ABSTRACT
In this work, a poly-orthophenylene diamine substrate is decorated with gold nanoparticles (GNPs) and then with single-stranded DNA (ss-DNA) aptamer immobilized on the surface of a pencil graphite electrode (PGE) for the detection and determination of plasma insulin. In this procedure, a polymer layer is formed on the surface of the graphite electrode using anodic oxidation of orthophenylene diamine monomers. The parameters affecting the biosensor sensitivity including the potential applied to form the polymer layer, incubation time, concentration of immobilized ss-DNA, and the presence of MgCl2 (as salt) are evaluated. Electrochemical impedance spectroscopy and cyclic voltammetry are then used to characterize the biosensor. The biosensor is employed under optimal conditions to obtain figures of merit, which reveal a linear range and a limit of detection of 1.0-1000.0nmolL-1 and 0.27nmolL-1, respectively. Finally, the aptasensor is employed for the determination of insulin in real plasma and urine samples to verify its performance and effectiveness.
Subject(s)
Biosensing Techniques/methods , Dielectric Spectroscopy/methods , Electrodes , Insulin/analysis , Polymers/chemistry , DNA, Single-Stranded/chemistry , Gold/chemistry , Graphite/chemistry , Metal Nanoparticles/chemistry , Phenylenediamines/chemistryABSTRACT
A combination of polytetrafluorethylene membrane-based liquid three-phase micro-extraction and voltammetry was used for the micro-separation and determination of buprenorphine. Type of the organic solvent used, pH levels of the donor and acceptor phases, salt concentration, extraction time, stirring rate, and electrochemical parameters as the essential factors affecting the liquid three-phase micro-extraction of buprenorphine were investigated. Differential pulse voltammetry exhibited two linear dynamic ranges of 1.0-109.0 pmol L(-1) and 0.109 nmol L(-1)-0.11 µmol L(-1) of buprenorphine and the detection limit was found to be as low as 0.6 pmol L(-1) of buprenorphine. Also, the effects of a number of common substances potentially interfering with selectivity were studied. The results indicate that the proposed method is highly selective and sensitive for buprenorphine detection in real samples such as human urine and plasma of both drug-addict and non-addict human subjects.
Subject(s)
Buprenorphine , Electrochemical Techniques , Liquid Phase Microextraction/instrumentation , Morphine Dependence , Narcotics , Polytetrafluoroethylene/chemistry , Buprenorphine/blood , Buprenorphine/urine , Calibration , Electrodes , Graphite/chemistry , Humans , Hydrogen-Ion Concentration , Limit of Detection , Liquid Phase Microextraction/methods , Membranes, Artificial , Morphine Dependence/blood , Morphine Dependence/urine , Narcotics/blood , Narcotics/urine , Sodium Chloride/chemistry , SolventsABSTRACT
In this paper, we describe a new combination method based on polytetrafluorethylene (PTFE) film-based liquid three-phase micro extraction coupled with differential pulse voltammetry (DPV) for the micro extraction and quantification of atorvastatin calcium (ATC) at the ultra-trace level. Different factors affecting the liquid-three phases micro extraction of atorvastatin calcium, including organic solvent, pH of the donor and acceptor phases, concentration of salt, extraction time, stirring rate and electrochemical factors, were investigated, and the optimal extraction conditions were established. The final stable signal was achieved after a 50 min extraction time, which was used for analytical applications. An enrichment factor of 21 was achieved, and the relative standard deviation (RSD) of the method was 4.5% (n = 4). Differential pulse voltammetry exhibited two wide linear dynamic ranges of 20.0-1000.0 pmol L(-1) and 0.001-11.0 µmol L(-1) of ATC. The detection limit was found to be 8.1 pmol L(-1) ATC. Finally, the proposed method was used as a new combination method for the determination of atorvastatin calcium in real samples, such as human urine and plasma.
Subject(s)
Heptanoic Acids/analysis , Heptanoic Acids/isolation & purification , Liquid Phase Microextraction , Polytetrafluoroethylene/chemistry , Pyrroles/analysis , Pyrroles/isolation & purification , Atorvastatin , Electrochemistry , Heptanoic Acids/blood , Heptanoic Acids/urine , Humans , Hydrogen-Ion Concentration , Limit of Detection , Osmolar Concentration , Pyrroles/blood , Pyrroles/urine , Solvents/chemistry , Time FactorsABSTRACT
In this work, p-aminophenol-multiwall carbon nanotubes-TiO(2) is proposed as a sensor for the rapid, sensitive, and highly selective voltammetric determination of penicillamine (PA) in the presence of uric acid (UA). The electrochemical behavior of the compounds at this modified electrode was studied by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). The results indicated that the chemically modified electrode exhibits efficient electrocatalytic activity in the oxidation of PA which occurs at a potential of about 530 mV, less positive than that for the unmodified carbon nanotubes paste electrode at pH 6.0. Peak potentials of PA and UA were separated with a difference of 215 mV using DPV. These conditions were sufficient to allow for the determination of PA and UA, both individually and simultaneously. At pH 6.0, the catalytic peak currents were linearly dependent on PA and UA concentrations in the ranges 0.4-200 micromol L(-1) PA and 3.0-1000 micromol L(-1) UA. Detection limits for PA and UA were 0.1 and 1.1 micromol L(-1), respectively. The RSD% for 1.2 and 1.5 micromol L(-1) PA were 1.6% and 2.1%, respectively, whereas they were 1.5% and 1.1% for 15.0 and 30.0 micromol L(-1) UA, respectively. Finally, the sensor was examined as a selective, simple, and precise new electrochemical sensor for the determination of PA in real samples in the presence of UA in drugs and urine.