Search

A simple and sensitive chemiluminometric method was developed for the determination of celecoxib, a nonsteroidal anti-inflammatory drug. It is based on the sensitization of Ce(IV)-Na2SO3 chemiluminescence reaction by celecoxib in the presence of Tb(III) ions. The mechanism of chemiluminescence reaction was studied by obtaining fluorescence and chemiluminescence spectra. The effects of various chemical parameters on chemiluminescence intensity were investigated and optimized. Under the optimum conditions, a linear relationship was obtained between the enhanced chemiluminescence intensity and the concentration of celecoxib in the range of 0.01–0.15 μg/mL, with a limit of detection of 2.5 ng/mL. Study of interferences confirmed the selectivity of the developed method for analysis of pharmaceutical and biological samples. The method was applied to the determination of celecoxib in pharmaceutical formulations and human plasma samples, and also to dissolution studies with satisfactory results.

A simple and sensitive chemiluminometric method is described for the determination of tetracycline (TC) and oxytetracycline (OTC) in their hydrochloride form on the basis of drastic enhancement of the chemiluminescence (CL) from the luminol/L-cysteine-capped CdTe quantum dots (QDs)/sodium periodate system, caused by the presence of TC and OTC hydrochloride. The method uses pH value at which tetracyclines have proven to be stable. Response surface methodology was exploited for optimizing the experimental conditions. The synthesized QDs were characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), UV–vis spectroscopy, and photoluminescence spectroscopy. A possible mechanism of the CL system was proposed based on the CL spectra and the effect of some specific radical-scavengers on the system. Under the optimum conditions linear dynamic ranges of 5.0×10−8–6.0×10−6 mol L−1 and 5.0×10−8–8.0×10−6 mol L−1 were observed for TC and OTC, respectively with corresponding detection limits of 2.2×10−8 mol L−1 and 3.0×10−8 mol L−1. The precision (RSD%) for five replicate determinations of TC and OTC were respectively no more than 3.4% and 4.0%. The method was satisfactorily applied to the determination of TC.HCl and OTC.HCl in water samples, pharmaceutical formulations, and honey.

A simple and highly sensitive chemiluminescence (CL) method is reported for the determination of naphazoline hydrochloride (NH). It was found that the weak CL from the reaction of luminol and KIO4 in an alkaline medium could be highly amplified by cysteine-capped cadmium telluride quantum dots (QDs) and the enhanced CL was effectively quenched by NH and this finding was utilized as a basis for the determination of NH. The QDs were synthesized in aqueous medium and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and UV-vis and photoluminescence spectroscopy. A possible mechanism was proposed for the CL system based on radical identification experiments, along with CL spectrum of the system. The experimental parameters were optimized by the reliable response surface methodology (RSM). Under the optimized experimental conditions, the proposed method allowed the determination of NH over the range of 5.0 × 10(-10) -2.0 × 10(-7) mol/L (r(2) = 0.9993, n = 10). The precision (RSD%) of the method, obtained from five replicate determinations of 2.0 and 150 nmol/L NH, was found to be 1.0% and 1.3%, respectively. The method was successfully applied to the determination of NH in pharmaceutical formulations and human urine and serum samples with results corroborated with the aid of those obtained from a standard method.

The chemiluminescence (CL) of water-soluble fluorescent carbon dots (C-dots) induced by direct chemical oxidation was investigated. C-dots were prepared by solvothermal method and characterized by fluorescence spectra and transmission electron microscopy. It was found that K3Fe(CN)6 could directly oxidize C-dots to produce a relatively intense CL emission. The mechanism of CL generation was investigated based on the fluorescence and CL emission spectra and the effect of radical scavengers on the CL intensity. The inhibitive effect of some metal ions and biologically important molecules on the CL intensity of the system was examined and the potential of the system for the determination of these species at trace levels was studied. In order to evaluate the capability of method to real sample analysis, it was applied to the determination of Cr(VI) and adrenaline in water and injection samples, respectively.

We show that the very weak chemiluminescence (CL) of the Ce(IV)-thiosulfate system is enhanced by a factor of ~150 in the presence of fluorescent carbon dots (C-dots). The C-dots were prepared by a solvothermal method and characterized by fluorescence spectra and transmission electron microscopy. Possible mechanisms that lead to the effect were elucidated by recording fluorescence and CL spectra. It is found that dopamine at even nanomolar levels exerts a diminishing effect on the enhancement of CL. This was exploited to design a method for the determination of dopamine in the concentration range from 2.5 nM to 20 μM, with a limit of detection (at 3 s) of 1.0 nM. Dopamine was determined by this method in spiked human plasma samples with satisfactory results.

