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 × 10−8 to 2.0 × 10−6 mol L−1 (2.60–104 ng mL−1) with a correlation coefficient of R2 = 0.9993 (n = 18) and a detection limit of 5.5 × 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.