Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Biological samples”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 901 records · Page 50Linked to original sources
PubMed1982

The estimation of low levels of 14C in biological samples by alkaline extraction and liquid scintillation counting.

A liquid extraction method capable of accurately estimating low levels of 14C in blood and faecal samples is described. The lower limit of detection is about 4 pCi of 14C per g wet wt of ovine faeces and the lowest level of quantitative determination is 33 pCi per g. Extraction of soluble material is efficient and 14C present in the extract as n-[1-14C]hexadecane, D-[U-14C]glucose, [1-14C]stearic acid, [1-14C]methionine, or Na2 14CO3 is estimated without loss. The aqueous extraction medium used contains 2.5% (v/v) Synperonic NP9 (a non-ionic emulsifier) and 3.5% NaOH and samples are decolorised using hydrogen peroxide. The extract is counted without neutralisation in an inexpensive scintillation mixture based on an emulsifiable oil rather than on an aromatic solvent. It consists of White Spirit 100 (53.8% v/v), Synperonic NP9 (30.8% v/v), octan-2-ol (10.8% v/v), benzyl alcohol (4.6% v/v) and 2,5-diphenyl oxazole (3 g/l). Ethanediol added with the aqueous alkaline extract acts as a third cosurfactant. The advantage of this mixture over one based on an aromatic solvent is that it has a much larger capacity for the concentrated blood and faecal extracts.

Animals↗
PubMed1991

Rapid electrodialytic clean-up of biological samples for high-performance liquid chromatography.

A sample clean-up system employing electrodialysis with size-selective and charge-selective membranes is described. When applied to the treatment of 0.5-ml milk samples containing sulfamethazine, the system produced an undiluted, clear solution in 3 min and eliminated the components in untreated milk that caused column fouling and double peaks. In contrast to conventional liquid- and solid-phase extraction procedures, electrodialytic clean-up is readily automated and uses no organic solvents.

Animals↗
PubMed1992

Improved determination of individual molecular species of phosphatidylcholine in biological samples by high-performance liquid chromatography with internal standards.

Phosphatidylcholine isolated from samples of bile, liver and plasma was converted into 1,2-diradylglycerobenzoate molecular species by hydrolysis with phospholipase C and reaction with benzoic anhydride. Up to seventeen molecular species were separated and determined by reversed-phase high-performance liquid chromatography with detection at 230 nm. The major improvement introduced here was the use of distearoylphosphatidylcholine as the internal standard, which corrected the results for incomplete hydrolysis and benzoylation. Other improvements concerned the clean-up of benzoyl derivatives and the chromatographic separation. The analytical results obtained were validated by comparison with the results of either lipid phosphorus or gas chromatographic determinations.

Bile↗
PubMed1992

Indirect photometric detection of polyamines in biological samples separated by high-performance capillary electrophoresis.

A rapid separation of polyamines and some related amino acids in cultured tumor cells by high-performance capillary zone electrophoresis with indirect photometric detection is demonstrated. 60 cm x 75 microns I.D. fused-silica capillary was used for the separation and quinine sulfate was used as a background electrolyte (BGE). Several polyamines (putrescine, spermidine and spermine), amino acids (lysine, arginine, histidine) and simple cations (K+, Na+) were easily separated in less than 10 min. Using the indirect photometric detection method, femtomole amounts of polyamines extracted from the tumor cells were detected from nanoliter injection volumes, and the signal response was linear over two orders of magnitude.

Animals↗
PubMed1993

Direct chiral separation of almokalant on Chiralcel OD and Chiralpak AD for liquid chromatographic assay of biological samples.

