Biomedical subjects

P Viñas

Publications and source records attributed to P Viñas.

At least 19 recordsLinked to original sources

PubMed2004

Purge-and-trap capillary gas chromatography with atomic emission detection for volatile halogenated organic compounds determination in waters and beverages.

A method for the simultaneous determination of 10 volatile halogenated organic compounds (VHOCs), including four trihalomethanes (THMs), in waters and beverages was developed. The analytes were stripped from the aqueous sample by a flow of helium, preconcentrated in a capillary trap and thermally desorbed using a purge-and-trap (PT) system. This was followed by capillary gas chromatography with microwave-induced plasma atomic emission spectrometry (GC-AED). For element-specific detection, three wavelengths were monitored, corresponding to chlorine (479 nm), bromine (478 nm) and iodine (193 nm). Each chromatographic run took 21 min, including the purge time. After careful choice of the experimental conditions, the performance of the system was evaluated. Calibration curves were obtained by plotting peak area versus concentration and the correlation coefficients for linear calibration were at least 0.9987. Detection limits, calculated for 5 ml sample volume, ranged from 0.05 microg l(-1) for chloroform to 0.5 microg l(-1) for tetrachloromethane. The method was successfully applied to the quantitative analysis of water samples of different origin and also of several beer and juice samples. The tap water samples analyzed contain variable concentrations of the four trihalomethanes, ranging from 1.0 to 66.5 microg l(-1), depending of the compound. Whereas chloroform, bromodichloromethane and bromoform were found in some of the juice samples, only chloroform was detected in the beer samples. The method is reliable and can be used for routine monitoring in water and beverages.

Beverages↗

PubMed2003

Placental lead and outcome of pregnancy.

Prenatal exposure to lead produces toxic effects in the human fetus, including an increased risk of preterm delivery, low birth weight and impaired mental development. Since we believe that placental lead could be a good biomarker for fetal exposure, we assessed the relation of placental lead to intrauterine fetal growth and some adverse outcomes of pregnancy. Low concentrations of lead were found in the population studied (N, 89; mean, 113.4 ng/g dry tissue; S.D., 58.0). The cases were divided into two groups based on delivery outcome. In the group of placentas from premature rupture of membranes and preterm labor (gestational age <or=37 weeks), higher lead levels were recorded than in the placentas from term pregnancies. The proportion of abnormal pregnancy outcome in the group of placentas with lead concentrations above 120 ng/g was 40.6 versus 8.8% in placentas below this concentration. Higher placental lead levels, in general, were not related to smaller weight, head and abdominal circumference or shorter length at birth.

Adult↗

PubMed2003

Placental cadmium and lipid peroxidation in smoking women related to newborn anthropometric measurements.

Smoking during pregnancy is known to be harmful for fetal growth, and cigarette smoke is the major source of cadmium exposure in the general population. Some authors suggest that cadmium accumulated in placenta may be the main cause of the decreased fetal growth shown by infants born to smoking mothers. The aim of our study was to assess any relationship between smoking during pregnancy, placental cadmium levels, placental lipid peroxidation, and anthropometric measurements of newly born babies. The mean values of placental cadmium were significantly higher in smoking mothers, who also produced offspring with reduced neonatal weight, length, head and abdominal circumferences. Lipid peroxidation correlated negatively with birth weight and abdominal circumference. Our results suggest that the cadmium accumulated in placenta is not the reason for reduced fetal growth in smoking mothers and that placental peroxidation is not enhanced by smoking, although the outcome of pregnancy seems to be negatively influenced by lipid peroxidation.

Adult↗

PubMed2003

Stability of arsenobetaine levels in manufactured baby foods.

The stability of arsenobetaine in baby foods under different experimental conditions is evaluated. Total arsenic was analyzed by electrothermal atomic absorption spectrometry, and the speciation of arsenicals was carried out by coupling liquid chromatography to hydride generation-atomic absorption spectrometry. The highest arsenic levels in the analyzed baby foods corresponded to those containing plaice (2 to 3 microg/g). The speciation data indicated that arsenobetaine, a nontoxic species, was the only arsenical present in the baby foods analyzed at levels between 0.2 and 3 microg/g. Two different procedures for extracting arsenicals from baby foods, involving a water-methanol-chloroform mixture and enzymatic hydrolysis, were tested, and similar results were obtained. Furthermore, the arsenobetaine levels remained unchanged when the baby foods were stored for different times or when the samples were freeze-dried, thus confirming the stability of arsenobetaine and the nonappearance of other arsenic species by interconversion. The reliability of the procedure was checked by analyzing a certified reference material.

