Spectrofluorimetric determination of acrivastine in spiked human urine and pharmaceuticals

A spectrofluorimetric method to determine acrivastine is proposed and applied to its determination in human urine and pharmaceuticals. The fluorimetric method allows the determination of 58-2000 ng ml(-1) of acrivastine in aqueous solutions containing acetic acid-sodium acetate buffer (pH 6.5) with lambda(exc)=230 nm and lambda(em)=380 nm.     

Spectrofluorimetric kinetic determination of selenium (IV) by flow injection analysis in cationic micellar medium

A sensitive catalytic kinetic spectrofluorimetric method for determining ng ml(-1) of selenium by flow injection analysis has been developed. The method, based on the catalytic effect of Se (IV) on the reduction of resorufin by sulphide, in the presence of cetylpyridinium chloride, is monitored spectrofluorimetrically (lambda(ex)=480 nm; lambda(em)=583 nm). The linearity range of the calibration graph is dependent on the concentration of sulphide. The variables affecting the rate of the reaction were investigated. The method is simple, rapid, precise, sensitive, and widely applicable. The limit of detection is 1 ng ml(-1) Se (IV), and the calibration range is 5-1000 ng ml(-1). Sampling rate is 60 samples h(-1), and the relative standard deviation of 12 determinations of 100 ng ml(-1) Se was 0.76%. The determination of Se (IV) in the presence of Se (VI) and total selenium is described. The method was applied to the determination of Se in selenium tablets, and several synthetic samples.     

Direct determination of salicylamide in serum by matrix isopotential synchronous fluorimetry

A method for the determination of salicylamide at concentrations between 25 and 350 ng ml(-1) by use of matrix isopotential synchronous fluorescence spectrometry (MISF) in combination with derivative techniques is proposed. The method allows the determination of compounds in samples with unknown background fluorescence without the need for tedious pre-separation. Synchronous scans are performed along a trajectory that connects points of identical intensity in a three-dimensional fluorescence spectrum. The unknown analytical signal of the serum is suppressed from the MISF spectrum, by calculating its first derivative at lambda(exc)=324 nm and lambda(em)=392 nm. In order to ensure maximum sensitivity and adequate selectivity, the experimental variables affecting the fluorescence intensity of the salicylamide band at lambda(exc)=328 nm and lambda(em)=418 nm were studied. Based on the results, the determination was performed in an aqueous medium at pH 12 that was adjusted with a sodium phosphate/hydrogen phosphate buffer. Calibration graphs were subjected to a comprehensive statistical analysis. The error propagation has been considered in order to calculate the detection limit by the criterium of Clayton.     

Utility of oxidation-reduction reaction for the determination of ranitidine hydrochloride in pure form,in dosage forms and in the presence of its oxidative degradates

Three simple, accurate and sensitive colorimetric methods (A, B and C) for the determination of ranitidine HCl (RHCl) in bulk sample, in dosage forms and in the presence of its oxidative degradates are described. The first method A is based on the oxidation of the drug by N-bromosuccinimide (NBS) and determination of the unreacted NBS by measurement of the decrease in absorbance of amaranth dye (AM) at a suitable lambda(max)=520 nm. The methods B and C involve the addition of excess Ce(4+) and determination of the unreacted oxidant by decrease the red color of chromotrope 2R (C2R) at a suitable lambda(max)=528 nm for method B or decrease the orange pink color of rhodamine 6G (Rh6G) at a suitable lambda(max)=526 nm for method C. Regression analysis of Beer-Lambert plots showed good correlation in the concentration ranges 0.2-3.6, 0.1-2.8 and 0.1-2.6 microg ml(-1) for methods A, B and C, respectively. The apparent molar absorptivity. Sandell sensitivity, detection and quantitation limits were calculated. For more accurate results, Ringbom optimum concentration ranges were 0.3-3.4, 0.2-2.6 and 0.2-2.4 microg ml(-1) for methods A, B and C, respectively. Analyzing pure and dosage forms containing RHCl tested the validity of the proposed methods. The relative standard deviations were 相似文献   

Non-protected fluid room-temperature phosphorimetric procedure for the direct determination of naftopidil in biological fluids

