SEARCH · PubMed Health

Results for “Colorimetry”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 487 records · Page 27Linked to original sources

PubMed1987

Definition and analysis of dietary fibre.

The definition of dietary fibre as "non-starch polysaccharides plus lignin", that has now been widely accepted, is chemically more distinct than earlier definitions, but still implies some difficulties in its demarcation. In practice, analytical problems and limitations are important, since definition and analysis of dietary fibre are closely related. The delimitation towards more or less undigestible starch fractions, highly soluble polysaccharides, oligosaccharides, and undigestible protein is discussed, as well as phytate, tannins and some other components. Methods for analysis of dietary fibre are based on one or more of three different principles: 1) Weighing after removal of non-fibre components, 2) Colorimetric carbohydrate determinations 3) Specific determination of monomeric constituents by gas-liquid chromatography (GLC) or high performance liquid chromatography (HPLC). Gravimetric methods, using enzymatic degradation of protein and starch, are generally preferred for assay of total dietary fibre, or soluble and insoluble fibre separately. Colorimetric methods are used mainly for determining uronic acids as a measure of pectins. Detailed methods usually employ GLC determination of monomers after acid hydrolysis, but HPLC appear to develop as a convenient alternative. Uronic acids are determined separately by colorimetry or decarboxylation, and lignin usually as Klason lignin, i.e. acid insoluble material.

Chromatography, Gas↗

PubMedDate not supplied

Stability-indicating methods for determining omeprazole and octylonium bromide in the presence of their degradation products.

Four stability-indicating assays were developed for determining omeprazole and octylonium bromide. Omeprazole is photodegraded and estimated in the presence of its degradation products sulphenamide (I) and benzimidazole sulphide (II) by 2 methods. The first method depends on use of first-, second-, and third-derivative spectrophotometry at 290.4, 320.6, and 311.6 nm, respectively. The second method is based on applying the charge-transfer technique with chloranil as pi acceptor to form a complex with omeprazole, the absorbance of which is measured at 377 nm. These methods determine omeprazole in concentration ranges of 5-20 micrograms/mL by first-, second-, and third-derivative spectrophotometry and 10-50 micrograms/mL by charge-transfer complexation with mean accuracies of 99.92 +/- 0.73, 99.71 +/- 1.02, 99.64 +/- 0.66, and 100.24 +/- 0.81%, respectively. Octylonium bromide is determined by a densitometric method using thin-layer chromatography in the presence of its degradation products p-[2-(n-octyoxy)benzoyl]-aminobenzoic acid (III) and diethyl-(2-hydroxyethyl)-methyl ammonium bromide (IV) without any interferences. Alternatively, octylonium bromide is evaluated by a colorimetric method using the acid dye rose bengal. The ion pair formed is extracted in chloroform at pH 4, and its absorbance is measured at 562 nm. These methods determine octylonium bromide in the presence of its degradation products in concentration ranges of 0.1-0.5 microgram/microL by densitometry and 4.5-22.5 micrograms/mL by colorimetry, with mean accuracies of 100.21 +/- 0.93 and 99.73 +/- 0.89%, respectively. The suggested methods were used to determine drugs in bulk powder, laboratory-prepared mixtures, and pharmaceutical dosage forms. Results were compared statistically with those obtained with reference methods.

Anti-Ulcer Agents↗

PubMed1999

Sun and skin. Role of phototype and skin colour.

The study of the biological effects of sun on the skin is one of the most topical questions in the recent dermatological literature. Interest in these effects has grown since it was demonstrated that the sun accelerates intrinsic skin ageing and is a principal factor for skin cancer. Skin damage caused by the sun is mainly due to UV radiation. Skin damage certainly has ancient roots, but has undergone sudden changes since man began to migrate to different geographical areas, for example when northern European populations colonised sunny areas close to equator. It is not a coincidence that the highest incidence of sun induced neoplasias is observed among white population of Australia. This epidemiological finding focused the interest towards the identification of phenotypic factors conditioning skin response to sunlight, and hence towards the definition of the so called phototype. After the fundamental work of Fitzpatrick based on sun exposure history more recent studies have shown that skin response to UV-rays can be predicted, to a good approximation, by skin colorimetry. Therefore this simple, cheap and non invasive measurement enables to predict sun reactivity skin type and to evaluate the melanoma risk.

