Patent ID: 8497130

Claim:
A method for determining the partition coefficient of an analyte using a sensor operable to measure the presence or amount of analyte in an electrolyte solution of predetermined permittivity ∈, said sensor comprising: (a) two electrically conducting electrodes on an electrically insulating substrate, and separated by a distance L, where L is between 10 nm and 10 μm; and (b) a chemiresistor film, wherein the impedance of the chemiresistor film changes in the presence of an analyte; wherein the chemiresistor film is in contact with the electrodes; wherein the sensor comprises a voltage means configured to provide a low frequency f<f 0 =100 Hz signal or DC voltage across said electrodes; and wherein the apparent area A of a double layer capacitor formed by the electrodes and the chemiresistor film in the electrolyte solution is less than half of A 0 , A 0 = d 2 ⁢ ⁢ π ⁢ ⁢ f 0 ⁢ ɛɛ 0 ⁢ R , where ∈ 0 and d are predetermined and R is the resistance of the electrodes and the chemiresistor film in the electrolyte solution, said method comprising the steps of: (i) contacting said chemiresistor film with two or more solutions of said analyte wherein said two or more solutions of said analyte are of known but different concentrations; (ii) measuring the change in impedance of said chemiresistor film for each of said two or more solutions; (iii) fitting a line to the log-log plot of change in the impedance of the nanoparticle film versus concentration of said analyte; (iv) calculating the value of the logarithm of the slope of said fitted line; (v) comparing the value of the logarithm of the slope of said fitted line to a standard curve correlating the logarithm of said slope of said fitted line to the logarithm of the partition coefficient to thereby determine said partition coefficient of said analyte.