A novel chemiluminescence (CL) system based on the oxidation of bromide by permanganate in sulfuric acid medium is introduced. The enhancing effect of silver nanoparticles (NPs), synthesized by chemical reduction method, on this reaction was studied. It was demonstrated that spherical silver nanoparticles with average size of 18 nm had a most remarkable catalytic effect on this reaction. CL emission wavelengths and UV-vis spectra were used to characterize the system and propose a possible mechanism. Furthermore, it was found that captopril inhibits the action of NPs and decreases the intensity of CL. Based on this phenomenon, a new CL method was developed for the determination of captopril in the 3.0 × 10(-10) to 1.0 × 10(-7) mol L(-1) concentration range with a detection limit (3s) of 0.12 nmol L(-1). The method was successfully applied to the determination of captopril in pharmaceutical formulations, human urine and serum samples.

A simple and sensitive flow injection chemiluminescence (FI-CL) method was developed for the determination of naphazoline hydrochloride (NPZ). The method is based on the enhancing effect of NPZ on the weak CL signal from the reaction of KIO4 with H2 O2 . Experimental parameters that affected the CL signal, including the pH of the KIO4 solution, concentrations of KIO4 , H2 O2 and disodium-EDTA and flow rate were optimized. Under the optimum conditions, the increment of CL intensity was linearly proportional to the concentration of NPZ in the range 5.0 × 10(-6) to 70 × 10(-6) mol/L. The detection limit was 1.0 × 10(-6) mol/L and the relative standard deviation for 50 × 10(-6) mol/L NPZ solution was 2.8% (n = 11). In addition, a high throughput of 120 samples/h was achieved. The utility of this method was demonstrated by determining NPZ in pharmaceuticals.

A highly selective and simple chemiluminescence (CL) method for determination of penicillin G potassium (PGK) was developed. In the proposed method, CL was elicited from PGK upon its oxidation with H2O2. The light emission was enhanced in the presence of N-cetyl-N,N,N-trimethylammonium bromide (CTMAB). An experimental design, central composite design (CCD), was used to realize the optimized variables, including pH, surfactant (CTMAB) and H2O2 concentrations. Under optimum condition, the calibration graph was linear in the range 3.3 × 10−3–3.3 × 10−1 mmol/L, with a detection limit of 8.8 × 10−4 mmol/L for PGK. The precision was calculated by analysing samples containing 1.6 × 10−1 mmol/L PGK (n = 5) and the relative standard deviation (RSD) was 1.40%. The utility of this method was demonstrated by determining PGK in pharmaceutical formulations for injection. The proposed method was validated by a reference method. Copyright © 2011 John Wiley & Sons, Ltd.

A simple and selective method for penicillin V potassium (PVK) determination by chemiluminescence (CL) was developed. Oxidation of PVK by alkaline hydrogen peroxide produces CL, which is greatly enhanced by N, N-dimethyl formamide (DMF) and N-cetyl-N,N,N-trimethylammonium bromide (CTMAB). Optimum conditions were established using luminometry. There is a linear relationship between the chemiluminescent peak height and the amount of PVK within the range 0.5–129.5 mg L−1, with a detection limit of 0.2 mg L−1. The coefficient of variation was 1.2% for 40 mg L−1 PVK solution (n = 7). The method is very simple, has high sensitivity and good selectivity, and is usable for process control. It was successfully utilized for the determination of PVK in pharmaceuticals and spiked human urine.

An enhanced thiosemicarbazide(TSC)-H 2O2 chemiluminescence (CL) system was established and proposed as a new analytical method for determination of b-lactam antibiotics, ampicillin sodium and amoxicillin at microgram levels. The method is based on the inhibition of CL emission accompanying oxidation of TSC by H 2O2 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 mg amoxicillin, and 35-350 mg ampicillin sodium. The detection limits are 8 mg for amoxicillin and 9 mg for ampicillin sodium. The relative standard deviations of six replicate measurements of 200 mg amoxicillin and 200 mg 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. Copyright © 2008 John Wiley & Sons, Ltd.

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.

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.

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 0.1–1.3 ppm. The limit of detection was 10 ppb. The relative standard deviation for five determinations of 0.5 ppm 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.

A novel spectrophotometric method is described for the determination of epinephrine (EP) and norepinephrine (NE). The method is based on the development of a red colour with sodium bismuthate, as a sensitive chromogenic reagent, in aqueous medium at pH 3. Oxidation of these catecholamines produces aminochrome derivatives which can be measured spectrophotometrically at 486.0 nm. Calibration graphs are linear in the range 4.8-800 (micromol l(-1)) for epinephrine bitartarate and 4.8-600 (micromol l(-1)) for norepinephrine bitartarate with detection limits of 0.26 (micromol l(-1)) and 2.46 (micromol l(-1)) for epinephrine and norepinephrine bitartarate salts, respectively. The method has successfully been applied to determination of these catecholamines in pharmaceutical preparations.

