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At least 253 records · Page 14Linked to original sources
PubMed1987

High-performance liquid chromatography-fluorometry for the determination of thiols in biological samples using N-[4-(6-dimethylamino-2-benzofuranyl) phenyl]-maleimide.

The selective determination of thiols in biological samples was investigated by high-performance liquid chromatography using N-[4-(6-dimethylamino-2-benzofuranyl)phenyl] maleimide, which was found to give fluorescent products when treated with certain thiols. Six kinds of thiol (reduced glutathione, cysteine, N-acetylcysteine, cysteamine, homocysteine and coenzyme A) could be separated simultaneously within ca. 12 min and determined at final level of sensitivity. The method was successfully applied to the determination of thiols in rat tissues and plasma and in human normal serum.

Animals↗
PubMed1997

Simultaneous identification and quantitation of fluoxetine and its metabolite, norfluoxetine, in biological samples by GC-MS.

A sensitive method for the quantitation of fluoxetine and norfluoxetine in biological samples was developed. Blood, urine, and tissue samples were alkalinized and extracted with N-butyl chloride. The extracts were derivatized with pentafluoropropionic anhydride before gas chromatography-mass spectrometry (GC-MS). Selected ions were monitored at m/z 117 and 294 for fluoxetine; m/z 117, 176, and 280 for norfluoxetine; and m/z 122 and 299 for the internal standard fluoxetine-d5. The within-run and between-run precision as well as recovery were determined for both analytes. The empirical limit of detection was determined to be 12.5 micrograms/L for both fluoxetine and norfluoxetine, whereas the empirical limit of quantitation was 25 micrograms/L for both drugs. Calibration curves were linear in the range of 50-1000 micrograms/L for both analytes. Some drugs that were known or suspected of interfering with high-performance liquid chromatography and GC methods for fluoxetine and norfluoxetine were tested for interference. This is the only reported method that combines the use of a deuterated internal standard, selected ion monitoring by GC-MS, and derivatization for the identification and quantitation of fluoxetine and norfluoxetine.

Antidepressive Agents, Second-Generation↗
PubMed1991

[A gamma spectrometer for measurements of radionuclide concentrations in biological samples].

A CAMAC spectrometer with a scintillation detector was developed for radioactivity measurements in environmental and biological samples. The spectrometer allows one to use an additional single channel analyser for rapid isotope control and to use simultaneously a number of ADCs in a concurrent mode. A technique of efficiency calibration is described which simulates the volume sample measurement with a point reference source of photon radiation and a cylindrical water-equivalent plate-stack phantom. The minimum detectable radionuclide concentration was found to be equal 5.10(-5) Ci/kg.

Environmental Monitoring↗
PubMed1997

Logistics and design issues in the use of biological samples in observational epidemiology.

Standard epidemiological study designs are well suited to answering questions involving the collection of biological samples. However, different designs are better suited--both for design and logistic reasons--to different questions. The strengths and weaknesses of each design are discussed in relation to markers of exposure, susceptibility and early outcome, and to markers used to classify cancers into biologically defined subsets.

Animals↗
PubMed2001

Microwave heated vapor-phase digestion method for biological sample materials.

A microwave heated, vapor-phase nitric acid-hydrogen peroxide digestion method for pulverized, biological sample materials was developed. Sample masses up to 200 mg were digested using calibrated quartz inserts inside first generation type, low-pressure, Teflon-PFA microwave vessels. In the first step, samples were digested in the vapor-phase for 80 min using a progressive heating pattern. Three mL of 70% nitric acid and 0.5 mL of 30% hydrogen peroxide were used as digestion reagents. In the second step, the small residue left after first step digestion was dissolved in 1.4% nitric acid or additionally with 0.5% hydrofluoric acid by heating for 15 min. The digestion method was optimized using pike (Esox lucius) muscle as a test material. The method was further optimized using three certified reference materials. Ca, Cu, Fe, Mg and Zn were determined from NIST-SRM 1577a bovine liver by ICP-AES. Cr and Ni were determined from NIST-SRM 8433 corn bran and NRCC DOLT-2 dogfish liver by GFAAS. For all elements the values obtained were close or within certified limits. Spike recoveries were between 96 to 107%. Digestion efficiency ranged from 91 to 99%.

Animals↗
PubMed2006

Using low-E resonators to reduce RF heating in biological samples for static solid-state NMR up to 900 MHz.

RF heating of solid-state biological samples is known to be a destabilizing factor in high-field NMR experiments that shortens the sample lifetime by continuous dehydration during the high-power cross-polarization and decoupling pulses. In this work, we describe specially designed, large volume, low-E 15N-1H solid-state NMR probes developed for 600 and 900 MHz PISEMA studies of dilute membrane proteins oriented in hydrated and dielectrically lossy lipid bilayers. The probes use an orthogonal coil design in which separate resonators pursue their own aims at the respective frequencies, resulting in a simplified and more efficient matching network. Sample heating at the 1H frequency is minimized by a loop-gap resonator which produces a homogeneous magnetic field B1 with low electric field E. Within the loop-gap resonator, a multi-turn solenoid closely matching the shape of the sample serves as an efficient observe coil. We compare power dissipation in a typical lossy bilayer sample in the new low-E probe and in a previously reported 15N-1H probe which uses a double-tuned 4-turn solenoid. RF loss in the sample is measured in each probe by observing changes in the 1H 360 degrees pulse lengths. For the same values of 1H B1 field, sample heating in the new probe was found to be smaller by an order of magnitude. Applications of the low-E design to the PISEMA study of membrane proteins in their native hydrated bilayer environment are demonstrated at 600 and 900 MHz.

