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PubMed1992

An enzymatic method for measuring serum mannitol and its use in hemodialysis patients.

We evaluated two chemical methods for quantifying mannitol in serum, based on the oxidation of mannitol by periodate, and measurement of the formaldehyde formed with chromotropic acid (colorimetry) or acetylacetone (fluorometry). We found interference in these methods by serum glycerol. Additionally, a high-performance liquid chromatography (HPLC) method was evaluated and found to be specific but impractical for routine use. We therefore, developed an enzymatic fluorometric procedure, based on the oxidation of mannitol by beta-NAD to fructose and NADH, in the presence of the enzyme mannitol dehydrogenase (MD). MD is not commercially available and was partially purified from cultures of Leuconostoc mesenteroides. This new method is specific, sensitive, simple, and accurate and is proposed as the method of choice for measuring mannitol in the serum of patients who received this sugar alcohol during routine hemodialysis treatment.

Chromatography, High Pressure Liquid↗

PubMed1978

Hypochromia as a clinical sign of tuberculosis in the tropics.

The skin colour of 106 Nigerian tuberculosis patients was measured by colorimetry; and a relative hypochromia, particularly of the face, was found to be associated with tuberculous infection. The hypochromia reached a significant degree compared to a group of 126 control patients with other medical conditions from whom tuberculosis had been excluded. Successful treatment of the tuberculosis resulted in re-pigmentation. It is suggested that relative hypochromia should be included in the list of non-specific signs which may be looked for when considering tuberculosis in the differential diagnosis of chronic cough, and debilitating disease, in the African. The hypochromia of protein-calorie malnutrition was not included in the study, but its importance in relation to coincident tuberculosis is noted. A simple method of measuring skin colour in the consulting room needs to be developed.

Adolescent↗

PubMed1977

The suitability of the dry ashing procedure for determination of arsenic in marine samples.

The dry ashing procedure with Mg/(NO3)2/Mgo ashing aid, followed by arsenic determination by colorimetry, has been compared to an X-ray fluorescence method for determination of arsenic in marine samples. Good agreement between these techniques indicated the suitability of the dry ashing, colorimetric procedure for determination of "fish-arsenic". A wet digestion procedure using HNO3-H2SO4-HC104 was also shown to be suitable.

Animals↗

PubMed1979

Determination of vitamin D in foods: a review.

Determining vitamin D content in foods is difficult because in natural foods of highest vitamin D activity, and even in vitamin D-fortified foods, only small quantities are present, and many other compounds are extracted along with vitamin D that cause difficulties in purifying the extract or in the spectrophotometry or colorimetry that follows. Several physicochemical methods--such as spectrophotometric, colorimetric, thin-layer chromatographic, adsorption, partition, gas-liquid, and high-performance column chromatographic--have been tried for assay foods for vitamin D, but none of them have been accepted for official or routine use; they are time consuming and expensive, or lack the required sensitivity, precision, or accuracy. Curative biological assays, based on degree of healing of a leg bone of rats previously made rachitic, is the generally accepted method to determine vitamin D content of foods. However, that method also requires too much time and is expensive. The recently developed high-performance liquid chromatographic method may offer the most for establishing a satisfactory physicochemical method for determining vitamin D in foods. Many of the difficulties and problems in assaying foods for vitamin D are discussed.

Animals↗

PubMed1979

Field evaluation of selected monitoring methods for phosgene in air.

Four selected methods have been evaluated and field tested as candidates for a specific, continuous procedure for monitoring phosgene in air at or below concentrations of 0.05 ppm. The methods evaluated were automated colorimetry, gas chromatography, infrared spectrophotometry and a recently developed paper tape monitor. A standard manual colorimetric procedure was used as a reference method. The paper tape, infrared and automated gas chromatographic techniques most closely fulfilled the criteria set forth for an "ideal", selective, continuous procedure for phosgene.

Air Pollutants↗

PubMed1992

Performance of laboratories measuring silica in the Proficiency Analytical Testing program.

