Metal-free buffer for ion selective electrode-based assays

A method of assaying a test sample for a predetermined analyte by an ion selective electrode, whereby the effects of an anionic interfering compound present in the test sample are substantially reduced, comprising:

• a) adding a sufficient amount of a buffer composition to the test sample to provide a suitable buffered pH to assay for the predetermined analyte and to form an assay solution, said buffer composition being essentially free of heavy metals, and said buffer composition comprising:
• 1) a from about 0.3% to about 5% by weight of borate compound to reduce the effects of the anionic interfering compound and to buffer the test sample;
• 2) a sufficient amount of an alkalinity adjusting compound to provide a suitable pH to assay for the predetermined analyte;
• 3) and water;
• and
• b) analyzing the assay solution for the predetermined analyte by means of an ion selective electrode capable of sensing the predetermined analyte.

A method of assaying a test sample for total carbon dioxide concentration, wherein the effects of an anionic interfering compound present in the test sample are substantially reduced, comprising:

• a) adding a sufficient amount of a buffer composition to the test sample to adjust the pH of the test sample to a sufficient level to convert a portion of the carbon dioxide present in the test sample in a free form and to convert a portion of the carbon dioxide present in the test sample in a fixed form to carbonate ions and to form an assay solution, said buffer composition being essentially free of heavy metals, and said buffer composition having a pH above 8, and comprising from about 0.3% to about 5% by weight of a borate compound to reduce the effects of the interfering compound and to buffer the test sample, an alkalinity adjusting compound to provide a pH of above 8, and water;
• b) analyzing the assay solution by means of an ion selective electrode that is capable of sensing carbonate ions;
• and
• c) correlating the ion selective electrode analysis for carbonate ions to the concentration of total carbon dioxide in the test sample.

A composition for use in an ion selective electrode-based assay of a test sample for a predetermined analyte selected from the group consisting of carbonate ion, chloride ion, sodium ion, potassium ion and combinations thereof, said composition comprising from about 0.3% to about 5% by weight of a borate compound;

• from about 0.1% to about 2% by weight of either an alkaline alkalinity adjusting compound selected from the group consisting of ammonium hydroxide, sodium hydroxide, potassium hydroxide, lithium hydroxide, barium hydroxide, magnesium hydroxide, calcium hydroxide, a monoalkylammonium hydroxide, a dialkylammonium hydroxide, a trialkylammonium hydroxide, a tetraalkylammonium hydroxide and combinations thereof, wherein the alkyl group includes from one to four carbon atoms, or an acidic alkalinity adjusting compound to provide a suitable pH to assay for the predetermined analyte;
• a buffer compound in addition to the borate compound;
• and water, wherein the composition is essentially free of heavy metals and has a pH of less than about 5 or greater than about 11;
• and wherein the borate compound substantially reduces the effects of an anionic interfering compound present in the test sample.