Fluorescent microscopic determination of cadmium in water samples with the self-ordered ring of α,β,γ,δ-tetra(5-sulfophenyl)porphine formed on the solid support of glass slides Original Research Article

A self-ordered ring (SOR) technique is first proposed for the determination of trace metal ions based on the capillary effect of solvent on a solid support. At pH 9.1, α,β,γ,δ-tetra(5-sulfophenyl)porphine could form an SOR on the surfaces of hydrophobic glass slides with the aid of poly(vinyl alcohol), and the fluorescence intensity of the SOR was found to be quantitatively quenched by Cd(II). An SOR method for the determination of Cd(II) was established in the range 1.0×10−14 to 2.0×10−13 mol, and the limit of detection was 5 fmol (3σ). Water samples were analyzed with an R.S.D. of 3.2–3.8%. The quantification basis of the SOR method, the relationships between the radius of the SOR and volume of the droplet are theoretically discussed.