An unknown impurity formed during stability sample analysis by a gradient reversed phase ultra-high pressure liquid chromatography (UHPLC) of varenicline tablets at 0.2% level. A simple isocratic preparative method was developed to isolate the unknown impurity with 20 min run time. This unknown impurity was identified and characterized by using spectroscopic techniques. Based on the spectral da...

We applied HPLC technique to quantitatively analyze sinomenine in cubosome nanoparticles. The chromatographic method was performed by using an isocratic system. The mobile phase was composed of methanol-PBS(pH6.8)-triethylamine (50 : 50 : 0.1%) with a flow rate of 1 mL/min; the detection wavelength was at 265 nm. Sinomenine can be successfully separated with good linearity (the regression equat...

This paper describes a reserved-phase high-performance liquid chromatographic (HPLC) method for detecting malachite green (MG) and leuco-malachite green (LMG) using an isocratic toxic organic solvent/reagent-free mobile phase. Chromatographic separations were performed an Inertsil WP300 C4 with 0.02 mol/L octane sulfonic acid–ethanol mobile phase and a photodiode-array detector. The total run t...

We describe a versatile high-performance liquid-chromatographic method for determining homocysteine and other plasma sulfhydryls. Using three different procedures for preparation of plasma, we determined total, free (non-protein-bound), and reduced forms of homocysteine, cysteine, glutathione, cysteinylglycine, and gamma-glutamylcysteine in human plasma. Sample preparation involves disulfide re...

GRADIENT ION CHROMATOGRAPHY WAS USED FOR THE SEPARATION OF EIGHT SUGARS: arabitol, cellobiose, fructose, fucose, lactulose, melibiose, N-acetyl-D-glucosamine, and raffinose. The separation method was optimized using a combination of simplex or genetic algorithm with the isocratic-to-gradient retention modeling. Both the simplex and genetic algorithms provided well separated chromatograms in a s...

A reversed-phase liquid chromatographic method for the determination of 1,7,7-trimethyl-bicyclo(2,2,1)heptan-2-one in a cream formulation is developed and validated. The separation was achieved using an isocratic mobile phase, on a Lichrosorb C8 column. The calibration curve is linear (r(2)= 0.9999) from 25-175% of the analytical concentration of 1.0 mg/ml. The mean percent standard deviation v...

We present procedures for determining theophylline in 50 mul of serum. The drug is extracted into a small volume of solvent that contains an internal standard, 8-chlorotheophylline. The extract is Analyzed by isocratic reversedphase chromatography, with measurement of eluted theophylline at 273 nm. Day-to-day reproducibility within 5% is attainable for the concentration range 5--20 mg/liter. Ot...

New UPLC method was developed for determination of sitagliptin and metformin using Symmetry C18 column (100 mm × 2.1 mm, 2.2 μm) and isocratic elution (methanol 20%), pH (3.5) as a mobile phase. The ultraviolet detector was operated at 220 nm and the column temperature was 50°C. Linearity parameters were acceptable over the concentration ranges of 2-12 μgml(-1) and 5-35 μgml(-1) for sitagliptin...

A labour- and time-effective analytical procedure for determination of ivermectin in medicated feed at recommended level of 2.0 mg kg(-1) has been developed and validated. The analyte was extracted from grinded feed samples with acetonitrile and derivatisated with N-methylimidazole and trifluoracetic anhydride. The fluorescent derivatives were analysed by liquid chromatography method using C8 c...

A selective and sensitive liquid chromatographic method has been developed for simultaneous determination of zonisamide and its four related substances in pharmaceutical dosage forms. The assay involved an isocratic elution in perfectsil Target C18 column using a mobile phase composition of disodium hydrogen phosphate buffer, acetonitrile and methanol (650:150:200 v/v, pH adjusted to 3±0.05) wi...