Biopolymers↗
PubMed1977

Determination of selenium in biological samples by gas-liquid chromatography with electron-capture detection.

Selenium can be determined quantitatively in biological samples after nitric acid-magnesium nitrate digestion and formation of 5-nitropiazselenole, by extraction into toluene for gas-liquid chromatography with electron-capture detection. The method is suitable for the determination of selenium in orchard leaves, bovine liver and human placenta, hair, blood and urine.

Chromatography, Gas↗
PubMed1993

Pulsed UV laser generated short-lived free radicals from biological samples.

EPR characterization of the short-lived free radicals generated by pulsed UV laser ablation of biological samples has been investigated using a spin trap method. The obtained EPR spectra suggest that the trapped short-lived free radicals generated by excimer laser ablation of collagen and myocardium are identical. The obtained results are discussed in association with the production scheme of free radicals and an empirical mechanism of laser generated short-lived free radicals.

Collagen↗
PubMed1997

[Selective extraction of organotin from biological sample by supercritical fluid extraction].

The preliminary separation and concentration of organotin compounds from the matrix of biological samples is necessary, due to the very low content of organotin and the fat included in samples will largely interfere the analysis of organotins. In this work, supercritical fluid extraction (SFE) for the preliminary separation and concentration of organotin has been studied. Pure CO2 was used as mobile phase. The extractives can be used to supercritical fluid chromatographic (SFC) analysis of organotins. The model sample was prepared by adding diphenyltin (DPT) to soya powder. The effects of the pressure and temperature on SFE were investigated. A small amount of fat was also extracted together with organotins. Extract was injected into SFC system, in which a Kapcell Pak ODS column was used for separation of organotin and fat. The effect of pressure on the extraction percentage of DPT and fat was investigated at 40 degrees C. At lower pressure (10-15 MPa), a maximum extraction efficiency (63%) was attained for DPT, while the fat is extracted only 28.3%. The increase in temperature is advantageous for the selective extraction of DPT. However, the extraction efficiency of DPT decreased as the extraction temperature was increased. When a lower pressure (10 MPa) and a higher temperature (50 degrees C) were used, the organotin (DPT) was extracted up to a maximum (59.9%) within 30 min, while fat was extracted only 4.9%.

Chromatography, Supercritical Fluid↗
PubMed1991

[Usefulness of warning flags in the handling of biological samples in an emergency room].

The present study evaluates the utility of biohazard precautions labels for identifying biological samples of patients with probable severe transmissible infectious diseases. The study was performed in a total of 633 patients in the emergency department of a General Hospital. In an anonymous way we determine the presence or absence of serological markers of HIV and hepatitis B infection (HBsAg) and we evaluated the labeling of the sample. Our results demonstrate the very low usefulness of this common procedure: a total of 54.5% of HIV positive patients and 87.5% of those positive to HBsAg were not marked correctly. We discuss the necessity of using universal precautions instead of labeling samples in the current way.

Blood Specimen Collection↗
PubMed1978

Automated analysis of common basic amino acids, mono-, di-, and polyamines, phenolicamines, and indoleamines in crude biological samples.

A fully automated, fast, and sensitive method for the separation of common basic amino acids and mono-, di-, and polyamines as well as phenolic- and indoleamines is described. Picomole level determination of hydroxytryptophan, tryptophan, histidine, lysine, ethanol amine, arginine, noradrenaline, diaminopropane, putrescine, histamine, cadaverine, dopamine, hexamethylenediamine, agmatine, tyramine, phenethylamine, serotonin, 5,6-dihydroxytryptamine, 5-methoxytryptamine, tryptamine, spermidine, and spermine is carried out by ion-exchange column chromatography on a single sample in 170 min of total analysis. This method is well suited for crude extracts without preliminary purification, thus reducing preparative losses. The reproducibility of the method has been studied and the percentage recovery of the different compounds after column chromatography is reported. Its application to crude samples from different biological sources such as microorganisms, vegetables, platelets, and urine is presented. This method could serve as a powerful tool for the analysis of these amino compounds in which there is currently a considerable interest.

Adult↗
PubMed1983

Kinetics of protein agglomeration. A nephelometric method for the determination of total protein in biological samples.

The kinetics of agglomeration of proteins precipitating in a viscous solution was measured by light scattering. The resulting transitory maximum was linearly proportional to the mass of protein over three orders of magnitude. The change in scattering intensity is described as a change in scattering symmetry due to a continuous increase in particle size. This method is both fast (minutes) and sensitive (30 ng protein) and is independent of the chemical composition of the different protein species and is barely influenced by size and shape of the proteins. By solubilising the protein samples in an alkaline dodecyl sulfate solution this method can be applied to all types of biological samples (e.g. tissue homogenates, membrane proteins) and also to all types of biological preparations containing detergents as well as urea, sucrose, salts and lipids.

