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Biomedical subjects

E Millán

Publications and source records attributed to E Millán.

9 recordsLinked to original sources
PubMed2006

A convenient method for epichlorohydrin determination in water using headspace-solid-phase microextraction and gas chromatography.

A simple procedure for epychlorohydrin determination in water is presented. In order to optimize the epichlorohydrin extraction conditions in water using headspace (HS)-solid-phase microextraction (SPME), followed by gas chromatography, an experimental design in two steps is performed. Firstly, a 2(5-2) fractional factorial design for screening the significant variables is used. Secondly, a central composite design for optimizing them is carried out. The best experimental conditions are the followings: poly(dimethysiloxane)-divinylbenzene coating fiber; 20 min extraction time; 5 degrees C extraction temperature; 300 g/L sodium chloride; and 20 mL HS volume in a 40-mL vial. Using the previous extraction conditions with gas chromatography (GC)-flame ionization detection equipment, a limit of detection (LOD) of 1.8 microg/L and a relative standard deviation (RSD) of 3.8% (for 25 microg/L) are obtained. With a GC electron capture detection equipment the RSD is 6.6% (for 5 microg/L), and the LOD found is lower (0.08 microg/L). The method is applied to the analysis of water from four treatment plants at the entrance and effluent stream. The standard addition method is used to quantitate the epichlorohydrin that is found in the raw water of the three wastewater treatment plants.

Chromatography, Gas↗
PubMed2003

Phenylisothiocyanate and dansyl chloride precolumn derivatizations for the high-performance liquid chromatography analysis of the antitumoral agent ES-285 in dog plasma.

Chromophor and fluorophor addition reactions involving phenylisothiocyanate (PITC) and dansyl chloride (DC) were optimized to adapt two high-performance liquid chromatography (HPLC) procedures designed for the accurate determination of the novel antitumoral agent ES-285 in Beagle dog plasma. ES-285 was reacted with PITC at 60 degrees C for 15 min in the presence of triethylamine. The dansyl derivative was obtained by reaction of ES-285 with dansyl chloride in a basic medium at 80 degrees C for 20 min. Both reactions also worked for ES-299, a compound structurally related to ES-285 which was used as internal standard. The treatment of ES-285 and ES-299 spiked plasma samples with a basic phosphate buffer and MeOH permitted the extraction of the drug from the matrix. The purification of the analytes was carried out by solid-phase extraction followed by precolumn derivatization with PITC and DC. The phenylisothiocyanate adducts were analyzed by isocratic HPLC with UV detection at 254 nm. The ES-285 and ES-299 derivatives were eluted from a C(18) column at approximately 6.9 and approximately 8.1 min, respectively. The eluent ACN-water (95:5, v/v) was delivered to the column at a flow-rate of 1 ml/min and the analysis was completed in 15 min. The dansyl derivatives were analysed by a two-HPLC column system with fluorescence detection and gradient elution. The column temperature was maintained at 40 degrees C. The analysis lasted 55 min with the elution of ES-285 and ES-299 derivatives at approximately 35.2 and approximately 37.9 min, respectively. The PITC- and DC-based procedures were characterized by limits of quantification of 20 and 15 ng/ml, respectively. Both procedures were validated according to the ICH and FDA guidelines. They were selective for ES-285 and provided accurate, precise and reproducible results. ES-299 was shown to be a suitable internal standard. The HPLC procedure involving derivatization with DC was more sensitive and permitted to process plasma sample volumes as low as 100 microl. On the other hand, the PITC-based procedure characterised by a quite similar LOQ permitted a higher throughput but implied the processing of a 500-microl plasma volume.

Alkanes↗
PubMed2003

Assessment of tin and butyltin species in estuarine superficial sediments from Gipuzkoa, Spain.

Ten superficial sediments from river estuaries of Gipuzkoa (North Spain) were collected and analyzed for nine metals (including tin, Sn) and butyltin compounds (monobutyltin, MBT; dibutyltin, DBT; tributyltin, TBT). Total metal concentration in the fine fraction (<63 micrometer) of the sediment was determined in aqua regia--hydrofluoric acid extracts by atomic absorption spectrometry. The butyltin species (BTs) were firstly extracted from the sediments with hydrochloric acid-methanol mixture. After derivatization with sodium tetraethyl borate, the organotin compounds were extracted by solid phase microextraction (SPME) in headspace mode. A fiber coated with 100 micrometer poly(dimethylsiloxane) was used for SPME. The organotin species were analyzed by gas chromatography-flame ionization detection. Analysis of the certified reference sediment (PACS-2) shown the suitability of the procedures for determination of metal contents and DBT-TBT species in contaminated sediments. Factorial analysis was used to examine the main sources of metals. Three factors represented more than 89% of the total variance of the metal system, and the Sn was related with Cu-Zn-Pb suggesting the same pollution source. The BTs concentrations in the area were high (TBT ranged from 0.05 to 5.48 mg Sn kg(-1)). The percentage of total butyltin species ( summation operator BTs) respect to the total Sn amount was higher than 4% in all the sediments, showing in the Bidasoa river estuary a remarkable value higher than 20%. Hence, the studied estuarine sediments reflect a pollution that is related with historical industrial and fishing activities of the area.

