Commercial Pharmaceutical Tablets Research Articles

Yeast-Derived Carbon Dot/Cuprous Oxide Composite Electrochemical Sensor for Paracetamol

A novel yeast-derived carbon dot/cuprous oxide nanocomposite (Y-CDs/Cu2O) electrochemical sensor was developed for paracetamol. The Y-CDs were prepared by a one-step hydrothermal treatment and composited with Cu2O nanoparticles via ultrasonication assembly. Transmission electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy were conducted to characterize the morphology and structure of the synthesized nanomaterials systematically. After modification onto a glassy carbon electrode, the resulting sensor displayed excellent electrochemical performances toward paracetamol with a wide linear range (0.5–100 μM), low limit of detection (LOD, 90 nM), good repeatability, and stability (retaining 94% of initial response after 4 weeks). Remarkably, the electrochemical sensor presented good selectivity against potentially coexisting species. Satisfactory results were obtained for the analysis of commercial pharmaceutical tablets and human serum. The attractive sensitivity could be ascribed to the ultra-small size and surface-abundant functional groups of Y-CDs as well as the superior electroconductivity of Cu2O. Thus, the synergistic effect illustrates the Y-CD-Cu2O hybrid structure is promising for constructing high-performance electrochemical sensors.

Synergistic incorporation of Ag into nickel hydroxide nanostructure to enhance the electroctrocatalytic determination of nitrofurantoin

In this work the chemical precipitation method was applied for synthesizing Ag/Ni(OH)2 nanocomposites. Then, this nanocomposite was employed as an electrode modifier to achieve selective and sensitive determination of nitrofurantoin using the differential pulse voltammetry (DPV) technique. By preparing the suspension, a synthesized sample was utilized for modification of the glassy carbon electrode (GCE) surface. The structure and morphological details of Ag/Ni(OH)2 nanocomposites were assessed with Transmission Electron Microscopy (TEM), Energy-dispersive X-ray spectroscopy (EDX), Fourier transforms infrared (FT-IR), Field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and element map techniques. The linear range of concentration was 0.11–13 µM and 13–212 µM and the obtained limit detection (LOD) was 0.079 µM. High sensitivity and long-term stability, suitable linear range, appropriate repeatability, low detection limit, an easy synthesis method, low cost, and short analysis time can be considered as the main advantages of this method. Finally, this sensor was successfully used to determine nitrofurantoin in commercial pharmaceutical tablets and serum blood samples.

An inexpensive paracetamol sensor based on an acid-activated carbon fiber microelectrode

Paracetamol, a contaminant of emerging concern, has been detected in different bodies of water, where it can impact ecological and human health. To quantify this paracetamol, electroanalytical methods have gained support. Thus, the present study developed a simple, inexpensive, and environmentally friendly method for paracetamol quantification using a carbon fiber microelectrode based on commercial carbon fiber. To improve the carbon fiber microelectrode's paracetamol sensitivity and selectivity, it was subjected to an activation process via electrochemical oxidation in an acid medium (H2SO4 or HNO3), using 20 consecutive cycles of cyclic voltammetry. The treated (activated) carbon fiber microelectrode was characterized using scanning electron microscopy and electrochemical techniques, including chronoamperometry and electrochemical impedance spectroscopy. The H2SO4-activated carbon fiber microelectrode exhibited enhanced figures of merit, with a linear dynamic range of paracetamol detection from 0.5 to 11 μmol L−1 and a limit of detection of 0.21 μmol L−1 under optimized conditions. The method was optimized by quantifying paracetamol in commercial pharmaceutical tablets, spiked running tap water, and river water (Pita River, Quito, Ecuador, latitude −0.364955°, longitude −78.404538°); the respective recovery values were 102.89, 103.93, and 112.40%. The results demonstrated an acceptable level of accuracy and the promising applicability of this carbon fiber microelectrode as a sensor to detect paracetamol.

