A molecularly imprinted polymerized high internal phase emulsion adsorbent for sensitive chemiluminescence determination of clopidogrel.

A molecularly imprinted polymerized high internal phase emulsion (MIP-polyHIPE) adsorbent was used for selective separating and preconcentrating the anti-plaque drug, clopidogrel. For the first time in this study, chemiluminescence (CL) methods were evaluated for the determination of clopidogrel. The synthesis of adsorbents by the emulsion templating method showed that the sensitivity of the method can be increased up to 42 times. The determination of clopidogrel was evaluated by Ru(phen)32+-Cerium (IV), KMnO4-H2SO4, KMnO4-H2SO4-Na2SO3, and luminol-H2O2 CL systems. According to the results, only the Ru(phen)32+-Cerium (IV) CL system showed a reasonable sensitivity for clopidogrel. Using MIP-polyHIPE adsorbent, the linear range, the limit of detection, and relative standard deviation for clopidogrel in this system were respectively 1.0 × 10-9-8.0 × 10-8 mol L-1, 3.0 × 10-10 mol L-1, and 6.3% (n = 4, 1.0 × 10-8). The proposed method was employed for determining clopidogrel in pharmaceuticals and blood serum samples. The results showed the good sensitivity and accuracy of the proposed method.

Electro-catalytic amplified sensor for determination of N-acetylcysteine in the presence of theophylline confirmed by experimental coupled theoretical investigation.

The 1,l/-bis(2-phenylethan-1-ol)ferrocene, 1-butyl-3-methylimidazolium hexafluoro phosphate (BMPF6) and NiO-SWCNTs were used to modify carbon paste electrode (BPOFc/BMPF6/NiO-SWCNTs/CPE), which could act as an electro-catalytic tool for the analysis of N-acetylcysteine in this work. The BPOFc/BMPF6/NiO-SWCNTs/CPE with high electrical conductivity showed two completely separate signals with oxidation potentials of 432 and 970 mV for the first time that is sufficient for the determination of N-acetylcysteine in the presence of theophylline. The BPOFc/BMPF6/NiO-SWCNTs/CPE showed linear dynamic ranges of 0.02-300.0 µM and 1.0-350.0 µM with the detection limit of ~ 8.0 nM and 0.6 µM for the measurement of N-acetylcysteine and theophylline, respectively. In the second part, understanding the nature of interaction, quantum conductance modulation, electronic properties, charge density, and adsorption behavior of N-acetylcysteine on NiO-SWCNTs surface from first-principle studies through the use of theoretical investigation is vital for designing high-performance sensor materials. The N-acetylcysteine molecule was chemisorbed on the NiO-SWCNTs surface by suitable adsorption energies (- 1.102 to - 5.042 eV) and reasonable charge transfer between N-acetylcysteine and NiO-SWCNTs.

Voltammetric Determination of Glutathionein Pharmaceutical and Biological Samples Using Multiwall Carbon Nanotubes Paste Electrode in the Presence of Rutin as a Mediator.

A new sensitive and selective electrochemical sensor was developed for electrocatalytic determination of glutathione (GSH) in pharmaceutical and biological samples. GSH is a tripeptidethiol present in all eukaryotic and probiotic cells. A voltammetric study of GSH has been carried out at the surface of carbon paste electrode modified with multiwall carbon nanotubes in the presence of rutin as a mediator. The electrochemical oxidation of GSH was investigated by cyclic voltammetry, chronoamperometry and square wave voltammetry (SWV) techniques. Under the optimized conditions, the peak current was linear to GSH concentration over the concentration range of 0.3 to 180µmol L-1 using SWV. The detection limit was 0.09µmol L-1. The proposed method was successfully applied to the determination of GSH in the urine, tablet and hemolysed erythrocyte samples.

Voltammetric Determination of Penicillamine Using a Carbon Paste Electrode Modified with Multiwall Carbon Nanotubes In the Presence of Methyldopa as a Mediator.

