Analysis of trace levels of sulfonamides in surface water and soil samples by liquid chromatography-fluorescence.

Methods are reported for determining six sulfonamides used as veterinary drugs in water and soil samples. Analytes are isolated from water samples by solid-phase extraction on HBL cartridges and pre-concentration factors of up to 250 were obtained. Soil samples are treated using microwave-assisted extraction of analytes with acetonitrile and further clean up by solid-phase extraction. Determination is carried out by high-performance liquid chromatography using fluorimetric detection with precolumn derivatization with fluorescamine. The separation of the derivatized sulfonamides is performed on an octadecyl column using binary gradient elution with acetate buffer/acetonitrile mixtures. For water analysis, the detection limits of the whole process are in the low nanogram per liter level and recovery rates range from 70 to 104%, with standard deviations 2-11%. For soil analysis, extraction efficiency is evaluated using three soil samples with different physicochemical characteristics. Recovery rates range from 60 to 98% and detection limits are between 1 and 6ngg(-1).

Validation of a method for the analysis of quinolones residues in bovine muscle by liquid chromatography with electrospray ionisation tandem mass spectrometry detection.

A liquid chromatography-tandem mass spectrometry method for the determination and confirmation of nine quinolones was optimised and validated according to Commission Decision 2002/657/EC. Analytes were extracted from veal muscle with water and extracts purified with 96-well plates Oasis HLB cartridges. Separation was carried out in a silica-based C(18) column (50mmx2.1mm) with mobile phases consisting of water/acetonitrile mixtures containing acetic acid. Linear calibration curves in the ranges 4-400 and 50-800ngg(-1), with correlation coefficients at least 0.995, were obtained for all the analytes. At concentration levels above 10ngg(-1), quantification errors were lower than 10% and repeatability and within-laboratory reproducibility standard deviations below 6% and 10%, respectively. Decision limits and detection capabilities are reported.

Determination of quinolones in water samples by solid-phase extraction and liquid chromatography with fluorimetric detection.

A method is reported for the determination, in water samples, of 10 quinolones which are used as veterinary drugs. Analytes are isolated from samples by solid-phase extraction (SPE) and analysed by reversed-phase high-performance liquid chromatography using fluorimetric detection. A solid-phase extraction procedure based on retention on HBL OASIS cartridges and elution with a mixture of acetonitrile-water in basic medium is suitable for pre-concentration of the analytes. Pre-concentration factors up to 250 can be obtained. The quinolones are separated with an octyl silica-based column and mobile phases consisting of aqueous oxalic acid solutions and acetonitrile mixtures. The attained detection limits of the whole process are in the ng l(-1) level when 250 ml of water sample is processed. Recovery rates, from natural water samples spiked at 2060 ng l(-1) level, range from 70 to 100% and common standard deviation are about 6-12%.

Analysis of quinolone residues in edible animal products.

A comprehensive review on the analysis of quinolone antibacterials is presented. The review covers most of the methods described for the determination of quinolone residues in edible animal products. Sample handling, chromatographic conditions and detection methods have been discussed. A summary of the most relevant information about the analytical procedures has been included.

Fast-scanning fluorescence spectroscopy as a detection system in liquid chromatography for confirmatory analysis of flumequine and oxolinic acid.

Oxolinic acid and flumequine were analysed by reversed-phase liquid chromatography after extraction from the sample matrix with dichloromethane and partitioning with NaOH. The detection system consisted of a fast-scanning fluorescence detector, which provides the full spectra of the eluting peaks and can thus be used to confirm the identity of analytes. Determination was performed by partial least squares (PLS) and three-way PLS over the three-dimensional data, i.e. fluorescence intensity versus retention time and excitation wavelength. In both cases, similar results, with prediction errors around 4%, were obtained. The method was successfully applied to the analysis of salmon, pork and chicken muscle spiked up to 300 ng g(-1).

Determination of macrolide antibiotics by liquid chromatography.

