Determination of 3,4,5-Trihydroxybenzoic Acid Exploiting a Visible-Light-Driven Photoelectrochemical Platform: Application in Wine and Tea Samples

The present work is based on the development and application of a photoelectrochemical method for the amperometric determination of 3,4,5-trihydroxybenzoic acid in different samples. The method is based on the use of a photoelectrochemical platform based on a glass slide coated with fluorine-doped tin oxide, which has been modified with cadmium sulfide and poly(D-glucosamine) and subjected to a light-emitting diode (LED) lamp. The photoelectrochemical platform was sensitive to the increase of the concentration of the antioxidant 3,4,5-trihydroxybenzoic acid in the solution. Under the optimized experimental conditions, the photoelectrochemical method presented a linear response for a 3,4,5-trihydroxybenzoic acid concentration ranging from 0.2 up to 500 μmol L-1. The method was applied to 3,4,5-trihydroxybenzoic acid determination in samples of wines and teas with recoveries between 95.88 and 101.72%. The results obtained suggest that the developed platform is a promising tool for quantifying the 3,4,5-trihydroxybenzoic acid.

Modification of Electrode Using Arrowroot Starch Membrane for Uric Acid Determination

Arrowroot starch membrane-modified glassy carbon electrode were constructed for the determination of uric acid. The membrane consist of arrowroot starch, polyvinyl alcohol, uric acid, and crosslinker. The crosslinker used was sodium tripolyphosphate, citric acid, and glutaraldehyde. Carbon material was added to increase the sensitivity. The composition of membrane influences the electrodes sensitivity. The best composition of arrowroot starch membrane is UA1 using 0.1% uric acid in membrane and STPP as crosslinker. The linearity concentration, sensitivity, and detection limit were 100-500 µM, 0.0509 A/M and 76 µM, respectively.

Determination of Folic Acid in Multivitamin Preparations by Reversed Phase HPLC

A great variety of components in multivitamin preparations containing folic acid, and a variety of test methods and conditions of folic acid determination proposed by manufacturers, require alignment of test procedures for products with similar composition.The aim of the study was to compare the results of experimental verification of folic acid determination procedures which use reversed phase high-performance liquid chromatography (RP HPLC) with isocratic elution mode. Materials and methods: The Agilent 1260 Infinity II LC system with a diode array detector (280 nm), isocratic elution mode, C8- and C18-bonded silica gel chromatographic columns, model mixtures containing folic acid, cyanocobalamin, ferrous sulfate, and potassium iodide, were used in the study.Results: The lowest relative standard deviation of the folic acid peak area (RSD=0.09%), and the lowest asymmetry factor (As=1.04) for folic acid were observed for the model mixture “ferrous sulfate+folic acid+cyanocobalamin” and the following test conditions. Column: 250×4.0 mm, silica gel for chromatography, octylsilyl (C8), endcapped; mobile phase: methanol‒phosphate buffer (12:88), pH 6.6; column temperature: 25ºС. The study demonstrated the feasibility of using these conditions for determination of pteroic acid impurity with simultaneous precipitation of interfering ferrous ions, using ethylenediaminetetraacetic acid solution, pH 9.5, as a solvent.Conclusions: RP HPLC can be recommended as an optimal aligned test procedure for determination of folic acid in combination products. It is recommended to use a solution containing folic and pteroic acids for system suitability testing.

Development and Validation of Tranexamic Acid Determination in Human Plasma by HPLC-MS/MS method

Introduction. Tranexamic acid is one of the most common drugs used to stop bleeding after trauma, in surgery and gynecology. The most common analytical method for the determination of this compound is reversed-phase high-performance liquid chromatography (HPLC). However, this compound belongs to the group of so-called poorly retained compounds due to its chemical structure. It is necessary to develop an analytical method that will allow the determination of tranexamic acid in human blood plasma with the least time, resource costs and without the use of specialized columns.Aim. The aim of this study is to develop a method for tranexamic acid in human plasma by high performance liquid chromatography with tandem mass-spectrometry (HPLC-MS/MS) for pharmacokinetic studies.Materials and methods. Determination of tranexamic acid in plasma by HPLC-MS/MS. The samples were processed by acetonitrile protein precipitation.Results and discussion. This method was validated by next parameters: selectivity, matrix effect, calibration curve, accuracy, precision, recovery, lower limit of quantification, carry-over effect and stability.Conclusion. The method of the determination of tranexamic acid in human plasma was developed and validated by HPLC-MS/MS. The linearity in plasma sample was achieved in the concentration range of 100.00–15000.00 ng/ml. Method could be applied to tranexamic acid determination in plasma for pharmacokinetics and bioequivalence studies.