Preparation of a diclofenac potentiometric sensor and its application to pharmaceutical analysis and to drug recovery from biological fluids

Design of an electrochemical platform for the determination of diclofenac sodium utilizing a graphenized pencil graphite electrode modified with a Cu–Al layered double hydroxide/chicken feet yellow membrane

A novel electrochemical sensor based on a Cu–Al layered double hydroxide (Cu–Al LDH)/chicken feet yellow membrane (CFYM) modified graphenized pencil graphite electrode (GPGE) was designed.

Optical Biosensors for Therapeutic Drug Monitoring

Therapeutic drug monitoring (TDM) is a fundamental tool when administering drugs that have a limited dosage or high toxicity, which could endanger the lives of patients. To carry out this monitoring, one can use different biological fluids, including blood, plasma, serum, and urine, among others. The help of specialized methodologies for TDM will allow for the pharmacodynamic and pharmacokinetic analysis of drugs and help adjust the dose before or during their administration. Techniques that are more versatile and label free for the rapid quantification of drugs employ biosensors, devices that consist of one element for biological recognition coupled to a signal transducer. Among biosensors are those of the optical biosensor type, which have been used for the quantification of different molecules of clinical interest, such as antibiotics, anticonvulsants, anti-cancer drugs, and heart failure. This review presents an overview of TDM at the global level considering various aspects and clinical applications. In addition, we review the contributions of optical biosensors to TDM.

A Box-Behnken Optimized Methodology for the Quantification of Diclofenac using a Carbon Paste-Multiwalled Carbon Nanotubes Electrode

Background:

Diclofenac is a widely used nonsteroidal anti-inflammatory drug. Recent studies have shown that frequent consumption of this drug in high concentrations can cause heart diseases, so strict control of diclofenac’s quantity in commercial drugs is necessary. This paper presents the development of an optimized voltammetric methodology for the quantification of diclofenac, which offers some advantages over other electrochemical and accepted methods.

Objective:

Optimize with a Box-Behnken design the differential pulse voltammetry parameters towards the quantification of diclofenac in pharmaceutical samples.

Methods:

Diclofenac behavior in the working electrode was evaluated by cyclic voltammetry, in order to stablish the best conditions for diclofenac’s quantification. A Box-Behnken design was then used to optimize the differential pulse voltammetry parameters and stablish the analytical behavior of the proposed methodology. Commercial tablets were prepared for analysis according to the Pharmacopeia, the DPV optimized methodology was used to quantify diclofenac in the samples, and the results were statistically compared with those obtained with the official methodology.

Results:

After optimization, the analytical parameters found were: correlation coefficient of 0.998, detection limit of 0.001 µM, quantification limit of 0.0033 µM and sensitivity of 0.299 µA.µM-1. The statistical analysis showed there were no significant differences between the results obtained with the proposed methodology and those obtained with the official methodology.

Conclusion:

The statistical analysis showed that the proposed methodology is as reliable as the official spectrophotometric one for the quantification of diclofenac in commercial drugs, with very competitive analytical parameters, and even better to others found with more complex electrodes.

Differential pulse voltammetric determination of diclofenac in pharmaceutical preparations and human serum

<p>This article describes a differential pulse voltammetric (DPV) method for the determination of diclofenac in pharmaceutical preparations and human serum. The proposed method was based on electro-oxidation of diclofenac at platinum electrode in 0.1 M TBAClO₄/acetonitrile solution. The well-defined two oxidation peaks were observed at 0.87 and 1.27 V, respectively. Calibration curves that obtained by using current values measured for second peak were linear over the concentration range of 1.5-17.5 μg mL^-1and 2-20 μg mL^-1 in supporting electrolyte and serum, respectively. Precision and accuracy were also checked in all media. Intra- and inter-day precision values for diclofenac were less than 3.87, and accuracy (relative error) was better than 4.12%. The method developed in this study is accurate, precise and can be easily applied to Diclomec, Dicloflam and Voltaren tablets as pharmaceutical preparation. In addition, the proposed technique was successfully applied to spiked human serum samples. No electro-active interferences from the endogenous substances were found in human serum.</p>

Comparative study of normal, micro- & nano-sized iron oxide effect in potentiometric determination of fluconazole in biological fluids

Three novel fluconazole (FLU) selective electrodes were investigated with di-octyl phthalate as a plasticizer in a polymeric matrix of polyvinyl chloride and 2-hydroxypropyl-β-cyclodextrin as an ionophore.