The liquid chromatographic separation of seven macrolides used in food producing animals in the European Union has been studied. Separation was performed by using an end-capped high-purity silica-based C18 column and mobile phases consisting of phosphate buffer (pH 2.5)-acetonitrile mixtures. The effect of pH and acetonitrile percentage on the separation was examined. Two UV-based detection systems, wavelength programming and diode array, were assayed. Detection limits were in the range 6-33 microg l(-1) for spiramycin, tilmicosin, tylosin, kitasamicin and josamicin and about 400 microg l(-1) for erythromycin and oleandomycin. The suitability of the method for multiresidue determination of the five macrolides is demonstrated by the analysis of spiked samples of chicken muscle.

Application of principal component regression to luminescence data for the screening of ciprofloxacin and enrofloxacin in animal tissues.

A new screening method for the analysis of enrofloxacin and ciprofloxacin in edible animal tissues is described. The method is based on the application of principal component regression to luminescence measurements after reaction of quinolones with terbium(III) in a micellar medium. The method was used, first, to discriminate between quinolone-containing or quinolone-not-containing samples (concentration below the detection limit) and, then, to quantify the sum of both analytes. Standards in a pure-water matrix, using the first three principal components, were used for the determination. RRMSE range from 4 to 10% depending on the analyte. Calibration was successfully applied to the analysis of spiked chicken and trout muscle at concentrations between 10 and 50 micrograms kg-1.

Determination of butyltin and phenyltin species by reversed-phase liquid chromatography and fluorimetric detection.

Chromatographic separation of monobutyltin (MBT), monophenyltin (MPhT), dibutyltin (DBT), diphenyltin (DPhT), tributyltin (TBT) and triphenyltin (TPhT) was studied using end-capped reversed-phases (RP) and methanol-acetic acid-water or acetronitrile-acetic acid-water mixtures as mobile phases. Several RP columns were evaluated, and the effect of acetic acid, oxalic acid, triethylamine, and organic modifier on peak shape and retention was examined. A method based on gradient elution RPLC and fluorimetric detection is proposed for the determination of DBT, DPhT, TBT and TPhT. The sensitivity of the method makes it suitable for environmental analysis.

Liquid chromatography with fluorimetric detection of triorganotin compounds in marine biological materials.

Several extraction methods have been evaluated for marine biological materials with regard to tributyltin and triphenyltin determination by liquid chromatography with post-column fluorimetric detection using fisetin as a fluorogenic reagent. Extraction with ethyl acetate in a hydrochloric acid medium has been shown to be the most appropriate extraction method and it has been successfully applied to fish (sea bass) reference material from the National Institute for Environmental Studies (NIES-11) and to a candidate reference material.

Determination of ciprofloxacin and enrofloxacin in edible animal tissues by terbium-sensitized luminescence.

A terbium-sensitized luminescence method is described for the determination of the sum of residues of enrofloxacin and its major metabolite ciprofloxacin in edible animal tissues. Several parameters affecting both detection and extraction were studied. Analytes were extracted from spiked samples of chicken and trout tissues with pH 7.4 buffer-dichloromethane. The organic extract was evaporated and the residue dissolved in aqueous nitric acid and defatted with hexane. Determination was carried out directly in the aqueous phase (in a micellar medium). The calibration curves were linear up to 75 micrograms l-1. The detection limit was 3.5 micrograms kg-1 (for a 5 g sample) and the repeatability was 7.0% (n = 7). The sensitivity was similar for both quinolones and therefore calibration can be carried out with either ciprofloxacin or enrofloxacin. In any case, the differences were < 10%.

Analytical procedures for the determination of organotin compounds in sediment and biota: a critical review.

Analytical procedures reported over the last 10 years for the determination of organotin compounds in sediment and biota have been critically reviewed in terms of sample handling, sensitivity, analytical cost, environmental acceptance, accuracy and precision. Critical steps in the analytical procedures are identified. Finally, research needs in extraction and determination are suggested.

Labelling of organotin compounds for fluorimetric detection.

