Spectrophotometric determination of sulfide ion with watersoluble porphyrin complex of silver. (I).

Abstract

Silver complex of α, β, γ, δ-tetrakis(4-sulfophenyl) porphine (Ag2-TPPS) was quantitatively formed within 1 min at room temperature in the pH range of 11.0 to 12.5. The complex easily relases the porphyrin in the presence of base anions such as S2-, CN-, I-, glutathione and L-cysteine within 5 min at room temperature in the above pH range. Based on this reaction, spectrophotometric determination of 10-7 mol dm-3 levels of sulfide ion was developed. The Soret band of TPPS and the Ag2-TPPS complex at pH 12.0 and I=0.5 were located at wavelength of 414 nm (e=41.4 × 104) and at 443 nm (e=7.9 × 104), respectively. A recommended procedure : 1.0 cm3 of 10-4 mol dm-3 TPPS solution, 10cm3 of 2.5 mol dm-3 sodium nitrate solution, 2.0 cm3 of 10-4 mol dm-3 Ag(I) solution, and 5 cm3 of 1 mol dm-3 sodium hydroxide solution are taken into a 50 cm3 of amber-volumetric flask. After standing for 5 min, 30 cm3 of sample solution containing less than 2.0μg of sulfide is added and is diluted to 50 cm3 with water. After 10 min, the absorbance at 414 nm against water is measured. The calibration curve was found to be linear in the range of 02.0 × 10-6 mol dm-3. The relative standard deviation was 3.75% for [S2-]T= 5 × 10-7 mol dm-3 (8 determinations). The detection limits was 7 x 10-8 mol dm-3 (S/N=3). The tolerance limits of diverse ions for determination of [S2-]T = 5 × 10-7 mol dm-3 were 5 × 10-4 mol dm-3 for NO3-, CI-, SO42-, K+ and Na+, and 5 × 10-5 mol dm-3 for Ba2+, Ca2+ and Fe3+. However, 5 × 10-7 mol dm-3 of I-, CN-, Cd2+, glutathione and L-cysteine were interfered. As Ag2-TPPS complex reacts rapidly with various kinds of soft bases, it is expected as a highly sensitive and selective chromogenic reagent of postcolumn detection system in the LC for these ions.