Non-protected fluid room temperature phosphorescence, NPRTP, has been applied to the determination of naftopidil in biological fluids. The proposed method is based on obtaining a phosphorescence signal from naftopidil using potassium iodide as heavy atom perturber and sodium sulfite as a deoxygenating reagent without a protected medium. Optimized conditions for the determination were 1.4 mol L= KI, 5.0 x l0(-3) mol L(-1) sodium sulfite, pH 6.5 (adjusted with sodium hydrogen phosphate-dihydrogen phosphate buffer solution, 5.0 x 10(-2) mol L(-1). The delay time, gate time, and time between flashes were 70 micros, 400 micros, and 5 ms, respectively. The maximum phosphorescence signal appeared instantly and the intensity was measured at lambda(ex)=287 nm and lambda(em)=525 nm. The response obtained was linearly dependent on concentration in the range 50 to 600 ng mL(-1). The detection limit, according to error-propagation theory, was 7.93 ng mL(-1) and the detection limit as proposed by Clayton was 11.12 ng mL(-1). The repeatability was studied by using ten solutions of 400 ng mL(-1) naftopidil; if the theory of error propagation is assumed the relative error is 0.88%. The standard deviation of replicates was found to be 3.5 ng mL(-1). This method was successfully applied to the analysis of naftopidil in human serum and urine with recoveries of 104.0 +/- 0.6% for serum and 106.0 +/- 1.0% for urine.     

Flow injection determination of iron by its catalytic effect on the oxidation of 3,3',5,5'-tetramethylbenzidine by hydrogen peroxide

A flow injection-photometric method has been developed for the determination of iron(II+III). The method is based on the catalytic effect of iron(III) on the hydrogen peroxide oxidation of 3,3',5,5'-tetramethylbenzidine to form a blue compound (lambda(max)=650 nm). In this catalyzed reaction, 1,10-phenanthroline acted as an effective activator. Iron(II) is also determined, being oxidized by hydrogen peroxide. Calibration graphs for iron(II) and iron(III) obtained under the optimized conditions were identical with each other and linear in the range 0.2-200 ng ml(-1) with a detection limit of 0.05 ng ml(-1) iron. The reproducibility was satisfactory with a relative S.D. of 1.0% for ten determinations of 5 ng ml(-1) iron(III). The proposed method was successfully applied to the determination of iron in river and lake water samples and can be determined free iron species.     

Sensitive flow injection colorimetry of nitrite by catalytic coupling of N-phenyl-p-phenylenediamine with N,N-dimethylaniline

A rapid, sensitive and selective flow-injection colorimetry method is proposed for the determination of trace amounts of nitrite. It is based on the nitrite's catalytic effect on the oxidative coupling of N-phenyl-p-phenylenediamine with N,N-dimethylaniline to produce a green dye (lambda(max)=735 nm) in the presence of bromate. The change in absorbances of the dye were monitored in continuos flow mode. Linear calibration curves were obtained for the nitrite concentration range 2.0-100 ng ml(-1). The proposed method had a low detection limit (0.6 ng ml(-1)) and high sample throughput (approximately 30 samples h(-1)). The RSD for 10 and 50 ng ml(-1) nitrite were 2.4 and 1.3% (n=10), respectively. The method has been successfully applied to the determination of nitrite in river water samples.     

Trace determination of zinc in standard alloys, environmental and pharmaceutical samples by fourth derivative spectrophotometry using 1-2-(thiazolylazo)-2-naphthol as reagent and ammonium tetraphenylborate supported on naphthalene as adsorbent

A highly sensitive, selective, economical and rapid method for the trace determination of zinc using fourth derivative spectrophotometry has been proposed with 1-2-(thiazolylazo)-2-naphthol (TAN) as an analytical reagent and ammonium tetraphenylborate (ATPB)-naphthalene as an adsorbent. Zn-TAN is quantitatively retained on ATPB naphthalene in the pH range 6.5-9.5. The calibration plot is linear in the concentration range 0.02-1.4 mug ml(-1) Zn of DMF solution. The sensitivity of the method as determined from the slope of the calibration plot is 2.640 (d(4)A/dlambda(4))/(mug ml(-1)). Nine replicate determinations of 5.0 mug of zinc in 5 ml of DMF give a mean signal height of 2.660 (peak to peak height between lambda(1)=597 nm and lambda(2)=585 nm) with a relative standard deviation of 1.1%. The various conditions have been optimized and the developed method has been used for the determination of zinc in standard alloys, environmental and pharmaceutical samples.     

