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At least 127 records · Page 7Linked to original sources
PubMed1987

Determination of pseudo-alpha- and pseudo-beta-DL-glucose by gas-liquid chromatography, high-performance liquid chromatography, and enzymatic colorimetry with glucose 2-oxidase.

Three methods have been developed for measuring pseudo-alpha- and pseudo-beta-DL-glucose (pseudo-beta-D-glucose), synthetic compounds in which the ring oxygens of alpha- and beta-DL-glucose (beta-D-glucose) have been replaced by a methylene group. Moderate sensitivity in the determination of these pseudo-glucoses dissolved in human serum was obtained by GLC (0.1 nmol) and HPLC (0.5 nmol). The colorimetric determination with glucose 2-oxidase, peroxidase, and 2,2'-azino-di-(3-ethylbenzothiazoline-6-sulfonic acid) was satisfactory for the assay of pseudo-alpha- and pseudo-beta-DL-glucose (respective sensitivities: 25 and 5 nmol). The addition of hexokinase to the colorimetric assay system made it possible to eliminate glucose present in the sample, such as serum, and the remaining pseudo-alpha- or pseudo-beta-DL-glucose in the sample solution could then be measured by a colorimetric method using glucose 2-oxidase. The methods described can be used for biochemical studies involving pseudo-alpha- and pseudo-beta-DL-glucose.

Chromatography, Gas↗
PubMed1978

Serum methionine: its rapid determination by continuous-flow colorimetry.

A rapid automated method for the determination of serum methionine is presented for use with the Technicon AutoAnalyzer system. It is based on the decolorisation of halide platinates by organic sulphides, including methionine. The 5--95% reference range from 249 sera from hospital patients (excluding those with liver and renal diseases and diabetes) was 20--60 mumol/l, mean 35 mumol/l. The S.D. of the method for 40 duplicate samples was 2.2 mumol/l. Recoveries ranged from 101--105%. This measurement facilitates the clinical evaluation of liver disease, especially acute liver failure, kidney disease and diabetes mellitus.

Autoanalysis↗
PubMed1988

Colorimetry of dehydroalanine residues preserved as 'lost side chains' in thyroglobulin.

We developed a new assay method for dehydroalanine residues in thyroglobulin, which had been proposed to be the 'lost side chains' during thyroid hormonogenesis. Thyroglobulin preparations were labeled with 4-aminothiophenol at 30 degrees C for 10 days. Under the conditions, the reagent reacted only with dehydroalanine and cysteine residues. The 4-aminothiophenol bound to cysteine was eliminated by reductive cleavage. The 4-aminothiophenol-labeled dehydroalanine (4-aminophenylcysteine) residues were liberated by acidic hydrolysis, converted to a colored derivative by the Bratton-Marshall reaction and quantified colorimetrically. The number of dehydroalanine residues was the same as that of hormone residues in each thyroglobulin preparation. The results indicate that when one hormone residue is produced by the coupling of two iodotyrosine residues, the 'lost side chain' is preserved as one dehydroalanine residue in the thyroglobulin molecule.

Alanine↗
PubMedDate not supplied

Analytical comparison of an enzyme-amperometric method for chlorocresol determination in ointments with colorimetry and liquid chromatography.

The direct determination of chlorocresol in n-hexane extracts of commercial ointments was successfully performed using an enzyme-amperometric probe for analysis of phenols and working in previously characterized and optimized non-aqueous solvents. The analytical data obtained were compared with those found by using classical HPLC or chemical spectrophotometric method for determination of phenols.

Biosensing Techniques↗
PubMed1997

Intravascular carbon dioxide monitoring using micro-flow colorimetry.

An intravascular carbon dioxide sensor is investigated which employs continuous perfusion of micro-quantities of reagent through silicone membrane tubing in contact with blood. Blood is sampled from a vessel by periodic withdrawal-reinfusion through a catheter and passes by the sensor membrane tubing integrated into the catheter system. Blood CO2 equilibrates across the silicone membrane causing a color change in the reagent micro-flow stream that is detected by an optical cell external to the vessel. In vivo trials on pigs demonstrate a stable sensor response, a fast response time, and high signal-to-noise ratios. The sensor also exhibits an immunity to temperature changes, reduced intravascular blood flow, photobleaching, and leaching. It has a 2 min response time, a +/-2 mmHg resolution, and minimal drift over a 12 h duration. Using a pig model, measured values compared with true values indicate a 0.998 correlation coefficient, a 1.3 mmHg precision, and a 1.7 mmHg bias.

Animals↗
PubMed2004

Lipase assay in soils by copper soap colorimetry.

