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T A Walmsley

Publications and source records attributed to T A Walmsley.

33 records · Page 2Linked to original sources
PubMed1984

Optimal conditions for 4-hydroxybenzoyl- and 2-furoylhydrazine as reagents for the determination of carbohydrates, including ketosamines.

4- Hydroxybenzoylhydrazine ( PAHBAH ) reacts with glucose in hot aqueous solution when alkali exceeds aroylhydrazine concentration. The related 2- furoylhydrazine ( FAH ) reacts at lower alkali concentrations, making this an attractive alternative carbohydrate reagent since it is (unlike PAHBAH ) freely water soluble. FAH reacts with monosaccharides more slowly than does PAHBAH , giving about half the color. Its specificity and behavior with a bismuth catalyst parallel those of PAHBAH . Solutions which contain 0.05 mol/liter PAHBAH with 1.5 mmol/liter bismuth III (as tartrate complex) and 0.5 mol/liter sodium hydroxide, or 0.01 mol/liter FAH with 1.5 mmol/liter bismuth III and 0.1 mol/liter sodium hydroxide are sensitive reagents for quantitative analysis, giving stable colors with many carbohydrates within 10 min at 75 degrees C. Ketosamines react more rapidly than glucose at lower temperatures and undergo similar reactions in less alkaline solutions. At pH less than 8, the reaction is specific for these 1- aminohexoses , and FAH can be used as a reagent for their assay.

Autoanalysis↗
PubMed1983

Microsampling on the Technicon SMAC system.

The sample volume needed for a Technicon SMAC continuous-flow analyzer has been reduced for routine operation. Two options are available: 141 microL for a 17-test profile, or 224 microL, which allows the direct-sampling assays for creatinine and iron to be included. The sample decrease is achieved by the sequential dialysis of creatinine and iron, an increased sample dilution from sixfold to ninefold, the strict minimization of diluted sample stream wastage, and development of more sensitive methods for glucose and alkaline phosphatase to allow greater use of the diluted sample stream. A glycine-containing diluent increases the sensitivity of the iron method by 25% and prevents the protein precipitation that plagues the continuous-flow analysis for iron in plasma. No deterioration in performance of the analyzer has been detected during nine months of routine operation at the reduced sample size. Added advantages are the decreased consumption of calibration materials and an increased ability to do repeat tests.

Alkaline Phosphatase↗
PubMed1982

Measurement of magnesium by continuous-flow colorimetry.

We describe the application to the Technicon SMAC system of a micellar-improved calmagite method for the measurement of magnesium. In this continuous-flow method a dialyzer is not needed, because protein interference is negligible. Sample interaction was estimated to be 3%. The increased sensitivity of the method allows for a small sample volume (37 microL/min). Results obtained agreed well with those by an atomic absorption procedure (x): SMAC magnesium - 0.971 x + 0.030 mmol/L (n = 58). The estimated total error for the SMAC procedure was less than 50 mumol/L at two analyte concentrations: 0.50 and 1.50 mmol/L. The inclusion of magnesium estimation on SMAC should extend the screening function of this analyzer.

Colorimetry↗
PubMed1981

Analytical errors in clinical laboratories as assessed by an interlaboratory survey.

Combined errors ar the commonest systematic errors in laboratory results and occur with most tests studied. In these errors, results are reduced (or, less commonly, increased) by a factor, and this effect is compensated by the addition (or subtraction) of a constant amount. The effect is that results are in error in opposite direction at high and low levels. Inconsistency is predominant and is due mainly to imprecision, although for some tests (iron, cholesterol, calcium, and triglycerides among those studied) other factors such as non-specificity are significant. An interlaboratory survey based upon external method assessment using linear regression analysis provided objective information about analytical error in laboratories which is not usually obtained, while at the same time meeting the usual functions of surveys in the quality audit of performance.

Data Collection↗
PubMed1979

Effects of sample-diluent interactions on surface tension and pressures in continuous flow manifolds.

When a plasma sample is aspirated into a continuous flow analyser the internal pressure of the manifold increases. The pressure change is the result of insufficient detergent present to bind all the protein in the sample, and is a potential source of inaccuracy and imprecision in the assay. It is recommended that Brij 35 be used at a concentration 10 times above the binding capacity of the albumin in the sample, to minimise changes in pressure between samples.

