Ultrasound-assisted electromembrane extraction of clonazepam from plasma and determination using capillary electrophoresis.

In this work, ultrasound-assisted electromembrane extraction (UA-EME) coupled with capillary electrophoresis (CE) and diode array detection (DAD) was developed for the determination of clonazepam from plasma samples. A comparative study was carried out between conventional EME and UA-EME methods to investigate the influence of the ultrasound waves on the extraction efficiency. The central composite design was used for the optimization of the variables affecting these methods to achieve the best extraction efficiency. Under optimal extraction conditions, the UA-EME provided better extraction recovery in a shorter time (58% in 13 min) than the EME method (42% in 30 min). Ultrasound reduces the extraction time and increased recovery by reducing the thickness of the barrier layer. In addition, this method provided a higher pre-concentration factor (203) and a lower limit of detection (3 ng mL-1) with good repeatability (RSDs were less than 10.11%).

A twin purification/enrichment procedure based on two versatile solid/liquid extracting agents for efficient uptake of ultra-trace levels of lorazepam and clonazepam from complex bio-matrices.

In this research work, two consecutive dispersive solid/liquid phase microextractions based on efficient extraction media were developed for the influential and clean pre-concentration of clonazepam and lorazepam from complicated bio-samples. The magnetism nature of the proposed nanoadsorbent proceeded the clean-up step conveniently and swiftly (∼5min), pursued by a further enrichment via a highly effective and rapid emulsification microextraction process (∼4min) based on a deep eutectic solvent (DES). Finally, the instrumental analysis step was practicable via high performance liquid chromatography-ultraviolet detection. The solid phase used was an adequate magnetic nanocomposite termed as polythiophene-sodium dodecyl benzene sulfonate/iron oxide (PTh-DBSNa/Fe3O4), easily and cost-effectively prepared by the impressive co-precipitation method followed by the efficient in situ sonochemical oxidative polymerization approach. The identification techniques viz. FESEM, XRD, and EDX certified the supreme physico-chemical properties of this effective nanosorbent. Also the powerful liquid extraction agent, DES, based on bio-degradable choline chloride, possessed a high efficiency, tolerable safety, low cost, and facile and mild synthesis route. The parameters involved in this versatile hyphenated procedure, efficiently evaluated via the central composite design (CCD), showed that the best extraction conditions consisted of an initial pH value of 7.2, 17mg of the PTh-DBSNa/Fe3O4 nanocomposite, 20 air-agitation cycles (first step), 245µL of methanol, 250µL of DES, 440µL of THF, and 8 air-agitation cycles (second step). Under the optimal conditions, the understudied drugs could be accurately determined in the wide linear dynamic ranges (LDRs) of 4.0-3000ngmL-1 and 2.0-2000ngmL-1 for clonazepam and lorazepam, respectively, with low limits of detection (LODs) ranged from 0.7 to 1.0ngmL-1. The enrichment factor (EF) and percentage extraction recovery (%ER) values were found to be 75 and 57% for clonazepam and 56 and 42% for lorazepam at the spiked level of 75.0ngmL-1, possessing proper repeatabilities (relative standard deviation values (RSDs) below 5.9%, n=3). These valid analytical features provided quite accurate drug analyses at therapeutically low spans and levels below potentially toxic domains, implying a proper purification/enrichment of the proposed microextraction procedure.

Development and application of novel clonazepam molecularly imprinted coatings for stir bar sorptive extraction.

The molecularly imprinted magnetic stir bar coatings were created based on graft-functional Fe3O4 nanoparticles with magnetic field-induced self-assembly. The magnetic complex including clonazepam as template, the graft-functional Fe3O4 nanoparticles and methacrylic acid as monomers was pre-assembled through π-π interaction and hydrogen bonding, then was directionally adsorbed on the surface of magnetic stir bar under the magnetic induction. The molecularly imprinted coating with well-ordered structure was generated by one-step copolymerization based on the cross linking of ethylene glycol dimethacrylate. The molecularly imprinted coating with multiple recognition sites could be manufactured and applied in polar solvents, and showed superior selectivity and fast binding kinetics for benzodiazepines. The analytes in herbal health foods, treated by stir bar sorptive extraction, were determined by HPLC-UV. Good linearity was observed in the range of 0.01-2 µg mL(-1). The content of clonazepam in the herbal health foods was found to be 44 ng g(-1), and the average recoveries were 89.8-103.3% with a relative standard deviation (RSD) <6.5%, demonstrating the successful application in real sample analysis.

Development of an ultra-high-performance liquid chromatography coupled to high-resolution quadrupole-Orbitrap mass spectrometry method for the rapid detection and confirmation of illegal adulterated sedative-hypnotics in dietary supplements.

A novel method using ultra-high performance liquid chromatography coupled to hybrid quadrupole-Orbitrap high-resolution mass spectrometry (UHPLC-Q-Orbitrap) was developed and validated for the simultaneous screening, identification and quantification of sedative-hypnotics in dietary supplements. Chromatographic conditions were optimised and a full data-dependent MS(2) scan (MS/dd-MS(2)) in positive and negative ion mode was used. A single injection was sufficient to perform the simultaneous screening and identification/quantification of samples. The response showed a good linear relationship with analyte concentrations over wide ranges (e.g., 1.0-1000 ng g(-1) for diazepam) with all the determination coefficients (r(2)) > 0.9985. The method was validated, obtaining accuracy (intra- and inter-day) in the range of 94.5-105.3% and precision (intra- and inter-day) in the range of 0.4-8.9%, respectively. The detection limits (LODs) were in the range of 0.3-1.0 ng g(-1) for different analytes. Recoveries were performed and ranged from 74.1% to 90.2%, while all matrix effects were over the range of 85.4-93.6%. Finally, this method was used to detect sedative-hypnotics in commercial dietary supplements. Of a total of 45 batches of dietary supplements, only three batches were found to be positive samples with concentrations of diazepam, clonazepam and alprazolam at high levels (≥ 8.22 mg g(-1)).