Sensitive spectrofluorimetric determination of the prokinetic drug prucalopride succinate based on supramolecular aggregation approach with evaluation of method greenness: application to content uniformity test.

The prokinetic drug, prucalopride (PCP) succinate, was determined using a new spectrofluorimetric approach with a highly sensitive, rapid, and simple procedure. The method exploited the enhancement of the inherent native fluorescence of PCP by micellar aggregation with sodium lauryl sulfate (SLS) as an anionic surfactant. Different factors that could affect the fluorescence intensity were carefully studied in order to achieve the maximal fluorescence signal. Measurement of the enhanced fluorescence was done at 354 nm after the excitation at 276 nm. The fluorescence intensity-concentration plot was rectilinear in the concentration range of 50-600 ng/ml with detection and quantitation limits of 13.9 and 42.1 ng/ml, respectively. The method underwent validation according to the International Council for Harmonisation criteria in order to assess its analytical performance, and promising results were achieved that proved the validity and reliability of the method. Furthermore, the method was employed effectively for the analysis of the cited drug in commercial pharmaceutical tablets.

Thermal analysis by variable temperature infrared spectroscopy with a button sample holder and Peltier heating/cooling

An apparatus and methodology for variable temperature infrared spectroscopy measurements of neat samples contained in a button sample holder are described. Sample heating and cooling are achieved by applying voltage to stacked Peltier thermoelectric devices. Between 0 and 150°C, samples can be heated and cooled at 2°C s-1 rates, facilitating temperature step heating/cooling profiles with minimal delay between isothermal infrared spectrum measurements. Examples of correlating temperature-dependent spectral variations with specific sample changes are provided for α-quartz heating/cooling, ibuprofen melting, and acetylsalicylic acid thermal decomposition. Trends in α-quartz infrared spectra obtained with a step heating/cooling temperature profile are used to evaluate spectrum measurement reproducibility. Detection of vibration band intensity variations of less than 1% resulting from a 10°C sample temperature increment illustrates the measurement sensitivity. By comparing infrared spectra obtained at different temperatures, reversible and irreversible sample changes are identified. Infrared spectra acquired during linear ramp heating are employed to determine the ibuprofen melting point, which confirms the temperature measurement accuracy of the apparatus. Selective analysis is demonstrated by determining isoconversion effective activation energies for processes involved in the thermal decomposition of the acetylsalicylic acid component of a commercial pharmaceutical tablet.

Sensitive and highly selective colorimetric biosensing of vitamin-C and vitamin-B1 by flavoring agent-based silver nanoparticles.

A sensitive scheme was established for the detection of vitamin C (Ascorbic acid) and vitamin B1 (Thiamin HCl) using Maltol capped AgNPs (McAgNPs) as colorimetric sensor. The designed scheme showed an instant alteration in color from yellow to orange and green for vitamin-C and vitamin B1 sequentially. The probe was sensitive in a concentration range of (0-1µM) with limit of detection 0.064 and 0.038µM for vitamin C and vitamin B1 sequentially. The interaction mechanism between vitamin C and vitamin B1 and McAgNPs was evaluated by visible spectroscopy, FTIR, and AFM. Vitamin C attaches on the surface of nanoparticles by C=O group, while OH, C-S-C, and NH2 groups are involved in the binding of vitamin B1 with McAgNPs. The Vit-C/Vit-B1-McAgNPs complexes were stable over a wide range of pHs. The size of McAgNPs increased after the interaction of vitamin C/vitamin B1 from 30-40nm to 500 and 400nm sequentially. The scheme was successfully applied for the detection of vitamin C and vitamin B1 in urine, plasma, water, and commercial pharmaceutical tablets with good recoveries. The scheme was ascertained to be more sensitive than many other formerly described schemes.

