Biomedical subjects

J Simal Gándara

Publications and source records attributed to J Simal Gándara.

6 recordsLinked to original sources

PubMed2004

Development of a rapid method based on solid-phase extraction and liquid chromatography with ultraviolet absorbance detection for the determination of polyphenols in alcohol-free beers.

An analytical method based on solid-phase extraction (SPE) and followed by liquid chromatographic separation and ultraviolet detection (HPLC-UV) is proposed for the determination of 10 phenolic compounds which participate on beer stability and sensory properties in alcohol-free beers. Acetonitrile was found to be the most appropriate solvent for the elution of polyphenolic compounds adsorbed on C18 cartridges. The performance of the method was assessed by the evaluation of parameters such as absolute recovery (generally higher than 60%), repeatability (lower than 10%), linearity (r2 higher than 0.993) and limits of quantitation (ranging from 1 to 37 microg/L); no matrix effects were observed. The polyphenol content of different Spanish alcohol-free beers is presented. Five phenolic compounds such as protocatechuic, p-coumaric, ferulic, caffeic acids, and (+)-catechin were identified at levels lower than 10 mg/L.

Beer↗

PubMed2003

Multiresidue method for fourteen fungicides in white grapes by liquid-liquid and solid-phase extraction followed by liquid chromatography-diode array detection.

A quantitative, selective and sensitive HPLC method for the analysis of 14 fungicides in white grapes for vinification is described. The proposed method is based on liquid-liquid extraction (LLE) and solid-phase extraction (SPE) followed by liquid chromatography and diode array detection (HPLC-DAD). Dichloromethane-acetone (75:25, v/v) was the most appropriate solvent mix for extracting fungicides in white grapes. Silica cartridges resulted the most appropriate for extract purification purposes. Quality parameters of the proposed multiresidue method presented good recovery (ca. 85% for almost all target compounds) and precision (between 1.5 and 16%), and detection limits lower than maxima residual limits set by the 76/895/ECC and 90/642/ECC Directive. Five different white grapes for vinification produced in Rias Baixas area in Galicia (NW Spain) were analyzed in order to assess the performance of the method with real samples and to determine whether the concentration of the pesticides used exceed their maxima residue levels (MRLs). Results showed that grape concentrations for those identified fungicides were lower than those established by European legislation.

Chromatography, High Pressure Liquid↗

PubMed2001

Determination of sulfamethazine and trimethoprim in liquid feed premixes by HPLC and diode array detection, with an analysis of the uncertainty of the analytical results.

Sulfamethazine (SMZ) and trimethoprim (TMP) are antibacterials used in veterinary practice. This paper describes a method for their determination in veterinary liquid feed premixes that is based on liquid chromatography with diode array detection. Gradient elution with methanol and ammonium acetate achieved excellent separation of the two analytes within 15 min without any interference from the matrix. Absorbance of the column effluent was monitored at 264 nm for SMZ and at 230 nm for TMP. Detailed analyses of the uncertainties of determinations afford estimated expanded uncertainties of, respectively, 0.2 and 0.1 w/v % for typical SMZ and TMP concentrations of 10.7 and 2.1 w/v %, respectively. At the lower end of the calibrated range of the method, the dominant source of uncertainty is the preparation of standards and the construction of the calibration line.

Animal Feed↗

PubMedDate not supplied

Overall migration and specific migration of bisphenol A diglycidyl ether monomer and m-xylylenediamine hardener from an optimized epoxy-amine formulation into water-based food simulants.

The overall and specific migrations of BADGE n = 0 monomer and m-XDA hardener from a BEPOX LAB 889 (Gairesa internal code), epoxy system cured at room temperature, into three water-based food simulants are studied. Hydrolysis of BADGE n = 0 was observed in all of these simulants, giving more polar products. We thus propose changing the EEC Directives, which at present only legislate for levels of BADGE n = 0 monomer in the simulants, to include the hydrolysis products of BADGE monomers. Another alternative would be to express all the migration levels due to BADGE and its derived products in terms of BADGE itself.

Benzhydryl Compounds↗

PubMedDate not supplied

Sensitive and rapid reversed-phase liquid chromatography-fluorescence method for determining bisphenol A diglycidyl ether in aqueous-based food simulants.

A method has been developed for determination of bisphenol A diglycidyl ether (BADGE) in 3 aqueous-based food simulants: water, 15% (v/v) ethanol, and 3% (w/v) acetic acid. BADGE is extracted with C18 cartridges and the extract is concentrated under a stream of nitrogen. BADGE is quantitated by reversed-phase liquid chromatography with fluorescence detection. Relative precision at 200 micrograms/L was 3.4%, the detection limit of the method was 0.1 micrograms/L, and recoveries of spiking concentrations from 1 to 8 micrograms/L were nearly 100%. Relative standard deviations for the method ranged from 3.5 to 5.9%, depending on the identity of the spiked aqueous-based food simulant.

Acetates↗

PubMedDate not supplied

Determination of biphenyl residues in citrus fruit by derivative infrared spectrophotometry.

A method for determination of biphenyl residues in whole citrus fruit is described. The mascerated fruit was distilled in an acid medium, the distillate was extracted with cyclohexane, and biphenyl was determined in the extract using various measures obtained by first and second derivative infrared (IR) spectrophotometry. Calculations were performed by PE680 and SNGLE programs on data obtained using a Perkin-Elmer Model 3600 data station. The relative precision of the determinations at 70 ppm was 1.8 to 2.0%; the detection limit was 5 ppm in all measurements, and recovery of spiking concentrations of 20 to 80 ppm ranged from 90.2 +/- 5.5% (for the amplitude of the 739 cm-1 peak of the first derivative) to 97.5 +/- 2.0% (for the trough-to-peak difference from the 737 cm-1 minimum to the 743 cm-1 maximum of the second derivative.

Biphenyl Compounds↗