The development of an electrochemical sensor for the determination of cyanide in physiological solutions

Hydrogen cyanide gas produced during fires can cause poisoning from smoke inhalation. Blood cyanide concentrations in healthy subjects are sub-micromolar. Toxic or fatal blood concentrations are generally considered to be greater than 40 μmol dm −3 but concentrations in survivors can exceed 200 μmol dm −3, while values exceeding 400 μmol dm −3 have been recorded from fatalities. Cyanide in blood is either free in plasma or bound to ferric haemoglobin. Current analytical techniques require sample pre-treatment, generally with extraction of the cyanide from the sample. An amperometric test was developed which could determine free cyanide at physiological pH in a solution of albumin and other blood constituents without sample pre-treatment, with a calibration range exceeding 400 μmol dm −3 and a limit of detection (LOD; using three standard deviations) of 4 μmol dm −3 which is lower than would be treated clinically.