Biomedical subjects

A M Carro

Publications and source records attributed to A M Carro.

13 recordsLinked to original sources

PubMed2006

Multicriteria optimisation of a simultaneous supercritical fluid extraction and clean-up procedure for the determination of persistent organohalogenated pollutants in aquaculture samples.

A useful tool based on a single-step extraction and clean-up procedure for the determination of 15 organohalogenated pollutants (including brominated flame retardants) in aquaculture samples, using aluminium oxide basic and acidic silica gel in the supercritical extraction cell followed by gas chromatography with electron capture detection or mass spectrometry has been developed. This effective clean-up step ensures a minimum of chromatographic difficulties related to complex matrix components such as aquaculture feed. The extraction procedure has been screened by a fractional factorial design for the preliminary statistically significant parameters. The factors selected were extraction temperature, pressure, static extraction time, dynamic extraction time and carbon dioxide flow rate. The Doehlert design, followed by a multicriteria decision-making strategy, was then performed in order to determine the optimum conditions for the two most significant factors: pressure (165 bar) and dynamic extraction time (27 min). Under optimal conditions, the procedure developed with GC-MS/MS provides an excellent linearity, detection (0.01-0.2 ng g(-1)) and quantification limits (0.05-0.8 ng g(-1)) for most of the analytes investigated. The feasibility of the proposed supercritical fluid extraction method was validated by analysing two reference materials and fish feed and shellfish samples with satisfactory results.

Animal Feed↗

PubMed2005

Multi-residue screening of chlorinated and brominated compounds from aquaculture samples using matrix solid-phase dispersion--gas chromatography-mass spectrometry.

An effective multiresidual method for the trace analysis of fifteen compounds from a diverse group of pesticides, polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyl (PCBs) and polybrominated biphenyl (PBBs) in aquaculture feed is described. The analytical procedure is based on the matrix solid-phase dispersion (MSPD) of feed sample and subsequent elution with hexane. The MSPD process was evaluated using an asymmetrical experimental design 2(3)3(2)//9. Factors such as C18 sorbent amount, kind of adsorbents, solvent volume and elution mode were considered. The results suggest that the operational MSPD conditions are elution with pressure, 1 g of C18, basic alumina as adsorbent and 30 mL of hexane. The overall method including MSPD procedure and GC coupled to mass spectrometry (MS/MS) has been applied to several samples of aquaculture feed and marine species. Precision and accuracy of the analytical method were determined using the reference material from the International Atomic Energy Agency (IAEA-406), showing a good agreement to the referenced values.

Aquaculture↗

PubMed2005

Selective extraction of trace levels of polychlorinated and polybrominated contaminants by supercritical fluid-solid-phase microextraction and determination by gas chromatography/mass spectrometry. Application to aquaculture fish feed and cultured marine species.

The persistence, ubiquity, and toxicity of polyhalogenated compounds, together with their presence in fish feed, make it necessary to monitor these organic pollutants in the routine quality assurance programs of aquaculture activities, as this food chain is a source of these toxic compounds for human consumers. A new approach based on simultaneous supercritical fluid extraction-sample cleanup, followed by solid-phase microextraction-gas chromatography/mass spectrometry (SFE-SPME-GC/MS/MS) has been developed as an advantageous analytical tool for the determination of 15 organohalogenated compounds (including pesticides, polychlorinated and polybrominated biphenyls, and polybrominated diphenyl ethers) in aquaculture feed at very low levels. The influence of several parameters in the efficiency of the SPE/SPME combination was systematically investigated by chemometric approaches. In the optimal conditions, the developed procedure provides an excellent linearity, detection, and quantification limits (below 10 pg/g) for most of the analytes investigated, being at the same time advantageous in terms of rapidity, convenience, and avoiding the need of toxic organic solvents. The procedure was applied to the analysis of aquaculture feed and cultured marine species and tested for accuracy against IAEA 406 reference material.

Animal Feed↗

PubMed2004

Strategic sample composition in the screening of polycyclic aromatic hydrocarbons in drinking water samples using liquid chromatography with fluorimetric detection.

The screening of polycyclic aromatic hydrocarbons in water samples by means of the strategic sample composition (SSC) technique is presented. SSC uses special supersaturated composition matrices to perform sample composition and analysed the results obtained in the analytical determination of these composite samples by means of evolutionary assisted regression procedures providing estimations of the concentration levels of analytes in each individual sample specimen. Here, 12 composite samples were prepared by departing from 26 water sample specimens, five of which were spiked with known amounts of several polycyclic aromatic hydrocarbons (PAHs). These composite samples were analysed by HPLC using fluorescence detection. Concentration levels spiked were, in some cases clearly higher than allowed limits for drinking waters, whereas in other cases are just in the limit or even down these limits. The study shows the ability of SSC to detect the really contaminated samples and guiding the analyst in taking the adequate decisions.

