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At least 703 records · Page 39Linked to original sources
PubMed2001

Determination of silicon in biological samples by ICP-OES after non-oxidative decomposition under alkaline conditions.

A non-oxidative alkaline sample digestion procedure using tetramethylammonium hydroxide and a high pressure, microwave assisted autoclave digestion system was developed. The silicon concentrations of the digested samples were measured by inductively coupled axial plasma optical emission spectrometry (ICP-OES). Details of the digestion conditions as well as the optimised instrumental parameters for ICP-OES are described. The method was developed and tested using silicon-spiked ascorbic acid and applied to samples of animal tissue and organs. The total silicon content of two different reference materials, NIST 1577b Bovine liver and BCR 184 Bovine Muscle having neither certified nor informational values for Si was determined. The results obtained are compared with the results of independent methods such as wavelength dispersive x-ray fluorescence spectrometry (WDXRF) and solid sampling electrothermal atomic absorption spectrometry (ETAAS). The method described achieves a limit of detection of 2 mg kg(-1) using 100 mg of solid biological or organic material and covers a concentration range of up to 500 mg kg(-1).

Animals↗
PubMed2002

First- and second-order multivariate calibration applied to biological samples: determination of anti-inflammatories in serum and urine.

First- and second-order multivariate calibration of fluorescence data have been compared as regards the determination of anti-inflammatories and metabolites in the biological fluids serum and urine. The simultaneous resolution of naproxen-salicylic acid mixtures in serum and naproxen-salicylic acid-salicyluric acid mixtures in urine was accomplished and employed for a discussion of the relative advantages of the applied chemometric tools. The analysis of second-order fluorescence excitation-emission matrices was performed using iteratively reweighted generalized rank annihilation method (IRGRAM), parallel factor analysis (PARAFAC), and self-weighted alternating trilinear decomposition (SWATLD). The results were compared with first-order fluorescence emission data analyzed with partial least-squares regression (PLS). In all cases, the performance of the methods was improved through the formation of inclusion complexes of the analytes with beta-cyclodextrin. The concentration ranges in which the analytes could be determined were as follows: naproxen, 0-250 ng mL(-1) in serum and 0-200 ng mL(-1) in urine; salicylic acid, 0-500 ng mL(-1) in serum and 0-300 ng mL(-1) in urine, and salicyluric acid, 0-300 ng mL(-1) in urine.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1990

Chelation ion chromatography as a method for trace elemental analysis in complex environmental and biological samples.

The development and evaluation of a new method for the determination of trace transition and rare-earth elements based on the combination of chelation and ion chromatography are described. The new method, chelation ion chromatography (Chelation IC), uses a chelating column to concentrate and separate transition and rare-earth elements from the common alkali and alkaline-earth metals, as well as other matrix components, prior to analysis by ion chromatography. The sample fraction from the chelating column contains only the concentrated analyte ions, thus eliminating interfering matrix components from complex matrices such as seawater and digested biological, botanical, and geological materials. This combination of chelation and ion chromatography provides a technique that makes possible the determination of trace elements in complex matrices that have proven to be difficult or impossible to analyze by ion chromatography or conventional atomic spectroscopy techniques.

Animals↗
PubMed1986

Handling of environmental and biological samples via pre-column technologies.

Sample handling is still a weak point in chromatography and in analytical chemistry in general. One consideration is the automation potential of new procedures. Solid-liquid extraction techniques in combination with pre-column technology are particularly promising in this regards. The construction and geometry of pre-columns both for conventional and narrow-bore HPLC are of major importance, since band broadening should be kept at a minimum for an optimal functioning of the analytical system. The various operations that can be carried out with such a pre-column are trace-enrichment, clean-up of the sample which depends on the type of adsorbents used in the precolumn, i.e., polar or apolar materials, ion exchangers or metal covered surfaces, etc., protection of the analytical column, field sampling and storage of samples and as a substrate for on-column chemical derivatizations. These various operations are demonstrated with practical examples from the fields of environmental and biological analysis. The selectivity can be further enhanced by coupling pre-column technology with selective detection models such as diode array UV, electrochemical or fluorescence detection. This enables the construction of optimal and integrated analysis systems which are fully automated and microprocessor controlled. They can also be made compatible with miniaturized LC-technology.

