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At least 289 records · Page 16Linked to original sources
PubMed2002

Colorimetric determination of chloride in biological samples by using mercuric nitrate and diphenylcarbazone.

A colorimetic method is outlined for the determination of the chloride ion in biological samples (blood serum, plasma, and urine). The present method is based on the quantitative reduction of free mercuric ions by chloride ions. Chloride ions form an indissociable complex with mercuric ions. The remaining free mercuric ions form a purple complex with diphenylcarbazone with an absorption maximum at 550 nm. The reduction of color intensity at 550 nm is directly proportional to chloride concentration in the sample. The linear concentration range in the final reaction mixture was 0-100 microM with a correlation coefficient of -0.9997. The coefficient of variation for the 50 microM chloride ion in the final reaction mixture was 0.9% (n = 6). The analyzed value of chloride concentration in the human control serum Accutrol Normal (Sigma) was 101+/-4 mM (mean+/-SD, n = 12). The certified value of chloride in Accutrol Normal by Sigma is 102 mM, with a mean in the range 91-113 mM. This method was applied to the measurement of urinary chloride excretion in experimental rats. During 16-h urine collection, no food was given and rats had free access to purified water. The urinary excretion rate of chloride was 23.6+/-9.3 micromol/h (mean+/-SD, n = 8) and 126.2+/-28.0 micromol/h (n = 8) for rats fed a normal diet (2.6 g NaCl/kg diet) and a high-salt diet (82.6 g NaCl/kg diet) for 70 d prior to urine collection, respectively. This method is appropriate for low concentrations of chloride in samples or when sample volume is limiting, as in many animal studies such as metabolic urine collection from rats.

Animals↗
PubMedDate not supplied

Determination of avermectin B1 in biological samples by immunoaffinity column cleanup and liquid chromatography with UV detection.

A simple and specific procedure for determination of avermectin B1 in biological samples is described. A specific anti-avermectin B1 immunosorbent was developed. Avermectin B1 was extracted from cattle plasma, cattle meat, and pear samples. The extracts were cleaned up on a solid-phase extraction column (C18) and an immunoaffinity column. Avermectin B1 was determined by reversed-phase liquid chromatography with UV detection at 245 nm. Recoveries of avermectin B1 from samples spiked at levels of 6 and 60 parts per billion (ppb) ranged from 80 to 86%, with coefficients of variation of 5-14%. The limit of detection was 2 ppb. The procedure provides a simple and sensitive method for monitoring avermectin B1 residues in biological matrixes.

Animals↗
PubMed1983

Determination of beta-phenylethylamine as its isothiocyanate derivative in biological samples by gas chromatography mass spectrometry.

A detailed procedure of a gas chromatographic mass spectrometric assay for beta-phenylethylamine in biological samples, after its reaction with carbon disulphide to form the isothiocyanate derivative, is presented. Our method has advantages over the previous methods with the pentafluoropropionic derivative of beta-phenylethylamine in that the isothiocyanate derivative of beta-phenylethylamine is much more stable than the pentafluoropropionic derivative and that the background in selected ion monitoring is very low. Using the present method, the levels of beta-phenylethylamine in human urine, untreated and pargyline-treated rat brain were found to be 15.3 micrograms 24 h-1, 1.4 and 160 ng g-1 wet weight, respectively.

Animals↗
PubMed2006

Methylmercury determination in biological samples using electrothermal atomic absorption spectrometry after acid leaching extraction.

An efficient and sensitive method for the determination of methylmercury in biological samples was developed based on acid leaching extraction of methylmercury into toluene. Methylmercury in the organic phase was determined by electrothermal atomic absorption spectrometry (ETAAS). The methylmercury signal was enhanced and the reproducibility increased by formation of certain complexes and addition of Pd-DDC modifier. The complex of methylmercury with DDC produced the optimum analytical signal in terms of sensitivity and reproducibility compared to complexes with dithizone, cysteine, 1,10-phenanthroline, and diethyldithiocarbamate. Method performance was optimized by modifying parameters such as temperature of mineralization, atomization, and gas flow rate. The limit of detection for methylmercury determination was 0.015 mug g(-1) and the RSD of the whole procedure was 12% for human teeth samples (n=5) and 15.8% for hair samples (n=5). The method's accuracy was investigated by using NIES-13 and by spiking the samples with different amounts of methylmercury. The results were in good agreement with the certified values and the recoveries were 88-95%.