Mercury(II) and methylmercury cations at the sub-ppb level were adsorbed quantitatively from aqueous solution onto a column packed with dithizone immobilized on sodium dodecyl sulfate coated alumina. The trapped mercury was then back-extracted into the aqueous phase with 1 M hydrobromic acid and determined by cold vapour atomic absorption spectrometry by utilizing the reaction with sodium tetrahydroborate. Mercury(II) and methylmercury cations were completely recovered from water with a preconcentration factor of 100. The analytical procedure was applied to the determination of mercury(II) and methylmercury in river and tap water.

A simple and highly sensitive chemiluminescence (CL) method is reported for the determination of naphazoline hydrochloride (NH). It was found that the weak CL from the reaction of luminol and KIO4 in an alkaline medium could be highly amplified by cysteine-capped cadmium telluride quantum dots (QDs) and the enhanced CL was effectively quenched by NH and this finding was utilized as a basis for the determination of NH. The QDs were synthesized in aqueous medium and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and UV-vis and photoluminescence spectroscopy. A possible mechanism was proposed for the CL system based on radical identification experiments, along with CL spectrum of the system. The experimental parameters were optimized by the reliable response surface methodology (RSM). Under the optimized experimental conditions, the proposed method allowed the determination of NH over the range of 5.0 × 10(-10) -2.0 × 10(-7) mol/L (r(2) = 0.9993, n = 10). The precision (RSD%) of the method, obtained from five replicate determinations of 2.0 and 150 nmol/L NH, was found to be 1.0% and 1.3%, respectively. The method was successfully applied to the determination of NH in pharmaceutical formulations and human urine and serum samples with results corroborated with the aid of those obtained from a standard method.

A simple and inexpensive method for determining chromium (VI) in drinking water by spectrophotometry after preconcentration with sodium dodecyl sulphate (SDS) coated alumina column is described. Chromium(VI) is reacted with diphenylcarbazide (DPC) and the Cr-DPC complex is quantitatively adsorbed onto a SDS coated alumina column from 800 ml of sample solution. The complex is then eluted with a 8 ml mixture of methanol, acetone and hydrochloric acid and determined by spectrophotometry. Total chromium can be determined after oxidation of chromium (III) to chromium (VI) by KMnO4. The relative standard deviation (10 replicate analyses) at the 10 μg l−1 of chromium (VI) and 10 μg l−1 of total chromium were 3.5% and 3.4% and corresponding limits of detection (based on 3 σ) were 0.040 μg l−1 and 0.033 μg l−1, respectively.

A simple and convenient method has been developed for the speciation of chromium(III) and chromium(VI) in aqueous solutions using a sodium dodecyl sulphate coated alumina micro-column (1.5 cm x 5 mm i.d.) and graphite furnace-atomic absorption spectrometry (GF-AAS). Under the optimized conditions (pH 0.6, adjusted with hydrochloric acid; flow rate, 1 ml min(-1)) chromium(VI) is retained on the column and chromium(III) is collected and determined by GF-AAS. Total chromium is directly determined by GF-AAS and chromium(VI) is calculated by difference. The relative standard deviations (10 replicate analyses) at the 20 mug l(-1) level for chromium(III) and chromium(VI) and at the 40 mug l(-1) level for total chromium were 1.4%, 3.6% and 1.8%, and the corresponding limits of detection (based on 3sigma) were 0.57 mug ml(-1), 0.61 mug ml(-1) and 0.35 mug l(-1) respectively. No large interference effects have been observed from other investigated species and the method has been successfully applied to a range of water samples.

A simple and sensitive flow injection chemiluminescence (FI-CL) method was developed for the determination of naphazoline hydrochloride (NPZ). The method is based on the enhancing effect of NPZ on the weak CL signal from the reaction of KIO4 with H2 O2 . Experimental parameters that affected the CL signal, including the pH of the KIO4 solution, concentrations of KIO4 , H2 O2 and disodium-EDTA and flow rate were optimized. Under the optimum conditions, the increment of CL intensity was linearly proportional to the concentration of NPZ in the range 5.0 × 10(-6) to 70 × 10(-6) mol/L. The detection limit was 1.0 × 10(-6) mol/L and the relative standard deviation for 50 × 10(-6) mol/L NPZ solution was 2.8% (n = 11). In addition, a high throughput of 120 samples/h was achieved. The utility of this method was demonstrated by determining NPZ in pharmaceuticals.