Determination of diclofenac in pharmaceutical preparations by voltammetry and gas chromatography methods

Rapid, sensitive and specific methods were developed for the determination of diclofenac in pharmaceutical preparations by linear sweep voltammetry (LSV) and gas chromatography (GC) with mass spectrometry (MS) detection. The linearity was established over the concentration range of 5–35 μg/mL for LSV and 0.25–5 μg/mL for GC–MS method. The intra- and inter-day relative standard deviation (RSD) was less than 4.39% and 4.62% for LSV and GC–MS, respectively. Limits of quantification (LOQ) were determined as 4.8 and 0.15 μg/mL for LSV and GC–MS, respectively. No interference was found from tablet excipients at the selected assay conditions. The methods were applied for the quality control of commercial diclofenac dosage forms to quantify the drug and to check the formulation content uniformity.

Simultaneous determination of EDTA, sorbic acid, and diclofenac sodium in pharmaceutical preparations using high-performance liquid chromatography

A simple high-performance liquid chromatographic method for simultaneous determination of ethylenediaminetetraacetic acid (EDTA), sorbic acid, and diclofenac sodium was developed and validated. Separation was achieved on a C(18) column (10 cm×4.6 mm) using gradient elution. The mobile phase consisted of acetonitrile-ammonium dihydrogen phosphate buffer solution (0.01 M, pH=2.5, containing 0.8% tetra-n-butyl ammonium hydroxide). The detector wavelength was set at 254 nm. Under these conditions, separation of three compounds was achieved in less than 10 min. The effect of two metal salts and metal concentration on peak area of EDTA was investigated. The pH effect on retention of EDTA and sorbic acid was studied. The method showed linearity for EDTA, sorbic acid, and diclofenac in the ranges of 2.5-100.0, 5.0-200.0, and 20.0-120.0 μg/mL, respectively. The within- and between-day relative standard deviations ranged from 0.52 to 1.94%, 0.50 to 1.34%, and 0.78 to 1.67% for EDTA, sorbic acid, and diclofenac, respectively. The recovery of EDTA, sorbic acid, and diclofenac from pharmaceutical preparation ranged from 96.0-102.0%, 99.7-101.5%, to 97.0-102.5%, respectively. To the best of our knowledge, this is the first report about simultaneous determination of EDTA, sorbic acid, and diclofenac.

Manganese(III) porphyrin-based potentiometric sensors for diclofenac assay in pharmaceutical preparations

Two manganese(III) porphyrins: manganese(III) tetraphenylporphyrin chloride and manganese(III)-tetrakis(3-hydroxyphenyl)porphyrin chloride were tested as ionophores for the construction of new diclofenac-selective electrodes. The electroactive material was incorporated either in PVC or a sol-gel matrix. The effect of different plasticizers and additives (anionic and cationic) on the potentiometric response was studied. The best results were obtained for the PVC membrane plasticized with dioctylphtalate and having sodium tetraphenylborate as a lipophilic anionic additive incorporated. The sensor response was linear in the concentration range 3 × 10(-6) - 1 × 10(-2) M with a slope of -59.7 mV/dec diclofenac, a detection limit of 1.5 × 10(-6) M and very good selectivity coefficients. It was used for the determination of diclofenac in pharmaceutical preparations, by direct potentiometry. The results were compared with those obtained by the HPLC reference method and a good agreement was found between the two methods.

Electrochemical biosensors in pharmaceutical analysis

Given the increasing demand for practical and low-cost analytical techniques, biosensors have attracted attention for use in the quality analysis of drugs, medicines, and other analytes of interest in the pharmaceutical area. Biosensors allow quantification not only of the active component in pharmaceutical formulations, but also the analysis of degradation products and metabolites in biological fluids. Thus, this article presents a brief review of biosensor use in pharmaceutical analysis, focusing on enzymatic electrochemical sensors.