Chromatography, High Pressure Liquid↗

PubMed2004

Applicability of solid-phase microextraction followed by on-fiber silylation for the determination of estrogens in water samples by gas chromatography-tandem mass spectrometry.

A solvent-free method for the determination of five estrogens in water samples at the low ng/l was optimized. Compounds were first concentrated on a polyacrylate (PA) solid-phase microextraction (SPME) fiber, directly exposed to the water sample, and then on-fiber silylated on the headspace of a vial containing 50 microl of N-methyl-N-(trimethylsilyl) trifluoroacetamide (MSTFA). Derivatized analytes were determined using GC with MS/MS detection. Influence of several factors on the efficiency of the microextraction step (e.g. time, sample volume, pH, ionic strength and fiber coating) is systematically described. Derivatization conditions were optimized in order to achieve the complete silylation of all hydroxyl groups contained in the structure of the compounds. Detection limits (from 0.2 to 3 ng/l) are compared with those obtained using the same detection technique and different sample preparation strategies, such as solid-phase extraction followed by silylation of the analytes in the organic extract and SPME without derivatization. The method was applied to the analysis of sewage water samples. Two of the investigated species were detected above the quantification limits of the procedure.

Estrogens↗

PubMed2004

Solid-phase microextraction with on-fiber derivatization for the analysis of anti-inflammatory drugs in water samples.

A sensitive and solvent-free procedure for the determination of non-steroidal acidic anti-inflammatory drugs in water samples was optimized using solid-phase microextraction (SPME) followed by on-fiber silylation of the acidic compounds and gas chromatography-mass spectrometry (GC-MS) determination. Microextraction was carried out directly over the filtered water samples using a polyacrylate fiber. Derivatization was performed placing the SPME fiber, loaded with the extracted analytes, in the headspace of a vial containing 50 microl of N-methyl-N-(tert-butyldimethylsilyl)-trifluoroacetamide (MTBSTFA). Derivatives were desorbed for 3 min in the GC injector. Influence of several parameters in the efficiency of microextraction (volume of sample, time, pH, type of fiber coating, etc.) and derivatization steps (time, temperature and volume of MTBSTFA) was systematically investigated. In the optimal conditions an excellent linearity over three orders of magnitude and quantification limits at the ng/l level (from 12 to 40 ng/l) were achieved. The proposed method was applied to the determination of acidic compounds in sewage water and results compared to those obtained using solid-phase extraction (SPE) followed by the derivatization of the compounds in the organic extract of the solid-phase extraction cartridge.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed2004

Determination of natural and synthetic estrogens in water by gas chromatography with mass spectrometric detection.

A procedure for the determination of six natural and synthetic estrogens (diethylstilbestrol, estrone, 17beta-estradiol, mestranol, 17alpha-ethinylestradiol and estriol) in water samples is described. Samples, up to 2000 ml, were concentrated using Oasis HLB solid-phase extraction cartridges. Analytes were derivatized with N-methyl-N-(trimethylsilyl)trifluoroacetamide and determined by GC-MS or GC-MS-MS. The reactivity of several silylation reagents versus aliphatic and aromatic hydroxyl groups contained in the structure of the selected analytes was evaluated. Influence of parameters such as sample pH, nature of the water samples and derivatization conditions on the performance of the whole analytical procedure was systematically studied. Under optimal conditions, quantification limits between 1 and 3 ng/l were achieved for the determination of the considered estrogens in sewage water.

Estrogens↗

PubMed2003

Determination of acidic drugs in sewage water by gas chromatography-mass spectrometry as tert.-butyldimethylsilyl derivatives.

A procedure is described for the determination of five acidic non-steroidal anti-inflammatory pharmaceuticals (ibuprofen, naproxen, ketoprofen, tolfenamic acid and diclofenac) in sewage water. The analytical method involves the concentration of water samples using a solid-phase extraction polymeric sorbent, functionalized with N-vinylpyrrolidone. Analytes were eluted with ethyl acetate. derivatized using N-methyl-N-(tert.-butyldimethylsilyl)trifluoroacetamide (MTBSTFA) and analyzed by GC-MS. Influence of time, temperature and volume of MTBSTFA in the yield of the derivatization step were studied in detail using a factorial central composite design. Quantification limits of the analytical procedure for 500 ml of sewage water ranged from 20 to 50 ng/l. Recoveries from 90 to 115% were found for sewage water samples spiked with the studied compounds at the low ng/ml level. Results obtained for real samples show the presence of ibuprofen and naproxen in both influent and effluent of a sewage water treatment plant.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed2002

Methylmercury determination in biological samples by derivatization, solid-phase microextraction and gas chromatography with microwave-induced plasma atomic emission spectrometry.

