Sensitive determination of sulfate in drinks and vegetables digests by Rayleigh light scattering technique

In this paper, a novel and sensitive method based on Rayleigh light scattering technique (RLS) was proposed for the determination of sulfate using a conventional spectrofluorometer. Sulfate was transformed to BaSO4 particles, which displayed intense light scattering in aqueous solutions. The effects of factors such as wavelength, acidity, stabilizers and interferents were studied in detail. The RLS intensity of the BaSO4 suspension was obtained in 0.1 mol L(-1) of [H+] and the addition of 2 mL of cationic polyacrylamide (CPAM) with 7.05 x 10(-3) mmol mL(-1) charged cations and 1.0 mL of BaCl2.2H2O (5.0%) at 510 nm. In the range of 8-400 microg mL(-1), RLS intensity was linear to the concentration of BaSO4, and the detection limit was 0.3 microg mL(-1). To determine the feasibility of the proposed method, some samples of water, drinks, and vegetables digests were analyzed, and the results were in agreement with the standard turbidimetric method. Good recovery results were also obtained in the range of 94-105%. Although this method was limited in stability, it was characterized with simplicity, sensitivity, reliability, and little interference.