Colorimetry↗

PubMedDate not supplied

Polymerization color changes of esthetic restoratives.

The color changes of three different types of tooth-colored restoratives during polymerization were investigated using colorimetry. L*, a*, b* color parameters of five different shades of Z100 (a mini-filled composite resin), Fuji II LC (a resin-modified glass-ionomer cement), and Dyract (a polyacid-modified composite resin) were taken precure and postcure. The results showed that the restoratives evaluated all underwent color changes during polymerization. The polymerization changes in color parameters were shade and not material dependent. Changes in L* parameter or lightness during polymerization were significant for all material and shade combinations and had the greatest influence on the overall polymerization color change. As the color change was perceivable by the human eye for most shades of materials, the clinical practice of polymerizing some material on, or adjacent to, the undried tooth to confirm shades of esthetic restoratives before restorative procedures is prudent.

Colorimetry↗

PubMedDate not supplied

[A clinical assessment of a colorimetric method for the determination of glycosylated hemoglobin--the diabetes test].

135 patients with diabetes mellitus were studied for the level of glycated hemoglobin (GH) with the aid of the colorimetric method diabetes test involving the use of 0.3 N oxaloacetic acid, 0.06 M thiobarbituric acid, colorimetry on the spectrophotometer with the wavelength of 443 nm. No correlation was established or only weak relationship between the level of GH and chief clinical manifestations of diabetes mellitus, such as indices for metabolism, clinical presentation of the illness, degree of microangiopathy. There was no correlation between the above method and isoelectrofocusing in capillaries. Little value can be attached to GH level in controlling diabetes mellitus.

Adult↗

PubMed1975

Method for diphenylhydantoin and phenobarbital assay by gas chromatography.

A rapid and easy method for determination of diphenylhydantoin and phenobarbital in plasma by gas liquid chromatography which provides monitoring of epileptic patients therapy is described. These drugs are extracted from plasma by partitioning between cholroform and buffered aqueous phase. The final extract is evaporated to dryness and the residue dissolved in an internal standard (methaqualone) solution. An amount of the final extract is injected tnto OV1 3% column at 230degreeC without previous derivative formation. The results are compared to those obtained by thin layer chromatography followed by colorimetry.

Buffers↗

PubMed2001

Ca2+ and phosphate releases from calcified Chara cell walls in concentrated KCl solution.

Ca2+ and P(i) (inorganic phosphate) releases from isolated calcified and uncalcified Chara cell walls were measured with a Ca(2+)-selective electrode and colorimetry, and their ionic relations were analysed on the basis of the electroneutrality rule. The results showed that (1) not only Ca2+ but also P(i) can be released from isolated calcified Chara cell walls into pure deionized water and 100 mM KCl solution, and (2) the positive charge due to the Ca2+ released cannot be neutralized only by the negative charge from the simultaneously released P(i). These findings suggest that calcium bands of calcified Chara cell walls are composed of mainly CaCO(3) and CaHPO(4) and some anions other than P(i) should be released simultaneously with the Ca2+ and P(i). More Ca2+ and P(i) can be solubilized from isolated Chara cell walls in 100 mM KCl solution than in pure deionized water. The pH value of 100 mM KCl solution in which isolated uncalcified young Chara cell walls have been immersed is a little lower than that of pure deionized water in which the same isolated uncalcified young Chara cell walls have been immersed, suggesting that some acidic substances are solubilized by 100 mM KCl. To explain this from the viewpoint of solution chemistry, the solubilities of pure CaCO(3) and pure CaHPO(4) in water and 100 mM KCl solution were measured with a Ca2+ -selective electrode and their pH values with a glass pH electrode. The conclusion reached was that the Ca2+ release from isolated Chara cell walls is accompanied by the release of P(i), CO(2-)(3) and acidic substances. This suggests that the so-called calcium bands and/or ionic relations, including ion exchange, in Chara cell walls are chemically or physicochemically more complex than they are currently considered to be.