Flow-injection determination of copper(II) based on its catalysis on the redox reaction of cysteine with iron(III) in the presence of 1,10-phenanthroline

A redox reaction of cysteine with iron(III) proceeds slowly in the presence of 1,10-phenanthroline (phen). However, this reaction is accelerated in the presence of copper(II) as a catalyst, producing an iron(II)-phen complex (lambda(max)=510 nm). A sensitive spectrophotometric flow-injection method is proposed for the determination of copper(II) based on its catalytic action on this redox reaction. The dynamic range was 0.1-10 ng ml(-1) of copper(II) with a relative standard deviation of 1.0% (n=10) for 1.0 ng ml(-1) of copper(II) at a sampling rate of 30 h(-1). The detection limit (S/N=3) is 0.04 ng ml(-1). The proposed method was successfully applied to the determination of copper in river water as a certified reference material.     

Reverse flow-injection manifold for spectrofluorimetric determination of aluminum in drinking water

A simple reverse flow-injection (rFIA) manifold for the direct determination of aluminum in drinking water is proposed. This rapid and sensitive method is based on the formation of an Al(3+) complex with salicylaldehyde picolinoylhydrazone (SAPH), which shows a maximum blue-green fluorescence (lambda(ex)=384 nm, lambda(em)= 468 nm) at pH 5.4. Operative conditions both for batch and rFIA procedures were investigated including reagent concentration, buffer solutions, injection loop, reacting coil and wavelengths used for the fluorimetric detection. The tolerance limits of foreign ions have been also evaluated, before and after the addition of masking agents. The reverse flow-injection procedure allows determination of Al(3+) at ppb level (LOD: 1.9 mug l(-1)) within a working range of 5-30 mug l(-1). The proposed method was successfully employed for the determination of Al(3+) in several commercial drinking, soft drinking (as certified reference material), and tap water samples.     

Deprotonation and dimerization of maleimide in the triplet state: a laser flash photolysis study with optical and conductometric detection

The photochemistry of maleimide in aqueous solution is governed by the coexistence of up to three different triplet states, the keto triplet (lambda(max)=250, 330 nm, lambda(min)=290 nm, pK(a)=4.4+/-0.1, tau=5 micros), the deprotonated or enolate triplet (lambda(max)=360, 260 nm, lambda(min)=320 nm, shoulder at 370-380 nm) and a dimer triplet. This biradical is formed by the addition of the keto triplet to the double bond of a ground state maleimide in competition with electron transfer, (k( (3)MI+MI)=2.6 x 10(9) dm(3) mol(-1) s(-1)). Its spectrum is identical to that of the maleimide H-adduct radical (lambda(max)=370-380 (broad), 255 nm (narrow), lambda(min)=290 nm) and its lifetime is 110 ns. While protolysis is confined to maleimide and aqueous solutions, the dimer triplet is also found in acetonitrile. Dimer triplet formation is also observed with N-ethylmaleimide. Time-resolved conductometry and buffer experiments were used to characterise excited state protolysis. Multi-wavelength "global analysis" of the time profiles allowed the separation of the transient spectra and study of the kinetics of the monomer and dimer triplets. The cyclobutane dimer yield (determined by GC) is independent of maleimide concentration. This indicates that the dimer triplet does not contribute significantly to the initiation of free-radical polymerisation. Time-dependent Hartree-Fock calculations agree with the experimental data and further confirm the proposed mechanisms.     

Simultaneous stereoselective analysis of tramadol and its primary phase I metabolites in plasma by liquid chromatography. Application to a pharmacokinetic study in humans

This paper describes a bioanalytical method involving a simple liquid-liquid extraction for the simultaneous HPLC determination of the enantiomers of tramadol, the active metabolite O-desmethyltramadol (M1), and the other main metabolite N-desmethyltramadol (M2) in biological samples. Chromatography was performed at 5 degrees C on a Chiracel OD-R column containing cellulose tris(3,5-dimethylphenylcarbamate) as chiral selector, preceded by a achiral end-capped C8 column (LiChrospher 60-RP-selected B 5 microm, 250 mm x 4 mm). The mobile phase was a mixture of phosphate buffer containing sodium perchlorate (1 M) adjusted to pH 2.5-acetonitrile-N,N-dimethyloctylamine (74.8:25:0.2). The flow rate was 0.5 ml/min. Fluorescence detection (lambda(ex) 200 nm/lambda(em) 301 nm) was used. Fluconazol was selected as internal standard. The limit of quantitation of each enantiomer of tramadol and their metabolites was 0.5 ng/ml (sample size = 0.5 ml). The chiral conditions and the LC optimisation were investigated in order to select the most appropriate operating conditions. The method developed has also been validated. Mean recoveries above of 95% for each enantiomer were obtained. Calibration curves for tramadol enantiomers (range 1-500 ng/ml), M1 enantiomers (range 0.5-100 ng/ml), and M2 enantiomers (range 0.5-250 ng/ml) were linear with coefficients of correlation better than 0.996. Within-day variation determined on four different concentrations showed acceptable values. The relative standard deviation (R.S.D.) was determined to be less than 10%. This method was successfully used to investigate plasma concentration of enantiomers of tramadol, O-desmethyltramadol and N-desmethyltramadol in a pharmacokinetic study.     