Autoanalysis↗
PubMed1994

Determination of cobalt in biological samples by radiochemical neutron activation analysis employing reverse-phase chromatography.

We report the final part of our "on-line yield" pilot program in this article. This last part deals with aspects of accuracy and precision of the determination of cobalt in biological materials by RNAA with on-line yield determination. To obtain an insight into the accuracy of the technique, certified reference materials were analyzed, and for selected materials, results obtained by INAA and RNAA of identical samples have been compared. It shows that the mineralization in our RNAA scheme may be a sample-related source of systematic errors that is not related to the presence or absence of HF. Finally, we present some critical notes on pros and cons of the practice of on-line yield concept and some ideas for further research.

Animals↗
PubMedDate not supplied

Application of HPLC-thermospray ionization mass spectrometry for the analysis of triprolidine and its metabolite hydroxymethyltriprolidine in biological samples.

High-performance liquid chromatography coupled to positive ion mode thermospray ionization mass spectrometry has been used to characterize triprolidine and its known metabolite hydroxymethyltriprolidine. The method allows direct analysis of these compounds in complex biological matrices. Analysis of an extract from a microbial biotransformation experiment with triprolidine was performed and the results included two baseline-resolved chromatographic peaks. The [M + H]+ ion obtained from the mass spectrum of the first peak was consistent with that of hydroxymethyltriprolidine, and the mass spectrum of the second peak corresponded to triprolidine. Under the described conditions, the minimum detectable level of triprolidine without filament enhancement was estimated at about 10 micrograms injected on column.

Chromatography, High Pressure Liquid↗
PubMed2000

Solid-phase extraction and liquid chromatographic quantitation of quinfamide in biological samples.

This paper describes a high-performance liquid chromatographic method for the assay of quinfamide and its main metabolite, 1-(dichloroacetyl)-1,2,3,4,-tetrahydro-6-quinolinol, in plasma, urine and feces. It requires 1 ml of biological fluid, an extraction using Sep-Pack cartridges and acetonitrile for drug elution. Analysis was performed on a CN column (5 microm) using water-acetonitrile-methanol (40:50:10) as a mobile phase at 269 nm. Results showed that the assay was linear in the range between 0.08 and 2.0 microg/ml. The limit of quantitation was 0.08 microg/ml. Maximum assay coefficient of variation was 14%. Recovery obtained in plasma, urine and feces ranged from 82% to 98%.

Amebicides↗
PubMed1999

Cytokine measurement in biological samples after physicochemical treatment for inactivation of biosafety level 4 viral agents.

Physicochemical techniques such as gamma-irradiation, membrane disruption by detergents like sodium dodecyl sulfate (SDS), and fixation with formaldehyde or paraformaldehyde are routinely used to inactivate biological specimens from patients and animals infected with Filoviruses and Arena viruses that must be studied in BSL 4 facilities. The effects of these inactivation techniques on the levels of immunologically active proteins like cytokines and chemokines are not known. Therefore, we investigated the effect of several decontamination techniques on the immunoreactivity and bioactivity of the inflammatory cytokines IL-1beta, IL-6, TNF-alpha, IL-12, and IFN-gamma, the anti-inflammatory cytokine IL-10, and the chemokine IL-8 in biological specimens. SDS (96%-100% reduction), paraformaldehyde treatment (11%-100% reduction), and heat denaturation (75%-100% reduction) were found to decrease markedly the levels of all cytokines and chemokines as measured by enzyme-linked immunosorbent assays. In contrast, gamma-irradiation was found to have little or no effect on the immunoreactivity of these cytokines/chemokines and on the biological activity of tumor necrosis factor (TNF) alpha. Our data suggest that, of the agents tested, gamma-irradiation is the preferred technique for inactivation of biological specimens containing viral agents that require the use of BSL 4 for immunological studies.

Anti-Infective Agents, Local↗
PubMed1977

Rapid chemical dehydration of biologic samples for scanning electron microscopy using 2,2-dimethoxypropane.

