Patent ID: 7045310

Claim:
A method for measuring the concentration of an analyte in a sample of a liquid, said method comprising contacting said sample with predetermined amounts of (1) a specific binding partner for said analyte, and (2) a detectable compound of the formula: wherein R and R 1 are the same or different and are 2,2′-bipyridyl, 4,4′-disubstituted-2,2′-bipyridyl, 5-5′-disubstituted,-2,2′-bipyridyl, 1,10-phenanthrolinyl, 4,7-disubstituted-1,10-phenanthrolinyl, or 5,6-disubstituted-1,10-phenanthrolinyl, wherein each substituent is a methyl, ethyl, or phenyl group, R 5 is 4-substituted-2,2′-bipyridyl or 4,4′-disubstituted-2,2′-bipyridyl wherein the 4-substituent is the group B-(L) k -Q(CH 2 ) i - and the 4′-substituent is a methyl, ethyl or phenyl group; R, R 1 and R 5 are coordinated to Os through their nitrogen atoms; Q is O, S, or NR 4 wherein R 4 is hydrogen, methyl or ethyl; —L— is a divalent linker; k is 1 or 0; i is 1, 2, 3, 4, 5 or 6; B comprises a ligand that binds to the specific binding partner and is selected so that the detectable compound binds competitively with the analyte to said binding partner; d is +2 or +3; X and Y are anions selected from monovalent anions chloride, bromide, iodide, fluoride, tetrafluoroborate, perchlorate, and nitrate and divalent anions sulfate, carbonate or sulfite wherein x and y are independently 0, 1, 2, or 3 so that the net charge of X x Y y is −2 or −3; and determining electrochemically the concentration of the detectable compound not bound to the specific binding partner, wherein the concentration of the detectable compound not bound to the specific binding partner is proportional to the concentration of analyte present in the sample of fluid.