Control solution for use in testing an electrochemical system

A method of distinguishing a control solution from a sample in an electrochemical test sensor is performed. The method includes adding a control marker to the control solution. The control solution includes the control marker and analyte. The test sensor includes working and counter electrodes, and a reagent. A potential is applied to the test sensor to oxidize the control marker and the analyte. The resulting electrical current is measured. A potential is applied to the test sensor lower than the other potential in which the potential is sufficient to oxidize the analyte and not the control marker. The resulting electrical current is measured. Determining whether a control solution or a sample is present based on the measured electrical currents. To increase the measured current, a salt may be added to the control solution in an amount sufficient to increase the electrical current by at least 5% as compared to a control solution in the absence of a salt.