Calcification, Physiologic↗

PubMedDate not supplied

Resistance to staining, flexural strength, and chemical solubility of core porcelains for all-ceramic crowns.

PURPOSE: The increased demand for tooth-colored restorations has prompted the use of ceramics in areas that are subject to masticatory stresses. To maximize the strength of these restorations, manufacturers and clinicians advocate placement of core materials in lieu of veneering materials in areas that are more susceptible to fracture. The objectives of this study were to determine the: resistance to staining of three core porcelains used for all-ceramic restorations, Procera, IPS Empress, and In-Ceram, through the use of colorimetry and visual observation; flexural strength of these porcelains under a three-point bend test; and chemical solubility in a controlled environment. MATERIALS AND METHODS: L*a*b* values were obtained for each specimen before and after immersion in a saturated solution of methylene blue in ethanol for 24 hours. Visual observation was also performed to ascertain color differences before and after staining. A three-point bend test was used to determine flexural strength. A reflux-condenser type, three-piece extraction apparatus was used with 4% acetic acid solution for 16 hours to determine solubility. Each sample was weighed before and after the reflux procedure to ascertain percentage weight loss. RESULTS: The mean delta E obtained for IPS Empress was 14.5; In-Ceram was 9.2, and Procera was 9.0. Flexural strength obtained for IPS Empress, In-Ceram, and Procera was 176.9 MPa, 323.4 MPa, and 464.3 MPa, respectively. Weight loss of IPS Empress, In-Ceram, and Procera was 0.056%, 0.734%, and 0.003%, respectively. CONCLUSION: IPS Empress showed the least resistance to staining. IPS Empress had the lowest flexural strength, while Procera had the highest. In-Ceram demonstrated the highest chemical solubility.

Acetates↗

PubMedDate not supplied

Color stability of a resin-modified glass ionomer cement.

The color stability of a resin-modified glass ionomer cement (Fuji II LC) was investigated over six months using colorimetry. Five shades (A2, A3, A4, B3 and C4) were selected and 10 square specimens (7 mm wide and long, and 1.5 mm deep) were made for each shade using special grit molds. CIE L*, a*, b* color parameters of the specimens were taken at one day, one week, one month, three months and six months. Results were subjected to MANOVA and ANOVA/Scheffe's test at significance level 0.05. The effects of time on color parameters (L*, a*, b* values) were found to be shade dependent. All shades exhibited a decrease in L* values over time. With the exception of shade B3, significant differences in L* values were observed at six months. A general decrease in b* values was also observed but differences among the various time intervals were not significant except for shades A3 and C4. No apparent trends were observed for changes in a* values. For all shades, the largest color change (delta E) was observed between one day and one week. The color stability of the resin-modified glass ionomer investigated was shade dependent. A general decrease in lightness and yellow chroma was observed.

Analysis of Variance↗

PubMed1999

[Expression of interleukin-6 and its receptors in peripheral blood of patients with systemic lupus erythematosus].