A method for the extraction and gas chromatographic determination of methylmercury in biological matrices is presented. By combining the advantages of two extraction techniques-microwave-assisted extraction (MAE) and solid-phase microextraction (SPME)--the separation of methylmercury from biological samples is possible. Specifically, the procedure involves microwave extraction with 3 M hydrochloric acid, followed by aqueous-phase derivatization with sodium tetraphenylborate and headspace SPME with a silica fibre coated with polydimethylsiloxane (PDMS). For optimization of the derivatization-SPME procedure, a central composite experimental design with alpha = 1.682 and two central points was used to model gas-chromatographic peak areas as functions of pH, extraction temperature and sorption time. A desirability function was then used for the simultaneous optimization for methylmercury and Hg(II). The optimal derivatization-SPME conditions identified were close to pH 5, temperature 100 degrees C, and sorption time 15 min. The identification and quantification of the extracted methylmercury is carried out by gas chromatography with microwave-induced plasma atomic emission spectrometry detection. The validity of the new procedure is shown by the results of analyses of certified reference materials.

Calibration↗

PubMed2002

Strategically designed sample composition for fastest screening of polychlorinated biphenyl congeners in water samples.

A new strategy for preparing composite samples of special interest and applicability in environmental screening studies is presented. The use of supersaturated experimental design matrices to conduct the sample composition of water sample specimens in screening studies is demonstrated. In contrast to well known conventional sample composition, this strategic approach provides analytical objects allowing the accurate prediction of analyte concentration levels in the original individual sample specimens while fixing the number of experiments to be carried out down to the very number of sample specimens. This will be of special importance when dealing with analytes that require complicated, labour intensive and expensive analytical processes. To reach this goal, two main conditions must be fulfilled. The first one is the sparsity effect (Pareto principle) which holds for the specimens in the sampling campaign. This means that the number of really anomalous or contaminated specimens, as compared to the total number of specimens to be analysed, is low. In environmental screening studies, frequently this situation can be reasonably assumed. The second condition is to have an effective manner to develop and solve the experimental designs required to build-up the composite samples. The challenging problem of screening PCBs in water samples has been tackled to show the usefulness of this strategic approach by combining chemometrically assisted sample composition and rapid analysis using solid-phase microextraction of the composite samples.

Environmental Monitoring↗

PubMed2001

Simultaneous optimization of the solid-phase extraction of organochlorine and organophosphorus pesticides using the desirability function.

In a multi-response situation [solid-phase extraction (SPE) of 18 organochlorine and nine organophosphorus pesticides from aqueous solution], several response variables are considered, and the optimization problem is more complex than in the single response case. Experimental design combined with desirability function was applied for the optimization of the SPE of these pesticides in order to obtain optimum operating conditions for routine work. This multi-criterion approach was developed for the simultaneous optimization of multiple responses and it is simple, easy to apply and permits the user to make subjective judgments on the importance of each response. The desirability function is based on the search for a global optimum [D = f (Y1, Y2, ..., Yn)] by the transformation of the measured property to a dimensionless scale for each criterion. The experimental design strategy involved a central composite design. A compromise between conflicting goals, such as achievement of good yields with SPE recoveries of ca. 100% for a large number of analytes with inherent chemical differences, was found by means of the desirability function D.

Chromatography, Gas↗

PubMed2000

Experimental design of a microwave-assisted extraction-derivatization method for the analysis of methylmercury.

A simultaneous microwave-assisted extraction-derivatization procedure was developed and optimized for methylmercury analysis from biological samples. The analyte was derivatized with sodium tetraphenylborate forming a more hydrophobic compound, methylphenylmercury, which was extractable in toluene. The microwave extraction-derivatization procedure was optimized using experimental design, 2(5-1) fractional factorial. This chemometrical approach considers main effects as well as interactions of the influential parameters, indicating that temperature and its interaction with NaBPh4 and acetic acid volumes were the variables that significantly affected methylmercury recoveries.

Calibration↗

PubMed2000

Application of chromatographic and electrophoretic methodology to the speciation of organomercury compounds in food analysis.

Trace metals such as mercury, especially its organic compounds, are an important risk to the environment and to man due to their accumulation in the food chain. For this reason, the routine determination of the very toxic methylmercury, and of other organic and inorganic mercury compounds in marine and land animals, vegetables, fruits and fresh water is of increasing importance in health and environmental control programmes throughout the world. The majority of speciation methods for organomercurials involve a series of fundamental steps for the identification and quantification of samples of biological origin: extraction or isolation from the matrix; derivatisation and concentration; detection; separation of different species of interest and of interference. Each of these steps, as part of the chromatographic analysis of MeHg and of other organomercurials is revised in this study using food samples.

Chromatography↗