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At least 973 records · Page 54Linked to original sources
PubMed1992

Use of derivatization reactions with adsorptive stripping voltammetry for determining fotemustine in biological samples.

A method is described for determining the new fotemustine antineoplastic in human serum. The method is based on the derivatization of the original molecule by means of diazotization and coupling reactions. The derivatization product is determined by means of adsorptive stripping voltammetry. The calibration graphs were linear over the range 6 x 10(-9)-8 x 10(-7) and 6 x 10(-10)-8 x 10(-8) M, according to whether the coupling reagent was 1-naphthylamine or 1-naphthol, respectively. At the same time, the detection limits are 4.1 x 10(-9) and 1.4 x 10(-10) M, respectively. The method was applied to determine this antineoplastic in human serum, after a liquid-liquid extraction process, from which recovery factors of 95.6% has been obtained.

Antineoplastic Agents↗
PubMed2004

Toward fingerprinting cellular lipidomes directly from biological samples by two-dimensional electrospray ionization mass spectrometry.

Cellular lipids are composed of linear combinations of aliphatic chains covalently attached to backbones and/or head groups that collectively represent the cellular lipidome. Herein we present a novel two-dimensional electrospray ionization mass spectrometric approach to fingerprint most of the major and many of the minor lipid classes in the hepatic cellular lipidome, which collectively represent >80% of the total lipid mass, directly from their chloroform extracts. Through lipid class-selective intrasource ionization and subsequent analysis of two-dimensional cross-peak intensities, the chemical identity and mass composition of individual molecular species of most mouse hepatic lipid classes were determined from its chloroform extract. This new integrated platform provides a robust foundation for the automated analysis of multidimensional mass spectra to advance the level of analytical scripting in lipidomics to a new plateau.

Animals↗
PubMed2005

Micell-mediated extraction for the spectrophotometric determination of nitrite in water and biological samples based on its reaction with p-nitroaniline in the presence of diphenylamine.

A cloud point extraction process using the nonionic surfactant Triton X-100 to extract nitrite from aqueous solution was investigated. The method is based on the color reaction of nitrite with p-nitroaniline in the presence of diphenylamine in acid media and micell-mediated extraction of an azo product. The optimal extraction and reaction conditions (e.g., acid concentration, reagent concentration, effect of time) were studied, and the analytical characteristics of the method (e.g., limit of detection, linear range, molar absorptivity, preconcentration, and improvement factors) were obtained. Linearity was obeyed in the range of 2-40 ng ml(-1) of nitrite ion. The detection limit of the method is 0.87 ng ml(-1) of nitrite ion. The interference effect of some anions and cations was also tested. The method was applied to the determination of nitrite in tap water, waste water, and human urine samples.

Aniline Compounds↗
PubMed2005

A cryogenic optical waveguide spectrometer for the measurement of low-temperature absorption spectra of dilute biological samples.

A cryogenic optical waveguide spectrometer that uses a Teflon-AF 2400 liquid core waveguide is described. In comparison to standard low-temperature absorption techniques, the liquid core waveguide approach not only affords the use of microliter samples but also provides significant improvements in sensitivity. Here we show low-temperature absorption spectra of various flavoproteins, including DNA photolyase, measured using this new technique. The technique has high reproducibility and can afford the detection of 15 ng of flavoprotein. In addition, the technique requires several hundredfold less protein than standard low-temperature techniques for the same sensitivity. The performance of the spectrometer in the ultraviolet (UV) region is investigated experimentally and compared with standard UV absorption techniques. Results indicate that, below 300 nm, the observed absorbances deviate from the Beer-Lambert law.

Cold Temperature↗
PubMed2005

Response rates in a case-control study: effect of disclosure of biologic sample collection in the initial contact letter.

PURPOSE: Participants in epidemiology studies are often asked to complete an interview and to provide biospecimens. In a population-based case-control study of kidney cancer involving an interview and optional biospecimens, we examined whether mentioning the biospecimens in the initial contact letter adversely affects willingness to be interviewed. METHODS: Eligible cases (n = 434) and controls (n = 775) in Detroit were alternately assigned to receive one of two versions of the contact letter. Both explained that the study involves an interview with 100 dollars compensation plus an optional component with additional compensation; only one disclosed that the optional component involved biospecimens. RESULTS: There were no meaningful differences between the groups in willingness to be interviewed. However, among 303 cases and 351 controls already interviewed, the proportion providing biospecimens was higher in the fully informed group: for blood, the differences were 10.8 (95% CI, 2.0, 19.5) for cases and 6.7% (95% CI, -1.7, 15.1) for controls. Findings were similar for saliva. CONCLUSIONS: In a study involving an interview and optional biospecimens, informing people about the samples in the contact letter seems preferable to a non-specific reference to a second study component. Both approaches yielded similar interview participation rates, but biospecimen participation rates were higher among those informed about the samples in the contact letter.

Adult↗
PubMed2004

Chemical treatment of mica for atomic force microscopy can affect biological sample conformation.

An important aspect in the preparation of substrate materials to use in atomic force microscopy lies in the question of interactions introduced by treatments designed to immobilize the sample over the substrate. Here we used a mica substrate that was chemically modified with cationic nickel to immobilize actin filaments (F-actin). Chemical modification could be followed quantitatively by measuring the interaction force between the scanning tip and the mica surface. This approach allowed us to observe polymeric F-actin in a structure that resembles an actin gel. It also improved sample throughput and conferred sample stability as well as repeatability from run to run.

