Mixed ionophore ion-selective electrode for the improved detection of urea in blood

A method of operating a multiple-use sensor array, said method comprising:

• (i) providing a multiple-use sensor array arranged in a measuring chamber, said sensor array comprising two or more different ion-selective electrodes including a first ion-selective electrode and a second ion-selective electrode, said first ion-selective electrode including a membrane comprising (a) a first ionophore and (b) at least one second ionophore, said second ion-selective electrode including a membrane comprising at least one of the at least one second ionophores, said first ionophore not being present in any ion-selective electrode in the sensor array other than in the first ion-selective electrode;
• (ii) in sequence contacting the sensor array with one or more rinse solutions and optionally one or more calibration solutions, each of said rinse solutions being substantially devoid of the ion for which said first ionophore is selective;
• (iii) subsequently contacting the sensor array with a sample of biological origin.