A new fluorescence reagent: Synthesis, characterization and application for speciation of arsenic (III)/(VI) species in tea samples.

A sensitive and selective fluorimetric method for the rapid determination of trace amounts of As(III)/As(V) species in certain tea samples forms the basis of the study. 3',6'-bis(diethylamino)-2-{[(1E)-(4,5-dimethyl-2-furyl)methylene]amino}spiro[isoindole-1,9'-xanthen]-3(2H)-one (DMBD), was synthesized and characterized as a new fluorescence reagent for the speciation of As(III)/As(V) species. As(III) was quantitatively recovered with fluorescence reagent at concentrations between 0.5 and 1.5 mol L-1 of HNO3, while As(V) was not quantitatively recovered at any pH. The optimum conditions for the speciation of As(III)/As(V) species were investigated on certain commonly tested experimental parameters such as acidity and pH of the sample, amount of reagent, effects of temperature, and interfering ions etc. In order to determine trace amounts of total arsenic, KI and l(+) ascorbic acid were used to reduce As(V) to the trivalent state in the sample solution prior to determination. The concentration of As(V) in the sample solution were calculated by the difference in concentration between As(III) and the total arsenic in the sample solution. The study yielded a linear function of the concentration of As(III) in the 0-5 mg L-1 range with a detection limit of 0.22 µg L-1. The relative standard deviation was found to be 0.3% for the 0.5 mg L-1 As(III) level. The proposed method was successfully applied for the determination of trace amounts of As(III) and As(V) in certain tea samples. The results of analysis of the certified reference material (INCT-TL-1 tea sample) was found to be in good agreement with the certified value.