Determination of diclofenac on a dysprosium nanowire- modified carbon paste electrode accomplished in a flow injection system by advanced filtering

A new detection technique called Fast Fourier Transform Square-Wave Voltammetry (FFT SWV) is based on measurements of electrode admittance as a function of potential. The response of the detector (microelectrode), which is generated by a redox processes, is fast, which makes the method suitable for most applications involving flowing electrolytes. The carbon paste electrode was modified by nanostructures to improve sensitivity. Synthesized dysprosium nanowires provide a more effective nanotube-like surface [1-4] so they are good candidates for use as a modifier for electrochemical reactions. The redox properties of diclofenac were used for its determination in human serum and urine samples. The support electrolyte that provided a more defined and intense peak current for diclofenac determination was a 0.05 mol L(-1) acetate buffer pH = 4.0. The drug presented an irreversible oxidation peak at 850 mV vs. Ag/AgCl on a modified nanowire carbon paste electrode which produced high current and reduced the oxidation potential by about 100 mV. Furthermore, the signal-to-noise ratio was significantly increased by application of a discrete Fast Fourier Transform (FFT) method, background subtraction and two-dimensional integration of the electrode response over a selected potential range and time window. To obtain the much sensivity the effective parameters such as frequency, amplitude and pH was optimized. As a result, C(DL) of 2.0 × 10(-9) M and an LOQ of 5.0 × 10(-9) M were found for the determination for diclofenac. A good recovery was obtained for assay spiked urine samples and a good quantification of diclofenac was achieved in a commercial formulation.

Quantitative determination of diclofenac sodium in solid dosage forms by FT-Raman spectroscopy

The FT-Raman quantification of diclofenac sodium in tablets and capsules was performed with the help of the partial least squares (PLS), principal component regression (PCR) and counter-propagation artificial neural networks (CP-ANN) methods. For the analysed tablets, calibration models were built using unnormalised spectra and spectra normalised by the intensity of a selected band of an internal standard. Different pre-processing methods were applied for the capsules. To compare the predictive ability of the models, the relative standard errors of prediction (RSEP) were calculated. The 5 x 5 CP-ANN and PLS methods gave models of comparable quality, which were usually more efficient than the PCR ones. The RSEP error values for the tablets were in the range of 2.4-3.8% for the calibration and 2.6-3.5% for the validation data sets and for the three procedures applied. For capsules, the RSEP errors were in the range of 0.8-1.9% and 1.4-1.7% for the calibration and validation samples, respectively. Five commercial products containing 25, 50 or 75 mg of diclofenac sodium per tablet/capsule were quantified. Concentrations found from the Raman data analysis agree with the results of the reference analysis and correlate strongly with the declared values with the recovery of 99.5-101.3%, 99.7-102.0% and 99.9-101.2% for the PLS, PCR and CP-ANN methods, respectively. The proposed procedure can be a fast and convenient alternative to the standard pharmacopoeial methods of diclofenac sodium quantification in solid dosage forms.

PVC Membrane Sensors for Potentiometric Determination of Acebutolol

The construction and general performance characteristics of two novelpotentiometric membrane sensors responsive to the acebutolol are described. Thesensors are based on the use of ion-association complexes of acebutolol (AC) withtetraphenylborate(TPB) (I) and phosphomolybdate(PM) (II) as exchange sites in a PVCmatrix. The sensors show a fast, stable and near- Nernstian for the mono charge cationof AC over the concentration range 1×10-3 - ~10-6 M at 25 °C over the pH range 2.0 -6.0 with cationic slope of 51.5 ± 0.5 and 53.0 ± 0.5 per concentration decade for AC-Iand AC-II sensors respectively. The lower detection limit is 6×10-6 M and 4×0-6 M withthe response time 20-30 s in the same order of both sensors. Selectivity coefficients ofAC related to a number of interfering cation and some organic compounds wereinvestigated. There are negligible interferences are caused by most of the investigatedspecies. The direct determination of 3 - 370 μg/ml of AC shows an average recovery of 99.4 and 99.5% and a mean relative standard deviation of 1 . 5 % at 100.0 μg/ml forsensor I and II respectively. The results obtained by determination of AC in tablets usingthe proposed sensors which comparable favorably with those obtained by the Britishpharmacopoeia method. In the present investigation the electrodes have been utilized asend point indicator for some precipitation titration reactions.

