A rapid method for the determination of lasalocid in animal tissues and eggs by high performance liquid chromatography with fluorescence detection and confirmation by LC-MS-MS

A simple and rapid method has been developed for the extraction of lasalocid from chicken muscle, eggs and liver and kidney from chicken, pig, sheep and calf. This method allows the screening of a large number of samples, i.e. 30-40 within a working day, and has an overall analysis time of 90 min. Lasalocid standard solution can be detected at 1 ng ml-1 by both HPLC-fluorescence (HPLC-F) and LC-MS-MS; the limit of quantification in fortified samples by the described method is 1 ng g-1. Results show good repeatability and mean 'spiked' recoveries by HPLC-F in the range of 10 to 200 ng g-1 (ppb) of 103, 87, 107, 97, 97, 103, 93, 109 and 100% in chicken muscle, chicken liver, egg, pig liver, pig kidney, sheep liver, sheep kidney, calf liver and calf kidney, respectively. For concentrations between 1 and 6 ng g-1 of spiked lasalocid in eggs and chicken liver by LC-MS-MS, the average recoveries were 76 and 59%, respectively.     

The determination of DNA based on light-scattering of a complex formed with histone

The interaction of histone with nucleic acids was characterized by light-scattering measurement using a common spectrofluorometer. Thereby, a sensitive and convenient method for the determination of nucleic acids was established. At pH 4.5-6.5, the interaction of histone with nucleic acids resulted in considerable light-scattering , and four characteristic peaks at 298, 450, 503, and 551 nm were observed. The light-scattering was applied to the determination of nucleic acids. The experiments indicated that, under optimal conditions, a linear relationship was obtained between the light-scattering intensity (I(LS)) and the concentration of nucleic acids. The linear ranges were 0.02-2.0 mug ml(-1) for fish sperm DNA (fsDNA), 0.05-1.5 mug ml(-1) for calf thymus DNA (ctDNA), 0.05-2.5 mug ml(-1) for Herring testis DNA (HtDNA), and 0.05-1.5 mug ml(-1) for human placenta DNA (hpDNA). The detection limits were 2.0 ng for fish sperm DNA, 2.0 ng for calf thymus DNA, 5.0 ng for Herring testis DNA, and 3.0 ng for human placenta DNA. The nucleic acids in yeast cell extraction were determined by simple vortex extraction. The results were satisfactory, and the recovery rates were in the range of 88-108%.     

Use of time-resolved lanthanide-sensitized luminescence for the kinetic determination of p-aminobenzoic acid

Lanthanide-sensitized luminescence was for the first time used to develop a simple kinetic method for the determination of p-aminobenzoic acid. The method is based on the formation of a complex with terbium(III) in the presence of trioctylphosphine oxide as synergistic agent and Triton X-100 as micellar medium. The high initial rate of the complex formation required the use of stopped-flow mixing technique in order to make kinetic measurements which, in addition, allows the method to be automated. Its analytical features compare very favourably with those described by using solid-surface room temperature phosphorescence in terms of rapidity, precision and selectivity. The initial rate is obtained within only 0.2 s after the reactants are mixed, which allows ready application of the proposed method to routine analyses. The calibration graph is linear over the range 0.08-4.0 mug ml(-1)p-aminobenzoic acid and the detection limit is 0.02 mug ml(-1). The relative standard deviation is close to 2%. The kinetic methodology avoids the effect of the sample matrix allowing the direct determination of this compound in pharmaceutical preparations. Analytical recoveries ranged between 98.6 and 113.0%.     

Determination for micro amounts of nucleic acids by a resonance light scattering technique with dequalinium chloride

Based on the strong enhancement effect of nucleic acids on resonance light scattering of dequalinium chloride, the determination method for micro amounts of nucleic acids has been developed. Under the experimental conditions (5.0x10(-5) mol l(-1) dequalinium, pH 7.0, at room temperature) the linear range of this assay is 0.04-10.0 mug ml(-1) for calf thymus DNA and fish sperm DNA, and 0.04-35.0 mug ml(-1) for yeast RNA. The detection limits (3sigma) are 6.2 ng ml(-1) for calf thymus DNA, 7.4 ng ml(-1) for fish sperm DNA, and 7.0 ng ml(-1) for yeast RNA, respectively. Almost no interference can be observed from ionic strength, proteins, nucleoside, and most of the metal ions. Six synthetic samples were determined satisfactorily.     

