Biomedical subjects

P Fernández-Hernando

Publications and source records attributed to P Fernández-Hernando.

5 recordsLinked to original sources

PubMed2006

Liquid chromatography-UV diode-array detection method for multi-residue determination of macrolide antibiotics in sheep's milk.

A rapid, simple and sensitive liquid chromatography-UV diode-array detection method was developed for the simultaneous determination of seven macrolides (erythromycin, oleandomycin, roxithromycin, josamycin, spiramycin, tylosin and ivermectin) in sheep's milk. The column, mobile phase, temperature and flow rate were optimised to provide the best resolution of these analytes. The extraction of the antibiotic residues involves the treatment of protein-free samples with a combination of concentrated sodium hydroxide and ethyl acetate. Necessary defatting is achieved by alkaline hydrolysis. The recovery of each antibiotic was between 55% and 77%, with relative standard deviations ranging from 1% to 6.5%. The limit of quantification was 72.4 microg/kg for ivermectin, 48.3 microg/kg for roxithromycin, and 24.1 microg/kg for erythromycin, oleandomycin, spiramycin, josamycin and tylosin. The procedure was successfully used in the multi-residue determination of these macrolides at levels below the maximum concentrations legally allowed in milk samples.

Animals↗

PubMed2004

Simultaneous determination of maneb and its main metabolites in tomatoes by liquid chromatography using diode array ultraviolet absorbance detection.

Liquid chromatography (LC) with diode array ultraviolet absorbance (DAD UV) detection is used for the simultaneous determination of the fungicide maneb and its main metabolites (ethylenethiourea--ETU, ethylenebis (isothiocyanate) sulfide--EBIS, and ethyleneurea--EU) in tomatoes. The identity of EBIS, one of the main UV degradation products of maneb, was verified by both DAD UV detection and mass spectrometry. The analytes were extracted three times with 3 mL of 1:1:1 acetonitrile-dichloromethane-chloroform by 2 min of mechanical shaking and separated on a C-18 column by gradient elution with an acetonitrile-methanol-aqueous 100mM sodium dodecylsulfate (SDS) mixture. The quantification limits of 0.45, 0.04, and 0.35 mg kg(-1) obtained for maneb, ETU, and EU, respectively, show that the proposed method is suitable for their determination in tomatoes.

Chromatography, Liquid↗

PubMed2004

Optimization of a matrix solid-phase dispersion method with subsequent clean-up for the determination of ethylene bisdithiocarbamate residues in almond samples.

A matrix solid-phase dispersion (MSPD) method with subsequent clean-up has been developed to isolate the ethylene bisdithiocarbamate (EBDC) main metabolites (ethylenethiourea, ETU, and ethylenebis [isothiocyanate] sulphide, EBIS) in almond samples. The optimized experimental set-up configuration involved 0.2 g of almond sample, washed sand as MSPD support and NaOH as defatting agent. A subsequent purification step on alumina using acetonitrile as extraction solvent was enough to remove all interferent matrix components, including the fatty material, and provide clean extracts. Quantitative analysis was performed by reversed phase liquid chromatography (RPLC) with diode-array ultraviolet absorbance (DAD UV) detector. Analytes recoveries were between 76 and 85% with relative standard deviations ranging from 3 to 12%. The low limits of quantification of 0.05 and 0.07 mg kg(-1) achieved for ETU and EBIS, respectively, make the method useful for the determination of EBDC residues on almond samples.

Chromatography, Liquid↗

PubMed2003

Evaluation of pesticide uptake by Lupinus seeds.

Pesticide uptake by seeds depends on the properties of the chemical, such as structure, stability, log k(ow) and diffusion rate, type of water, pH, temperature, content of organic matter and composition, and on seed characteristics such as permeability of the seed coat. The efficiency with which Lupinus angustifolius seeds retain different herbicides (simazine, atrazine, isoproturon, linuron,) and insecticides (carbaryl, fenamiphos, permethrin) was evaluated using both a batch and a continuous system. Factors which affect pesticide uptake by seeds, such as flow rate, seed biomass, pesticide concentration, contact time, pH, seed saturation and also the speed of the retention process for 17 days, were tested. L. angustifolius showed a high retention capacity for the above mentioned pesticides. The extraction of pesticides from seeds using different organic solvents, such as methanol, acetonitrile, ethyl acetate and n-hexane was evaluated and no pesticide residues were detected in any of the solvents tested. This could be attributed to the capacity of the seed to degrade the pesticides. From the results obtained, L. angustifolius seems to be a promising seed to be applied for phytoremediation of industrial effluents or contaminated water.

Biodegradation, Environmental↗

PubMed1999

Trace elements and electrolytes in human resting mixed saliva after exercise.

OBJECTIVES: Exercise is known to cause changes in the concentration of salivary components such as amylase, Na, and Cl. The aim of this investigation was to evaluate the effect of physical exercise on the levels of trace elements and electrolytes in whole (mixed) saliva. METHODS: Forty subjects performed a maximal exercise test on a cycle ergometer. Samples of saliva were obtained before and immediately after the exercise test. Sample concentrations of Fe, Mg, Sc, Cr, Mn, Co, Cu, Zn, Se, Sr, Ag, Sb, Cs, and Hg were determined by inductively coupled plasma mass spectrometry and concentrations of Ca and Na by atomic absorption spectrometry. RESULTS: After exercise, Mg and Na levels showed a significant increase (p < 0.05) while Mn levels fell (p < 0.05). Zn/Cu molar ratios were unaffected by exercise. CONCLUSIONS: Intense physical exercise induced changes in the concentrations of only three (Na, Mg, and Mn) of the 16 elements analysed in the saliva samples. Further research is needed to assess the clinical implications of these findings.

Adult↗