Development of Green Methods for the Determination of Elemental Impurities in Commercial Pharmaceutical Tablets

In this study, two methods based on the use of diluted acids were developed: microwave-assisted wet digestion (MAWD) and microwave-assisted ultraviolet digestion (MAWD-UV). These methods are evaluated for the digestion of oral pharmaceutical drugs and further determination of elemental impurities from classes 1 (As, Cd, Hg and Pb) and 2A (Co, Ni and V) by inductively coupled plasma optical emission spectrometry (ICP-OES). Commercial drugs for the treatment of type 2 diabetes are used. No prior comminution is performed. For MAWD, the optimized conditions were 2 mol L−1 or 3 mol L−1 HNO3, 1 mL of 50% H2O2 and a 45 min or 55 min irradiation program. For MAWD-UV, the condition using 1 mol L−1 HNO3, 1.6 mL of 50% H2O2 and a 55 min irradiation program enabled the digestion of all samples. In this way, efficient methods are proposed for the digestion of commercial pharmaceutical tablets for further determination of class 1 and 2A elemental impurities (ICH Q3D guidelines).

Separation and determination of simvastatin on ZIC-HILIC stationary phases by hydrophilic interaction chromatography in pharmaceutical material products

The hydrophilic interaction chromatography (HILIC) technique outperforms other methods in terms of precision and sensitivity. The development and optimization of a HILIC method for validating a separation method for simvastatin estimation in pharmaceutical formulations necessitated determining the optimal mobile phase, buffer concentration, and pH value. The proposed HILIC methods using two columns demonstrated high precision (RSD less than 1%) and a robust linear relationship between the calibration graph and simvastatin concentration ranges of 0.05–4 µg mL−1 with a coefficient of determination (R2) of 0.9996 and 0.9994 for simvastatin. The HILIC methods provided excellent validated LOD (0.023 and 0.015 µg mL−1) and LOQ (0.069–0.045 µg mL−1) values for simvastatin. The HILIC approach was successfully used to estimate simvastatin in commercial pharmaceutical tablets, resulting in an excellent simvastatin recovery > 99%. Using statistical tests, the findings of the HILIC method were compared to the British pharmacopoeia protocol for simvastatin drug. There was no difference in accuracy between the methods.

Determination of folic acid by capillary zone electrophoresis with indirect chemiluminescence detection.

A capillary electrophoresis method with on-line inhibited chemiluminescence (CL) detection was first used to determine folic acid (FA). This method was established based on the quenching effect of FA on the CL reaction of luminol with a Ag(iii) complex in alkaline medium. The separation was conducted with a 20.0 mM sodium borate buffer containing 1.0 mmol L−1 luminol. Under optimized conditions, FA was baseline separated and detected in less than 10 min. The limit of detection of FA was 1.3 mg L−1, with a linear range of 5.0–150.0 mg L−1 (r = 0.9953). The RSD value was 2.8% for intra-day precision and 5.4% inter-day precision. The recoveries of the standard addition of tablets and human urine ranged from 90.3% to 107.5% and from 82.0 to 105.7%, respectively. The proposed method was successfully applied to determine FA contents in commercial pharmaceutical tablets and human urine samples. Results suggested that this method was simple and robust.

SIMULTANEOUS ESTIMATION OF CLONAZEPAM AND METRONIDAZOLE IN PHARMACEUTICAL TABLETS BY REVERSED-PHASE HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY MODE WITH UV DETECTION

