Solubility of TINOPAL CBS-X fluorescent dye at different EDTA concentrations and pH values: Implications regarding its applicability in field tracer tests

•Precipitation and dissolution of TINOPAL CBS-X result in false transport parameters.•Water chemistry is urgent for reliable results using TINOPAL CBS-X in tracer tests.•TINOPAL CBS-X should be prepared in appropriate solutions to avoid precipitation.•EDTA is impractical for dissolution of TINOPAL CBS-X in waters of elevated hardness.