Acids↗
PubMed1983

A versatile cation-exchange procedure of measuring the seven major forms of vitamin B6 in biological samples.

A cation-exchange procedure for detecting nanogram quantities of all seven common vitamin B6 metabolites in a variety of biological samples is presented. The procedure uses gradient elution with a single column to effect separation of the seven compounds within 40 to 60 min, depending on the complexity of the sample. Postcolumn addition of buffer and bisulfite ion permits sensitive fluorometric detection of all B6 compounds at the same wavelengths (330 nm activation, 400 nm emission).

Adrenal Glands↗
PubMed1991

Determination of NAD pyrophosphorylase activity in biological samples.

A sensitive and simple method was developed for the accurate measurement of NAD pyrophosphorylase (NMN adenylyltransferase; EC 2.7.7.1) activity in biological samples. The reaction product of [4-3H]NAD was separated from the substrates [4-3H]NMN and ATP by HPLC. Under the standardized conditions of the assay, the enzyme activity in human chronic myelogenous leukemia K562 cells was found mainly in the nucleus (97%) with a sp act of 183.5 +/- 3.5 nmol/h/mg protein. The Km's for substrates NMN and ATP were 0.11 +/- 0.01 mM and 0.55 +/- 0.04 mM, respectively. This technique is highly reproducible with a 5% variation (SD) in five separate determinations. The lowest number of cells used for this enzyme assay was 41,000 with a protein content of 4 micrograms. The range of NAD produced during the assay was 2 to 200 microM. NAD pyrophosphorylase activities in the mononuclear cells of leukemic patients, human ovarian carcinoma cells, and rat liver were assayed.

Adenosine Triphosphate↗
PubMed1992

"On-line internal surface reversed-phase cleaning": the direct HPLC analysis of crude biological samples. Application to the kinetics of degradation of oligonucleotides in cell culture medium.

An "on-line" HPLC analysis of crude biological samples is described. A precolumn of internal surface reversed-phase material allows the passage of proteins and other unwanted products while retaining analytes which are transferred, concentrated and chromatographed on a conventional reverse-phase or ion-exchange HPLC column. This protocol allows precise kinetics of the degradation of an oligonucleotide in cell culture to be obtained without radiolabeling or sample preparation.

Chromatography, High Pressure Liquid↗
PubMed1991

Determination of the new morpholino anthracycline MX2.HCl and its metabolites in biological samples by high-performance liquid chromatography.

Methods for determining concentrations of a new morpholino anthracycline MX2.HCl and its metabolites in biological samples using reversed-phase high-performance liquid chromatography and fluorescence detection are described. The limits of detection were less than 1 ng/ml for all compounds after extraction from 0.5 ml of plasma using C18 Sep-Pak cartridges and consecutive solvent extraction. The recoveries from rat plasma ranged from 72.0 to 89.3%. The peak-height ratio of the fluorescence intensities of these compounds versus internal standard showed a linear correlation for concentrations up to at least 500 ng/ml in the plasma (correlation coefficient r greater than 0.999). The within-day and between-day precisions of this assay were in the range 0.8-8.7% (n = 5) and 2.0-3.5% (n = 5), respectively. The concentrations of these compounds in the blood and urine can be also determined by a slight modification of the extraction procedure.

Animals↗
PubMed1993

Specific and sensitive high-performance liquid chromatographic method with fluorescence detection for measurement of lometrexol and its polyglutamates in biologic samples.

A reversed-phase high-performance liquid chromatographic (HPLC) assay is described for the quantitative determination of lometrexol in biological samples; the assay is rapid, simple, specific, and highly sensitive. The method requires the dissociation of lometrexol from folate-binding proteins present in blood and formation of a fluorescent oxidized derivative of the compound. The dissociation of lometrexol from folate-binding proteins was achieved by acidification to pH 3.5 using ammonium formate, followed by serum protein precipitation with perchloric acid. The protein-free lometrexol was subsequently oxidized by MnO2 at 90 degrees C for 10 min. Chromatographic separation of lometrexol without interference was achieved on a C18 reversed-phase column with a convex gradient, using acetonitrile-0.1% ammonium formate, pH 7.0, as the mobile phase. In human serum and urine the calibration curve was linear between 5 and 300 nM. The lower limit of quantification was 5 nM. The method has been applied successfully to measure serum and urinary levels of lometrexol in patients.