Clonazepam (CLO) plays a significant role in treating seizures, myoclonic seizures, and other clinical infections, while metronidazole (MTZ) is an antiprotozoal, antibacterial drug. The reversed-phase high performance liquid chromatographic (RP-HPLC) technique has provided greater precision and sensitivity over other methods, especially the colorimetric and spectrophotometric. This study aimed to implement a simple method in pure and pharmaceutical tablets for the simultaneous determination of CLO and MTZ. The RPHPLC method's development and optimization for validating a separation method for the simultaneous estimation of both drugs in pharmaceutical formulation involved studying the optimum mobile phase, buffer concentration, and the pH value. Under the chromatographic conditions, RP-HPLC system achieved excellent separation on a Phenomenex HyperClone BDS (250 x 4.60 mm, 130A, and 5μ) at a temperature of 45°C and the following conditions: 65:35% acetonitrile:acetic acid and sodium acetate buffer solution (NaOAc/HAc) as mobile phase (pH 3.5); 20 μL injection volume at a flow rate of 0.75 mL/min and detection wavelength of 310 nm. The proposed RP-HPLC procedure demonstrated high precision (RSD% 1%), as well as the good linear relationship of the calibration graph at concentration ranges of 50-160, 35-100 ppb with a coefficient of determination (r2) of the regression line of 0.9996 and 0.9997 for metronidazole and clonazepam respectively. The proposed method offered excellent validated values for both LOD (4.24 and 3.06 ppb) and LOQ (14.15– 10.21 ppb) for both metronidazole and clonazepam drugs, respectively. The RP-HPLC method has been successfully applied to estimate metronidazole and clonazepam in the well-known commercial pharmaceutical tablets and gave an excellent recovery> 98% for both drugs. The results of the method was compared with the standard pharmacopeial method for both drugs using statistical tests, which indicated no difference in accuracy between the methods

Calibration transfer between modelled and commercial pharmaceutical tablet for API quantification using backscattering NIR, Raman and transmission Raman spectroscopy (TRS)

Backscattering NIR, Raman (BSR) and transmission Raman spectroscopy (TRS) coupled with chemometrics have shown to be rapid and non-invasive tools for the quantification of active pharmaceutical ingredient (API) content in tablets. However, the developed models are generally specifically related to the measurement conditions and sample characteristics. In this study, a number of calibration transfer methods, including DS, PDS, DWPDS, GLSW and SST, were evaluated for the spectra correction between modelled tablets produced in the laboratory and commercial samples. Results showed that the NIR and BSR spectra of commercial tablet corrected by DWPDS and PDS, respectively, enabled accurate API predictions with the high ratio of prediction error to deviation (RPDP) values of 2.33 and 3.03. The most successfully approach was achieved with DS corrected TRS data and SiPLS modelling (161 variables) and yielded RMSEP of 0.72 %, R2P of 0.946 and RPDP of 4.35. The proposed calibration transfer strategy offers the opportunities to analyse samples produced in different conditions; in the future, its implication will find extensively process control and quality assurance applications and benefit all possible users in the entire pharmaceutical industry.

Cloud point extraction method for the sensitive determination of metoclopramide hydrochloride in pharmaceutical dosage forms

In this work, a simple and very sensitive cloud point extraction (CPE) process was developed for the determination of trace amount of metoclopramide hydrochloride (MTH) in pharmaceutical dosage forms. The method is based on the extraction of the azo-dye results from the coupling reaction of diazotized MTH with p-coumaric acid (p-CA) using nonionic surfactant (Triton X114). The extracted azo-dye in the surfactant rich phase was dissolved in ethanol and detected spectrophotometrically at λmax 480 nm. The reaction was studied using both batch and CPE methods (with and without extraction) and a simple comparison between the two methods was performed. The conditions that may be affected by the extraction process and the sensitivity of methods were carefully studied. Using optimal conditions, the linearity of calibration curves was in the range of 0.4-13 and 0.05-4µg/mL and limits of detection of 0.044 and 0.028 µg/mL of MTH for batch and CPE methods respectively. Average recoveries for samples were detected to be between 97-101 %for both methods, with the relative standard deviation (RSD %) best than 2.7 % and 4.5 % for both methods, respectively. The suggested methods were applied successfully for assay of MTH in commercial pharmaceutical tablets.