A statistical study was performed on the results reported by laboratories analyzing silica samples in the first 101 rounds of the Proficiency Analytical Testing (PAT) program. Five laboratories participated in the first round of the PAT program in 1972, and participation grew to 130 laboratories before falling to 105 in Round 101. The laboratories use all three of the major methods of analysis: colorimetry, x-ray diffractometry, and infrared spectroscopy. The objectives of the study were to determine bias between methods, the variability associated with the methods, and any changes in bias or variability caused by a number of factors. The colorimetric method has consistently given the lowest results, particularly at higher loadings. X-ray diffractometry results were biased higher than infrared spectroscopy results during one period but not in the following period. Between the two periods, the procedures and materials used to prepare PAT samples changed in a number of ways, but the switch to quartz dust with a smaller particle size is a likely explanation for the bias difference. Generally, silica analyses have improved in precision over time, and this improvement has taken place for all three of the methods. The colorimetric method has shown the poorest precision of the three methods, but, unlike the differences in bias, the differences in precision have diminished considerably over time. Precision estimates from other studies were compared to those from this study to learn more about sources of variability. The largest source of variability, the differences between laboratories, was large even when laboratories used the same method, as they did in a collaborative study of silica methods.

Air Pollutants, Occupational↗

PubMed1977

A colorimetric study of coffee and tea staining of four composite resins.

Colorimetric measurements were made on four composite resins before and after controlled immersion treatments. The four composite resins were: Adaptic (Johnson and Johnson), Prestige (Lee Pharmaceuticals), Addent XV (3M Mfg. Co.) and Smile (Kerr Mfg. Co.). Specimens of each material were prepared with mylar surfaces and with abraded finished surfaces. Separate groups of specimens of the four materials were immersed in three separate solutions for 12 days at 55c. The three solutions used were: a control solution of distilled water and coffee and a solution of distilled water and tea. For all materials and surface finishes, immersion in coffee and tea produced significantly greater colour changes than distilled water. Coffee produced significantly greater colour changes than tea with the exception of 'Prestige' and 'Addent XV' with finished surfaces. When immersed in a tea solution, specimens of the same material with differing surface finishes showed greater differences in colour change than when immersed in control and coffee solutions. The relative colour changes of the four materials due to the immersion procedures were as follows: 'Adaptic' showed the least colour changes and "Smile' showed the most. 'Addent XV' and 'Prestige' tended to vary between the former two. Comparison and correlation of colorimetry results with visual assessment scores allowed for the expression of the objective measures in subjective terms suitable for clinical purposes.

Coffee↗

PubMed1992

Indirect spectral transmission ratio measurements of the aging crystalline lens nucleus.

A new objective approach to characterize color and opalescence in the lens nucleus, using wavelength indexed transmission ratios (TR) is described. Transmission ratios, i.e. the transmissivity per unit lens thickness, for the whole visible spectral range (390-720 nm) were calculated using fast scanning spectral colorimetry (FSSC). The lowest transmission ratios values were obtained in the blue part of the spectrum in general and at 450 nm in particular. They inversely followed the subjectively determined LOCS II color grading. The difference between transmission ratios at the absorbed part of the spectrum (less than 500 nm) and the non-absorbed part (greater than 550 nm) also reflects the LOCS II color grading. The overall mean transmission ratios for all wavelengths in the spectrum gives an index that closely followed the nuclear opalescence grading of the LOCS II system. The transmission ratios are theoretically independent of the spectral characteristics of the incident light as long as it contains suprathreshold energies in the whole measured spectral range.

Absorption↗

PubMed1977

Effect of succinimide on hyperoxaluria in the rat estimated value of the different dosing methods of oxaluria.

In the female rat intoxicated with ethylene glycol the oxaluria increases with the degree of intoxication. The increase is less in the animals treated with succinimide. The comparative study of the results of the dosages made with gas-liquid-chromatography and by various colorimetric methods show that this later gives varying results and underestimates high concentrations of oxalic acid. The result is that any study based on results of dosages of urinary oxalic acid made by colorimetry must be taken with some reserve, and this on whether the oxalic lithiasis is experimentally induced or human, or whether its evolution is spontaneous or influenced by a therapeutic.

Animals↗

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↗

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↗

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↗

PubMed1992

Nonradioactive southwestern analysis using chemiluminescent detection.

