RESUMO
A simple and sensitive flow-injection chemiluminescence (CL) method has been developed for the determination of gentamicin sulfate. The method is based on the inhibitory effect of gentamicin on the CL emission accompanying oxidation of luminol by H2 O2 in an alkaline medium in the presence of Cu(II) as a catalyst. Inhibition was caused by the formation of a strong complex between analyte and the catalyst. Experimental variables, including the concentrations of luminol (µmol/L), H2 O2 (mol/L), Cu(II) (mol/L) and NaOH (mol/L), were optimized using a central composite design. Under optimum conditions, the plot of CL intensity versus gentamicin concentration was found to have two linear ranges. One range was at low concentrations from 1.0 to 10.0 mg/L and the other was from 10.0 to 30.0 mg/L. Precision was calculated by analyzing samples containing 5.0 mg/L gentamicin (n = 11) and the relative standard deviation (RSD) was 1.7%. Also, a high injection throughput of 120 samples/h was achieved. This method was successfully applied to the determination of gentamicin sulfate in pharmaceutical formulations and water samples.
Assuntos
Análise de Injeção de Fluxo/métodos , Gentamicinas/química , Medições Luminescentes/métodos , Água Doce/química , Poluentes Químicos da Água/químicaRESUMO
A novel chemiluminescence (CL) reaction, captopril-H2O2, for determination of Cu(II) at nanogram per milliliter level in batch-type system has been described. The method relies on the catalytic effect of Cu(II) on the oxidation of captopril with hydrogen peroxide in alkaline medium. The optimization step was performed using univariate methodology and the factors studied were: pH and concentrations of the utilized reagents. Under the optimum conditions, calibration plot was linear in the range of 0.1-2.0 ppm. Limit of detection was 30 ppb and relative standard deviation for five replicate determinations of 0.8 ppm Cu(II) was 1.89%. The proposed method was successfully applied to the determination of Cu(II) in human scalp hair and cereals, rice and wheat, flour with satisfactory selectivity and sensitivity. The results were validated by comparison with a standard method (FAAS). The possible mechanism of the new CL reaction has also been discussed.
Assuntos
Captopril/química , Cobre/análise , Grão Comestível/química , Farinha/análise , Cabelo/química , Medições Luminescentes/métodos , Catálise , Humanos , Peróxido de Hidrogênio/química , Concentração de Íons de Hidrogênio , Medições Luminescentes/instrumentação , Conformação Molecular , Oxirredução , Sensibilidade e EspecificidadeRESUMO
In this paper, oscillating chemiluminescence (CL), 1,10-phenanthroline H2O2-KSCN-CuSO4-NaOH system, was studied in a batch reactor. The system described is a novel, slowly damped oscillating CL system, generated by coupling the well-known Epstein-Orban, H2O2-KSCN-CuSO4-NaOH chemical oscillator reaction with the CL reaction involving the oxidation of 1,10-phenanthroline by hydrogen peroxide, catalyzed by copper(II) in alkaline medium. In this system, the CL reaction acts as a detector or indicator system of the far-from-equilibrium dynamic system. Narrow and slightly asymmetric light pulses of 1.2 s half-width are emitted at 440 nm with an emitted light time of 200-1000 s, induction period of 3.5-357 s and oscillation period of 28-304 s depending on the reagent concentrations. In this report the effect of the concentration variation of components involved in the oscillating CL system on the induction period, the oscillation period and amplitude was investigated and the parameters were plotted with respect to reagent concentrations. Copper concentration showed a significant effect on the oscillation period. The possible mechanism for the oscillating CL reaction was also discussed.
Assuntos
Medições Luminescentes/métodos , Fenômenos Químicos , Sulfato de Cobre/química , Peróxido de Hidrogênio/química , Indicadores e Reagentes , Fenantrolinas/química , Hidróxido de Sódio/química , Tiocianatos/químicaRESUMO
An enhanced thiosemicarbazide(TSC)-H2O2 chemiluminescence (CL) system was established and proposed as a new analytical method for determination of beta-lactam antibiotics, ampicillin sodium and amoxicillin at microgram levels. The method is based on the inhibition of CL emission accompanying oxidation of TSC by H2O2 in alkaline medium. The effect of anionic, cationic, and non-ionic surfactants on the CL emission of the system was studied. Both N-cetyl-N,N,N-trimethylammonium bromide (CTMAB) and Triton X-100, unlike sodium dodecyl sulfate (SDS), reinforced the CL intensity and were efficient to approximately the same level. The effect of the presence of eight non-aqueous solvents on the CL system was also investigated. Upon addition of both of the non-ionic surfactant, Triton X-100, and the non-aqueous solvent, N,N-dimethyl formamide (DMF), the intensity of the CL reaction was increased 100-fold. This method allows the measurement of 25-545 microg amoxicillin, and 35-350 microg ampicillin sodium. The detection limits are 8 microg for amoxicillin and 9 microg for ampicillin sodium. The relative standard deviations of six replicate measurements of 200 microg amoxicillin and 200 microg ampicillin sodium were 1.9 and 2.1%, respectively. The effect of foreign species on the determination of amoxicillin and ampicillin sodium was also examined. The proposed method was successfully applied to the determination of ampicillin sodium and amoxicillin in some pharmaceutical dosage forms.