Development and validation of spectrophotometric methods for the sensitive and selective determination of lamotrigine in pharmaceuticals using bromocresol purple

Three simple, selective and sensitive methods have been developed and validated for the determination of lamotrigine (LMT) in pure drug and in tablets. The first method (method A) is based on the formation of ion-pair complex between LMT and the dye, bromocresol purple (BCP) at pH 2.40±0.01 which was extracted into dichloromethane (DCM) and the absorbance of yellow ion-pair complex was measured at 410 nm. In the second and third methods (method B and method C), the drug-dye ion-pair was dissolved either in ethanol and the resulting acid form of the dye was measured at 410 nm or in ethanolic potassium hydroxide and the resulting base form of the dye was measured at 600 nm. Under the optimized conditions, Beer's law was obeyed over 2.0-20.0 μg/mL, 150-1500 ng/mL and 50-600 ng/mL for method A, method B and method C, respectively, and the corresponding molar absorptivity values were 1.018×104, 1.43×105 and 4.21×105 L/mol/cm. The Sandell sensitivity values of 0.0252, 0.0018 and 0.0006 μg/cm2 for method A, method B and method C, respectively, and the corresponding values for limits of detection and quantification were also reported for all three methods. The molar ratio of the formed ion-pair complex was found to be 1: 1 as deduced by Job's method for method A, and the calculated stability constant was also reported. Over the linear ranges applicable, the accuracy and precision of the methods were evaluated on intra-day and inter-day basis; the reported mean accuracy values are 99.50±1.09%, 99.99±1.11% and 100.72±0.62% for method A, method B, and method C, respectively; the relative error (RE) was ≤ 2.57% and the relative standard deviation (RSD) was ≤ 2.01%. Application of the proposed methods to bulk powder and commercial pharmaceutical tablets are also presented.

Portable and benchtop Raman spectrometers coupled to cluster analysis to identify quinine sulfate polymorphs in solid dosage forms and antimalarial drug quantification in solution by AuNPs-SERS with MCR-ALS.

This paper proposes for the first time: (a) a qualitative analytical method based on portable and benchtop backscattering Raman spectrometers coupled to hierarchical cluster analysis (HCA) and multivariate curve resolution - alternating least-squares (MCR-ALS) to identify two polymorphs of antimalarial quinine sulfate in commercial pharmaceutical tablets in their intact forms and (b) a quantitative analytical method based on gold nanoparticles (AuNPs) as active substrates for surface-enhanced Raman scattering (SERS) in combination with MCR-ALS to quantify quinine sulfate in commercial pharmaceutical tablets in solution. The pure concentration and spectral profiles recovered by MCR-ALS proved that both formulations present different polymorphs. These results were also confirmed by two clusters observed in the HCA model, according to their similarities within and among the samples that provided useful information about the homogeneity of different pharmaceutical manufacturing processes. AuNPs-SERS coupled to MCR-ALS was able to quantify quinine sulfate in the calibration range from 150.00 to 200.00 ng mL-1 even with the strong overlapping spectral profile of the background SERS signal, proving that it is a powerful ultrahigh sensitivity analytical method. This reduced linearity was validated throughout a large calibration range from 25.00 to 175.00 μg mL-1 used in a reference analytical method based on high performance liquid chromatography with a diode array detector (HPLC-DAD) coupled to MCR-ALS for analytical validation purposes, even in the presence of a coeluted compound. The analytical methods developed herein are fast, because second-order chromatographic data and first-order SERS spectroscopic data were obtained in less than 6 and 2 min, respectively. Concentrations of quinine sulfate were estimated with low root mean square error of prediction (RMSEP) values and a low relative error of prediction (REP%) in the range 1.8-4.5%.

