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Biomedical subjects

G D Christian

Publications and source records attributed to G D Christian.

At least 37 records · Page 2Linked to original sources
PubMed1984

Flow injection analysis-atomic absorption determination of serum zinc.

Flow injection analysis-atomic absorption (FIA-AA) determination of zinc in human serum samples is demonstrated. The same samples were analyzed for zinc by conventional atomic absorption spectrometry and no significant difference was found between the two methods. Proteins were precipitated from samples by adding equal volumes of 25% (w/v) trichloroacetic acid and 100-microliter aliquots of the protein-free-filtrate were injected. Precision was +/-3.47% relative standard deviation. The frequency of measurements can be as high as 180 per hour. No pump was used, only the negative pressure from the nebulizer was utilized to aspirate the carrier stream. Simple 1:5 dilution of sample with water, followed by FIA-AA measurements, gave higher zinc levels. The effect of sample volume and the length of dispersion coil on the FIA signal was studied.

Humans↗
PubMed1979

A coupled enzymatic method to measure blood lactate by amperometric monitoring of the rate of oxygen depletion with a Clark oxygen electrode.

A rapid, sensitive and reliable method to measure lactate in blood is described. The method is based on the enzymatic oxidation of lactate to pyruvate in the presence of nicotinamide adenine dinucleotide (NAD+) and lactate dehydrogenase (LDH). The reaction product, NADH, is then oxidized by molecular oxygen, carried in the buffered reagent medium, in the presence of horeseradish peroxidase and other cofactors. The maximum rate of oxygen depletion, which is directly proportional to the amount of lactate ion present in the sample, is amperometrically monitored by a membrane oxygen electrode. No sample pretreatment is required in the present procedure other than dilution, and a comparison study between the described method and a spectrophotometric method shows good correlation.

Buffers↗
PubMed1978

Enzymatic determination of blood ethanol, with amperometric measurement of rate of oxygen depletion.

A rapid electrochemical measurement of blood ethanol is proposed. Alcohol is oxidized by NAD+ in the presence of alcohol dehydrogenase; and the NADH produced is aerobically oxidized by horseradish peroxidase. The rate of depletion of buffer-carried oxygen, which is directly proportional to the alcohol concentration in the sample, is amperometrically monitored with a membrane oxygen-sensing electrode. Only a 5-microliter sample of whole blood is required, with no deproteinization, incubation, extraction, or dilution. Results, obtained in less than 1 min, correlate well with those obtained by gas-chromatographic and spectrophotometric methods.

Alcohol Oxidoreductases↗
PubMed1977

Enzymatic assay of total cholesterol in serum or plasma by amperometric measurement of rate of oxygen depletion following saponification.

A method for serum or plasma cholesterol assay involving amperometric measurement of the rate of oxygen depletion in the cholesterol oxidase-catalyzed oxidation of cholesterol is described. The hydrolysis of the serum cholesterol esters is accomplished by saponification of 50 mul of sample with 0.2 ml of ethanolic KOH (1.0 mol/1) containing 0.5% Triton X-100 for 5 min at 75 degrees C. The rate of oxygen consumption in a 25-mul aliquot of this is measured with a Clark electrode in a Beckman Glucose Analyzer and the assay takes about one minute after incubation; results are read digitally on the instrument. The analyzer cell contains 1 ml of 1 M phosphate buffer, pH 7.4, with 100 mg sodium cholate/100 ml and 0.1-0.2 U cholesterol oxidase.

Buffers↗