High-performance liquid chromatographic assay of pirlimycin in human serum and urine using 9-fluorenylmethylchloroformate

A reversed-phase high-performance liquid chromatographic (HPLC) assay method has been developed for determining pirlimycin in human serum and urine. The method involves chloroform extraction of pirlimycin free base followed by derivatization with 9-fluorenylmethylchloroformate to form a carbamate ester. The reaction is rapid, reproducible, and quantitative. 9-Fluorenylmethylchloroformate reacts with amines to form derivatives sensitive to both ultraviolet and fluorescence detection. Human serum and urine samples following 50-mg and 500-mg single oral doses of pirlimycin were analyzed. The samples were chromatographed on an RP-18 Spherisorb 5-micron, 250 X 4.6 mm I.D. reversed-phase HPLC column. The eluent for the serum assay was acetonitrile-water (58:42) containing 0.02% acetic acid, and for the urine assay was acetonitrile-methanol-tetrahydrofuran-water (48:2:1:49). Fluoranthene was used as an internal standard. The assay sensitivity by ultraviolet detection (lambda max = 264) was about 5 ng/ml and by fluorescence detection (lambda excitation = 270 nm, lambda emission = 300 nm) was 0.1 ng/ml. Statistical analysis indicates an average drug recovery of 101 +/- 4.2% from serum and 102.0 +/- 2.62% from urine.     

Simultaneous determination of ethanol and glycerol in wines by a flow injection-pervaporation approach with in parallel photometric and fluorimetric detection

A simultaneous method for the determination of ethanol and glycerol in wines based on the coupling of pervaporation-chemical derivatisation-photometric detection for ethanol and biochemical derivatisation-fluorimetric detection for glycerol is proposed. After separation by pervaporation the ethanol is collected in a K(2)Cr(2)O(7) acceptor stream and the Cr(3+) formed is driven to the spectrophotometer and monitored at 600 nm. The determination of glycerol is based on its oxidation by oxidised beta-nicotinamide adenine dinucleotide (beta-NAD(+)) catalysed by glycerol dehydrogenase immobilised on controlled-pore glass, the reduced form of the coenzyme (NADH) being spectrofluorimetrically monitored (lambda(ex)=340 nm, lambda(em)=460 nm). The linear determination range is between 1-20% for ethanol and 2-8 g l(-1) for glycerol, with RSDs 3 and 2%, respectively. The method applied to red and white Spanish wines, compares well with the official methods for these analytes.     

Simultaneous determination of gallium and indium with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol in cationic micellar medium using derivative spectrophotometry.

A new derivative spectrophotometric method for rapid and selective trace analysis of Ga3+ and In3+ and for their simultaneous determination using 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol in a cationic micellar medium is reported. Molar absorptivity and Sandell's sensitivity of 1:1 Ga+ and In3+ complexes at their lambda(max) 553 nm and 558 nm are: 7.22 x 10(4) l mol(-1) cm(-1) and 5.85 x 10(4) l mol(-1) cm(-1), and 0.96 ng cm(-2) and 1.96 ng cm(-2), respectively. Linearity is observed in the concentration range 0.023-0.700 microg ml(-1) for gallium and 0.076-1.52 microg ml(-1) for indium; IUPAC detection limit is 0.012 and 0.035 ng ml(-1), respectively. These metal ions interfere with the determination of each other. However, 0.07-0.70 microg ml(-1) Ga3+ and 0.115-1.150 microg ml(-1) In3+ could be determined simultaneously when present together by the derivative method without any prior separation. The proposed procedures have been successfully applied for the individual and simultaneous determination of gallium and indium in synthetic binary mixtures, standard reference materials and environmental samples.     

