The aim of this paper is to develop sensitive, accurate, reproducible and robust RP-HPLC with fluorescence detection for estimation of donepezil (DZ) in rabbit plasma using silodosin as the internal standard (IS). The prepared samples were quantified on reversed phase column Luna C18(2) (150 × 4.6 mm i.d., 5 µm particle size) operated at room temperature using the mobile phase consisting of methanol: 0.1% acetic acid (50 : 50, v/v) at a flow rate of 1 ml min−1. The method was fully validated according to bioanalytical validation guidelines of FDA in terms of system suitability, selectivity, sensitivity, precision and stability. It was found that the increase in peak areas followed the increase of DZ concentration in the range of 2.56–200.00 ng ml−1 with LOD of 0.85 ng ml−1. The method was successfully applied for the determination of DZ in rabbit plasma using manual shaking dispersive liquid–liquid microextraction.

The aim of this paper is to develop sensitive, accurate, reproducible and robust RP-HPLC with fluorescence detection for estimation of donepezil (DZ) in rabbit plasma using silodosin as the internal standard (IS). The prepared samples were quantified on reversed phase column Luna C18(2) (150 × 4.6 mm i.d., 5 µm particle size) operated at room temperature using the mobile phase consisting of methanol: 0.1% acetic acid (50 : 50, v/v) at a flow rate of 1 ml min−1. The method was fully validated according to bioanalytical validation guidelines of FDA in terms of system suitability, selectivity, sensitivity, precision and stability. It was found that the increase in peak areas followed the increase of DZ concentration in the range of 2.56–200.00 ng ml−1 with LOD of 0.85 ng ml−1. The method was successfully applied for the determination of DZ in rabbit plasma using manual shaking dispersive liquid–liquid microextraction.

Cost-effective, green, simple and reliable transmission Fourier-transform infrared (FTIR) spectroscopic method was developed for simultaneous analysis of hypoglycemic drugs in their binary mixtures for the first time. The FTIR method was applied for the determination of vildagliptin (VILD), glimepiride (GLIM) and pioglitazone (PIOG) in binary mixture with metformin (METF). The method was validated according to the International Conference on Harmonization (ICH) guidelines. The obtained results (expressed in peak areas) are linear with concentration in the range of 0.61–20, 0.26–24 and 0.37–4 μg/mg for VILD, PIOG and GLIM, respectively while the linearity ranges for METF were 0.40–200, 0.26–800 and 0.19–1000 μg/mg with VILD, PIOG and GLIM, respectively. The limits of detection (LODs) were 0.20, 0.08 and 0.12 μg/mg for VILD, PIOG and GLIM, respectively while METF LODs were 0.13, 0.08 and 0.06 μg/mg with VILD, PIOG and GLIM, respectively. The FTIR method has been successfully applied for the determination of the cited binary mixtures in its pharmaceutical tablets and the obtained results showed satisfactory % recovery.

This paper describes the decoration of pencil graphite electrode (PGE) with a thin film of solochrome black T (SBT) and N-doped carbon nanodots (N-CNDs)/ cobalt nanoparticles (CoNPs) to amplify signal of the measurement. This nanocomposite was chosen to enhance surface activity and electron transfer toward donepezil HCl (DZ HCl) oxidation. The physical properties of nanocomposite were characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), electron impedance spectroscopy (ESI) and energy dispersive X-ray (EDX) spectroscopy. Cyclic voltammetry was utilized to quantify DZ HCl at the modified PGE in Britton-Robinson buffer (pH = 6.5). Under optimized experimental conditions, peak current increased with the increase in the concentration of DZ HCl and was linear between the range of 1.5 nM–400 μM with a relatively low detection limit of 0.0005 μM. Due to high sensitivity, simplicity and cost-effectiveness of the designated sensor; it was used as a simple method for detecting DZ HCl in rabbit plasma and during its pharmacokinetic study.

This paper describes the decoration of pencil graphite electrode (PGE) with a thin film of solochrome black T (SBT) and N-doped carbon nanodots (N-CNDs)/ cobalt nanoparticles (CoNPs) to amplify signal of the measurement. This nanocomposite was chosen to enhance surface activity and electron transfer toward donepezil HCl (DZ HCl) oxidation. The physical properties of nanocomposite were characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), electron impedance spectroscopy (ESI) and energy dispersive X-ray (EDX) spectroscopy. Cyclic voltammetry was utilized to quantify DZ HCl at the modified PGE in Britton-Robinson buffer (pH = 6.5). Under optimized experimental conditions, peak current increased with the increase in the concentration of DZ HCl and was linear between the range of 1.5 nM–400 μM with a relatively low detection limit of 0.0005 μM. Due to high sensitivity, simplicity and cost-effectiveness of the designated sensor; it was used as a simple method for detecting DZ HCl in rabbit plasma and during its pharmacokinetic study.

This paper describes the decoration of pencil graphite electrode (PGE) with a thin film of solochrome black T (SBT) and N-doped carbon nanodots (N-CNDs)/ cobalt nanoparticles (CoNPs) to amplify signal of the measurement. This nanocomposite was chosen to enhance surface activity and electron transfer toward donepezil HCl (DZ HCl) oxidation. The physical properties of nanocomposite were characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), electron impedance spectroscopy (ESI) and energy dispersive X-ray (EDX) spectroscopy. Cyclic voltammetry was utilized to quantify DZ HCl at the modified PGE in Britton-Robinson buffer (pH = 6.5). Under optimized experimental conditions, peak current increased with the increase in the concentration of DZ HCl and was linear between the range of 1.5 nM–400 μM with a relatively low detection limit of 0.0005 μM. Due to high sensitivity, simplicity and cost-effectiveness of the designated sensor; it was used as a simple method for detecting DZ HCl in rabbit plasma and during its pharmacokinetic study.

