Determination of penicillamine, tiopronin and glutathione in pharmaceutical formulations by kinetic spectrophotometry

A novel and simple method for the determination of penicillamine (PEN), tiopronin (mercaptopropionyl glycine, MPG) and glutathione (GSH) in pharmaceutical formulations by kinetic spectrophotometry has been developed and validated. It is based on the redox reaction where the thiol compound (RSH) reduces CuII-neocuproine complex to CuI-neocuproine complex. The non-steady state signal of the formed CuI- neocuproine complex is measured at 458 nm. The initial rate and fixed time (at 1 min) methods were validated. The calibration graph was linear in the concentration range from 8.0 × 10‒7 to 8.0 × 10‒5 mol L–1 for the initial rate method and from 6.0 × 10‒7 to 6.0 × 10‒5 mol L–1 for the fixed time method, with the detection limits of 2.4 × 10‒7 and 1.4 × 10‒7 mol L–1, resp. Levels of PEN, MPG and GSH in pharmaceutical formulations were successfully assayed by both methods. The advantages of the presented methods include sensitivity, short analysis time, ease of application and low cost

Flow-injection Determination of Glutathione, Penicillamine and Tiopronin Based on the Reduction of Copper(II)-neocuproine Reagent

A new flow-injection spectrophotometric method for the determination of glutathione (GSH), penicillamine (PEN) and tiopronin (mercaptopropionyl glycine, MPG) in pharmaceutical formulations is reported. The method is based on the reduction of Cu(II)-neocuproine reagent to Cu(I)-neocuproine by GSH, PEN or MPG in buffered medium (pH = 3) to form a stable coloured complex (λmax = 458 nm). Experimental conditions were optimized by univariate method, resulting with linear calibration curves in concentration range from 2 × 10−6 to 3 × 10−5 mol L−1 for GSH, 6 × 10−7 to 4 × 10−5 mol L−1 for PEN and 4 × 10−7 to 4 × 10−5 mol L−1 for MPG. The achieved analytical frequency was 180 h−1 for GSH and PEN and 120 h−1 for MPG. The proposed method was successfully applied for determination of GSH, PEN and MPG in pharmaceutical formulations, and the usual excipients in pharmaceuticals did not interfere with the analysis. This work is licensed under a Creative Commons Attribution 4.0 International License

Spectrophotometric Determination of N-acetyl-L-Cysteine in Pharmaceutical Formulations by Flow Injection and Sequential Injection Analysis: Comparison of the Methods

N-acetyl-L-cysteine (NAC), a sulfhydryl-containing compound, is mainly used as a mucolytic and as an antidote for acetaminophen overdose. Flow injection and sequential injection systems were designed and optimized with the aim of providing precise, accurate and reliable flow methods for NAC determination in pharmaceuticals with very low sample and reagent consumption. Proposed methods are based on a redox reaction wherein NAC reduces a complex of Cu(II) and bathocuproine disulfonate (BCS) to orange [Cu(BCS)2]3– complex, which absorption was measured at λmax = 483 nm. The optimized FIA and SIA configuration yielded a linear calibration curve with correlation coefficients (R2 = 0.9999 and R2 = 0.9996) in the concentration range of 3.0 × 10–7 – 3.0 × 10–5 mol L–1 and analytical frequency of 120 h–1 for the FIA method and 4.0 × 10–7 – 4.0 × 10–5 mol L–1, at sampling rate 60 h–1 for the SIA method. The proposed flow methods were successfully applied for the determination of NAC in pharmaceutical products, as the results showed good agreement with the standard method prescribed by Pharmacopoeia. Recoveries were in the range from 98.4 % to 101.9 % for the FIA method and from 97.2 % to 101.8 % for the SIA method