Assuntos
Antibacterianos/análise , Medições Luminescentes/métodos , beta-Lactamas/análise , Amoxicilina/análise , Ampicilina/análise , Peróxido de Hidrogênio , SemicarbazidasRESUMO
Oscillating chemical reactions are complex systems involving a large number of chemical species. In oscillating chemical reactions, some species, usually reaction intermediates, exhibit fluctuations in their concentration. In this report, a novel slowly-damped oscillating chemiluminescence produced by the addition of thiosemicarbazide (TSC) to the oscillating system H2O2-KSCN-CuSO4-NaOH was investigated. Narrow and slightly asymmetric light pulses of 1.5 s half-width are emitted at 440 nm, with an oscillation period of 22-363 s, an induction period of 9-397 s and an emitted light time of 700-1500 s, depending on reagent concentrations. In this study the dependence of the induction period and the oscillation period on the reagent concentrations was investigated and both parameters were plotted with respect to reagent concentrations. Copper concentration showed a significant effect on the oscillation period. A possible mechanism for the oscillating chemiluminescence reaction is discussed.
Assuntos
Luminescência , Oscilometria/métodos , Semicarbazidas/química , Sulfato de Cobre , Peróxido de Hidrogênio , Medições Luminescentes , Hidróxido de Sódio , TiocianatosRESUMO
A novel, rapid and sensitive CuO nanosheets (NSs) amplified flow-injection chemiluminescence (CL) system, luminol-H2O2-CuO nanosheets, was developed for determination of the vancomycin hydrochloride for the first time. It was found that vancomycin could efficiently inhibit the CL intensity of luminol-H2O2-CuO nanosheets system in alkaline medium. Under the optimum conditions, the inhibited CL intensity was linearly proportional to the concentration of vancomycin over the ranges of 0.5-18.0 and 18.0-40.0 mg L(-1), with a detection limit (3σ) of 0.1 mg L(-1). The precision was calculated by analyzing samples containing 5.0 mg L(-1) vancomycin (n=11) and the relative standard deviation (RSD) was 2.8%. Also, a high injection throughput of 120 sample h(-1) was obtained. The CuO nanosheets were synthesized by a sonochemical method. Also, X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses were employed to characterize the CuO nanosheets. The method was successfully employed to determine vancomycin hydrochloride in environmental water samples, pharmaceutical formulation and spiked human serum.
Assuntos
Antibacterianos/análise , Antibacterianos/sangue , Cobre/química , Nanoestruturas/química , Vancomicina/análise , Vancomicina/sangue , Análise de Injeção de Fluxo/métodos , Humanos , Peróxido de Hidrogênio/química , Limite de Detecção , Medições Luminescentes/métodos , Luminol/química , Preparações Farmacêuticas/química , Água/análise , Difração de Raios XRESUMO
A novel selenium nanoparticles (Se NPs)-amplified chemiluminescence (CL) reaction, Se NPs-potassium permanganate-dinitrobutylphenol (DNBP), for the determination of DNBP at gram per milliliter level is described. In the present study, it was found that direct reaction of DNBP with potassium permanganate (KMnO4) in the acidic mediums elicited light emission, which was greatly enhanced by selenium nanoparticles. Under optimum conditions, the CL intensity is linearly related to the concentration of DNBP in the range of 1.0×10(-7)-8.0×10(-5)g mL(-1) with a detection limit (3σ) of 3.1×10(-8) g mL(-1). The relative standard deviation for 11 determinations of 2.5×10(-5) gm L(-1) DNBP is 2.07%. The Se NPs were prepared by the chemical hydrothermal method. It was found that catalytic properties of Se NPs were higher than those of microparticles (MPs). In addition, scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to characterize the Se NPs. Appropriate sensitivity, selectivity and precision were among notable features of the proposed method. The method was successfully applied to the determination of DNBP in the water samples of different origins. Moreover, the possible mechanism for the new CL reaction was also discussed.
Assuntos
2,4-Dinitrofenol/análogos & derivados , Medições Luminescentes/métodos , Nanopartículas/química , Praguicidas/análise , Selênio/química , Poluentes Químicos da Água/análise , 2,4-Dinitrofenol/análise , Água Doce/análise , Limite de Detecção , Luminescência , Nanopartículas/ultraestrutura , Permanganato de Potássio/químicaRESUMO
Oscillating chemical reactions are complex systems, involving a large number of chemical species. In an oscillating chemical reaction, some species, usually a reaction intermediate, exhibit fluctuation in its concentration. In this report, oscillating chemiluminescence produced by the addition of thiosemicarbazide (TSC) to the oscillating system H(2)O(2)-KSCN-CuSO(4)-NaOH was investigated using luminometry method. The effects of complexing agents, triethylenetetramine (TETA) and D-penicillamine, on the behavior of the oscillating system were investigated. Moreover, the influence of non-aqueous solvents, dimethyl sulfoxide (DMSO), nitromethane and acetonitrile, was studied. In the presence of solvents with high protophility, the chemiluminescence (CL) intensity was increased (sevenfold), the light emitting and oscillating time was enhanced by threefold. In addition, the effect of presence of non-ionic, cationic, and anionic surfactants was investigated. Non-ionic surfactant increased the intensity of the oscillating CL reaction by 4.5-fold.
RESUMO
A novel chemiluminescence (CL) reaction, thiosemicarbazide (TSC)-H(2)O(2), for the determination of copper at nanogram per milliliter level in batch type is described. The method is based on the catalytic effect of copper(II) on the oxidation of TSC with hydrogen peroxide to produce light emission. The emitted light was observed by using a conventional fluorescence detector. In the optimum conditions, calibration graph was linear in the range of 0.1-1.3ppm. The limit of detection was 10ppb. The relative standard deviation for five determinations of 0.5ppm copper(II) was 1.93%. The proposed method permitted the selective and sensitive determination of Cu(II) in human hair and wheat flour with sufficient precision. The possible mechanism for the new chemiluminescence reaction was also discussed.