Use of New Photochemical-Sensing Membrane in Determination of Hexavalent Chromium

A new type of photochemical-sensing membrane for the determination of Cr(Ⅵ),based on the reversible fluorescence-quenching of the conductor wire compound,2-(2-(4-(2-(4-(2-(2,5-diheptyl-4-(2-thiophenyl-2-)-ethinyl)-phenyl)-ethinyl)-phenyl)-ethinyl)-2,5-diheptophenyl)-ethinyl) thiophene (FDB in short) was prepared by mixing an appropriate amount of FDB dissolved in 2 mL of tetrahydrofuran with 55.0 mg of polyvinyl chloride (PVC),105.0 mg of diiso-octyl-o-phthalate (DIOP) and 5.0 mg of sodium tetraphenylboron,and making into membrane.Fluorescence detection was made in a 0.60 mol·L-1 H2SO4 solution at the wavelengths of (λex) 371 nm and (λem) 407 nm.Linearity range for determination of Cr(Ⅵ) was kept between 3.78×10-6-1.26×10-3mol·L-1.Detection limit (3S/N) of 5.16×10-7mol·L-1 was found for the method.Time of response was less than 1 min.No interference by those common metal ions was observed.The proposed method was applied to the analysis of samples of lake and river water,giving results in consistency with the results found by the method of GB/T 7468-1987.Values of recovery found were in the range of 96.0%-106.3%.