A simple and rapid fluorimetric method for the microdetermination of isonicotinic acid hydrazide

A simple, rapid and sensitive fluorimetric method has been developed for the microdetermination of isonicotinic acid hydrazide, based on its formation of a hydrazone with 2-hydroxy-1-naphthaldehyde in acidic medium, in the presence of excess of scandium ions, and the consequent formation of a strongly fluorescent complex (lambda(ex) 430 nm, lambda(em) 510 nm) between the hydrazone and scandium in weakly acidic medium. Kinetic and equilibrium procedures for isonicotinic acid hydrazide determination are proposed. A calibration graph linear up to 5.00 mug/ml is obtained by both procedures, with a mean relative error of about 2.0%. The detection limit for the kinetic procedure is 0.4 ng/ml and for the equilibrium procedure about 0.2 ng/ml.     

The determination of 5 anticoccidial drugs (nicarbazin,lasalocid, monensin,salinomycin and narasin) in animal livers and eggs by liquid chromatography linked with tandem mass spectrometry (LC-MS-MS)

A method has been developed for the simultaneous extraction and determination of five of the most commonly used anticoccidial drugs (nicarbazin, lasalocid, monensin, narasin and salinomycin) from livers and eggs by LC-MS-MS. Results show good repeatability, with mean spiked recoveries for nicarbazin, lasalocid, monensin, narasin and salinomycin in poultry livers in the average range of 92-118%, and 86-110% in eggs. The detection limit is at 1 ng ml(-1) for all the named compounds and a quantitation level of 2.5 ng g(-1) has been achieved. A high throughput of samples is achievable using this method which allows the analysis of up to 40 samples by one analyst in a day.     

Spectrophotometric determination of aluminium by morin

A direct spectrophotometric method for the determination of aluminium with morin has been developed. Morin reacts in slightly acidic 50% ethanolic media (0.0001-0.0015 M H(2)SO(4)) with Al to give a deep-yellow chelate which has an absorption maximum at 421 nm. The average molar absorptivity and Sandell's sensitivity were found to be 5.3 x 10(3) l mol(-1) cm(-1) and 5 ng of Al cm(-2), respectively. The reaction is instantaneous and absorbance remains stable for 48 h. The colour system obeys Beer's law from 10 ng ml(-1) to 5.0 mug ml(-1) of Al; the stoichiometric composition of the chelate is 2:3 (Al:morin). The interference from over 50 cations, anions and complexing agents has been studied at 0.1 mug ml(-1) of Al. The method was applied successfully to some certified reference material samples (alloys and steels), environmental waters (inland and surface), biological samples (human blood, urine and gallstone), soils and complex synthetic mixtures.     

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.     

Water-soluble polymers for spectrophotometric and flow injection determination of cobalt with nitroso-R-salt

The water-soluble polymers poly(ethylenimine), quaternized poly(ethylenimine), and poly-4-vinyl-(N-benzyltrimethyl) ammonium chloride were found to be able to change the kinetics of the reaction of cobalt with nitroso-R-salt and the optical density of the cobalt complex formed. The optimum pH range for the complex formation was a wide range from 1 to 10 and at pH 2 the reaction developed instantly. The calibration graph was linear in the range 0.005-2 mug ml(-1). The effective molar absorptivity coefficient of the complex was equal to (2.8+/-0.08)10(3). A spectrophotometric determination method for cobalt with nitroso-R-salt in the presence of water-soluble polymers (before and after membrane preconcentration) and a colorimetric flow injection method were developed. For the flow injection-based spectrophotometric determination, the calibration graph was linear in the concentration range of 0-4.0 mug ml(-1) cobalt with a regression coefficient of 0.9992. The relative standard deviation (R.S.D.) for the determination of 1.0 mug ml(-1) cobalt was 0.9% (ten replicate injections), and at all concentration measured, the R.S.D. of the data was below 5.0%. The proposed FI procedure was applied to river water samples after membrane preconcentration of cobalt. The limit of detection was 4 ng ml(-1).     

Spectrophotometric multicomponent determination of sunset yellow, tartrazine and allura red in soft drink powder by double divisor-ratio spectra derivative, inverse least-squares and principal component regression methods

Double divisor-ratio spectra derivative (graphical method), classical least-squares and principal component regression (two numerical methods) methods were developed for the spectrophotometric multicomponent analysis of soft drink powders and synthetic mixtures containing three colorants without any chemical separation. The graphical method is based on the use of derivative signals of the ratio spectra using double divisor. In this method, the linear determination ranges were 2-8 mug ml(-1) sunset yellow, 4-18 mug ml(-1) tartrazine and 2-8 mug ml(-1) allura red in 0.1 M HCl. In the numerical methods, a training set was randomly prepared by using 18 samples containing between 0 and 8 mug ml(-1) of sunset yellow, 0-18 mug ml(-1) of tartrazine and 0-8 mug ml(-1) of allura red. The chemometric calibrations were calculated by using the prepared training set and its absorbances at seven points (from 375.0 to 550.0 nm) in the spectral region 325-584 nm. The proposed methods were validated by using synthetic ternary mixtures and applied to the simultaneous determination of three colorants in soft drink powders. The obtained results were statistically compared with each other.     

