Vol 74, No 6 (2019)

A simple, sensitive, precise, accurate, highly reproducible and economical, visible spectrophotometric method for the determination lurasidone in bulk form was developed and validated. The method is based on the formation of an oxidative coupling product by the reaction of lurasidone with 3-methylbenzothiazolin-2-one hydrazone as a chromogenic reagent in presence of ferric chloride. The linear regression analysis data for the calibration plot showed good linear relationship within the concentration range of 0–100 μg/mL with a correlation coefficient (r) value of 0.9997. The limits of detection and quantitation are 0.6 and 1.7 µg/mL, respectively. The method was tested and validated according to ICH guidelines. The results demonstrated that the procedure is accurate, precise and reproducible (RSD < 2%).

Absract

‒A simple, selective and sensitive hollow fiber solid phase microextraction (SPME) combined with HPLC for the determination of fluoxetine (FLX) and norfluoxetine (NFLX) in human urine and real water samples has been developed and fully validated. Two solid phase microextraction sorbents, β-cyclodextrin functionalized multi-walled carbon nanotubes (βCD-MWCNTs) and acyl chloride functionalized MWCNTs, were synthesized and placed in the surface and pores of polypropylene hollow fiber by sol‒gel technique. In order to compare the analytical performance of βCD-MWCNTs as a new SPME sorbent with acyl chloride functionalized MWCNTs and MWCNTs, the hollow fiber device was directly immersed into the sample solution under a magnetic stirring. The βCD-MWCNTs are quite effective for extraction of fluoxetine and norfluoxetine. The extraction parameters such as pH of donor phase, donor phase volume, stirring rate, extraction time, type and volume of desorption solvent, and desorption time were thoroughly optimized. Under optimal conditions, the proposed method shows good linearity in the range of 1‒340 and 0.9‒360 ng/mL with a correlation coefficients of 0.9952 and 0.9967, low limits of detection of 0.4 and 0.3 ng/mL, and the high pre-concentration factors of 144 and 151 for determination of FLX and NFLX, respectively. Usage of proposed method for determination of FLX and NFLX in human urine and real water samples demonstrated a promising, simple, selective and sensitive sample preparation and determination method that can be applied in routine analysis.

A rapid, specific, and sensitive ultra fast liquid chromatographic method for simultaneous determination of aspartame (ASP), acesulfame-K (ACE-K), caffeine (CAF) and sodium benzoate (SB) has been developed and validated. The chromatographic separation was achieved on a Shim-pack XR-ODS column within a run time of 3 min using acetonitrile‒pH 3 phosphate buffer (20 : 80, v/v) as the mobile phase at a flow rate 1.5 mL/min and the column temperature was set at 40°C. The elaborated method was validated according to the International Conference on Harmonization quidelines. Linear calibration graphs were in the ranges of 120‒280 µg/mL for ASP and ACE-K, 90‒210 µg/mL for CAF and 60‒140 µg/mL for SB. The limits of detection were 1.6, 4.3, 3.9 and 4.1 µg/mL for ASP, ACE-K, CAF and SB, respectively. The limits of quantitation were 5.2, 14.4, 12.9 and 13.7 µg/mL for ASP, ACE-K, CAF and SB, respectively. The intra- and inter-day precisions were less than 2%. The recoveries for the analytes were between 98.87‒99.73% and the precision values from 0.06 to 0.35.

Toxic metabolites (N-acetylisoniazid, pyrazinoic acid, and desacetylrifampicin) of first-line anti-tuberculosis drugs (ethambutol, pyrazinamide, rifampicin, and isoniazid) are identified by liquid chromatography–mass spectrometry, which is important in selecting the required dosages of these drugs for the maximum therapeutic effects and the reduction of side effects. Characteristic chromatographic profiles of blood plasma samples from donors with pulmonary tuberculosis (“pathology”) and a clinically healthy group (“norm”) are obtained and processed by principal component analysis and the k-nearest neighbor method. A perspective of this approach for obtaining of additional diagnostic criteria for pulmonary tuberculosis is shown.

A method is developed for the flow-injection amperometric determination of tryptophane and pyridoxine on a screen-printed electrode with electrodeposited gold nanoparticles. The dependence of the analytical signal on the concentrations of tryptophane and pyridoxine on the logarithmic coordinates is linear in the ranges from 5 × 10⁻⁷ to 5 × 10⁻³ and from 5 × 10⁻⁸× to 5 × 10^–3 M, respectively. A possibility of the simultaneous amperometric determination of tryptophane and pyridoxine on a dual screen-printed electrode modified by gold nanoparticles in a flow-injection system is shown. The developed method is approved in the determination of tryptophane and pyridoxine in medicinal preparations.

A standardized procedure is developed for the determination of chloramphenicol in food products of animal origin of different groups using HPLC with tandem mass spectrometric detection with a limit of detection of 0.2 µg/kg. The extraction of chloramphenicol from aqueous solutions with organic solvents was studied. Optimized procedures for the extraction of chloramphenicol, purification of the extracts, and preconcentration of the analyte and the use of the deuterated form of chloramphenicol ensure quantitative determination using an external calibration method with an internal standard with the maximum expanded uncertainty of the results 18.4%.

In order to determine the geographical origin and wine variety of white wines, we studied 153 samples of the white wines Riesling (49), Chardonnay (56), and Muscat (48) produced in the territory of the main wineries of geographical zones in the Krasnodar krai. The concentrations of trace and macro elements in wines were determined by inductively coupled plasma atomic emission spectrometry. Chemometric studies were performed using the STATISTICA Neural Networks. From a set of 15 trace and macro elements determined, 5 trace elements (Fe, Mg, Rb, Ti, and Na) were recognized by correlation analysis as the predictors of a constructed neural network model, which successfully identified the brands of wines. To determine the region of grape growing, a neural network model was constructed based on six predictors: five trace elements and a specified wine brand. A software was developed to automate the computations required.