A multiwall carbon nanotubes-modified carbon paste electrode (MWCNTs/MCPE) was fabricated and used to study the electrooxidation of penicillamine (PA) by electrochemical methods in the presence of methyldopa (MDOP) as a homogeneous mediator. The electrochemical oxidation of PA on the new sensor has been carefully studied. The kinetic parameters such as electron transfer coefficient, α, and catalytic reaction rate constant, K/h, were also determined using electrochemical approaches. The electrocatalytic oxidation peak current of PA showed a linear dependent on the PA concentrations and linear calibration curves were obtained in the ranges of 0.2-250.0 µM of PA concentration with square wave voltammetry (SWV) method. The detection limit (3σ) was determined as 0.1 µM. This sensor was also examined as a fast, selective, simple and precise new sensor for voltammetric determination of PA in real samples such as drug and urine.

Voltammmetric Determination of Captopril Using Multiwall Carbon Nanotubes Paste Electrode in the Presence of Isoproterenol as a Mediator.

The electrocatalytic oxidation of captopril (CAP) was studied by modified carbon nanotubes paste electrode in the presence of isoproterenol (ISPT) using cyclic voltammetry (CV), chronoamperometry and square wave voltammetry (SWV). Also, the values of catalytic rate constant (k), and electron transfer coefficient (α) for CAP were calculated. The mechanism of CA electrochemical behavior at the modified electrode surface was analyzed by various electrochemical methods in the presence of mediator. The prepared modified electrode showed voltammetric responses with high sensitivity for CAP, making it very suitable for the detection of CAP at trace levels. Under the optimized conditions, the peak current was linear to CAP concentration over the concentration range of 0.3 to 90 µmol L(-1) using SWV. The detection limit was 0.1 µmol L(-1). The proposed method was successfully applied for the determination of CAP in the urine, tablet and patient urine samples.

Multiway analysis applied to time-resolved chemiluminescence for simultaneous determination of paracetamol and codeine in pharmaceuticals.

This method is based on the enhancing effect of codeine (COD) and paracetamol (PAR) on the chemiluminescence (CL) reaction of Ru(phen)3 (2+) with Ce(IV). In the batch mode, COD gives a relatively sharp peak with the highest CL intensity at 4.0 s, whereas the maximum CL intensity of the PAR appears at ~60 s after injection of Ce(IV) solution. Whole CL time profiles allowed use of the time-resolved CL data in combination with multiway calibration techniques, as multiway partial least squares (N-PLS), for the quantitative determination of both COD and PAR in binary mixtures. In this work, we found that the impact of Ce(IV) concentration on the CL intensity was different for COD and PAR. Therefore, a Ce(IV) concentration mode was added to the time and sample modes to obtain 3D data. The percent relative standard deviation (%RSD) values for 10 determinations of 1.0 × 10(-5)  mol/L of COD and 1.0 × 10(-4)  mol/L of PAR were 6.1% and 8.7%, respectively. The limit of detection (LOD) values (S/N = 3) were 0.9 × 10(-8)  mol/L and 1.0 × 10(-6)  mol/L for COD and PAR, respectively. The proposed method was successfully applied to the determination of PAR and COD in commercial pharmaceutical formulations. Acceptable recoveries (90-110%) were obtained for the quantification of these drugs in the real samples. Copyright © 2016 John Wiley & Sons, Ltd.

Simple chemiluminescence determination of ketotifen using tris(1,10 phenanthroline)ruthenium(II)- Ce(IV) system.

A new method using chemiluminescence (CL) detection has been developed for the simple determination of ketotifen fumarate (KF). The method is based on the catalytic effect of KF in the CL reaction of tris(1,10 phenanthroline)ruthenium(II), Ru(phen)3 (2+), with Ce(IV) in sulfuric acid medium. The CL response was detected using a lab-made chemiluminometer. Effects of chemical variables were investigated and under optimum conditions, the CL intensity was proportional to the concentration of the drug over the range 0.34-34.00 µg mL(-1) KF. The limit of detection (S/N=3) was 0.09 µg mL(-1). Effects of common ingredients were investigated and the method was applied successfully for determining KF in pharmaceutical formulations and human plasma. The percent of relative standard deviation (n=11) at level of 3.4 µg mL(-1) of KF was 4.6% and the minimum sampling rate was 70 samples per hour. The possible CL mechanism is proposed based on the kinetic characteristic of the CL reaction, CL spectrum, UV-Vis and phosphorescence spectra.