OBJECTIVE: To investigate the level of interleukin-6 (IL-6) and soluble-IL-6 receptor (sIL-6R) in serum of patients with systemic lupus erythematosus (SLE) and its correlation with disease activity and to explore IL-6 signal transduction pathways in SLE patients. METHODS: By using MTT colorimetry and ELISA, the levels of IL-6 and sIL-6R in serum from 16 patients with SLE (9 active, 7 inactive), 17 with active rheumatoid arthritis (RA) and 29 controls were measured. The expressions of acute phase reaction factor (APRF) in peripheral blood mononuclear cells (PBMCs) were also detected by using electrophoresis mobility shift assays (EMSA) after the PBMCs were isolated and then stimulated by IL-6. RESULTS: Serum IL-6 and sIL-6R levels in active SLE patients were significantly higher than those in normal controls (P < 0.01), but were significantly lower than those in active RA patients (P < 0.01). Serum IL-6 rather than sIL-6R level in active SLE patients was significantly higher than that in inactive ones (P < 0.01). Serum IL-6 was correlated positively with the anti-dsDNA antibody (r = 0.658, P < 0.01), but not with CRP (r = 0.041, P > 0.05). There were no expression of APRF in PMNC from SLE patients and 8 normal controls, whereas PMNC from 11 RA patients expressed APRF activity (11/17). CONCLUSION: The level of IL-6 is a useful parameter for monitoring disease activity of SLE. In active SLE, no significant elevation of serum sIL-6R and no expression of APRF in PMBCs may be responsible for mild CRP elevation.

Adolescent↗

PubMed2001

[Aminopeptidase inhibitor Bestatin induces HL-60 cell apoptosis through activating caspase 3].

OBJECTIVE: To study the variation and significance of caspase 3 activity in the process of amino-peptidase inhibitor--bestatin (BS) inducing human leukemic cell apoptosis. METHODS: Cell apoptosis was evaluated by light microscopy, TUNEL labeling and flow cytometry (FCM). Caspase 3 activity was detected by colorimetry. The mitochondrial transmembrane potentials (DeltaPsi(m)) were detected by Rhodamine123 staining. RESULTS: The apoptotic morphology, apoptotic peak on FCM and positive Annexin V(FITC) on cell membrane showed that BS could induce HL-60 cell apoptosis in a dose- and time-dependent manner. Caspase 3 activity was significantly higher in the apoptotic cells than in control cells. The apoptosis induced by BS was inhibited by AC-DEVD-CHO. The DeltaPsi(m) of cells treated with BS declined. CONCLUSION: BS induces apoptosis of human acute leukemic cells through activation of caspase 3.

Aminopeptidases↗

PubMed2001

Portable, inexpensive instruments to quantify stratum corneum hydration and skin erythema: applications to clothing science.

The level of stratum corneum hydration is assessed by measurement of the changes in skin resistance and is referred to as the galvanic skin response or electrical skin resistance. Skin erythema may be assessed by measurement of skin blood flow, tristimulus colorimetry or narrow-band reflectance spectroscopy. Currently available measuring devices are relatively expensive. Presented here are two inexpensive, hand-held, portable instruments which conveniently measure stratum corneum hydration and skin erythema.

Body Water↗

PubMed2000

[Determination of furostanol saponins in Bulbus Allii Macroste].

OBJECTIVE: To establish an Ehrlich reaction-colorimetry method for determining furostanol saponins in Bulbus Allii Macroste. METHOD: Based on the coloration reaction between furostanol saponins and p-dimethylaminobenzaldehyde, the UV detection wavelength used was 515 nm, and the optimum conditions were selected on homogeneous design principle. RESULT: The standard curve of macrostemonoside G was linear in the concentration range of 0.1975-0.9880 mg.ml-1. The average recovery was 97.7% (RSD = 3.65%). CONCLUSION: The method is rapid, accurate and easy to operate.

Allium↗

PubMed1992

[HPLC used in the validation of simple methods for research of degradation products in essential drug tablets].

HPLC have been used to validate simple methods to be employed in developing countries (DC) for the quality control of drugs. As the important lack of analytical material in DC, colorimetric methods have been used. These are subjected to visual appreciation of the color intensity. Two essential drugs have been selected: aspirin, hydrochlorothiazide. For each compound, standardization of concentration's degradation product by colorimetry and HPLC have been achieved in proximity of the restricted norms of pharmacopoeia. These results have been applied to tablets exposed to stressed conditions (t(0) = 60 and humidity = 75%). The results obtained by colorimetric method were similar to HPLC's ones.

Aspirin↗

PubMedDate not supplied

[Possibilities of using telemedicine in preoperative examination of the lens nucleus density].