Flow injection fluorimetric determination of thiamine and copper based on the formation of thiochrome

The reaction, involving the oxidation of thiamine by copper(II) in basic solutions to fluorescent thiochrome, has been adapted to the determination of thiamine by flow-injection analysis. Linear calibration graphs are obtained between 0.30 and 6.02 mug/ml with a sampling rate of 50 samples/hr and a relative standard deviation of 0.53%. This reaction has also been adapted to the determination of copper(II) over the range 0.5-5.0 mug/ml. The applicability of both methods for determination of thiamine and copper is demonstrated by investigating the effect of potential interferences and by the analysis of real samples (pharmaceuticals for thiamine and ores and alloys for copper).     

Cloud point extraction of vanadium in parenteral solutions using a nonionic surfactant (PONPE 5.0) and determination by flow injection-inductively coupled plasma optical emission spectrometry

A preconcentration and determination methodology for vanadium at trace levels in parenteral solutions was developed. Cloud point extraction was successfully employed for the preconcentration of vanadium prior to inductively coupled plasma atomic optical emission spectrometry (ICP-OES) coupled to a flow injection (FI) system. The vanadium was extracted as vanadium-2-(5-bromo-2-pyridylazo)-5-diethylaminophenol [V-(5-Br-PADAP)] complex, at pH 3.7 mediated by micelles of the nonionic surfactant polyoxyethylene (5.0) nonylphenol (PONPE 5.0). The extracted surfactant-rich phase (100 mul) was mixed with 100 mul of ethanol and this final volume injected into ICP-OES for the vanadium determination. Under these conditions, the 50 ml sample solution preconcentration allowed raising an enrichment factor of 250-fold; however, it was possible to obtain a theoretical enrichment factor of 500-fold. The lower limit of detection (LOD) obtained under the optimal conditions was 16 ng l(-1). The precision for 10 replicate determinations at the 2.0 mug l(-1) V level was 2.3% relative standard deviation (RSD), calculated with the peak heights. The calibration graph using the preconcentration system for vanadium was linear with a correlation coefficient of 0.9996 at levels near the detection limits up to at least 50 mug l(-1). The method was successfully applied to the determination of vanadium in parenteral solution samples.     

Flow injection spectrophotometric determination of trace amounts of selenium

A simple, rapid and sensitive flow injection spectrophotometric method for determination of selenium (0.005-1.5 mug ml(-1)) is described. The method is based on the catalytic effect of Se(IV) on the reduction reaction of thionine (TN) with sulphide ion, monitored spectrophotometrically at 598 nm. The detection limit is 5 ng ml(-1) the relative standard deviation for eight replicate measurements is 1.1% for 1 mug ml(-1) of selenium. The sampling rate is 25-30 samples h(-1). The procedure was applied successfully to the determination of selenium in real samples.     

Determination of trace europium based on new fluorimetric system of europium(III) with thenoyltrifluoroacetone and N,N'-dinaphthyl-N,N'-diphenyl-3,6-dioxaoctanediamide

In the present paper, N,N'-dinaphthyl-N,N'-diphenyl-3,6-dioxaoctanediamide acts as a specific reagent for enhancing the fluorescence intensity of Eu(III) complex with thenoyl trifluoroacetone (TTA), the spectrofluorimetric determination of trace amounts of Eu(III) based on the above system was carried out and its luminescence mechanism was studied. The excitation and emission wavelengths are 343.6 and 613.3 nm, respectively. The fluorescence intensities vary linearly with the concentration of europium(III) in the range 3.647x10(-3)-3.039 mug ml(-1) for the original fluorescence with a detection limit down to 2.279x10(-4) mug ml(-1) and the standard deviation is 0.063 mug ml(-1) for 10 times measurements, and in the range 7.598x10(-4)-0.0243 mug ml(-1) (SD=0.035 for 15 times measurements), 0.06078-0.6100 mug ml(-1) (SD=0.52 for 10 times measurements) for the first derivative fluorescence signal with a detection limit down to 8.566x10(-5) mug ml(-1). The interferences of other rare earths and some of inorganic ions are described. This method is a direct, rapid, selective and sensitive analytical method for the determination of trivalent europium in rare earth ore samples and high purity of rare earth oxides.     