Chromatography, High Pressure Liquid↗
PubMed1995

Reversed-phase high-performance liquid chromatography of salmon calcitonin and its degradation products in biological samples using column switching and flow-through radioisotope detection.

For the determination of salmon calcitonin and its degradation products in biological samples, a reversed-phase HPLC method with column switching and flow-through radioisotope detection has been developed using high specific activity [125I]salmon calcitonin. Effects of the precolumn packing material and washing solvent were examined in terms of [125I]salmon calcitonin recovery. Spiked samples of [125I]salmon calcitonin in plasma and kidney homogenate were injected onto a LiChroprep RP-8 precolumn after dilution with 0.1% trifluoroacetic acid. After washing the polar interfering compounds with 0.1% trifluoroacetic acid, the concentrated [125I]salmon calcitonin and its degradation products were eluted and separated on a W-Porex C18 column with a gradient of 0.1% trifluoroacetic acid in acetonitrile-water. Detection and calibration of [125I]salmon calcitonin were possible down to picogram levels. Reproducible kinetic data for the degradation of intact [125I]salmon calcitonin were possible down to picogram levels. Reproducible kinetic data for the degradation of intact [125I]salmon calcitonin by rat kidney homogenate could be traced.

Animals↗
PubMed1986

Use of enzymatic solubilization of tissues and direct injection on pre-columns of large volumes for analysing biological samples by high-performance liquid chromatography.

A pre-column technique, which can be used to introduce all types of biological samples into high-performance liquid chromatographic systems, is described. Fluids are injected directly, whereas faeces are homogenized and centrifuged and tissue samples are solubilized by the enzyme subtilisin A. Acetonitrile is added to all samples (no precipitation of proteins is seen), fluids (10%), solubilized tissue (25%) and faeces (20%), to obtain better wettability of the packing and to counteract binding. Samples of up to 50 ml are injected onto a 6 X 4 mm I.D. pre-column from which the compounds are backflushed onto the analytical column. Different packing materials for the pre-column have been used; LiChroprep RP-18 gave the best results. This system has been used for a series of different drugs, using different analytical columns and different detectors. Both gradient and isocratic elution have been used. High recoveries, good reproducibility and low detection limits are seen for routine analysis. For metabolic work, a very large enrichment factor is obtained.

Biotransformation↗
PubMed1997

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

A simple specific assay was developed for the determination of acetaldehyde in biological samples. Acetaldehyde was derivatized to 2,4-dinitrophenylhydrazone, which was determined by gas chromatography with electron-capture detection. The use of this detection method is an important device to which no one drew notice. This procedure was very simple and so sensitive that as little as 500 fmol of acetaldehyde could be measured in aqueous solution. The calibration curve of acetaldehyde was linear at least up to 40 microM. Its recoveries from human plasma and rat liver homogenate were 96.5 and 95.7%, respectively.

Acetaldehyde↗
PubMed1991

Determination of trace iodine in food and biological samples by cathodic stripping voltammetry.

This paper describes a sensitive and selective method for the determination of iodine in food and biological samples. The method involves treatment of samples by combustion in an oxygen flask and determination of iodide by cathodic stripping voltammetry of the solid phase formed with the quaternary ammonium salt Zephiramine as the ionic associating agent; Br- is used as the complexing agent in the preconcentration process. We have studied the effect of concentration of Zephiramine, Br-, I-, and some other elements presented, deposition potential, preelectrolysis time, and scan rate, on the stripping curve shape and maximum stripping current. Determinations of trace iodine in table salt, laver, and eggs were demonstrated as practical examples.

Eggs↗
PubMed1995

[A sensitive method for detection of sympathomimetic amines in pentafluorobenzamide form in biological samples using gas chromatography].

A toxicological method of sensitive and specific confirmation of methamphetamine and other primary and secondary amines in biological samples after extractive perfluorobenzoylation is described. The method is based on the principle of gas chromatography with parallel specific nitrogen detection and electron capture detection. The other alternative is the gas chromatography combined with mass spectrometry in chemical ionization mode. The method described allows the detection of methamphetamine and amphetamine in urine in concentrations below 10 ng/ml.

Amphetamines↗