Biomedical subjects

Fernando M Lanças

Publications and source records attributed to Fernando M Lanças.

10 recordsLinked to original sources

PubMed2006

Optimization and validation of HPLC-UV-DAD and HPLC-APCI-MS methodologies for the determination of selected PAHs in water samples.

Polycyclic aromatic hydrocarbons (PAHs) are environmental contaminants resulting from emissions of a variety of sources including industrial combustion, discharge of fossil fuels, and residential heating. Because of their mutagenic and carcinogenic properties, the study of PAHs in environmental matrices is of great importance. In this work, the extraction of 9 out of the 16 PAH priority pollutants according to the U.S. Environmental Protection Agency is carried out through liquid-liquid extraction (LLE) and solid-phase extraction (SPE). The determination of PAHs is made by high-performance liquid chromatography with diode-array detection and liquid chromatography-atmospheric pressure chemical ionization mass spectrometry. Between the extraction techniques used, LLE is revealed to be efficient in the extraction of the higher molecular weight PAHs, though SPE is adequate for the extraction of all PAHs. In the real water samples analyzed, no PAH is detected under the analysis conditions used.

Atmospheric Pressure↗

PubMed2005

Automated microcolumn-switching system for drug analysis by direct injection of human plasma.

This study presents the application of a system that joins the known advantages of capillary liquid chromatography (e.g., higher concentration of the analytes and lower consumption of mobile phase) with those of column-switching using restricted access material (RAM) (sample clean up and extraction) to the analysis of fluoxetine in plasma samples. Automatically, the system loads the biological sample, while a RAM-BSA-C18 column (50 mm x 520 microm) excludes the macromolecules and focuses the analytes; afterwards, a second mobile phase elutes the analytes, in backflush mode, and provides the separation in a C18 analytical column (100 mm x 520 microm). We optimized the procedure for a total analysis time of 25 min. Using this approach the calibration curve shows r=0.998 with a linearity range from 20 to 500 ng ml(-1). Precision, calculated as relative standard deviation (RSD), was<20%. The developed miniaturized system showed to be adequate and attractive, demonstrating a large potential for sample preparation.

Automation↗

PubMed2005

Development of an improved heated interface for coupling solid-phase microextraction to high-performance liquid chromatography.

The aim of the study described in this report has been the development and the evaluation of a new improved interface to be operated under continuous heating, for on-line coupling solid-phase microextraction (SPME) to high-performance liquid chromatography (HPLC). Heating is desirable to increase desorption rate and decrease carryover. The results obtained have been compared with that obtained by off-line desorption and online desorption without heating. The SPME-HPLC interface described here has an inner volume of 60 microL, fixation for infinite points and a novel leak less sealing system. When the heating system was used, the area values were almost 10-fold higher than that obtained using the off-line mode. The obtained chromatograms showed an increasing of the area and height of chromatographic peaks and proved the excellent performance and reproducibility of the interface developed in this work.

Chemical Fractionation↗

PubMed2005

Determination of flavonoids in cultivated sugarcane leaves, bagasse, juice and in transgenic sugarcane by liquid chromatography-UV detection.

A high-performance liquid chromatography (HPLC) method with photo-diode array (DAD) detection was developed to separate and quantify flavonoids in sugarcane leaves and bagasse (= the crushed sugarcane refuse from juice extraction), and in sugarcane juice. Sugarcane flavonoids consist of a complex mixture of aglycones and glycosides (including flavonolignan glycosides), and the HPLC-UV method herein proposed is suitable for their quantification as total flavonoids. This method was applied to analyze samples of cultivated sugarcane, commercial juice and transgenic sugarcane leaves. Sugarcane leaves proved a promising source of flavonoids: an average of 1.10 mg of total flavonoids/g plant material was found in fresh leaves. Moreover, the flavonoid content of sugarcane juice (0.6 mg/mL) is comparable to other food sources of flavonoids previously reported. Transgenic sugarcane leaves ("Bowman-Birk" and "Kunitz") were compared with non-modified ("control") plant samples using the proposed HPLC-UV method, which indicated that the content of total flavonoids in transgenic plants is different from that in non-modified sugarcane.

Cellulose↗

PubMed2005

Ultratraces analysis of organochlorine pesticides in drinking water by solid phase extraction coupled with large volume injection/gas chromatography/mass spectrometry.

This study describes an SPE coupled with large volume injection (LVI) analytical method for the analysis of organochlorine pesticides, BHC (alpha, beta, delta), aldrin, endosulfan (alpha, beta), endrin, dieldrin, and DDT, from aqueous samples. Determination was carried out by GC with MS. The LODs of organochlorine pesticides were determined at 10 ng/L concentration levels, and the results show that SPE-LVI-GC/MS has the potential to accurately determine organochlorine pesticides in water, as it avoids analyte classes in the various steps of a typical extraction procedure.