A systematic study of the fluorescence of complexes of some flavone derivatives with organotin compounds in hexane and in an aqueous micellar medium on Triton X-100 is reported. Some relationships between fluorescence intensity and the structure of the fluorogenic reagent or that of the organotin compound can be deduced, and the most suitable reagent for each organotin species can be chosen on the basis of sensitivity and selectivity. Results point out that flavone derivatives are appropriate post-column derivatization reagents for organotin compounds in liquid chromatography.

Fluorescence of metal complexes of 8-hydroxyquinoline derivatives in aqueous micellar media.

The fluorescence characteristics of 8-hydroxyquinoline derivative complexes of A1(III), Ga(III), In(III), Zn(II), and Be(II) in differently charged micellar media are reported. For most of the chelates studied, large increases are observed in micellar media compared with those obtained in hydroorganic solvents. However, some exceptions are observed, of which the low fluorescence of Zn(II) chelates in anionic sodium lauryl sulfate media is the most noticeable.

Spectrofluorimetric method for the simultaneous determination of zinc and cadmium.

The simultaneous determination of zinc and cadmium using derivative synchronous and multiwavelength synchronous spectrofluorimetry is described. Effects of experimental variables on the fluorescence intensities and on the spectral resolution of the fluorescent chelates of these metals with 8-(p-toluenesulfonamido)-quinoline (TSQ) in a sodium lauryl sulfate micellar medium have been studied. Mixtures containing 10-200 µg L(-1) Zn and 15-250 µg L(-1) Cd have been analyzed with good results. The proposed method has been applied to a biological sample.

Solvent extraction of lead(II) with N-cyclohexyl-N-nitrosohydroxylamine into methyl isobutyl ketone.

The distribution equilibrium of the lead-cnha complex in the water-methyl isobutyl ketone (MIBK) system has been studied at 25 degrees . From graphical treatment of the equilibrium data, it was deduced that PbL(2) is the complex extracted. By use of the program LETAGROP-DISTR, values for the distribution and the stability constants of PbL(2) have been calculated: log K(DC) = 1.84 +/- 0.11; log beta(1) = 6.68 +/- 0.09 and log beta(2) = 10.28 +/- 0.09. On the basis of these results and those of previous studies, a method for determination of lead(II), copper(II) and cadmium(II) by atomic-absorption spectrometry, after extraction with cnha and 4-methylpyridine into MIBK, is proposed.

Solvent extraction of Cd(II) with N-cyclohexyl-N-nitrosohydroxylamine and 4-methylpyridine into methyl isobutyl ketone.

The distribution equilibria of the complexes cadmium-cnha and cadmium-cnha-4-methylpyridine in the water-methyl isobutyl ketone system have been studied at 25 degrees , by using (109)Cd as a radiotracer to measure the metal distribution ratio. A very sensitive method for detection of (109)Cd, based on the use of a liquid scintillator, has been developed. From the graphical treatment of the equilibrium data, it has been deduced that CdL(2) is the complex extracted in the absence of 4-methylpyridine, and that the adduct CdL(2)B is extracted when the second ligand is present. This model has been checked by treating the data with the program LETAGROP-DISTR and the following equilibrium constants have been obtained: stability constants of CdL(2), log beta(1) = 2.82 +/- 0.14, log beta(2) = 5.981 +/- 0.004; distribution constant of CdL(2), log K(DC) = -0.49 +/- 0.01; adduct formation constant of CdL(2)B, log K(s) = 2.70 +/- 0.07.

Solvent extraction of zinc with 5,7-dichloro-2-methyl-8-hydroxyquinoline into chloroform.

The distribution equilibria of the zinc complex with 5,7-dichloro-2-methyl-8-hydroxyquinoline in the water-chloroform system have been studied at 25 degrees . The influence of pH, reagent and metal concentrations, and the presence of sodium perchlorate in the aqueous phase has been determined. From quantitative evaluation of the extraction equilibrium data, it has been deduced that the complex extracted is the simple 1:2 chelate, ZnR(2), although at ligand concentrations higher than 0.3M, the self-adduct complex seems to begin to form. The extraction constant of the ZnR(2) species, refined by means of the program Letagrop-Distribution, has the value log K(ex) = - 6.15 +/- 0.07.