrile was used as solvent for extracting the drugs from the formulations and subsequently the samples were evaluated directly by derivative spectrophotometry. Simultaneous determination of the drugs can be carried out using the zero-crossing method for clidinium bromide at 220.8 nm and the graphical method for chlordiazepoxide at 283.6 nm. The calibration graphs were linear in the ranges from 0.983 to 21.62 mg/l of clidinium bromide and from 0. 740 to 12.0 mg/l of chlordiazepoxide. The ingredients commonly found in commercial pharmaceutical formulations do not interfere. The proposed method was applied to the determination of these drugs in tablets.

Acid hydrolysis of diazepam. Kinetic study of the reactions of 2-(N-methylamino)-5-chlorobenzophenone, with HCl in MeOH-H2O

In the acid hydrolysis of diazepam (1), several unusual products, apart from 2-(N-methylamino)-5-chlorobenzophenone (2) and glycine, were isolated. On the assumption that some of those products could arise from further degradation of 2, the reaction of this compound with 0.5-2 M HCl was studied, in 1:1 MeOH-H2O, at 60 and 80 degrees C. Several unexpected products were isolated from the reaction of 2 with HCl, namely, 2-amino-5-chlorobenzophenone (3), 2-(N,N-dimethylamino)-5-chlorobenzophenone (4), 2-(N-methylamino)-3,5-dichlorobenzophenone (5), 2-amino-3,5-dichlorobenzophenone (6), 2,4-dichloro-10-methyl-9,10- acridinone (7), and 2,4-dichloro-9,10-acridinone (8). The methyl transfers, the chlorination, and the cyclization reactions that give rise to products 3-8 are unexpected under the present reaction conditions. The rate of reaction of 2, as well as the rate of formation of compounds 3-6, was measured at several HCl concentrations.

Biopharmacological data and high-performance liquid chromatographic analysis of 1,4-benzodiazepines in biological fluids: A review

A review with 123 references on the analysis of 1,4-benzodiazepines in biological samples using HPLC is presented. Some important physico-chemical and biopharmacological data for the development of analytical methods are collected. Different methods of sample pretreatment, chromatographic conditions and detection systems are discussed.

Kinetics of the acid hydrolysis of diazepam, bromazepam, and flunitrazepam in aqueous and micellar systems

A kinetic study of the acid hydrolysis of aqueous diazepam, bromazepam, and flunitrazepam was carried out at 25 degrees C using a spectrophotometric method. For diazepam and flunitrazepam, the experimental pseudo first-order rate constant decreased as the acid concentration was increased. The contrary behavior was found in the case of bromazepam. A kinetic scheme that includes the hydrolysis reaction of both protonated and nonprotonated species of the drug can account for these results. Also, the kinetics of the acid hydrolysis of the same drugs in the presence of micellar aggregates [nonionic polyoxyethylene-23-dodecanol (Brij 35); cationic cetyl trymethyl ammonium bromide (CTAB); and anionic sodium decyl (SdeS), dodecyl (SDS), and tetradecyl (STS) sulfate] was studied at 25 degrees C. Negligible effects were observed in the cases of nonionic and cationic micelles. Anionic micelles produced an inhibitory effect in the reaction velocity. This effect increased as the hydrophobic nature of the surfactant increased. All these facts are interpreted quantitatively by means of a pseudophase model.