Acidified 2,2-dimethoxypropane (DMP) has been used as a rapid chemical dehydrating agent en route to plastic embedding and ulthrathin sectioning for conventional electron miscroscopy (J Histochem Cytochem 23:107, 1975). We have used DMP to dehydrate biologic specimens prior to critical point drying and metal coating for scanning electron microscopy. There is no difference in either the gross architecture or the fine surface structure of mouse small intestine and trachea, rat trachea and kidney, and cultured fibroblasts, between samples dehydrated in DMP for 5 min to 30 days and those conventionally dehydrated in ethanol or acetone. DMP dehydration is advantageous in speed, economy and apparent completeness.

Animals↗
PubMedDate not supplied

Current analytical methods for the detection of dityrosine, a biomarker of oxidative stress, in biological samples.

Dityrosine is a fluorescent molecule formed as a result of normal posttranslational processing. In many structural proteins, dityrosine confers resistance to proteolysis and physicochemical trauma as a stabilizing crosslink. Dityrosine has also been found in oxidative/nitrative stress under a variety of conditions and biological systems. In this regard, it has been used as an important biomarker for oxidatively modified proteins during UV and gamma-irradiation, aging, and exposure to oxygen free radicals, nitrogen dioxide, peroxynitrite, and lipid hydroperoxides. Renewed interest in dityrosine and other tyrosine oxidation products as clinical indicators of oxidative modification has driven the development of important techniques for the specific analysis and quantification of these molecules. The presence of elevated levels of dityrosine in mammalian tissue and urine samples has been measured by chromatographic separation followed by mass spectrometry GC-MS and HPLC-MS/MS. Increases in dityrosine levels have been associated with pathologies such as eye cataracts, atherosclerosis, acute inflammation, and Alzheimer's disease. The continued development of, and increased accessibility to, improved mass spectrometric instrumentation will expand the capability, feasibility, and sensitivity with which specific biomarkers like dityrosine can be measured.

Biomarkers↗
PubMed1982

A critical evaluation of LC-EC for the simultaneous determination of 5-hydroxytryptophan, 5-HT, 5-HIAA and HVA in biological samples using GC-MS for validation.

A method has been developed for LC-EC quantitation of 5-hydroxyindoles (5-HT, 5-HTP, 5-HIAA and N-acetyl-5-HT) and the catecholamine metabolite HVA from brain tissue and biological fluids such as CSF. It involves tissue homogenization in chromatographic buffer containing a non-biological internal standard, 5-hydroxyindole, that can be used to quantitate all the indoles of interest as well as HVA. Comparable chromatographic separations were obtained with conventional C18 stainless steel columns (5 and 10 um) and with the Waters C18 radial compression module with a 5 or 10 um C18 cartridge. The LC-EC quantitation of 5-HT, in brain tissue and of 5-HIAA and HVA in CSF has been validated by GC-MS-SIM. The LC-EC method is sensitive in the high pg range on a routine basis.

5-Hydroxytryptophan↗
PubMed1979

Simultaneous gas chromatographic determination of lorcainide hydrochloride and three of its principal metabolites in biological samples.

A method is described for the determination of the antiarrhythmic drug lorcainide hydrochloride and its three main metabolites in plasma, urine, faeces and tissues from man and animals. The procedure involves the extract of the parent drug, its metabolites and the internal standard from the biological materials at different alkaline pH values, back-extraction into sulphuric acid and re-extraction into the organic phase (heptane--isoamyl alcohol). After silylation of the different phenolic and the N-dealkylated metabolites, analyses were carried out by automated gas--liquid chromatography with electron-capture detection. The method has a sensitivity limit of 5 ng for lorcainide, and 10--20 ng for the various metabolites, per millilitre of plasma. The method was applied to urine, faeces, plasma and tissue samples from man and animals. It was also suitable for automatic sample analysis.

Acetanilides↗
PubMed1997

Assay for the (R)- and (S)-enantiomers of salsolinols in biological samples and foods with ion-pair high-performance liquid chromatography using beta-cyclodextrin as a chiral mobile phase additive.