Determination of diclofenac in pharmaceuticals and urine samples using a membrane sensor based on the ion associate of diclofenac with Rhodamine B

The potentiometric response characteristics of a diclofenac selective electrode, based on ion association in different plasticizers, were compared. The sensitivity, working range, detection limit and selectivity of membrane sensors demonstrated significant dependence on the type of plasticizers. The potentiometric unit presented a linear response toward diclofenac concentrations between 1 × 10−5 − 5 × 10−2 mol L−1, with slopes of approximately 60 mV dec−1, and exhibited a response time of 3 s. The potentiometric analysis of sodium diclofenac in pharmaceutical formulations was perfomed by the membrane electrode proposed and compared with the results of potentiometric titration given by the Pharmacopoeia of Ukraine.

Development of in situ ion selective sensors for dissolution

The dissolution of formulations of the drugs dapoxetine, paliperidone, cinnarizine, tetrazepam, mebeverine, loperamide, galantamine and ibuprofen was studied by an in-line potentiometric measurement system. The transpose of a Nikolskii-Eisenman type function performed the conversion of potential to percentage of dissolution. A novel gradient membrane electrode was developed especially for dissolution, varying continuously in composition from an ionically conducting rubber phase to an electronically conducting solid state PVC/graphite composite. The gradient part had a thickness of 200 microm. The electrodes life span exceeded 6 months. An ion exchange procedure was used to prepare them for one specific drug. This enabled us to use one universal electrode built to measure a wide array of drugs. The system parameters such as accuracy, reproducibility and linearity were presented with the data obtained for the drug dapoxetine. In dissolution, accurate measurements were possible from 10(-9) to 10(-3) M concentrations, for high log P drugs. The effect of t(90) response times on the measurement error was estimated. The t(90) response times of the electrodes were concentration dependent, and varied between 50 and 10 s for, respectively, 10(-6) and 10(-3) M concentrations. Potential drift was studied in detail. The measurements performed with these electrodes showed an accuracy of 1%, and inter- and intra electrode variabilities of 0.6 and 1.7%, respectively. The electrodes were successfully applied in colloidal media containing suspended matter, typically formed during dissolution of tablets. The advantages and pitfalls of potentiometry over the presently used techniques for dissolution testing are discussed.

Voltammetric determination of mefenamic acid at lanthanum hydroxide nanowires modified carbon paste electrodes

Lanthanum hydroxide nanowires modified carbon paste electrode (LNW/CPE) exhibiting an electrocatalytic response toward the oxidation of mefenamic acid (MFA) is described. The catalytic action of the LNW/CPE on the oxidation of MFA via one-electron and one-proton transfer is attributed to the formation of the porous construction and the increase of efficient surface of the electrode due to the adulteration of LNW with carbon powders. Using the LNW/CPE, a linear sweep voltammetric method for the determination of MFA and other drugs with diphenylamine parent is proposed. A linear range of 2.0 x 10(-11) to 4.0 x 10(-9)mol L(-1) is obtained along with a detection limit of 6.0 x 10(-12)mol L(-1).

Preparation of a Novel Iodide-Selective Electrode Based on Iodide-Miconazole Ion-Pair and Its Application to Pharmaceutical Analysis

An iodide-miconazole ion-paired complex was used as a suitable ion-exchanger for the preparation of a plasticized-PVC membrane electrode. Among different solvent mediators tested, dioctylsebacate exhibited the proper response characteristics, including Nernstian slope of the calibration curve, fast response time and good reproducibility of the emf values. The electrode exhibits a Nernstian slope of -59.8 +/- 0.5 mV decade(-1) for I- ion over a concentration range of 1.0 x 10(-5) - 1.0 x 10(-2) M with a limit of detection of 7.0 x 10(-6) M. The electrode displays a good selectivity for I- with respect to a number of inorganic and organic species. It canbe used over a pH range of 2.5 - 8.5. The membrane sensor was successfully applied to the determination of iodide in water samples and blood serum, as well as in pharmaceutical products such as iodoquinol and thyroxin.