Autoanalysis↗
PubMed1979

Factors in the choice of detergent in automated oestriol estimation.

Detergent must be added to the strongly acidic Kober reagent to obtain reproducible and well separated peaks in continuous flow analytical methods for oestriol in pregnancy urine. Brij 35 and other polyether detergents are not satisfactory because they or their impurities interfere in the reaction causing high blank response in colorimetric reactions and diminished fluorescence responses. In a single phase fluorometric method these detergents also caused turbidity or phase separation in the solution which passed through the fluorometer. Some anionic sulphate and sulphonate detergents were also unsatisfactory being immiscible with Kober reagent. Selected cationic and betaine detergents are shown to be possible alternatives, although one which is satisfactory in the kober reagent may be unsuitable for a dilution reagent. The betaine Empigen BB was found to be suitable for inclusion in both of these reagents.

Autoanalysis↗
PubMed1978

Some pitfalls in the quality control of alkaline phosphatase activity.

A study of the pH optimum of alkaline phosphatase activity in calibration and control serum preparations reveals a wide variation in pH optima. It is shown that as small an error of +/- 0.05 pH units in preparation of the buffered substrate results in an error in the order of +/- 5% in the response between the calibrating serum and patient specimens. It is recommended that a calibration serum should closely parallel the pH optimum of alkaline phosphatase in human sera and that a quality control serum containing alkaline phosphatase of alternative source to that present in the calibration serum be included with patient samples as a sensitive means of monitoring pH changes in the buffered substrate.

Alkaline Phosphatase↗
PubMed1978

Automated continuous flow determination of urine albumin by competition with dye-detergent binding.

A continuous flow automated method for urine albumin was developed based on the ability of albumin to displace bromophenol blue from a bromophenol blue detergent complex. The method is almost specific for albumin, giving a slight response with an alpha-globulin fraction from serum. Results agreed closely with rocket electrophoresis albumin estimates on urine samples, but significantly less closely with "total urine protein" estimates by an acid protein precipitation, followed by biuret colour reaction, procedure. This method is being used to replace the indefinite "total protein" test for most routine purposes.

Albuminuria↗
PubMed1978

Regression analysis in interlaboratory surveys: a case study with cholesterol and triglycerides.

1. A new interlaboratory survey design, that uses regression analysis to compare results from each laboratory with target values, was tested using cholesterol and triglyceride analyses. The fifty New Zealand laboratories involved showed considerable interlaboratory variation (CV = 8% to 27% for cholesterol, 13% to 113% for triglycerides), 30% and 40% of which was associated with systematic differences between laboratories. 2. End-of-period summaries using regression analysis confirmed the presence of systematic errors. These were either simple types caused apparently by incorrect standardisation (regression slope, B not equal to 1.0) or inappropriate blank correction (intercept, A not equal to zero) or complex types presumably due to nonlinearity or nonspecificity. Graphical display of results from each laboratory aided fault diagnosis and allowed the detection of between-run standardisation differences. 3. Method comparison studies were made: the only highly significant result being lower precision achieved by enzymatic cholesterol methods compared with other colorimetric methods.

Blood Chemical Analysis↗
PubMed1975

A thin layer chromatographic method for the separation and identification of the tryptophan metabolites present in whole human urine.

This paper reports a new thin layer chromatographic system which is able to separate a total of thirtyeight (38) tryptophan metabolites from a synthetic mixture in a period of three hours. The system consists of thin layers of silica gel GF254 which are eluted in two dimensions, employing in the first dimension a mixture of propanone, 2-propanol, water, ammonia (0.88) (50 : 40 : 7 : 3 V/V) and in the second dimension a mixture of chloroform, glacial acetic acid, methanol and water (65 : 20 : 10 : 5 V/V). A method whereby the separated tryptophan metabolites may be unambiguously identified in situ following the thin layer chromatography is also presented and discussed. This method utilises the effect of ultraviolet light, at 254 and 350 nm, and the colour reactions between the metabolites and four reagents namely, a modified Ehrlich, o-phthaldehyde, Pauly and Ninhydrin-cadmium acetate. A summary of the unsuccessful attempts to quantitate the modified Ehrlich positive metabolites by in situ reflectance densitometry is also given. Finally, it is demonstrated that the new system may be used to advantage to separate and identify tryptophan metabolites in studies of whole human urine.

Child↗