The MPEG-4 algorithm applicable to compression of video-images of the anterior eye segment and JPEG-2000 applicable to compression of static images of the lens and retina under the conditions of mydriasis were used to enable the telemedicine consultations. The compiled compression files were sent to the institute's E-Mail address by means of a voice modem through an analogue telephone line. The pixel structures of non-compression and compression images of the anterior eye segment and lenses were comparatively studied. The deviations of images' optic density versus non-compression images were found to be below or equal to 2.7%, thus, they can be attributed to a static error. The quantitative colorimetry of images was used, on the basis of a software-based color-regulating filter, to determine the lens-nucleus density and cataract-maturity degree. The differences between values of the green-canal brightness were found within the RGB model before and after the application of the filter in the posterior cortical strata and in the anterior lens-nucleus portion, which provided for classifying 6 stages of the lens-nucleus density and cataract maturity.

Algorithms↗

PubMed1992

Recent advances in methodology for analysis of phytate and inositol phosphates in foods.

This review summarises the methods available for the analysis of phytate and structurally related molecules, i.e., inositol polyphosphates. Phytate has been determined by colorimetry, low pressure ion exchange column chromatography, phosphorus-31 fourier transform nuclear magnetic resonance spectroscopy (31P FT NMR), near-infrared reflectance spectroscopy and high performance liquid chromatography (HPLC). Among these techniques anion exchange column chromatography and HPLC were shown to be best suited for separation of inositol phosphates. Since inositol phosphates do not have a characteristic absorption spectrum, their detection in HPLC analysis is limited to methods employing monitoring of refractive index, post column reaction products, conductivity or indirect detection although other detection methods may be feasible. As refractive index detection under isocratic eluent conditions is relatively easy to manipulate, anion-exchange HPLC methods using a low capacity column or ion-pair HPLC methods are recommended for the analysis of inositol phosphates in nutritional studies.

Chromatography↗

PubMed1992

Lactate measured in diluted and undiluted whole blood and plasma: comparison of methods and effect of hematocrit.

We evaluated a new analyzer that measures lactate in undiluted whole blood by direct (or undiluted) amperometry [Nova Stat Profile 7 Analyzer (SP7); Nova Biomedical, Waltham, MA] by comparing it with two other analyzers, one for measuring lactate in whole blood by indirect (or diluted) amperometry [Model 2300; Yellow Springs Instrument Co. (YSI), Yellow Springs, OH] and another for measuring lactate in plasma by enzymatic colorimetry (aca; Du Pont Co., Wilmington, DE). All between-method comparisons of the three methods showed that the results for plasma were comparable (Sy/x = 0.24-0.33 mmol/L). Within-method comparisons by the YSI differed substantially between plasma and whole blood (Sy/x = 0.48 mmol/L), but within-method comparisons by the SP7 produced better agreement between plasma and whole blood (Sy/x = 0.18 mmol/L). The difference between whole blood and plasma by YSI is related to hematocrit, with the greatest differences noted for samples with the highest hematocrit. Serum lactate measured by SP7 had between-day imprecision (CV) ranging from 12% at 0.5 mmol/L to 4.2% at 3.7 mmol/L, showed a linear standard curve to at least 11.5 mmol/L, and was independent of hematocrit. There was a mean bias of approximately 0.4 mmol/L for results in the reference range for both plasma and whole blood by SP7 compared with plasma results by either aca or YSI.

Autoanalysis↗

PubMed2003

[Assessing the content of formaldehyde in vermicelli in Changsha market].

In order to better supervise food safety for the residents, the extent of formaldehyde in vermicelli sold on Changsha market was assessed by the acetyl acetone colorimetry method. Results showed that among 106 samples, 61 were formaldehyde positive. The positive rate was 57.55% (61/106). The content of formaldehyde ranged from 0.011 mg/kg to 2.859 mg/kg, indicating severe contamination of vermicellis by formaldehyde in Changsha market and therefore, the food safety supervision work should be strengthened.

China↗