Arsenicals↗

PubMed2002

Determination of pesticides in waters by capillary gas chromatography with atomic emission detection.

Capillary gas chromatography with atomic emission detection (GC-AED) was successfully used to separate and quantify 14 pesticides (organochlorines, organophosphorus compounds and pyrethrins) in water samples after liquid-liquid extraction with ethyl acetate. Monitoring the emission lines for elements such as chlorine, bromine and sulfur ensures nearly specific chromatograms for these elements, and markedly increases selectivity. Calibration curves were obtained by plotting peak area versus concentration and the correlation coefficients relating to linearity were at least 0.999. Each chromatographic separation takes 21 min and, since two injections are necessary, it requires approximately 1 h to analyze one sample. The method shows a precision of 4.3-8.2% (RSD), depending on the compound. The application of liquid-liquid extraction with ethyl acetate led to recoveries from spiked samples ranging from 76 to 113%. The sensitivity and linearity for the elements chlorine, sulfur, nitrogen and phosphorus were checked under the optimized conditions at their customary emission wavelength. The sensitivity and linearity for these compounds decreased in the order (atom and emission wavelength) Cl (479 nm)>S (181 nm)>P (178 nm)>N (174 nm). A study of the GC-AED system's response to chlorine concentration in eight pesticide molecules was performed and a linear relationship was found with a correlation coefficient of 0.987.

Calibration↗

PubMed2001

A manifold for the automatic dilution of concentrated solutions in flame atomic absorption spectrometry.

A fully computer-controlled manifold is described which enables the automatic dilution and measurement of solutions which are too concentrated to be measured by direct aspiration in FAAS. The sample solution is propelled by a peristaltic pump equipped with two pump tubes of different diameters, the difference between the nebulizer uptake rate and the flow rate supplied by both tubes being compensated by solvent provided through a T-piece. The absorbance is averaged and the pump turning speed automatically increased or reduced until an absorbance value within the linear response of the spectrometer is obtained. To furnish very high dilution, the system automatically reverses the direction of the flow moved through one of the pump tubes, so that the net flow delivered by the pump is the difference between the flows propelled through the two pump tubes. In these circumstances, in addition to absorbance, the module of the Fourier transform obtained from the absorbance-time profile can be used as the analytical signal. Calibration is performed by use of a single standard solution. In this way, it is possible to determine copper in the 1-10,000 microg mL(-1) range with an RSD of 1.3-3%. Copper, zinc, calcium, and magnesium were determined in different samples to check the reliability of the procedure.

Journal Article↗

PubMed2001

Comparison of ion-pair and amide-based column reversed-phase liquid chromatography for the separation of thiamine-related compounds.

Two reversed-phase chromatographic methods for the separation of thiamine and related compounds are compared. The first procedure is based on the ion-pair technique using an octadecylsilica column, while the second uses a new amide-based stationary phase, which avoids the need to form ion-pairs, leading to narrower peaks and a simpler mobile phase. Analyses were performed by gradient elution and a photo-diode array was used for detection. Specificity was demonstrated by the retention characteristics, UV spectra and by comparing the peak purity index with commercial standards. The procedures were applied to the determination of thiamine-related compounds in pharmaceutical preparations and urine. No preliminary sample treatment was required.

Amides↗

PubMed2000

Selenium determination in biological fluids using Zeeman background correction electrothermal atomic absorption spectrometry.

Procedures for the direct determination of total selenium in urine, serum, and blood using electrothermal atomic absorption spectrometry are presented. In the selected experimental conditions, Zeeman correction is mandatory to compensate for the high background signals. The sample diluted and containing 0.1% (w/v) Triton X-100 is introduced directly into the electrothermal atomizer. A solution containing 15% (w/v) hydrogen peroxide, 0.65% (w/v) nitric acid, and 0.5% (w/v) nickel is injected separately into the atomizer. Calibration is carried out using the standard additions method. The detection limit is 30 pg selenium. If palladium, instead of nickel, is used as the chemical modifier, calibration can be carried out against aqueous standards, and the detection limit is 45 pg. In this case, three separate injections are required to prevent precipitation problems in the automatic injector. The reliability of the procedures is checked by analyzing three certified reference materials and by recovery studies. Mean recoveries are 99.7% for serum, 99.4% for urine, and 100.8% for blood samples. Relative standard deviation values are +/-4.0% for serum, +/-3.9% for urine, and +/-4.5% for blood.