Konkurentno uklanjanje teških metala iz binarne otopine

The removal of copper and cobalt ions from binary metal solutions on zeolite NaX by ion exchange process was investigated. Experiments were conducted in unbaffled glass reactor with a Rushton turbine as a stirrer. The dependence of ion exchange kinetics and the amount exchanged were tested using different initial concentrations of metal ions in mixtures. The results obtained indicate that the removal efficiency depends on the initial heavy metal concentrations in binary solutions. Experimental kinetics data were analysed using Ritchie and Weber-Morris models. According to AARD values, the rate in this study was reaction-controlled. This work is licensed under a Creative Commons Attribution 4.0 International License.Ispitano je uklanjanje iona bakra i kobalta iz binarnih otopina metala ionskom izmjenom na zeolitu NaX. Eksperimenti su provedeni u staklenom kotlastom reaktoru bez razbijala virova. Kao miješalo upotrijebljena je Rushtonova turbina. Ovisnost kinetike izmjene iona i izmijenjene količine iona metala ispitana je pri različitim početnim koncentracijama iona metala u smjesama. Prema dobivenim rezultatima, učinkovitost uklanjanja iona metala iz otopina ovisi o početnim koncentracijama metala u binarnim otopinama. Kinetički podatci dobiveni eksperimentom analizirani su Ritchievim i Weber-Morrisovim modelom. Prema vrijednostima AARD-a, ukupna brzina procesa u ovoj studiji kontrolirana je reakcijom. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna

Kinetic Spectrophotometric Determination of N-Acetyl-L-cysteine Ethyl Ester (NACET) Generating Chromogenic Copper(I)Ln Complexes with Different Ligands

Three simple, sensitive and robust kinetic spectrophotometric methods for the determination of a novel lipophilic thiol compound, N-acetyl-L-cysteine ethyl ester (NACET), have been developed and validated. The methods are based on the reduction of Cu(II)-ligand complex to Cu(I)-ligand complex with the analyte. Studied ligands were neocuproine, bicinchoninic acid (BCA) and bathocuproine disulfonic acid (BCS). The development of chromogenic complexes was followed using kinetic setup with spectrophotometric detection at 458, 562 and 483 nm for the reactions of NACET with neocuproine, BCA and BCS, respectively. The calculated reaction orders with respect to NACET concentration were found to be 1.07, 1.01, 1.07, respectively, thus confirming a first order of reaction. The initial rate and fixed time methods were utilized for constructing calibration curves. Assays limits of detection were 1.4 × 10–7, 3.2 × 10−7 and 6.0 × 10−8 mol L–1, respectively. The analytical performance of the methods, in terms of accuracy and precision, was established. This work is licensed under a Creative Commons Attribution 4.0 International License

Novel Kinetic Spectrophotometric Method for Determination of Tiopronin [N-(2-Mercaptopropionyl)-glycine]

Novel simple kinetic spectrophotometric method for the determination of tiopronin [N-(2-mercaptopropionyl)-glycine, MPG] in pharmaceutical formulation has been developed and validated. The proposed method is based on the coupled redox-complexation reaction whose first step is reduction of FeIII by MPG, while second one includes the complexation of FeII, resulted from preceding redox reaction, with 2,4,6-trypyridyl-s-triazine (TPTZ). The stable Fe(TPTZ)22+ complex exhibits an absorption maximum at = 593 nm. The initial rate and fixed time (at 3 min) methods were utilized for constructing the calibration graphs. The graphs were linear in concentration ranges from 1.0 10−6 to 1.0 10−4 mol L−1 for both methods with limits of detection 1.3 10−7 mol L−1 and 7.5 10−8 mol L−1 for the initial rate and fixed time method, respectively. The proposed methods were successfully applied for the determination of MPG in its commercial pharmaceutical formulation

Potentiometric Determination of N-(2–Mercaptopropionyl)-glycine Using an Electrode with AgI-based Membrane

Potentiometric methods for determination of N-(2 mercaptopropionyl)-glycine (MPG) using a commercial indicator electrode with AgI-based membrane are described. Heterogeneous and homogeneous chemical reactions important for the response of the sensor are discussed. For direct potentiometric measurements, equilibrium potentials recorded under continuous addition of standard MPG solution into 0.1 mol L–1 HClO4 as the background solution were considered relative to pMPG. Linear response with a slope of 59 ± 0.7 mV was obtained in the concentration range from 2.0 ´ 10–5 to 1.5 ´ 10–3 mol L–1. In the »kinetic« potentiometric experiment, the relationship between the potential change and the concentration of MPG was found to be linear for more than a one-decade range of the amount of MPG. The best analytical results were achieved using the potentiometric titration method. This method with 0.1 mol L–1 HClO4 as the background solution is recommended for the determination of MPG in pharmaceutical preparations