Environmental Monitoring↗
PubMed2001

Application of experimental design in a method for screening sediments for global determination of organic tin by electrothermal atomic absorption spectrometry (ETAAS).

An experimental design was developed to obtain a simple procedure for global determination of organic tin compounds in sediment. Sediment was extracted by a two-phase method and tin was determined in the organic extract by electrothermal atomic absorption spectrometry (ETAAS), with palladium as chemical modifier. A Plackett-Burman design for screening and a fractional central composite design (CCD) for optimizing were used for evaluation of the effects of several variables. The results showed that sediment mass, volume and concentration of extracting acid, pyrolysis and atomization temperatures, and modifier concentration affect the determination. Reference material PACS-2 was analyzed to evaluate the procedure. It was possible to extract 82% of the organotin content certified in the reference sediment. The limit of detection (LOD) was 0.08 microg g(-1) and the relative standard deviation was 4%. The method was applied to the analysis of estuarine superficial sediments from Gipuzkoa (Spain). The organotin content of these samples ranged from 0.7 to 7.7 microg g(-1), as tin, on a dry-weight basis.

Acetic Acid↗
PubMed2000

Determination of butyltin species in water and sediment by solid-phase microextraction-gas chromatography-flame ionization detection.

A procedure for determination of tetraethyltin (TeET) and tetrabutyltin (TeBT) in water by solid-phase microextraction (SPME) using the headspace approach has been developed. The method has been adapted for the simultaneous determination of mono-, di- and tributyltin species (MBT, DBT and TBT) after derivatization with sodium tetraethylborate in water and sediment samples. The analytical procedures were optimized with respect to stirring conditions, extraction time and extraction temperature. The pH and the amount of derivatizing reagent were also considered in derivatization reaction procedures. The analysis was carried out using gas chromatography equipped with flame ionization detection. The detection limits obtained for TeET and TeBT, in equilibrium conditions (room temperature for TeET and 40 degrees C for TeBT) were 28 and 20 ng/l (as Sn), respectively. The detection limit for butyltin species in water, which was limited by signals which are non-specific for the tin compounds and the sensitivity of the FID system, was found ca. 1 microg/l (as Sn). The SPME method was validated for analysis of sediments by analyzing the certified reference material PACS-2 finding a good agreement with the certified values.

Calibration↗
PubMed2000

Evaluation of heavy metal availability in polluted soils by two sequential extraction procedures using factor analysis.

Superficial soil and grass samples from 13 locations affected by several anthropogenic sources (mining, metal factory, traffic emissions) were collected in Gipuzkoa, northern Spain. The more labile metal fractions, the mobile (extracted by 0.01 mol l(-1) CaCl(2)) and the mobilisable (extracted by 0.005 mol l(-1) DTPA), were evaluated using a short sequential procedure with two steps. From the results a short-medium term potential lability of Cd, Cu, Zn and Pb can be concluded. The labile levels were compared with the results obtained using the Tessier sequential procedure. Factor analysis was used to check the associations between the total metal contents in soil and grass, as well as between the levels of the different sequential fractions and the total content in grass. Cd, Cu and Zn labile levels were related to total metal grass contents indicating its suitability for the availability studies in polluted soil-plant system.

Journal Article↗
PubMed1998

Evaluation of heavy metal lability in polluted soils by a cation exchange batch procedure.

A new extraction procedure with cationic exchange resins is proposed for the assessment of heavy metal lability in polluted soils. This method classifies soluble metal compounds in three levels according to their lability: very labile, moderately labile and non-labile. The concept of lability is based on the use of resins with different ability to interact with metals. The proposed procedure was applied to five samples of polluted soils. In the five soils, soluble Cd was found to be very labile, soluble Ni and Pb were mostly non-labile, Mn and Zn lability depended on the soil, while Cu had a fraction of moderately labile forms in four of the five soils. The resin extraction procedure was compared with the DTPA and CaCl2 extractions.

Journal Article↗
PubMed1990

[Community viral pneumonia in the adult population: a prospective multicenter study of 62 cases. The Pneumonia Study Group of the Community of Valencia].

The present work prospectively analyzes, in a multicentric study, viral pneumonias acquired in the community during one year. Were studied 510 patients diagnosed of pneumonia in hospital, or whom 62 (12.1%) had a viral origin. Influenza virus A and B were the most common causative agents (47.6% and 20.6% respectively). Smoking habit was present in 44% of patients, previous OCFA in 45% and other previous pathology in 64.4%. The greatest number of registered cases was during December. The most frequent radiologic finding was alveolar pattern. Evolution in general, was favourable with a low mortality rate (one case).

Adult↗