Laser induced fluorescence resonance energy transfer for detection of arsenic in water

Ingestion of arsenic by the human body through drinking water induces numerous diseases. Therefore, detection and estimation of arsenic concentration in water, especially in groundwater, is important to protect the human world from its toxicity. In this work we demonstrate a laser induced fluorescence resonance energy transfer (LIFRET) method for the determination of the arsenic concentration in water. The fluorescence resonance energy transfer (FRET) is observed in an aqueous solution of 1, 8-naphthalimide and rhodamine-B by exciting it with a laser radiation of wavelength 405 nm. It is observed that if arsenic contaminated water is added to the pure solution of 1, 8-naphthalimide and rhodamine-B the wavelength of the peak in its FRET spectrum shifts from its pure value at 632.45 nm (peak position of the FRET spectrum of a pure solution of 1, 8-naphthalimide and rhodamine-B). These shifts of wavelengths are towards the lower wavelength side, corresponding to an increase in the concentration of arsenic added to the solution. In the present work, based on the shifting of the peak wavelength value of the FRET spectra corresponding to different concentrations of arsenic, we have described a method for the estimation of arsenic in water up to a lowest limit of 0.000 01 gm l(-1) (the maximum permissible limit of arsenic in water according to the World Health Organisation). The LIFRET method described in this work is portable, relatively cost effective, more convenient and has the potential for any in situ measurement of arsenic in the ground water of arsenic contaminated areas.