Column-switching high-performance liquid chromatographic analysis of carbamazepine and its principal metabolite in human plasma with direct sample injection using an alkyl-diol silica (ADS) precolumn

In this paper, the on-line coupling of solid-phase extraction, based on a restricted-access support with high-performance reverse phase chromatography for the analysis of carbamazepine (CBZ) and carbamazepine-10,11-epoxide (CBZ-E) in human plasma samples is described. A precolumn packed with 25 mum C(18) alkyl-diol support is used for direct plasma injection. Using column-switching techniques, the analytes were enriched on the precolumn by a 5 mM phosphate buffer (pH 7) with 2% of methanol solution at a flow-rate of 0.8 ml min(-1), while proteins and endogenous hydrophilic substances in plasma were washed off to waste. The enriched analytes were then back-flushed onto the analytical C(18) column, separated by a mixture of 10 mM phosphate buffer (pH 7) acetonitrile (70:30 v/v) solution at a flow-rate of 1.0 ml min(-1) and detected by the ultraviolet absorbance set at 212 and 285 nm and without transfer loss. Linear calibration graphs were obtained for sample injection volumes of 50 (0.2-4.0 of mug of CBZ ml(-1) and 0.1-5.0 mug of CBZ-E ml(-1), respectively), and 20 mul (5.0-20.0 mug of CBZ ml(-1)); in either case the r-value was >0.9963. Recoveries from spiked plasma samples were quantitative for both analytes and the coefficients of variation were below 3.83%. The lowest samples concentrations that can be quantified with acceptable accuracy and precision was 0.2 mug CBZ ml(-1) and 0.1 mug CBZ-E ml(-1) when a sample volume of 50 mul was injected. Concentrations of 0.08 and 0.05 mug ml(-1) of CBZ and CBZ-E were considered the limit of detection for a signal-to-noise ratio of 3. Furthermore, the developed column-switching method was successfully applied to the determination of CBZ and CBZ-E in plasma samples of patients submitted to CBZ therapy.     

Simultaneous determination of manganese and zinc in mixtures using first- and second-derivative spectrophotometry

A new direct spectrophotometric determination of manganese with 5,8-dihydroxy-1,4-naphthoquinone (naphthazarin,NAZA) is reported. Absorption maximum, molar absorptivity and Sandell's sensitivity of 1:2 (M:L) complex are 695 nm, 1.88x10(4) l mol(-1) cm(-1) and 2.92 ng cm(-2), respectively. A linear calibration graph is obtained up to a concentration of 7.2 mug ml(-1) of manganese. The optimum range for determination (Ringbom) is between 0.20 and 6.8 mug ml(-1). A rapid method for simultaneous determination of manganese and zinc in their mixture using derivative spectra is described. The range 0.28-5.6 mug ml(-1) manganese could be determined in the presence of 0.33-6.8 mug ml(-1) zinc and vice versa. The developed method was applied to the simultaneous spectrophotometric determination of manganese and zinc in some synthetic mixtures and was found to give satisfactory results.     

Simultaneous determination of iron and zinc by pH gradient construction in a flow-injection system

A flow-injection method for the simultaneous determination of iron and zinc in the human hair with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) using a pH gradient technique has been developed. The linear range for the determination of iron is 0.1 approximately 1.8 mug ml(-1) and for zinc is 0.2 approximately 5.0 mug ml(-1). About 20 approximately 30 samples can be determined in 1 h. The proposed method is simple, rapid and accurate. It has been applied to the simultaneous determination of trace amounts of iron and zinc in the human hair with satisfactory results.     

Katalytische bestimmung von silberspuren in wabetariger lösung und nach extraktion

The application of the catalysed oxidation of Bromopyrogallol Red by potassium per- sulphate for silver determination is discussed. In aqueous solution silver concentrations of 0.5- 1 mug/ml can be determined and 1- 13 ng/ml in the presence of 1, 10-phenanthroline as activator. In combination with solvent extraction, catalytic determination of the extracted silver is possible even in presence of 200 mug of iron(III), cobalt(II) and palladium(II). By means of an automatic variant of the simultaneous comparison method a more sensitive determination (0.2-20 ng/ml) was achieved.     

Determination of serum selenium by hydride generation flame atomic absorption spectrometry

Serum is rapidly digested with a mixture of nitric and perchloric acids at a temperature of 180 +/- 10 degrees C, and hydrochloric acid is used to reduce selenium(VI) to selenium(IV). Selenium is determined by hydride generation flame atomic absorption spectrometry. The results show that this method has the advantages of being sensitive, accurate, rapid and simple. After the serum is digested and diluted, 4.0 ml is taken for the determination. The characteristic concentration, detection limit, variation coefficient, recovery rate and linear range are 2.93 mug 1(-1), 1.55 mug l(-1), 1.6-5.0%, 97.3-99.2% and 0.0-320.0 mug l(-1) respectively. Serum at 4 degrees C and in frozen state can be preserved for at least 7 and 14 days, respectively.     

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.