Abstract: A method of determining the total carbon dioxide concentration in plasma (TCO.sub.2 plasma) directly from a whole blood sample involves adjusting total carbon dioxide concentration measured in the whole blood sample (TCO.sub.2 whole blood) using a volume dilution factor (VDF) to give a value that is equivalent to TCO.sub.2 plasma.

Abstract: A CO.sub.2 electrode can be calibrated with two PCO.sub.2 calibration standard solutions having known pH values and known bicarbonate ion source concentrations. An O.sub.2 electrode can be calibrated using air as one calibration standard and a solution containing an excess of an O.sub.2 depleting agent as a second calibration standard.

Abstract: The magnesium ion content of a sample is determined by contacting the sample with a magnesium ion selective membrane including a 1,10-phenanthroline having an H group at positions 2 and 9. Examples of preferred 1,10-phenanthrolines include 4,7-diphenyl-1,10-phenanthroline, N-dodecyl-N-methyl-1,10-phenanthroline-4-carboxamide, 4-undecyl-1,10-phenanthroline, 4,7-diundecyl-1,10-phenanthroline and 5-nonyl-1,10-phenanthroline-4-carboxylate.

Abstract: An apparatus for correcting an initial measurement of the concentration of a first water soluble species dissolved in a water-based component of a biological fluid that also includes a second water soluble species and a volume occupying component, the initial measurement having been taken using an original sample of the fluid that had been diluted by an amount of additional aqueous solution to form a diluted sample is disclosed; the concentration of the second water soluble species is measured in an undiluted sample of the biological fluid to obtain a direct concentration and is measured using a diluted sample of the fluid to obtain an indirect concentration, and the initial measurement of concentration of the first species is adjusted based on a combination of the direct and indirect concentration determination of the second species.

Abstract: Correcting an initial measurement of the concentration of a first water soluble species dissolved in a water-based component of a biological fluid that also includes a second water soluble species and a volume occupying component, the initial measurement having been taken using an original sample of the fluid that had been diluted by an amount of additional aqueous solution to form a diluted sample is disclosed; the concentration of the second water soluble species is measured in an undiluted sample of the biological fluid to obtain a direct concentration and is measured using a diluted sample of the fluid to obtain an indirect concentration, and the initial measurement of concentration of the first species is adjusted based on a combination of the direct and indirect concentration determinations of the second species.

Abstract: A two electrode assembly in a polarographic cell includes a sensor electrode and a silver/silver chloride reference electrode in which silver metal is in contact with a substantial reservoir of silver chloride.

Abstract: An electrode for determining the lithium content of a liquid sample to be tested, has a membrane containing a lithium ion selective compound and a plasticizer, the improvement wherein the plasticizer is a liquid, lipophilic dialkyl phthalate compound or a liquid phenyl phenyl ether compound that has a strong electron withdrawing group at an ortho position on one of the phenyl rings. The ion selective compound has the formula: ##STR1## wherein A is an alkyl group having between 8 and 16 carbon atoms, B is an alkyl group having between 1 and 4 carbon atoms, and each C and D is, independently, a hydrogen atom or an alkyl group having between 1 and 16 carbon atoms, provided that both C and D are not alkyl groups having greater than 4 carbon atoms.

Abstract: An electrode assembly for polarographic assay of glucose in solution having a laminated membrane, the outer membrane being from 1 to 20 .mu.m thick and having a pore size of 10 to 125 .ANG., the inner membrane having a thickness of 2 to 4 .mu.m, and bonded to the outer membrane with immobilized glucose oxidase. Rapid assays are carried out by measuring the current difference before equilibrium is attained and at least 5 seconds after initial contact of sample with the outer membrane.

Abstract: A releasing reagent for releasing, as ionized calcium, protein-bound calcium in a biological sample for measurement of the ionized calcium, together with any ionized calcium originally present in the sample, using a calcium ion specific electrode, the releasing reagent including monochlorocoacetate salt, formate salt, and formic acid, in concentrations sufficient to render the pH of the sample, when mixed with the reagent, in the range of 4.0 to 5.5. Also disclosed is a method of measuring calcium in a liquid sample using such a releasing reagent.

Abstract: Hematocrit level of a blood sample is measured by flowing the sample along a liquid flow path and using electrodes in the flow path to obtain electrical signals representative of the sample's electrical conductivity and of the concentration of an ion species in the path, either before or after the sample measurement. Electrical signals are obtained for standardizing solution conductivity and ion species concentration. A tentative sample hematocrit value is derived from the sample and standardizing conductivity signals. Then the tentative hematocrit value is corrected with reference to the sample and standardizing ion concentration signals and to the known standardizing solution ion concentration value. A control solution of the ion species at known concentration is used for evaluating the hematocrit detection apparatus; the solution also includes an ion activity enhancing agent.

Abstract: In an electrode for determining the potassium ion content of a liquid sample to be tested, the electrode including a membrane having incorporated therein an ion selective component, the improvement in which the ion specific component is a compound of the formula: ##STR1## wherein each R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, R.sub.6, R.sub.7, and R.sub.8 is hydrogen or an alkyl group containing between one and about 20 carbon atoms, p is 0 or 1, n is one or more, and, each s and r, independently, is 1, 2, or 3, provided that, when p is 1, n is 8 or more.