Body Fluids↗

PubMed2000

Determination of phenols in wines by liquid chromatography with photodiode array and fluorescence detection.

A reversed-phase LC method, optimised for the separation of trans- and cis-resveratrol, catechin, epicatechin, quercetin and rutin, is reported. Analyses were performed on a reversed-phase column by gradient elution. Detection was carried out by photodiode array, although the use of a fluorimetric detector considerably lowered the detection limits for catechin, epicatechin and both resveratrol isomers. Identification by the two different detection systems was based on retention characteristics, UV spectra and peak purity index were compared with commercial standards. The procedures were applied to the determination of the phenolic compounds in different types of wines and musts.

Calibration↗

PubMed2000

Rapid determination of lead and cadmium in sewage sludge samples using electrothermal atomic absorption spectrometry with slurry sample introduction.

Lead and cadmium concentrations in sewage sludge samples are determined by suspending the ground samples in a solution containing 10% (v/v) concentrated hydrofluoric acid, 1% (v/v) concentrated nitric acid, 0.5% (m/v) dihydrogen ammonium phosphate and 0.1% (m/v) sodium hexametaphosphate. Aliquots of 20 microL of these suspensions (4 mg/mL) are diluted to 1000 microL with the same solution and then injected into the electrothermal atomizer. The drying stage is performed by programming a 400 degrees C temperature, a ramp time of 20 s and a hold time of 15 s on the power supply of the atomizer. No ashing step is used. Platform atomization is carried out at 1600 and 1800 degrees C for Pb and Cd, respectively. Calibration is performed using aqueous standards in the 5-75 and 0.2-5 microg/L Pb and Cd ranges, respectively. Results obtained for three certified reference materials and four samples demonstrate the reliability of the procedures described.

Cadmium↗

PubMed2000

Determination of copper, cobalt, nickel, and manganese in baby food slurries using electrothermal atomic absorption spectrometry.

The analytical conditions for the electrothermal atomic absorption spectrometric determination of copper, manganese, nickel, and cobalt in different types of baby foods using slurried samples are presented. Suspensions were prepared in a medium containing 0.1% w/v Triton X-100, 30% v/v concentrated hydrogen peroxide, 1% v/v concentrated nitric acid, 1% w/v ammonium dihydrogenphosphate (only for copper atomization), and one drop of silicon antifoam. The slurries were homogenized by using a potter and were introduced directly into the furnace. The amount of analyte extracted to the liquid phase was investigated. The graphite furnace conditions were optimized for each element. No matrix effect was observed, and calibration could be carried out using aqueous standard solutions. The detection limits were 3.4, 2.1, 5.4, and 3.7 pg for copper, manganese, nickel, and cobalt, respectively. The reliability of the procedures was checked by statistically comparing the results obtained with those found by using a previous microwave-oven mineralization stage and by analyzing several certified reference materials.

Cobalt↗

PubMed2000

Determination of arsenic in biological fluids by electrothermal atomic absorption spectrometry.

A procedure for the determination of the total content of arsenic in urine, serum and blood by electrothermal atomic absorption spectrometry (ETAAS) is described. Zeeman correction is used to compensate the high background signals. The samples are diluted (1 + 1 for urine and 1 + 3 for both serum and blood samples) in a medium containing 0.1% w/v Triton X-100 before being introduced directly into the furnace. A solution containing 15% w/v hydrogen peroxide, 0.65% w/v nitric acid and 0.5% w/v nickel is also introduced into the atomizer by means of a separate injection. Calibration is carried out against aqueous standards for blood and serum samples and using the standard additions method for urine samples. The detection limit is 20 pg (2 ng ml-1). The reliability of the procedure is checked by analyzing three certified reference materials and by recovery studies.

Arsenic↗

PubMed1997

Use of post-column fluorescence derivatization to develop a liquid chromatographic assay for ranitidine and its metabolites in biological fluids.