Optical properties of folic acid in phosphate buffer solutions: the influence of pH and UV irradiation on the UV-VIS absorption spectra and photoluminescence

Using UV-VIS absorption spectroscopy, photoluminescence (PL) and photoluminescence excitation (PLE), the photodegradation reactions of folic acid (FA) in phosphate buffer (PB) solutions were studied. Regardless of the PB solution’s pH, the UV-VIS spectra showed a gradual decrease in absorbance at 284 nm simultaneous with an increase in the absorbance of another band in the spectral range of 320–380 nm, which was downshifted under UV irradiation. The relative intensity of the FA PL band, situated in the spectral range 375–600 nm, was dependent on the pH of the PB solution. The FA PL intensity increased as increasing UV irradiation time up to 281 min. in PB solutions with pH values of 6.4 and 5.4. Under an emission wavelength of 500 nm, the position of the FA PLE spectrum changed as the PB solution pH varied from 7 to 5.4 and the irradiation time increased to 317 min. These changes were correlated with the formation of two photodegradation products, namely, pterine-6-carboxylic acid and p-amino-benzoyl-L-glutamic acid. According to UV-VIS spectroscopy and PL and PLE studies, the presence of various excipients in commercial pharmaceutical tablets does not affect the photodegradation of FA in PB solutions. Using IR spectroscopy, new evidences for the formation of the two photodegradation products of FA in PB solutions are shown.

Sensitive spectrofluorometric method for the determination of ascorbic acid in pharmaceutical nutritional supplements using acriflavine as a fluorescence reagent.

An easily performed, specific, sensitive, rapid, reliable and inexpensive procedure for the spectrofluorometric quantitation of ascorbic acid was proposed using acriflavine as a fluorescence quenching reagent. The procedure was based on the determined quenching effect of ascorbic acid on the natural fluorescence signal of acriflavine and the reaction between ascorbic acid and acriflavine in Britton-Robinson buffer solution (pH6) to produce an ion-associated complex. The reduction in acriflavine fluorescence intensity was detected at 505nm, while excitation occurred at 265nm. The relationship between quenching fluorescence intensity (∆F) and concentration of ascorbic acid was linear (R2 =0.9967) within the range 2-10μg/ml and with a detection limit of 0.08μg/ml. No significant interference was detected from other materials often found in pharmaceutical nutritional tablets. The obtained results were compared with those from high-performance liquid chromatography and appeared in good agreement, with no important differences in precision or accuracy. The proposed spectrofluorimetric method was used to determine the amount of ascorbic acid in a number of commercial pharmaceutical nutritional supplement tablets with a 95% confidence performance.

Cu(HBTC)(4,4′-bipy)·3DMF nanorods supported on platinum electrode as an electrochemical sensing platform for efficient vitamin B12 detection

Abstract Monitoring of vitamin B12 is important in the quality control of various pharmaceutical products. In this work, we design an ultrasensitive electrochemical sensor for the detection of vitamin B12 employing Pt modified Cu(HBTC)(4,4′-bipy)·3DMF (Pt = Platinum; DMF = N,N′-dimethylformamide; 4,4′-bipy = 4,4′-bipyridine; HBTC = 1,3,5-benzenetricarboxylic acid) electrode as an efficient electrocatalyst. The copper (Cu) complex nanorods were synthesised by solvothermal method and characterised by different surface analytical techniques. Cyclic voltammetric analysis reveals that the modified electrode shows excellent electrocatalytic redox reversibility towards Co3+/Co2+ redox couple at −0.192 and -0.268 V (vs. Ag/AgCl) with a sensitivity of 0.104 µA µM−1, a low detection limit of 50 nM, a signal-to-noise ratio of 3 and a wide linear range of 0.1–188.2 µM. The novelty of the system is that both oxidation and reduction currents Co3+/Co2+ redox couple has been used for the calibration curve so that the analytical errors during the course of analysis would be minimised. The enhanced electrocatalytic ability of the material has enabled discrimination of vitamin B12 from potential interfering species. The fabricated electrode was applied for the detection of vitamin B12 in two commercial pharmaceutical tablets and the results were found to be satisfactory.

