Cost-effective green chromatographic method for the simultaneous determination of four commonly used direct-acting antiviral drugs in plasma and various pharmaceutical formulations

Validated LC/MS method for simultaneous determination of elbasvir and grazoprevir in human plasma

A sensitive and accurate LC/MS method for the determination of elbasvir (ELB) and grazoprevir (GZP) in human plasma was established using daclatasvir (DCT) as an internal standard. The analytes were separated on a Waters Spherisorb phenyl column (150mm×4.6mm ID, 5μm particle size) maintained at 40°C±2°C. Gradient elution, at a flow rate of 0.8mLmin-1, was used. The mobile phase consists of 90% of acetonitrile mixed to 10% of a 5mM ammonium formate buffer (+0.1% v/v of trimethylamine, pH was adjusted to 3.2 by formic acid) as phase A and 10% of acetonitrile mixed to 90% of the same buffer as phase B. Liquid-liquid extraction with ethyl acetate solvent was used to recuperate compounds from plasma. The method was validated over a concentration range of 2 and 100ng/mL for GZP and between 1 and 50ng/mL for ELB. The intra- and inter-day precision and accuracy of the quality control samples at low, medium, and high concentration levels exhibited relative standard deviations (RSD)<15%, and the accuracy values ranged from 94.2 to 107.8%. The robustness of the method was established using a two-level full factorial design.

Electrochemical sensor based on bio-inspired molecularly imprinted polymer for sofosbuvir detection

The electropolymerized molecularly imprinted polymers (MIP) have enabled the utilization of various functional monomers with superior selective recognition of the target analyte template. Methyldopa is an attractive synthetic dopamine analogue which has phenolic, carboxylic, and aminic functional groups. In this research, methyldopa was exploited to fabricate selective MIPs, for the detection of sofosbuvir (SFB), by a simple electropolymerization step onto a disposable pencil graphite electrode (PGE) substrate. The interaction between methyldopa, as a functional monomer, and a template has been investigated experimentally by UV spectroscopy. A polymethyldopa (PMD) polymer was electrografted onto PGE in the presence of SFB as a template. X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (ESI), and cyclic voltammetry (CV) were used for the characterization of the fabricated sensor. Differential pulse voltammetry (DPV) of a ferrocyanide/ferricyanide redox probe was employed to indirectly detect the SFB binding to the MIP cavities. The sensor shows a reproducible and linear response over a dynamic linear range from 1.0 × 10-11 M to 1.0 × 10-13 M of SFB with a limit of detection of 3.1 × 10-14 M. The sensor showed high selectivity for the target drug over structurally similar and co-administered interfering drugs, and this enabled its application to detect SFB in its pharmaceutical dosage form and in spiked human plasma samples.

Simple simultaneous determination of moxifloxacin and metronidazole in complex biological matrices

A simple, sensitive and rapid RP-HPLC method is presented, for the first time, for the simultaneous determination of moxifloxacin hydrochloride and metronidazole in different biological fluids including saliva and plasma without any matrix interference. The separation was performed using ACN and phosphate buffer (30 : 70% v/v) as the mobile phase on a Zorbax Eclipse Plus-C18 column attached to a guard column. The method was validated according to the FDA guidelines for bioanalytical method validation and was successfully applied for simultaneous determination of the studied drugs in saliva and plasma samples. The good precision and selectivity of the developed method allow it to be used for routine therapeutic drug monitoring of such drugs and it presents a simple and sensitive analytical tool for performing versatile pharmacokinetics and bioavailability studies. A DAD detector is valuable to determine each drug at its maximum wavelength to ensure high sensitivity. Determination of such a combination in saliva introduces a quick and non-invasive alternative to blood analysis.

The Ionic Associate of Metamizole as an Electrode-Active Component of a PVC Plasticized Membrane Electrode

The technology for manufacturing a film membrane of the metamizole-selective electrode containing ion associate metamizole-octadecylammonium ODAH+MT− as an electrode active component (EAC) has been proposed. The main potentiometric characteristics of the metamizole-selective electrode have been determined. The expediency of the proposed design of the metamizole selective electrode for the determination of metamizole in dosage forms has been substantiated. The best composition of the membrane (wt.%) of the metamizole-selective electrode has corresponded to: ODAH+MT−—5.3; 2-nitrophenyloctylether—63.1; poly(vinyl chloride)—31.6. Electrode-active component in the membrane phase functions as an ion associate ODAH+MT−. Potentiometric characteristics of metamizole-selective electrode have been determined, which corresponded to: linear range 1 × 10−2–1 × 10−4 with limit of detection 4.58 × 10−5 M, electrode function slope −48.5 mV/dec., working interval pH 4.5–7.3, response time 60 s. The potentiometric coefficients of selectivity of the metamizole-selective electrode with respect to various ions have been determined. The possibility of determining metamizole in a medicinal product has been tested. The results of the analyses show good agreement between the two methods (relative error less than 7.0%) with coefficients of variation less than 5% for MT-SE and iodometric methods.