Actin Cytoskeleton↗
PubMed2006

Design and characterization of a metalloproteinase inhibitor-tethered resin for the detection of active MMPs in biological samples.

Matrix metalloproteinases (MMPs), zinc-dependent endopeptidases, are implicated in tumor progression. We describe herein the development of a resin-immobilized, broad-spectrum synthetic MMP inhibitor for selective binding of the active forms of MMPs from different experimental samples. We confirmed the activity-based binding of MMPs to the inhibitor-tethered resin with purified human recombinant MMP-2, -9, and -14, samples of cultured cells, and tissue extracts. Our results show that only the free active MMPs, and not the zymogens or MMP/TIMP (enzyme-protein inhibitor) complexes, bound specifically to the resin. In our comparison of benign and carcinoma tissue extracts, we detected active MMP-2 and MMP-14 forms only in the cancerous tissue samples, indicating that a pool of the tumor MMPs is free of endogenous inhibitors (TIMPs), and is thus likely to contribute to proteolytic events that precipitate tumor metastasis.

Breast Neoplasms↗
PubMed2005

Separation of 3'-azido-2',3'-dideoxythymidine pronucleotide diastereoisomers in biological samples by CZE with cyclodextrin addition.

The possibility of using capillary electrophoresis as an alternative technique to HPLC for the separation of pronucleotide diastereoisomers of AZT was investigated. In the pH range 6.2-7.2 where the analytes are stable, a chiral additive, carboxymethyl-beta-CD, was found appropriate to enable the separation of the uncharged diastereoisomers. An experimental design strategy was used to study the influence of several parameters (CD and phosphate buffer concentration, methanol content of the electrolyte, injected volume, capillary length, electric field and separation temperature) on the separation and find suitable analytical conditions for monitoring the prodrugs in cell extracts. The diastereoisomers of the three tBuSATE phenylphosphotriester derivatives of AZT studied could be fully resolved within short analysis time (less than 10 min). Method validation results showed satisfactory results for linearity, accuracy and repeatability.

Buffers↗
PubMed2005

Evaluation of a focused sonication probe for arsenic speciation in environmental and biological samples.

Arsenic speciation analysis suffers in general from high sample handling time required by sample preparation. In a previous work, ultrasonic probe has been proved to reduce sample treatment time for arsenic extraction in rice to only a few minutes. Base upon the obtained results, here several extraction media for chicken, fish and soil samples (SEAS G6RD-CT2001-00473) have been studied and evaluated employing the same technique. Chicken sample needed an enzymatic treatment in order to liberate the species linked to the protein matrix. Extraction of the major species in fish, AsB, was quantitatively achieved in water in 1 min. Also 1 min was enough to leach about 85% of species present in soils and sediments, mainly the inorganic ones, using H(3)PO(4). In all cases, no inter-conversion among As species was observed. The five species found in those samples were separated using an improved HPLC-ICP-MS method in only 11 min, with detection limits at the ng l(-1) level. The proposed methods were validated by analysing several Certified Reference Materials: SRM 1,568 a rice flour, CRM-627 tuna fish tissue, SOIL-7 soil and MURST-ISS-A1 Antarctic sediment.

Animals↗
PubMed2006

Molecularly imprinted polymers for the clean-up of a basic drug from environmental and biological samples.

A molecularly imprinted polymer (MIP) was synthesized and evaluated to selectively extract an alpha-blocker, i.e. alfuzosin, from human plasma. The synthesis of the MIP was performed in dichloromethane with methacrylic acid as monomer and the target drug as template. A first series of experiments was carried out in dichloromethane to estimate the potential of the MIP in its specific recognition medium, i.e. dichloromethane, by developing a selective procedure and by measuring the capacity of the sorbent. An optimized procedure was developed for the selective extraction of alfuzosin with a recovery close to 100% in this medium and a specific capacity of 1.3 micromol g(-1) of MIP was measured. A study in aqueous media was also carried out by a comprehensive approach of the retention mechanism in order to build a selective procedure of extraction. The effects of the amount and of the charge of cations were studied and an optimal pH value was defined to limit matrix effects. Then, the alfuzosin MIP was then directly used to selectively extract the target drug from human plasma with an extraction recovery of 60%. Lastly, a soil was extracted by a pressurized solvent and the resulting extract was cleaned up on the MIP, showing the possibility to use this selective sorbent for the sample treatment of various complex matrices.

Adrenergic alpha-Antagonists↗
PubMed2005

Perfluorooctanesulfonate and related fluorochemicals in biological samples from the north coast of Colombia.

Perfluorinated compounds are widespread pollutants of toxicological importance that have been detected in environmental matrices. However, little is known on their distribution in South America. In this study, distribution of perfluorooctanesulfonate (PFOS), perfluorooctanoic acid (PFOA), perfluorohexanesulfonate (PFHxS), and perfluorooctanesulfonamide (PFOSA) was determined in the bile of mullet, Mugil incilis, and in tissues of pelicans (Pelecanus occidentalis) collected from North Colombia. Analysis was performed by HPLC mass spectrometry after ion-pair extraction. PFOS was found in all bile samples and PFOA and PFHxS were detected at lower frequency. Average concentrations of PFOS, PFOA, and PFHxS in bile of fish from Cartagena Bay, an industrialized site, and Totumo marsh, a reference site, were 3673, 370, 489 and 713, 47.4, 1.27 ng/mL, respectively. PFOS concentrations in pelican organs decreased in the order of spleen>liver>lung>kidney>brain>heart>muscle. These results suggest, for the first time, that perfluorinated compounds are also found in wildlife from Latin American countries.

Alkanesulfonic Acids↗