Single‐Component Chemical Nose with a Hemicyanine Probe for Pattern‐Based Discrimination of Metal Ions†

Main observation and conclusion We report here a chemical nose utilizing the nonspecificity of a hemicyanine dye (probe P) containing three acetates and one deprotonatable phenol groups. Unlike conventional pattern‐based recognition that requires a combination of different probes, probe P alone is able to differentiate 9 different metals, generating distinctive absorption spectra and various patterns upon principle component analysis (PCA). River water samples and commercial mineral water samples were evaluated by the probe and were successfully distinguished.