Replacing radioactively labeled probes by nonradioactive ones and detection by chemiluminescence instead of colorimetry allows a nonhazardous handling and offers the possibility of easily reprobing filters in Southwestern analysis. Using the described procedure, we were able to determine the molecular weight of DNA-binding proteins and achieve a high signal-to-noise ratio.

Animals↗

PubMed1992

[A modified microanthrone method for the determination of inulin on nanogram scale].

The establishment of a method of determining minute amount of inulin on nanogram scale is essential for applying micropuncture technique to kidney research. In this experiment, we modified a classical microanthrone method which was used by Dirks et al. to determine inulin contained in tubular fluid. A spectrophotometer was installed with a special microcuvette to suit the colorimetry of 10 microliters solution. Linear relation between inulin concentration and absorption was observed in the range of inulin concentration from 2 to 32 nl per 10 microliters anthrone reagent. The accuracy of this microanthrone method was evaluated with inulin recovery test, the mean recovery rate being 101.2 +/- 3.5%. Since tubular fluid did not interfere with the determination of inulin, the tubular fluid which contained inulin could be added directly to anthrone reagent in actual practice. The mean single nephron glomerular filtration rate measured with this modified microanthrone method in 21 rats was 34.9 +/- 1.8 nl/min, which coincided well with the values reported in literature. The results indicate that the measurement of inulin with the above-mentioned microanthrone method is reliable and suitable for the micropuncture study.

Animals↗

PubMed1979

New fluorometric analysis for mandelic and phenylglyoxylic acids in urine as an index to styrene exposure.

I describe a new fluorometric method for determination of mandelic and phenylglyoxylic acids in urine, the fluorometry being preceded by extraction into ether and thin-layer chromatography. The chromatographically separated acids were quantitated after conversion to stable highly fluorescent derivatives by treatment with concentrated sulfuric acid. This method proves to be more precise, accurate, and reproducible than the existing colorimetric method. The limit of detection is 2 microgram of either acid per milliliter of urine with a CV of less than 15%. The standard curve for either acid is essentially linear from 2 to 100 microgram/mL of urine, with a correlation coefficient (r) of 0.97. No satisfactory correlation was obtained between the concentrations of either acid metabolite as measured in rat urine by fluorometry and colorimetry. The present method is considered suitable for routine biological monitoring of persons exposed to both high and low concentrations of styrene.

Animals↗

PubMed1979

Analysis of foods for iodine: interlaboratory study.

An accurate, reproducible method for less than or equal to 1 ppm iodine in foods is required for nutritional labeling. In order to ascertain the current status of iodine analysis in foods, 7 samples, representing different food classes, were analyzed by 8 laboratories. Six laboratories used their modifications of the Ce-As-I catalytic method preceded by alkaline dry ashing. Two laboratories used neutron activation analysis (NAA), with differing radiochemical separations. The study showed wide discrepancy in analytical results. Mean relative standard deviation for all laboratories was 77.9% between laboratories; 19.1% within-laboratories. Laboratories using NAA had only slightly better precision than did laboratories using the chemical method. The lowest level reported on the entire group of samples ranged among laboratories from 0.0089 to 0.65 ppm. Figures reported by a laboratory are, in general, consistently high or consistently low. The only differences in methodology which may possibly correlate with level of iodine obtained are the use of NAA technique and use of manual, rather than automated, colorimetry.

Colorimetry↗

PubMed1979

Microdiffusion and fluoride-specific electrode determination of fluoride in foods.

A simple and accurate method was developed for routine determination of fluoride in foods. Hydrogen fluoride is diffused 20 hr at 50 degrees C from fresh or freeze-dried samples (0.1 g dry wt) in polystyrene petri dishes containing 2 mL 40% HCIO4 and 0.3 g Ag2SO4, and is absorbed on the lids, previously spotted with 0.1 mL 0.5M NaOH. The absorbent layer is dissolved in 2 mL buffer solution, and the fluoride is measured potentiometrically. The method was verified by analysis of NBS Standard Reference Materials; recovery from 28 spiked infant foods (average = 99%, range = 75-135%); and comparison of results with colorimetry results for the same diffusates, after modification to handle 1 g samples. Relative standard deviations varied from 4 to 20% day to day. Detection limits were below 0.05 microgram/g dry weight.

Colorimetry↗