A new method based on a quartz crystal microbalance was developed for the determination of cyanide. As the sensitivity depends on pH, temperature and nitrogen flow rate, a modified simplex was used to optimise these experimental parameters. Two different versions of the proposed method were optimised. For the first version a sensitivity increase of 1.5 was observed after 27 runs, whereas for the second version a sensitivity increase of 1.7 was observed after 12 runs.