Application of CdO nanoparticle ionic liquid modified carbon paste electrode as a high sensitive biosensor for square wave voltammetric determination of NADH.

In this paper we report the synthesis and application of CdO nanoparticle (CdO/NPs) and 1,3-dipropylimidazolium bromide as high sensitive sensors for voltammetric determination of nicotinamide adenine dinucleotide (NADH) using carbon paste electrode. The cyclic voltammogram showed an irreversible oxidation peak at 0.68 V (vs. Ag/AgClsat), which corresponded to the oxidation of NADH. Compared to common carbon paste electrode, the electrochemical response was greatly improved for NADH electrooxidation at a surface of CdO/NP modified ionic liquid carbon paste electrode (IL/CdO/NP/CPE). The linear response range and detection limit were found to be 0.09-750 µmol L(-1) and 0.05 µmol L(-1), respectively. Result shows that other physiological species did not interfere in the determination of NADH at the surface of the proposed sensor in the optimum condition. The proposed sensor was successfully applied for the determination of NADH in tap water, urine and pharmaceutical serum samples.

Highly selective and sensitive voltammetric sensor based on modified multiwall carbon nanotube paste electrode for simultaneous determination of ascorbic acid, acetaminophen and tryptophan.

A carbon-paste electrode modified with multiwall carbon nanotubes (MWCNTs) was used for the sensitive and selective voltammetric determination of ascorbic acid (AA) in the presence of 3,4-dihydroxycinnamic acid (3,4-DHCA) as mediator. The mediated oxidation of AA at the modified electrode was investigated by cyclic voltammetry (CV), chronoamperommetry and electrochemical impedance spectroscopy (EIS). Also, the values of catalytic rate constant (k), and diffusion coefficient (D) for AA were calculated. Using square wave voltammetry (SWV), a highly selective and simultaneous determination of AA, acetaminophen (AC) and tryptophan (Trp) has been explored at the modified electrode. The modified electrode displayed strong function for resolving the overlapping voltammetric responses of AA, AC and Trp into three well-defined voltammetric peaks. In the mixture containing AA, AC and Trp, the three compounds can well separate from each other with potential differences of 200, 330 and 530 mV between AA and AC, AC and Trp and AA and Trp, respectively, which was large enough to determine AA, AC and Trp individually and simultaneously.

Simple chemiluminescence determination of pilocarpine in pharmaceuticals and human serum.

A new method using flow injection analysis (FIA) and chemiluminescence (CL) detection has been developed for the rapid, simple and precise determination of pilocarpine hydrochloride (PH). The method is based on the CL reaction of PH with tris(1, 10 phenanthroline)ruthenium(II), [Ru(phen)32+], and Ce(IV) in sulfuric acid medium. Effects of chemical variables were investigated using a central composite design (CCD) and the response surface methodology (RSM). Under optimum conditions, the CL intensity was proportional to the concentration of the drug in solution over the range 0.12-40.00 µg mL-1. The limit of detection (S/N = 3) was 34 ng mL-1. The method was applied successfully to the determination of PH in pharmaceutical formulations and spiked human serum. The relative standard deviation for determination of 7 replicates at a level of 1.5 µg mL-1 of PH was 0.6%. The minimum sampling rate was 70 samples per hour.

A simple and selective spectrophotometric flow injection determination of trace amounts of ruthenium by catalytic oxidation of safranin-O.

In this work, a simple, selective and rapid flow injection method has been developed for determination of ruthenium. The method is based on its catalytic effect on the oxidation of safranin-O by metaperiodate. The reaction was monitored spectrophotometrically by measuring safranin-O absorbance at lambdamax=521. The reagents and manifold variables, which have influences on the sensitivity, were investigated and the optimum conditions were established. The optimized conditions made it possible to determine ruthenium in the ranges of 0.4-20.0 ng/mL (DeltaA=0.2819CRu+1.1840) and 20.0-100.0 ng/mL (DeltaA=0.0984CRu+7.9391) with a detection limit of 0.095 ng/mL and a sample rate of 30+/-5 samples/h. Relative standard deviation for the five replicate measurements was less than 1.84%. The proposed method has been successfully applied for analysis of ultra trace amounts of ruthenium in real samples.