Selective extraction of clonazepam from human plasma and urine samples by molecularly imprinted polymeric beads.

A molecularly imprinted polymer (MIP) based on free-radical polymerization was prepared with 1-(N,N-biscarboxymethyl)amino-3-allylglycerol and N,N-dimethylacrylamide as functional monomers, N,N-methylene diacrylamide as the cross-linker, copper ion-clonazepam as the template and 2,2-azobis(2-methylbutyronitrile) as the initiator. The imprinted polymer was characterized by Fourier transform infrared spectroscopy, elemental analysis, thermo-gravimetric analysis, and SEM. The MIP of agglomerated microparticles with multipores was used for SPE. The imprinted polymer sorbent was selective for clonazepam. The optimum pH and sorption capacity were 5 and 0.18 mg/g at 20C, respectively. The profile of the drug uptake by the sorbent reflects good accessibility of the active sites in the imprinted polymer sorbent. The MIP-SPE was the most feasible technique for the extraction of clonazepam with a high recovery from human plasma and urine samples.

Computer-assisted design and synthesis of a highly selective smart adsorbent for extraction of clonazepam from human serum.

A computational approach was applied to screen functional monomers and polymerization solvents for rational design of molecular imprinted polymers (MIPs) as smart adsorbents for solid-phase extraction of clonazepam (CLO) form human serum. The comparison of the computed binding energies of the complexes formed between the template and functional monomers was conducted. The primary computational results were corrected by taking into calculation both the basis set superposition error (BSSE) and the effect of the polymerization solvent using the counterpoise (CP) correction and the polarizable continuum model, respectively. Based on the theoretical calculations, trifluoromethyl acrylic acid (TFMAA) and acrylonitrile (ACN) were found as the best and the worst functional monomers, correspondingly. To test the accuracy of the computational results, three MIPs were synthesized by different functional monomers and their Langmuir-Freundlich (LF) isotherms were studied. The experimental results obtained confirmed the computational results and indicated that the MIP synthesized using TFMAA had the highest affinity for CLO in human serum despite the presence of a vast spectrum of ions.

7-[125I]iodoclonazepam: purification by high-performance liquid chromatography for use in a very sensitive benzodiazepine radioimmunoassay of broad specificity.

The purification of 7-[125I]iodoclonazepam by high-performance liquid chromatography (HPLC) for use in a very sensitive benzodiazepine radioimmunoassay is described. A silica column is used with a non-aqueous eluent and sequential ultra-violet and gamma-ray detection. A commercially available antiserum is used at a dilution of 1:1000. Blood samples are diluted 10-fold with buffer before analysis and only 25 microliters of diluted sample are required per assay tube. Benzodiazepines, but not the radiolabel, appear to be bound by blood proteins in competition with the antiserum and so, if undiluted blood is assayed, erroneously low results are obtained. The minimal sample requirement and the high sensitivity of the assay described here largely avoid this problem while maintaining acceptable detection limits. For diazepam, the detection limit is 2.5 ng/ml in blood or urine (after correction for the initial 10-fold dilution) and therapeutic or sub-therapeutic levels of many other benzodiazepines can be detected. In practice, the assay is reliable, simple to perform and extremely economical.

Liquid chromatographic assay for serum clonazepam.

An improved reversed-phase liquid chromatographic assay for the anticonvulsant clonazepam in human serum is presented. The drug and two internal standards are extracted from serum with n-butyl chloride at pH 9.2, back-extracted into 2 N HCl, and then extracted at pH 11 into a solvent mixture of chloroform/isopropanol (9:1 by volume). The final extract is evaporated to dryness, reconstituted, and injected into a cyanopropylsilane liquid chromatography column with a mobile phase of 0.5 N acetic acid, acetonitrile, and n-butylamine (59:41:0.005 by volume, respectively). Linearity to 400 micrograms/L was demonstrated, and the detection limit was found to be approximately 5 micrograms/L. Relative recovery from serum as compared to water was approximately 100% for clonazepam and the two internal standards, flunitrazepam and desmethyldiazepam. Within-run precision at 40 micrograms/L was demonstrated by a coefficient of variation (CV) of 2.60% (flunitrazepam internal standard) and 2.53% (desmethyldiazepam internal standard). Between-day multiple analyst precision was demonstrated by a CV of 8.98% (mean 10.09 micrograms/L, n = 77) and 6.51% (mean 28.14 micrograms/L, n = 81) using either internal standard. Capacity factor diagrams reveal at least a dual mechanism separation. Chromatograms of the analysis of clonazepam and other benzodiazepines are presented. The extraction has been optimized for selectivity, thereby minimizing interference from drugs and other extraneous compounds. The chromatographic system has been optimized for speed, efficiency, resolution, and stability and avoids the problem of carbamazepine interference that is commonly encountered with other reversed-phase procedures using octylsilane or octadecylsilane columns.

Determination of clonazepam and its amino and acetamido metaoblites in human plasma by combined gas chromatography chemical ionization mass spectrometry and selected ion monitoring.

Our previously published gas chromatography chemical ionization mass spectrometry stable isotope dilution assay for clonazepam and its 7-amino metabolite in plasma has been modified to obtain more consistent recoveries of the amine metabolite and to permit the determination of the 7-acetamido metabolite of clonazepam. In addition, the manuscript describes the details of a method for a least squares analysis of the nonlinear standard curves associated with the use of certain stable isotope labeled analogs as internal standard.