Praseodymium molybdate nanoplates/reduced graphene oxide nanocomposite based electrode for simultaneous electrochemical determination of entacapone, levodopa and carbidopa

Entacapone is a prescription commonly used in combination with other medications for the treatment of Parkinson’s disease. Entacapone together with levodopa and carbidopa causes levodopa to have a longer effect in the brain. The objective of this work is using a new nanocomposite electrode based on praseodymium molybdate nanoplates/reduced graphene oxide for simultaneous determination of entacapone (EN), levodopa (LD) and carbidopa (CD). This nanocomposite was synthesized for the first time with two theoretical mass ratio through a facile sonochemical method and be characterized through FE-SEM, X-ray diffraction and FT-IR techniques. Mass ratio of 2:1 (PrMoOG2) was selected as the optimum ratio and used to conduct all determinations. Differential pulse voltammetry technique was used to carry out electrochemical determinations in 0.1 M PBS solution (pH 3.0) as supporting electrolyte. The detection limit of suggested modified electrode was 3.18 × 10−10 M for EN, 3.39 × 10−8 M for LD and 1.66 × 10−8 M for CD. The linear dynamic range of determinations were as follows: 0.009–200 μM for EN, 0.06–900 μM for LD and 0.03–800 μM for CD. To evaluate the validity of the recommended method, a commercial pharmaceutical tablets (Entadoram® 100 mg) was analyzed. Reproducibility, long life-time and multiple reusability of the electrode besides its detection limits and wide dynamic linear ranges, are the main advantages of the proposed sensor in this study.

Synthesis of organic motif tailored hybrid nanoframes: Exploiting in vitro bioactivity and heavy metal ion extraction applications

Hybrid nanoparticles (NPs) were designed by adsorbing a (13E,19E)-N1′,N3′-bis[4-(diethylamino)-2-hydroxybenzylidene]malonohydrazide (L) motif, on Fe3O4@SiO2 distorted hexagonal and cubic NPs. Electronic images of the synthesized hybrid NPs revealed distorted topographies with size of ∼50–70 nm. We exploited key in vitro features, topographies, thermal behaviours, spectroscopic data, magnetic properties and heavy metal ion extraction efficiencies of the prepared hybrids. Additionally, the discrete discussion on the surface areas of the synthesized NPs tackled with BET, are introduced. Characterization with FT-IR, SEM, TEM, XRD, BET, VSM, TGA, particle size analysis and Raman spectroscopic techniques revealed that the organic scaffold L is attached to the prepared Fe3O4@SiO2 NPs surface via adsorption or covalent interactions or some sort of charge/proton transfer. Antibacterial tests depicted that, L and Fe3O4@SiO2 NPs exhibited moderate to good antifungal activity against C. albicans, while synthesized key hybrids has shown good to high antibacterial activity against Gram-positive bacterium, S. aureus, two Gram-negative bacteria's, E. coli and P. aeruginosa, and antifungal activity against C. albicans. Also, the Zn2+ ion extraction efficiency of the key hybrids was tackled and validated with commercial pharmaceutical tablet analysis.

A novel potentiometric biosensor for determination of L-lysine in commercial pharmaceutical L-lysine tablet and capsule

The construction of an L-lysine biosensor on ammonium-selective poly(vinylchloride) (PVC) membrane electrode is described in this study. The construction procedure occurs in two stages: (I) the preparation of ammonium-selective poly(vinylchloride) (PVC) membrane electrode and (II) the chemical immobilization of lysine oxidase on this ammonium-selective electrode by using glutaraldehyde. The ammonium ions produced after enzymatic reaction were determined potentiometrically. The sensitivity of the lysine biosensor against ammonium ions and lysine were studied. The response time, linear working range, reproducibility and life time of the biosensor were also determined. The interfering effect of other amino acids on the biosensor performance was also studied and potentiometric selectivity coefficients were calculated. Although the biosensor responded mainly against tyrosine, a lot of amino acids and ascorbic acid that can be present in some real samples did not show any important interference. Additionally, lysine assay in commercial pharmaceutical lysine tablets and capsules was also successfully carried out. The results were in good agreement with previously reported values.