Sensitive and selective spectrofluorimetric determination of chromium(VI) in water by fluorescence enhancement

A new fluorogenic method for the selective and sensitive determination of chromium(VI) in acidic water using rhodamine B hydrazide was developed. This method was based on the oxidation of non-fluorescent rhodamine B hydrazide by potassium dichromate in acidic aqueous conditions to give rhodamine B, which was highly fluorescent, as a product. With the optimum condition described, the fluorescence enhancement at 585 nm was linearly related to the concentration of chromium(VI) in the range of 5.0 x 10(-8) to 2.0 x 10(-6) mol L(-1) (2.60-104 ng mL(-1)) with a correlation coefficient of R(2)=0.9993 (n=18) and a detection limit of 5.5 x 10(-9) mol L(-1) (0.29 ng mL(-1)). The R.S.D. was 2.2% (n=5). The proposed method was also applied to the determination of chromium(VI) in drinking water, river water and synthetic samples.