Chromatography, Gas↗

PubMed2005

Optimization of a methodology for the determination of organochlorine pesticides in surface water by SPME-GC/MS.

In the present work experimental conditions were optimized for the analysis of organochlorine traces in water matrix using solid-phase microextraction (SPME) followed by gas chromatography with mass selective detector. The parameters including time of exposure of the fiber in the aqueous sample, fiber type, agitation speed, pH, ionic forces, temperature of adsorption, and time of desorption were evaluated. The best conditions to analyze organochlorine were obtained by using higher than room temperature, agitation of the sample, extraction time of 40 min, and polyacrylate fiber.

Adsorption↗

PubMed2004

Preparation and use of packed capillary columns in chromatographic and related techniques.

In this paper general considerations related to the various approaches and parameters influencing the preparation of highly efficient and stable capillary columns for use in liquid chromatography and related techniques are presented and the column production process is discussed in some detail. The different packing methods available for delivering a packing material into a capillary column are discussed from a practical viewpoint. Packing with a gas (dry packing), packing with a liquid solvent or a mixture of solvents (slurry packing), packing with supercritical carbon dioxide, electrokinetic packing, and sol-gel packing technologies are introduced and discussed throughout the paper. Practical recommendations for obtaining highly efficient (high plate numbers) and stable capillary packed columns are also addressed and discussed.

Journal Article↗

PubMed2003

Solventless sample preparation for pesticides analysis in environmental water samples using solid-phase microextraction-high resolution gas chromatography/mass spectrometry (SPME-HRGC/MS).

Solid-phase micro-extraction (SPME) coupled on line with high resolution gas chromatography and mass spectrometric detection is described for the analysis of pesticides in environmental water samples. Experiments were performed in order to optimize the SPME extraction conditions for selected pesticides including tiomethon, trichorfon, dimethoate, diazinon, malathion, dicofol, methidathion, ethion, bromopropylate and pyrazophos from spiked water solutions. To enhance the SPME efficiency, experimental conditions including the fiber composition, stirring rate, temperature, adsorption time, desorption time and salt concentration were optimized. After validation, the SPME-GC/MS methodology was applied to real-world environmental water samples.

Acrylic Resins↗

PubMedDate not supplied

A HPTLC densitometric determination of flavonoids from Passiflora alata, P. edulis, P. incarnata and P. caerulea and comparison with HPLC method.

A high-performance thin layer chromatographic (HPTLC) method was developed in order to determine quantitatively the flavonoids in leaves of Passiflora alata, P. edulis, P. caerulea and P. incarnata. The content of orientin and isoorientin was determined, and the results were compared with those obtained using a quantitative HPLC-UV method. The latter employed rutin as standard and was developed to analyse flavonoid content from Passiflora leaves for the purpose of ensuring the quality of Passiflora phytomedicines. The results obtained using the two methods indicate that there are qualitative and quantitative differences in the flavonoids of the reference Passiflora species studied. The two methods were also employed to analyse commercial samples to illustrate their application in qualitative ('fingerprint') and quantitative determination, demonstrating their feasibility in the quality control of flavonoids from crude Passiflora drugs and phytomedicines. The HPLC conditions used are also suitable for the quantitative analysis of aqueous extracts (Passiflora infusions).

Anti-Anxiety Agents↗

PubMedDate not supplied

Simultaneous plasma lamotrigine analysis with carbamazepine, carbamazepine 10,11 epoxide, primidone, phenytoin, phenobarbital, and PEMA by micellar electrokinetic capillary chromatography (MECC).

The determination of lamotrigine (LTG) simultaneously with carbamazepine (CBZ), carbamazepine 10,11 epoxide (CBZ-E), primidone (PRM), phenytoin (PHT), phenobarbital (PB), and 2-phenyl-2-ethyl-malonamide (PEMA) in human plasma was developed using micellar electrokinetic capillary chromatography (MECC) with a diode-array detector. The reproducibility of both separation and quantitation with MECC analysis were appropriate for the intra- and interassay coefficients. The evaluated drugs concentration intervals of LTG, 0.5-10.0 micro g/mL; CBZ, 1.0-16.0 micro g/mL; PEMA, 1.0-20.0 micro g/mL; PB, 1.0-60.0 micro g/mL; PRM, 1.0-20.0 micro g/mL; PHT, 0.7-40.0 micro g/mL; and CBZ-E, 1.0-14.0 micro g/mL were linear with correlation coefficients higher than 0.987 and coefficients of the variation of the points of the calibration curve lower than 10%. The limit of quantitation of the investigated drugs in plasma varied from 0.5 to 1.0 micro g/mL, depending upon the drug. The MECC technique was sensitive enough to work with microsamples into the subtherapeutic, therapeutic, and toxic concentrations, as well as showed to be simple and efficient when applied to monitoring therapeutic drugs in patients treated with a combination of lamotrigine and other antiepileptic drugs such as hepatic enzyme-inducing agents.

Anticonvulsants↗