Biomedical subjects

M D Marazuela

Publications and source records attributed to M D Marazuela.

5 recordsLinked to original sources

PubMed2006

Development of a new sample pretreatment procedure based on pressurized liquid extraction for the determination of fluoroquinolone residues in table eggs.

A new method for the simultaneous determination of three fluoroquinolones (FQs) enrofloxacin (ENRO) ciprofloxacin (CIPRO) and sarafloxacin (SARA) in table eggs has been developed, applying pressurized liquid extraction (PLE) and liquid chromatography (LC) with fluorescence detection (LC-FLD). The influence of several extraction parameters (e.g. solvent mixture, temperature and extraction time) on FQs extraction efficiency and coextracted matrix interferents was evaluated using fortified control eggs and matrix matched standard curves. The results showed that FQs extraction efficiency depends mainly on solvent composition and the optimum extraction mixture was found to be phosphate 50mM, pH 3.0/acetonitrile (50:50, v/v). The optimized procedure employed 50% flush volume, 5min of static time and three extraction cycles at 70 degrees C and 1500psi. Method validation was performed according to the guidelines of the Directive 96/23/EC, using control egg samples, fortified with the target FQs in the range 50-1000ngg(-1) and applying the optimized extraction conditions on three different days, providing recoveries between 67-90% with RSDs lower than 11% in all cases. The decision limit (CCalpha) and detection capability (CCbeta) of the analytical method were found to be within the range 17-24ngg(-1) and 30-41ngg(-1), respectively. The method was successfully applied to the determination of ENRO and its metabolite CIPRO in incurred egg samples from ENRO-treated hens and LC-MS has been used and for confirmatory purposes.

Animals↗

PubMed2006

Molecularly imprinted polymers with a streamlined mimic for zearalenone analysis.

Molecularly imprinted polymers (MIPs) with selective recognition properties for zearalenone (ZON), an estrogenic mycotoxin, and structurally related compounds have been prepared using the non-covalent imprinting approach. A rationally designed ZON analogue, cyclododecyl 2,4-dihydroxybenzoate (CDHB), that exhibits resemblance to ZON in terms of size, shape and functionality has been synthesized and used as template for MIP preparation instead of the natural toxin. Several functional monomers have been evaluated to maximize the interactions with the template molecule during the polymerization process. The polymer material prepared with 1-allylpiperazine (1-ALPP) as functional monomer, trimethyl trimethacrylate (TRIM) as cross-linker and acetonitrile as porogen (in a 1:4:20 molar ratio) displayed superior binding capacities than any other of the MIPs tested. Selectivity of this material for ZON and structurally related and non-related compounds has been evaluated using it as stationary phase in liquid chromatography. Our results demonstrate that the imprinted polymer shows significant affinity in the porogenic solvent for the template mimic (CDHB) as well as for the ZON and other related target metabolites in food samples, dramatically improving the performance of previously reported MIPs for ZON recognition. Therefore, MIPs can be an excellent alternative for clean-up and preconcentration of the mycotoxin in contaminated food samples.

Chromatography, High Pressure Liquid↗

PubMed2004

Multiresidue determination of fluoroquinolones in milk by column liquid chromatography with fluorescence and ultraviolet absorbance detection.

Column liquid chromatography with fluorescence (FLD) and UV-diode array detection (UV-DAD) was used for the simultaneous determination of ciprofloxacin (CIPRO), enrofloxacin (ENRO), marbofloxacin (MARBO), danofloxacin (DANO) and sarafloxacin (SARA) residues in milk, using norfloxacin (NOR) as internal standard. Two solid-phase extraction (SPE) cartridges, were evaluated for sample clean-up and preconcentration, Strata X, based on a modified styrene-divinylbenzene polymer, and Strata Screen A, a mixed anion exchanger/C8 reversed-phase sorbent. The fluoroquinolones (FQs) were separated on a polar endcapped column (AQUA C18). The recoveries for raw milk spiked with the antibiotics at three concentrations close to the maximum residue limit (MRL), were 80-103% for ENRO, CIPRO and DANO, with relative standard deviations (R.S.D.) lower than 6.6%. SARA recoveries were 70% (R.S.D. = 7%) and values in the order of 95% (R.S.D. = 1.5%) were obtained for MARBO at the MRL level. The quantification limits ranged from 2.4 to l0 ng ml(-1) and are below the MRL established for these drugs by the European Union. The method was successfully applied to the analysis of ENRO and its metabolite CIPRO in an incurred milk sample.

Animals↗

PubMed2000

Fiber optic monitoring of carbamate pesticides using porous glass with covalently bound chlorophenol red.

An optical fiber biosensor for the determination of the pesticides propoxur (Baygon) and carbaryl, two of the most commonly used carbamate insecticides in vegetable crops, is described. A pH indicator, chlorophenol red, is used as optical transducer of the inhibition of the enzyme acetylcholinesterase by the analytes. The biorecognition element is covalently immobilized onto controlled pore glass beads (CPG) and packed in a thermostatized bioreactor connected to a flow-through cell that contains CPG-immobilized chlorophenol red placed at the common end of a bifurcated fiber optic bundle. In the presence of a constant acetylcholine concentration, the colour of the pH sensitive layer changes and the measured reflectance signal can be related to the carbamate concentration in the sample solution. The performance of the biosensor has been optimized using a flow injection system. The linear dynamic range for the determination of carbaryl and propoxur spans from 0.8 to 3.0 mg l(-1) and from 0.03 to 0.50 mg l(-1), respectively. The detection limit (3 s) of the biosensor for propoxur (0.4 ng) is lower than that measured for carbaryl (25 ng). Reproducibility, stability and interference studies of the optical device are reported. The biosensor has been applied to the determination of propoxur in spiked vegetables (onion and lettuce) using ultrasound extraction, achieving recovery values between 93 and 95% for onion samples at the different concentration levels assayed.

Acetylcholine↗

PubMed1997

Free cholesterol fiber-optic biosensor for serum samples with simplex optimization.

An optical fiber biosensor for free cholesterol monitoring in serum samples is described. Silicone-entrapped tris(4,7-diphenyl-1,10-phenanthroline) ruthenium(II) complex, the luminescence of which is sensitive to oxygen changes, is used as an optical transducer of the oxidation of cholesterol by cholesterol oxidase. The biocatalyst is entrapped in a graphite powder layer deposited onto the dyed silicone film. Optimization of some interdependent chemical variables which affect the performance of the biosensor has been achieved by application of a super-modified simplex method. The dynamic range of the biosensing membranes is found to be 0.15-3.0 mM of free cholesterol. Studies of the reproducibility, stability and interferences of the device, as well as the application of the sensor to measurements in serum samples, are reported. Simplex optimization has proven to be a very useful tool in the search for the optimal conditions for performing analyses with the optical fiber biosensor.

Biosensing Techniques↗