LC–MS/MS Determination of Apigenin in Rat Plasma and Application to Pharmacokinetic Study

Background: Apigenin, a natural plant flavone, has been shown to possess a variety of biological properties. Objective: In this report, a highly selective and sensitive LC-MS/MS method was developed and validated for the determination of apigenin in rat plasma. Methods: Analysts were separated on the HSS T3 column (1.8 μm 2.1×100 mm) using acetonitrile and 0.1% formic acid in 2 mM ammonium acetate buffer at a supply rate of 0.200 mL/min as eluent in gradient model. Results: Plasma samples were treated by protein precipitation using acetonitrile for the recovery ranging from 86.5% to 90.1% for apigenin. The calibration curves followed linearity in the concentration range of 0.50-500 ng/mL. The inter-day and intra-day precisions at different QC levels within 13.1% and the accuracies ranged from -10.6% to 8.6%. Conclusion: The assay has been successfully applied to the pharmacokinetic study of apigenin in rats.

Sequential Extraction of Potentially Toxic Metals: Alteration of Method for Cu-Ni Polluted Peat Soil of Industrial Barren

An evaluation of fraction composition and transformation of metal compounds emitted by metal ore processing enterprises and accumulated in soils is crucial for assessing the environmental risks of pollution and ecosystem benefit of remediation. The aim of this study was to develop a suitable sequential fractional procedure for metal pollutants for the peat soils matrix in the impact zone of a Cu-Ni smelter. Three experiment series were performed: (a) the study of the effect of ammonium acetate buffer pH in the range of 3.7–7.8 on the soil metal extraction; (b) the study of the effect of additional volume and frequency of soil treatment with solutions on the content of water-soluble, ammonium acetate extractable, and 0.1 N HNO3 extractable fractions; and, (c) the determination of the metal fraction composition in the modified technique. Soil treatment with ammonium acetate buffer with a pH range of 4.5–5.5 was the most appropriate for the determination of mobile compounds of Cu and other metals in highly polluted peat soil. Triple soil treatment with water and ammonium acetate is necessary for the complete extraction of the water-soluble and exchangeable fractions, respectively. Additionally, we propose a procedure of full extraction of the exchangeable metal fraction from peat soils while using single treatment with 0.1 N HNO3. This scheme allows evaluating geochemical mobility of metals and current environmental harm of polluted soils with a high content of organic matter.

DETERMINATION OF Cu(II) CONCENTRATION IN AQUEOUS MEDIUM USING INVERSION ELECTROCHEMICAL METHOD

Electrode materials based on titanium dioxide modified with zinc ions and gold nanoparticles, synthesized by sol-gel method, were used to determine the concentration of Cu (II) in liquids by stripping voltammetry method. Determination of Cu (II) was done using background solutions based on 0.4 M formic acid and ammonium acetate buffer (pH = 7.5) using the standard addition method with a potential scanning speed of 50 mV•s-1. The solution was stirred during the preliminary electrolysis at a potential of -1400 mV (vs silver-chloride reference electrode) for 120 seconds and then the potential was scanned from -1200 mV to + 200 mV. It is shown that the background solution based on ammonium acetate buffer provides a higher sensitivity and a good selectivity of peaks for the determination of copper compared to the background solution based on formic acid. Determined that value of the analytical signal of copper in the studied model solutions based on ammonium acetate and formic acid is proportional to the concentration of copper ions in the solution. To increase the selectivity of stripping voltammetry method in determining copper concentrations in solutions, an inversion spectral photoelectrochemical method was proposed, the essence of which is preliminary electroconcentration of the elements under investigation in the cathode potential region and subsequent measurement of the spectral photoelectrochemical characteristics of electroconcentration products. It has been found that in solutions of 1M ammonium acetate containing Cu2+ ions, the cathodic polarization of TiO2-based photoelectrode leads to the appearance of a cathode photocurrent and the values of photocurrent quantum yield increase with increasing content of copper ions in the solution. The spectral sensitivity of the surface layer corresponds to the absorption spectrum of Cu2O. The sensitivity of stripping voltammetry method to copper Cu (II) using the materials studied was 0.3 mg•l-1. It is shown that the inversion photoelectrochemical method is promising in the selective determination of copper concentration in liquids.

Determination of Genotoxic alkyl p-toluene Sulfonates in Cabazitaxel using LC-MS Method

Introduction: A suitable LC-MS method for the quantitative determination of genotoxic impurities such as alkyl p-toluene sulfonates in Cabazitaxel was developed. Alkyl p-toluene sulfonates were estimated by LC-MS method using Waters Symmetry C18 (75×4.6 mm), 3.5 µ column. Materials and Methods: Column temperature was maintained 40 °C. Injection volume was 10 µL and flow rate was set as 0.8 mL/min. Sampler temperature was maintained to 25 °C and run time was set as 25 minutes. The mobile phase was a mixture of ammonium acetate buffer and acetonitrile in 70:30(v/v) was used. Results: The method validation has been carried as per ICH guidelines. LOQ was found to be 2.66 µg/mL, 2.75 µg/mL and 2.55 µg/mL for MPTS, EPTS and IPPTS Alkyl p-Toluene Sulfonates (APTS) respectively. Conclusion: The proposed Liquid chromatography-Mass spectroscopy method that can quantify genotoxic APTS in Cabazitaxel at low-level concentration has been developed and validated as per ICH guidelines. Hence, the proposed method was recommended for the assay of genotoxic impurities of cabazitaxel in dosage forms in busy pharmaceutical laboratories.