The combination of xanthine oxidase inhibitor febuxostat (FBX) with acetaminophen (ACE) is widely used in the treatment of gout. A rapid, simple, selective, and precise densitometric method was developed and validated for the simultaneous estimation of FBX–ACE mixture in a synthetic binary mixture and in their pharmaceutical dosage forms. The method employed thin-layer chromatography (TLC) aluminum plates precoated with silica gel G 60 F254 as the stationary phase using chloroform-methanol-cyclohexane-acetic acid 96% (7:1:1:0.1, v/v) as the mobile phase. The optimized mobile phase selected for development gave compact bands (Rf values were 0.65 and 0.46 for FBX and ACE, respectively). Spectrodensitometric scanning integration was performed using dual-wavelength detection at 320 and 250 nm for FBX and ACE, respectively. The linear regression data for the calibration plots showed excellent linear relationship (r = 0.9997 and 0.9992 for FBX and ACE, respectively). The method was validated for precision, accuracy, robustness, and recovery. The limits of detection and quantification were calculated. The statistical analysis proved that the method is reproducible and selective for the estimation of this binary mixture.

The combination of xanthine oxidase inhibitor febuxostat (FBX) with acetaminophen (ACE) is widely used in the treatment of gout. A rapid, simple, selective, and precise densitometric method was developed and validated for the simultaneous estimation of FBX–ACE mixture in a synthetic binary mixture and in their pharmaceutical dosage forms. The method employed thin-layer chromatography (TLC) aluminum plates precoated with silica gel G 60 F254 as the stationary phase using chloroform-methanol-cyclohexane-acetic acid 96% (7:1:1:0.1, v/v) as the mobile phase. The optimized mobile phase selected for development gave compact bands (Rf values were 0.65 and 0.46 for FBX and ACE, respectively). Spectrodensitometric scanning integration was performed using dual-wavelength detection at 320 and 250 nm for FBX and ACE, respectively. The linear regression data for the calibration plots showed excellent linear relationship (r = 0.9997 and 0.9992 for FBX and ACE, respectively). The method was validated for precision, accuracy, robustness, and recovery. The limits of detection and quantification were calculated. The statistical analysis proved that the method is reproducible and selective for the estimation of this binary mixture.

The combination of xanthine oxidase inhibitor febuxostat (FBX) with acetaminophen (ACE) is widely used in the treatment of gout. A rapid, simple, selective, and precise densitometric method was developed and validated for the simultaneous estimation of FBX–ACE mixture in a synthetic binary mixture and in their pharmaceutical dosage forms. The method employed thin-layer chromatography (TLC) aluminum plates precoated with silica gel G 60 F254 as the stationary phase using chloroform-methanol-cyclohexane-acetic acid 96% (7:1:1:0.1, v/v) as the mobile phase. The optimized mobile phase selected for development gave compact bands (Rf values were 0.65 and 0.46 for FBX and ACE, respectively). Spectrodensitometric scanning integration was performed using dual-wavelength detection at 320 and 250 nm for FBX and ACE, respectively. The linear regression data for the calibration plots showed excellent linear relationship (r = 0.9997 and 0.9992 for FBX and ACE, respectively). The method was validated for precision, accuracy, robustness, and recovery. The limits of detection and quantification were calculated. The statistical analysis proved that the method is reproducible and selective for the estimation of this binary mixture.

If strong cation exchange chromatography (SCX) is combined with ion-pair chromatography, then the solute could be retained selectively with the power of mixed separation modes. This combination is termed selectivity enhanced strong cation exchange chromatography (SE-SCX). Macroporous polystyrene-divinylbenzene (PS/DVB) resin with sulfonate coating that conveys ion exchange and reversed phase characteristics was employed. Sodium dodecyl sulfate (SDS) was utilized as a selectivity modifier and an ion-pair reagent. This separation strategy is exploited for a challenging simultaneous separation of peptide variants having similar isoelectric points (pIs) and comparable retention behaviour. Insulin variants were used as a model in this study. The selective separation of insulin and five structurally-related analogues namely; ASPART, LISPRO, GLULISIN, GLARGIN, and DETEMIR was conducted using gradient elution mode. Three eluents were used for the separation of the target compounds. Eluent A was a mixture of acetonitrile and 10 mmol L-1 SDSat ratio (1:1) and was kept at 20% through the run. Eluent B was 20 mmol L-1 KH2PO4 adjusted at pH=4.0 and eluent C was eluent B plus 1 mol L-1 NaCl that was increased linearly till 80% at 20 min. It was found that the retention of the tested variants can be modeled mainly by electrostatic interaction that might be hydrophobically-assisted. The developed method was validated in accordance with ICH guidelines and was appropriate for the intended purposes. Finally, this study introduces SE-SCX as a new selective separation strategy for peptides and proteins that may open the door for novel mixed mode perspectives in protein analysis.