Sensors for detecting and distinguishing metals in a sample comprise phenol group-containing azo dyes, the phenol group having one hydroxy involved in reversible metal ion binding and a second hydroxy alkylated to an optically transparent substrate. The sensors have utility for detecting chromium, calcium, magnesium, copper, mercury, nickel, zinc, cobalt, manganese, cadmium, lead, tin, aluminum, potassium, sodium, or arsenic ions in a sample.

Provided herein are dyes for detecting and distinguishing metals in a sample, as well as compositions and methods comprising the same.

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