Animals↗
PubMed1997

Particle size distribution in ground biological samples.

Modern trace and retrospective analysis of Environmental Specimen Bank (ESB) samples require surplus material prepared and characterized as reference materials. Before the biological samples could be analyzed and stored for long periods at cryogenic temperatures, the materials have to be pre-crushed. As a second step, a milling and homogenization procedure has to follow. For this preparation, a grinding device is cooled with liquid nitrogen to a temperature of -190 degrees C. It is a significant condition for homogeneous samples that at least 90% of the particles should be smaller than 200 microns. In the German ESB the particle size distribution of the processed material is determined by means of a laser particle sizer. The decrease of particle sizes of deer liver and bream muscles after different grinding procedures as well as the consequences of ultrasonic treatment of the sample before particle size measurements have been investigated.

Animals↗
PubMed2006

Application of on-line electrochemical derivatization coupled with high-performance liquid chromatography electrospray ionization mass spectrometry for detection and quantitation of (p-chlorophenyl)aniline in biological samples.

A rapid, sensitive, and specific assay for detection and quantitation of (p-chlorophenyl)aniline (CPA) in biological samples was developed. The assay was established based on rapid electrochemical oxidation of CPA to a dimerized product (1.0 V vs Pd) with the enhanced detection sensitivity of electrospray mass spectrometer (ES/MS). A "head-to-tail" dimer ([M + H]+ at m/z 217) was exhibited as the predominant species after electrochemical conversion of CPA. Optimal detection sensitivity and specificity for the dimer of CPA that was present in the biological matrix (e.g., rat urine) were achieved through on-line electrochemistry (EC) coupled with high-performance liquid chromatography tandem mass spectrometry. No matrix-associated ion suppression was observed. The limit of detection (S/N approximately 6) was 20 ng/mL, and the limit of quantitation was 50 ng/mL. The calibration curve was exhibited to be quadratic over the range of 50-2000 ng/mL with r2 > 0.99 in various biological matrixes. The assay was validated and used to study the biotransformation of p-chlorophenyl isocyanate (CPIC) to CPA in rats administered intraperitoneally with CPIC (50 mg/kg). The present LC/EC/MS/MS assay of CPA brings important technical advantages to assist in the risk assessment of new chemical entities, which have the potential to produce anilines via biotransformation.

Aniline Compounds↗
PubMed1994

Rapid validation of molecular structures of biological samples by electrospray-mass spectrometry.

A short account is presented of the method of measuring molecular masses (M(r)) of pure biological samples by electrospray ionisation mass spectrometry. It is demonstrated that the technique yields M(r) values with an effective accuracy equal to or better than 0.008% of the calculated M(r), provided that the correct molecular structure is employed in the calculation. It is therefore recommended that this method of measuring M(r)'s should be considered to form an essential part of all studies aimed at elucidating the molecular structure of purified biological macromolecules or for confirming the identity of labelled samples of such molecules.

Animals↗
PubMed1983

Trace element analysis in biological samples by using XRF spectrometry with secondary radiation.

An x-ray fluorescence method for in vitro analysis of trace elements in biological samples is presented. The method is characterised by the use of an x-ray tube with secondary targets as a monoenergetic radiation source, and by 'infinitely thin' specimens. In the experimental work, different aspects have been examined in order to optimise the sensitivity of the method. It is shown that it is extremely important to use collimators of high purity materials and very pure and thin sample supports. Regarding the geometry, it is pointed out that a collimator between specimen and detector reduces the counting rate caused by scattering in air and other materials. Scattering in the biological matrix is reduced by preconcentration of biological liquids or tissues. The method has been applied to the analysis of blood serum samples. Typical sensitivities for Fe and Rb are 1.6 ng cm-2 and 1.5 ng cm-2 respectively, in a counting time of 10(3) s.

Blood Chemical Analysis↗
PubMed1986

A direct and sensitive determination of histamine in acid-deproteinized biological samples by high-performance liquid chromatography.

A convenient method for the routine measurement of histamine (HA) in biological samples was developed. This method does not require any preliminary purification or concentration of HA, and features high sensitivity, specificity, and reliability. The method consists of the direct application of the acid-deproteinized sample to high-performance liquid chromatography on a sulfonated polystyrene column with detection by means of a postcolumn fluorogenic reaction with o-phthaladehyde. The detection limit was found to be 0.1 pmol (signal-to-noise ratio = 3). The coefficient of variation for measurements of 10 pmol of standard histamine was 1.1%. Each chromatography takes only 10 min and therefore more than 50 samples can be measured in a day. The high sensitivity of the method allows it to be applied even to samples of very low HA concentration such as human plasma without any procedure for concentration of the sample, and further, only 0.1 ml of the sample is necessary for determination. The method was applied to compare the HA levels of the whole blood and plasma of man and various animals. Applications of the method to the supernatant of rat peritoneal mast cell incubates and to extracts of mouse brain and stomach are also described.

Acids↗