DETERMINATION OF CU(II) CONCENTRATION IN AQUEOUS MEDIUM USING INVERSION ELECTROCHEMICAL METHOD

Electrode materials based on titanium dioxide modified with zinc ions and gold nanoparticles, synthesized by sol-gel method, were used to determine the concentration of Cu (II) in liquids by stripping voltammetry method. Determination of Cu (II) was done using background solutions based on 0.4 M formic acid and ammonium acetate buffer (pH = 7.5) using the standard addition method with a potential scanning speed of 50 mV•s-1. The solution was stirred during the preliminary electrolysis at a potential of -1400 mV (vs silver-chloride reference electrode) for 120 seconds and then the potential was scanned from -1200 mV to + 200 mV. It is shown that the background solution based on ammonium acetate buffer provides a higher sensitivity and a good selectivity of peaks for the determination of copper compared to the background solution based on formic acid. Determined that value of the analytical signal of copper in the studied model solutions based on ammonium acetate and formic acid is proportional to the concentration of copper ions in the solution. To increase the selectivity of stripping voltammetry method in determining copper concentrations in solutions, an inversion spectral photoelectrochemical method was proposed, the essence of which is preliminary electroconcentration of the elements under investigation in the cathode potential region and subsequent measurement of the spectral photoelectrochemical characteristics of electroconcentration products. It has been found that in solutions of 1M ammonium acetate containing Cu2+ ions, the cathodic polarization of TiO2-based photoelectrode leads to the appearance of a cathode photocurrent and the values of photocurrent quantum yield increase with increasing content of copper ions in the solution. The spectral sensitivity of the surface layer corresponds to the absorption spectrum of Cu2O. The sensitivity of stripping voltammetry method to copper Cu (II) using the materials studied was 0.3 mg•l-1. It is shown that the inversion photoelectrochemical method is promising in the selective determination of copper concentration in liquids.

CENTRAL COMPOSITE DESIGN APPLIED IN HPLC OPTIMIZATION FOR ANALYSIS OF TARTRAZINE AND AURAMINE O IN POWDER DRINKS

Objective: This study was intended to optimize reversed-phase high-performance liquid chromatography (RP-HPLC) method for the determination of Tartrazine (TAR) and Auramin O (AUO) in powder drinks using experimental design of central composite design (CCD) approach. Methods: TAR and AUO in powder drink product has same properties, therefore both analytes were analysed using C18 column (XBridge Shield RP 18 250 mm x 4.6 mm i.d., 5 µm) using Shimadzu LC 20AD chromatograph equipped with photo-diode array (PDA) detector at 300-650 nm. Some factors responsible for RP-HPLC separation of TAR and AUO including the concentration of buffer, the ratio of mobile phase and flow rate were optimized using CCD. The responses evaluated were peak area, retention time, and tailing factor. The mobile phase used was acetonitrile and ammonium acetate buffer, and acetonitrile composition was optimized at 84-86% for separation of TAR and AUO, delivered at a flow rate of 0.8–1.2 ml/min, using ammonium acetate buffer at 19-21 mmol. Results: CCD showed that separation of TAR and AUO was influenced by flow rate, the ratio of acetonitrile and ammonium acetate concentration. These factors affected significantly to retention time, peak area, and tailing factor. The optimal condition obtained based on CCD was flow rate of 1.2 ml/min, the ratio of acetonitrile 86%, and ammonium acetate concentration of 19 mmol. Conclusion: CCD can be used to get optimum condition for analysis of TAR and AUO in powder drink product.

High Performance Liquid Chromatography Using Ultrasonic Extraction for Benzoic Acid Analysis in Curry Paste Samples

Benzoic acid analysis in curry paste samples were carried out by using high performance liquid chromatography using ultrasonic extraction. Methanol-0.05 M ammonium acetate buffer pH 4.40 in the ratio of 55:45 (%v/v) at a flow rate of 1.00 mL/min was used as the mobile phase and benzoic acid detection was performed at 226 nm using an UV-Visible detector. Under the optimum conditions, linearity of spiked samples ranged from 50 to 3,000 mg/kg. Matrix matched calibrations had determined that benzoic acid contents in southern sour, red, and green curry paste samples were 67.59, 78.62 and 72.33 mg/kg, respectively. Recoveries were obtained from 89.34 to 101.70%, 83.37 to 130.30% and 92.75 to 113.56% with R.S.D. ranged from 2.71 to 6.53%, 4.02 to 11.58% and 5.81 to 6.35%, for southern sour, red, and green curry paste samples, respectively.