The four isomers of almokalant, a new antiarrhythmic substance under investigation, were separated by liquid chromatography on a Chiralcel OD and a Chiralpak AD column containing cellulose and amylose tris(3,5-dimethylphenylcarbamate), respectively. Both chiral stationary phases separate almokalant into the four isomers, but the retention orders are different if the carbamate is derivatized on cellulose or amylose. The Chiralcel OD column was used for the separation and determination of the isomers in urine at levels down to 100 nmol/l for the first three eluted and 200 nmol/l for the last with a relative standard deviation of less than 15%. The fluorescence response was increased by post-column ionization after stereoselective separation on the Chiralpak AD column. The isomers of almokalant could be determined at levels down to 10 nmol/l in plasma with a relative standard deviation of less than 15%.

Amylose↗
PubMed1993

Speciation of inorganic and organotin compounds in biological samples by liquid chromatography with inductively coupled plasma mass spectrometric detection.

This paper describes the effect of inorganic tin chloride on the separation of trimethyl-, tributyl- and triphenyltin-chlorides by reversed-phase ion-pair high-performance liquid chromatography with detection by inductively coupled plasma mass spectrometry. The detection limits are 1.6 pg, 1.5 pg and 2.3 pg as tin for trimethyltin, tributyltin and triphenyltin, respectively. The relative standard deviation for ten injections of 20 ng of the tin compounds was less than 5%. Inorganic tin was held strongly on the columns used, to a greater extent on the silica column compared to the polymer column. Extraction and determination of tributyltin and triphenyltin as chlorides in fish tissue (certified reference material) and tuna fish (grocery store) were performed. The recovery study from fish tissue showed an efficiency of over 90% for both tributyltin and triphenyltin and over 60% recovery for spiked tuna.

Animals↗
PubMed1994

Comparison of UV absorption and electrospray mass spectrometry for the high-performance liquid chromatographic determination of domoic acid in shellfish and biological samples.

Domoic acid, a neurotoxic amino acid produced by the marine diatom Nitchia pungens multiseries, was determined in samples of anchovies, razor clams, mussels, crab, rat serum, urine and feces by HPLC with UV absorption and electrospray (ESI) mass spectrometric (MS) detection. Shellfish samples were extracted with methanol-water followed by clean-up of the extracts with solid-phase extraction cartridges (strong anion or strong cation exchange). An aliquot of the fraction containing the domoic acid was analysed by HPLC. HPLC column size, mobile phase composition and flow-rate were selected so that essentially the same conditions could be used for both HPLC-UV and HPLC-ESI-MS with selected ion monitoring (SIM) determinations. These included the use of acetonitrile-water-formic acid as the mobile phase, at a flow-rate of 0.2 ml/min (split 13:1 for HPLC-ESI-MS-SIM, 10 microliters/min to the mass spectrometer). The results indicated that extracts found positive by the HPLC-UV method could be readily confirmed directly by HPLC-ESI-MS-SIM without additional sample treatment down to levels of 0.1 micrograms/g of domoic acid. This study demonstrates the use of HPLC-ESI-MS-SIM for the routine confirmation of domoic acid in a wide variety of samples.

Animals↗
PubMed1992

Determination of prostaglandin metabolites in biological samples by competitive time-resolved fluoroimmunoassay.

We describe a time-resolved fluoroimmunoassay method for the determination of 13,14-dihydro-15-ketoprostaglandin E2 (PGEM) and 13,14-dihydro-15-ketoprostaglandin F2 alpha (PGFM) in femtomolar ranges. Polyclonal antibodies were raised in rabbits and the antigen was labelled with europium by the avidin-biotin technique. A second antibody, directed to rabbit IgG, was coated onto the solid phase. The IgG-PG-europium complex was bound by the second antibody, giving a rapid and complete separation of antibody-bound and free antigen. The detection limit was 0.2 pg/assay for PGFM and 1.2 pg/assay for PGEM. The intra-assay CV ranged from 4.6% to 9.3% and the interassay CV from 6.7% to 11.4%. A good correlation was obtained between the results from TR-FIA and RIA when the method was applied to the investigation of tissues from breast cancer. We conclude that the TR-FIA is more sensitive and much faster than the RIA and avoids the use of radioactive material.

Bacterial Proteins↗