Synthesis of a novel fluorescent probe and investigation on its interaction with nucleic acid and analytical application

A novel fluorescent probe N-(N-(2-(4-morpholinyl)ethyl)-4-acridinecarboxamide)-alpha-alanine (N-(N-(ME)-4-ACA)-alpha-ALA) was synthesized. The structure was characterized by 1H NMR, MS, elemental analysis, fluorescent and ultraviolet spectra. This new compound exhibited high binding affinity to DNA, intense fluorescence and high water solubility. Experiment indicated that the fluorescent intensity was quenched when DNA was added. A method for DNA determination based on the quenching fluorescence (lambda(ex)=258nm, lambda(em)=451nm) of N-(N-(ME)-4-ACA)-alpha-ALA was established. Under optimal conditions (pH 7.2, CN-(N-(ME)-4-ACA)-alpha-ALA)=3 x 10(-6) mol L(-1)), the linear range is 0.1-4.0 microg mL(-1) for both fish semen (fsDNA) and calf thymus DNA (ct-DNA). The corresponding determination limits are 4.6 ng mL(-1) for fsDNA and 5.1 ng mL(-1) for ct-DNA, respectively. The relative standard deviation is 1.0%. Thus this compound can be used as a DNA fluorescent probe. The experiments proved that the interaction mode between N-(N-(ME)-4-ACA)-alpha-ALA and DNA was groove binding. The modified Rosenthal's graphical method gave the binding constant of 1.0 x 10(6) L mol(-1) and a binding size of 0.31 base pairs per bound drug molecule.     

Kinetic spectrofluorimetric determination of silver, based on its catalytic effect on the oxidation of pyrocatechol-1-aldehyde 2-pyridylhydrazone by peroxodisulphate in the presence of 1,10-phenanthroline as activator

A kinetic fluorimetric method for the determination of silver is described, based on its catalytic effect on the oxidation of pyrocatechol-1-aldehyde 2-pyridylhydrazone by peroxodisulphate. In aqueous solution silver concentrations of 0.2-0.8 mug ml can be determined, and 10-80 ng ml in the presence of 1,10-phenanthroline as activator. The fluorescent species obtained (lambda(ex) 357 nm, lambda(em) 445 nm) results from oxidation of the reagent. The kinetic parameters and the interferences are reported, and the method is applied to the determination of silver in developed panchromatic plates.     

Simultaneous determination of aluminium and beryllium by first-derivative synchronous solid-phase spectrofluorimetry

A method for the simultaneous determination of aluminium and beryllium in mixtures by first-deravative synchronous solid-phase spectrofluorimetry has been developed. Aluminium and beryllium reacted with morin to give fluorescent complexes, which were fixed on a dextran-type resin. The fluoresnce of the resin, packed in a 1-mm silica cell, was measured directly with a solid-surface attachment. The constant wavelength difference chosen to optimize the determination was Deltalambda = lambda(em) = 75 nm. Aluminium was measured at lambda(em)lambda = 445/520 nm and beryllium at lambda(em)lambda(em) = 430/505 nm. The range of application is between 0.5 and 5.0 ng/ml for both aluminium and beryllium. The accuracy and precision of the method are reported. The method has been successfully applied to the determination of aluminium and beryllium in synthetic mixtures and natural waters.     

Determination of urea using high-performance liquid chromatography with fluorescence detection after automated derivatisation with xanthydrol

A high-performance liquid chromatography (HPLC) method for the determination of urea that incorporates automated derivatisation with xanthydrol (9H-xanthen-9-ol) is described. Unlike the classic xanthydrol approach for the determination of urea, which involves the precipitation of dixanthylurea (N,N'-di-9H-xanthen-9-ylurea), the derivatisation procedure employed in this method produces N-9H-xanthen-9-ylurea, which remains in solution and can be quantified using fluorescence detection (lambda(ex)=213 nm; lambda(em)=308 nm) after chromatographic separation from interferences. The limit of detection for urea was 5 x 10(-8) M (0.003 mg L(-1)). This method was applied to the determination of urea in human and animal urine and in wine.     

Frequency doubling scattering and second-order scattering spectra of phosphato-molybdate heteropoly acid-protein system and their analytical application

In the sulfuric acid medium, the reaction of heteropoly compounds with proteins could result in the enhancement of frequency doubling scattering (FDS) and second-order scattering (SOS). Based on the characteristic, a novel method for the determination of trace amounts of protein by using the FDS and SOS method has been developed. Their maximum scattering wavelengths, lambda(ex)/lambda(em), appear at 940/470 nm for FDS and 350/700 nm for SOS, respectively. In a certain range, the concentration of proteins is directly proportional to the enhanced intensity of FDS and SOS. The suitable reaction conditions, affecting factors as well as the influence of some coexisiting substances were investigated. The methods exhibited high sensitivity, and the detection limits were in the range of 8.6-39.3 ng ml(-1) depending on different methods. The method had good selectivity, and was applied to the determination of protein in synthetic samples and practical samples with satisfactory results.