A simple and sensitive method for the estimation of lipase activity in soils is reported. In this method, 50mg of soil is incubated with emulsified substrate, the fatty acids liberated are treated with cupric acetate-pyridine reagent, and the color developed is measured at 715 nm. Use of olive oil in this protocol leads to an estimation of true lipase activity in soils. The problem of released fatty acids getting adsorbed onto the soil colloids is obviated by the use of isooctane, and separate standards for different soils need not be developed. Among the various surfactants used for emulsification, polyvinyl alcohol is found to be the most effective. Incubation time of 20 min, soil concentration of 50 mg, pH 6.5, and incubation temperature of 37 degrees C were found to be the most suitable conditions for this assay. During the process of enrichment of the soils with oil, interference by the added oil is avoided by the maintenance of a suitable control, wherein 50 mg of soil is added after stopping the reaction. This assay is sensitive and it could be adopted to screen for lipase producers from enriched soils and oil-contaminated soils before resorting to isolation of the microbes by classical screening methods.

Colorimetry↗
PubMed2004

Measuring tobacco smoke exposure: quantifying nicotine/cotinine concentration in biological samples by colorimetry, chromatography and immunoassay methods.

Procedures to assess tobacco smoke exposure are reviewed and biomarkers used for determining the smoking status of an individual are compared. Methods used to extract these biomarkers from saliva, urine, and blood and the advantages and disadvantages of the assays are discussed. Finally, the procedures used to measure the levels of cortisol, a stress hormone speculated to be linked to nicotine metabolism, are discussed.

Chromatography, High Pressure Liquid↗
PubMed2006

Evaluation of antimicrobial activity of selected plant extracts by rapid XTT colorimetry and bacterial enumeration.

The aim of this study was to screen and evaluate the antimicrobial activity of indigenous Jordanian plant extracts, dissolved in dimethylsulfoxide, using the rapid XTT assay and viable count methods. XTT rapid assay was used for the initial screening of antimicrobial activity for the plant extracts. Antimicrobial activity of potentially active plant extracts was further assessed using the "viable plate count" method. Four degrees of antimicrobial activity (high, moderate, weak and inactive) against Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa, respectively, were recorded. The plant extracts of Hypericum triquetrifolium, Ballota undulata, Ruta chalepensis, Ononis natrix, Paronychia argentea and Marrubium vulgare had shown promising antimicrobial activity. This study showed that while both XTT and viable count methods are comparable when estimating the overall antimicrobial activity of experimental substances, there is no strong linear correlation between the two methods.

Anti-Infective Agents↗
PubMed1983

Urinary oxalate excretion, as determined by isotope dilution and indirect colorimetry.

A simple and reliable method for the determination of urinary oxalate excretion is described. Urinary oxalate is precipitated with calcium chloride, and the oxalate content of the precipitate is measured by an indirect colorimetric method developed by Neas and Guyon in 1972 [1]. For single urine samples, a correction is made for the incompleteness of the precipitation of calcium oxalate by isotope dilution. The range of normal values (5% limits) determined in 52 normal subjects was 0.121-0.325 mmol . 24 h-1 . m-2 for a 1-day collection period and 0.145-0.301 mmol . 24 h-1 . m-2 for a 3-day collection period. The within-assay CV of a control urine with a low oxalate concentration was 9% (n = 7) and the between-assay CV for the same control urine was 12% (n = 6). When the values obtained for oxalate excretion were normalized to body surface area, there was no significant difference between males and females; the main source of variation was the intra-individual variation.

Body Surface Area↗
PubMed1997

A comparison of subjective and objective measures of reduction of psoriasis with the use of ultrasound, reflectance colorimetry, computerized video image analysis, and nitric oxide production.

BACKGROUND: Studies of antipsoriatic therapy often rely on subjective scoring. Objective measures have been developed but have not previously been compared with subjective scoring. OBJECTIVE: Our purpose was to compare subjective and objective measures of reduction of psoriasis with topical therapy. METHODS: A 2-week, double-blind, left-to-right comparative trial of betamethasone valerate against white soft paraffin was performed in 12 patients. The subjective scores were erythema, elevation, scale, and a composite total. Objective measures were nitric oxide production measured by chemiluminescence; erythema reflectance; ultrasound scan for thickness, scale, and echo-poor zone; and computerized image analysis of video images. RESULTS: Subjective and objective measures had similar power to detect therapeutic effect. The subjective measures showed greater variation and relatively overestimated improvement. There was correlation between measures and estimates for area, redness, and thickness. Nitric oxide production was the most powerful objective measure. CONCLUSION: Thickness determined by ultrasound scan and nitric oxide production are useful measures of reduction of psoriasis, which lend themselves to more powerful statistical tests than subjective interval data.

Administration, Topical↗