Ranitidine and its main metabolites, ranitidine N-oxide and ranitidine S-oxide, were determined in plasma and urine after separation using reversed-phase liquid chromatography. The mobile phase consisted of an initial isocratic step with 7:93 (v/v) acetonitrile-7.5 mM phosphate buffer (pH 6) for 8 min, followed by a linear gradient up to a 25:75 (v/v) mixture over 1 min. Detection was carried out by a post-column fluorimetric derivatization based on the reaction of the drugs with sodium hypochlorite, giving rise to primary amines that reacted with o-phthalaldehyde and 2-mercaptoethanol to form highly fluorescent products. The calibration graphs, based on peak area, were linear in the range 0.1-4 microg/ml for all drugs. The detection limits were 30, 41 and 32 ng/ml (8.6, 12.5 and 9.1 pmol) for ranitidine S-oxide, ranitidine N-oxide and ranitidine, respectively. Chromatographic profiles obtained for plasma and urine samples showed no interference from endogenous compounds.

Anti-Ulcer Agents↗

PubMed1997

Determination of p-hydroxyphenylglycine by reaction with o-phthalaldehyde using a flow-injection fluorimetric procedure.

In the present study, new flow injection procedures for the determination of p-hydroxyphenylglycine using either photometric or fluorimetric detection are proposed. The methods are based on the reaction of the amino acid with o-phthalaldehyde and 2-mercaptoethanol. The calibration graphs based on peak area were linear in the ranges 20-300 ng ml-1 with fluorimetric detection and 5-60 micrograms ml-1 using the photometric mode. The detection limit calculated for the fluorimetric procedure was 10 ng ml-1. The method was applied to the determination of the free p-hydroxyphenylglycine present in industrial pharmaceutical samples of a Dane salt.

Flow Injection Analysis↗

PubMed1996

Indirect flame atomic absorption detection for the liquid chromatographic separation of alkaline metals.

Alkaline metals and ammonium ion are separated by cationic exchange liquid chromatography using a 60 microg ml(-1) aqueous copper solution as the mobile phase at 1.5 ml min(-1). Detection is carried out by measuring copper with an atomic absorption spectrometer directly interfaced to the chromatograph. A simple T-piece is used to compensate the difference between the nebulizer uptake rate and the chromatographic flow-rate with air. The method is applicable to the analysis of alkaline metals and ammonium in waters. Average recovery ( n = 16) was 100.3 +/- 4.0%.

Journal Article↗

PubMed1996

Extending the dynamic range of flame atomic absorption spectrometry: a comparison of procedures for the determination of several elements in milk and mineral waters using on-line dilution.

Three approaches based on continuous flow methodology are assessed for the purpose of extending the dynamic range of flame atomic absorption spectrometry. The determination of several elements in infant liquid and powdered milk and water samples is used to check the performances of the manifolds. Two of the systems are fully computer-controlled and permit a calibration graph to be obtained by using a single standard solution. The results confirm that continuous flow methodology is a reliable alternative to the time-consuming common dilution procedures based on glassware. Since the systems are versatile and permit a wide range of degrees of dilution to be obtained, they can be easily adapted for the automated or semi-automated analysis of other liquid samples which are too concentrated to be aspirated directly into the atomic absorption spectrometer.

Journal Article↗

PubMed1993

Determination of thiol-containing drugs by chemiluminescence-flow injection analysis.

A flow injection analysis procedure with chemiluminescence detection for the determination of both thiol-containing drugs and the amino acid cysteine is described. Procedures are based on the inhibition by the drugs of the chemiluminescence generated in the copper-catalysed oxidation of luminol by hydrogen peroxide. The proposed methods were applied to the determination of cysteine, N-acetylcysteine, penicillamine, 2-mercaptopropionylglycine and thiouracil in pharmaceuticals.

Acetylcysteine↗

PubMedDate not supplied

Fast determination of lead and copper in dairy products by graphite furnace atomic absorption spectrometry.

A rapid and direct procedure for determining lead and copper in dairy products by electrothermal atomic absorption spectrometry (ETAAS) is described. Samples are slurried in a medium containing 50% v/v hydrogen peroxide, 1% v/v nitric acid, 0.5% w/v dihydrogen phosphate, and 20% v/v ethanol and directly injected into the furnace with no previous mineralization. Calibration is performed with aqueous standards. Limits of determination were 0.4 and 2.4 ng/mL for copper and lead, respectively. The reliability of the procedure was checked by comparison with the acid mineralization procedure and by analyzing 3 certified reference milk samples.

Calibration↗