A chromatographic procedure was devised for the quantitative determination of the enantiomers of salsolinol and N-methylsalsolinol, which are biologically important alkaloids. The enantiomers of salsolinol and N-methylsalsolinol were completely separated using beta-cyclodextrin in a reversed-phase ion-pair system. The HPLC method was sensitive enough to detect the isoquinolines at a concentration less than 0.1 pmol per injection. The presence of (R)- and (S)-salsolinol was confirmed in fermented foods and beverages, while N-methylsalsolinol was not detected. On the other hand, the (R)-enantiomers of both salsolinol and N-methylsalsolinol were found to predominate in the human brain.

Beverages↗
PubMed1987

Detection of phospholipid peroxides in biological samples.

Peroxidation of membrane lipids has been hypothesized to play a key role in various types of tissue degeneration and pathology. Lipid peroxides are formed when oxygen reacts with an unsaturated fatty acid chain. Virtually all of the unsaturated fatty acids in biological systems are bound by ester linkages in phospholipids or triglycerides. Phospholipid and triglyceride peroxides are primary products of lipid peroxidation and have rarely been measured. Most of the commonly used methods for detection of lipid peroxidation are based on detection of malondialdehyde or other chemical species that are derived from oxidized fatty acids. This review presents an overview of recently developed methods aimed at identifying and measuring oxidized phospholipids and triglycerides which are direct evidence of the occurrence of lipid peroxidation in vivo.

Animals↗
PubMed1998

Detection of thioredoxin in human serum and biological samples using a sensitive sandwich ELISA with digoxigenin-labeled antibody.

Thioredoxin is a low molecular weight, redox active protein important in cellular proliferation, signal transduction and antioxidant function. Thioredoxin is secreted by normal as well as neoplastic cells and is potentially involved in paracrine cell communication as suggested by its co-cytokine activity. Thus, the thioredoxin level in biological fluids, cells and tissue homogenates could be an important indicator of physiological or pathophysiological conditions. Hence, an accurate and sensitive measurement is of paramount importance in studies involving thioredoxin. We present here an ultrasensitive enzyme linked immuno-absorbent assay (ELISA) for human thioredoxin using digoxigenin-labelled goat polyclonal anti-human thioredoxin. The assay could detect a minimum level of 15 pg/ml thioredoxin in human serum, cell culture media, and in cell and tissue samples. The assay was optimized for concentration of both antibodies, blocking agent, plates, incubation time and reaction volumes. Excellent linearity and reproducibility were obtained. The assay was applied to different baboon tissues and human serum samples. The intrassay coefficient of variation (CV) was between 6.0 to 14 and the interassay CV was from 1.6 to 11.1. Excellent parallelism of standards with serum samples, tissue homogenates or cell lysates was obtained. More than 90% recovery of human thioredoxin was observed in 10% human serum. The assay is easy to use, rapid, reproducible, but above all it is a quantitative, specific and sensitive way to measure thioredoxin in a variety of biological specimens.

Animals↗
PubMed1998

Precise quantitation of human parvovirus B19 DNA in biological samples by PCR.

An application of a quantitative PCR-based method was developed for the detection of human parvovirus B19 DNA. The procedure was characterised according to guidelines for the validation of analytical procedures. Furthermore, the reliability was demonstrated by the correct quantitation of samples of an international collaborative study. This application might be useful for studies focussed on removal and/or inactivation procedures of human parvovirus B19 as well as for general screening purposes of biological materials.

Base Sequence↗
PubMed2001

An attempt to correlate fat and protein content of biological samples with residual carbon after microwave-assisted digestion.

The residual carbon content of a variety of bovine-derived samples and forage was determined by inductively coupled plasma optical emission spectrometry with radial view configuration (ICP-OES) after microwave-assisted digestion under high pressure in a closed vessel. The original carbon concentration in the samples was determined by elemental analysis. The highest amount of original carbon content (64%) was found in viscera. After digestion, up to 75% of it was destroyed. Viscera presented the highest ether extract and blood exhibited a high crude protein content of up to 99%. The efficiency in destroying the organic matter in biological materials seemed to be related to their fat content and showed no significant difficulty for protein-rich samples. The correlation coefficient between the fat content of the samples and the residual carbon after acid decomposition was 0.9173 indicating a fair fit. However, no correlation was observed between % RC and the protein content.

Animals↗