A highly selective and simple chemiluminescence (CL) method for determination of penicillin G potassium (PGK) was developed. In the proposed method, CL was elicited from PGK upon its oxidation with H(2)O(2). The light emission was enhanced in the presence of N-cetyl-N,N,N-trimethylammonium bromide (CTMAB). An experimental design, central composite design (CCD), was used to realize the optimized variables, including pH, surfactant (CTMAB) and H(2)O(2) concentrations. Under optimum condition, the calibration graph was linear in the range 3.3 × 10(-3) -3.3 × 10(-1) mmol/L, with a detection limit of 8.8 × 10(-4) mmol/L for PGK. The precision was calculated by analysing samples containing 1.6 × 10(-1) mmol/L PGK (n = 5) and the relative standard deviation (RSD) was 1.40%. The utility of this method was demonstrated by determining PGK in pharmaceutical formulations for injection. The proposed method was validated by a reference method.

This month's featured article; ‘Oscillating chemiluminescence systems: state of the art’ is authored by Mortaza Iranifam, Marcela A. Segundo, Joao L. M. Santos, Jose L. F. C. Lima and Mohammad H. Sorouraddin. In this review, the authors present the first comprehensive account of the developments and current state of the art regarding Oscillating chemiluminescent systems. From Belousov–Zhabotinskii and horseradish peroxidase-catalyzed reactions through to Orban oscillators and more. This report pulls together many important developments in the field that have previously only been available scattered across periodicals and diff erent media. The cover image is a graphical representation of a biological Belousov–Zhabotinskii reaction composited against the oscillating CL behavior for 1,10-phenanthroline–H2O2–KSCN–CuSO4–NaOH system in a batch reactor.

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.

This paper describes simple and rapid methods for the fabrication of glass and polymeric chips for routine analytical applications. The methods are easily interfaced to the general laboratory environment and do not require special clean room facilities or expensive instruments. Glass microchips were fabricated by etching with HF solution. Microfluidic channels were designed with CAD program and transferred onto a sheet of commercial polymeric self-adhesive (PSA) film by a cutter plotter. The PSA film was used as a mask for etching process. The etching rate was about 7 microm min(-1). A cover glass plate was sealed on the top of etched substrate by using polycellulose (cellophane). Polymeric microchips were fabricated by sawing with a jigsaw. Commercial polycarbonate (PC) was used as a substrate and two iron sheets were used as leader masks. While this restricts us to the fabrication of straight channels, it is however, much faster and less complicated than the other methods. The chip comprised three polymeric plates and the channels were created in the middle plate. Thermal bonding was used to bond three layers of the microfluidic chip. With this method, we could achieve simple channels with the width of about 200 microm. The channel depth depends on the polymeric plate thickness. Fabricated channels were accurate without any sinuosity or sideshow.

A highly sensitive spectrophotometric method is described for the determination of trace amounts of osmium(VIII), based on its catalytic effect on the oxidation of carminic acid by hydrogen peroxide. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of carminic acid at 540 nm after 3 min of mixing the reagents. The optimum reaction conditions were 1x10(-4) mol l(-1) carminic acid, 0.013 mol l(-1) hydrogen peroxide and pH 10 at 25 degrees C. By using the recommended procedure, the calibration graph was linear from 0.1 to 1.5 ng ml(-1) of osmium; the detection limit was 0.02 ng ml(-1); the RSD for five replicate determinations of 0.2-1.4 ng ml(-1) was in the range of 1.8-4.7%. The influence of several foreign ions on osmium determination were studied and the effect of interfering ions were removed by extracting osmium into isobuthyl methyl ketone and back extracting into sodium hydroxide solution.

A highly sensitive and selective method is described for the determination of trace amounts of nitrite based on its effect on the oxidation of carminic acid with bromate. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of carminic acid at 490 nm after 3 min of mixing the reagents. The optimum reaction conditions were 1.8×10 −1 mol l −1 H 2 SO 4 , 3.8×10 −3 mol l −1 KBrO 3 , and 1.2×10 −4 mol l −1 carminic acid at 30°C. By using the recommended procedure, the calibration graph was linear from 0.2 to 14 ng ml −1 of nitrite; the detection limit was 0.04 ng ml −1 ; the R.S.D. for six replicate determinations of 6 ng ml −1 was 1.7%. The method is mostly free from interference, especially from large amounts of nitrate and ammonium ions. The proposed method was applied to the determination of nitrite in rain and river water.