Abstract: To 1 mL 0.05 mM 5,10,15,20-tetrakis(4-aminophenyl)porphine aqueous solution was added 1 mL 1 M HCl to give a final pH of 1 and a portion of standard nitrite (I) solution, and the mixture was diluted to 10 mL. After 30 min at 30°C, the change in absorbance due to diazotization was measured at 434 nm. The calibration graph was linear up to 0.4 µM-I (up to 18 ng/ml) with a detection limit of 4 nM (0.18 ng/ml). The RSD (n = 10) was 1% for 0.2 µM-I. Many foreign ions were tolerated in large amounts. The method was applied to the determination of nitrite in rain, spring and tap water. Interference by Fe(III) was masked by adding 1 mL 1 mM EDTA to the initial mixture. The results agreed with those obtained by ion chromatography and a FIA method.

Abstract: The FIA method for the determination of Co(II) involved the Cd(II) - 4,4',4'',4'''-(21H,23H-porphine-5,10,15,20-tetrayl) tetrabenzenesulfonic acid complex (CdL) as the chromogenic reagent, the exchange reaction CdL + Co2+ .fwdarw. CoL + Cd2+ and the selective photochemical decomposition of CdL to eliminate the reagent blank. A 100 µL sample was injected into a 2 µM-CdL stream (0.5 ml/min) at pH 8.8, which then merged with a carrier stream (0.5 ml/min) of 1 mM HCl at pH 4. After passage through a mixing coil (5 m x 0.8 mm i.d.) and a photodecomposition coil (3.5 m x 0.8 mm i.d.) irradiated with a 15 W fluorescent tube, the CoL complex was detected at 432 nm with use of a double-beam spectrophotometer with a 1 cm glass cell. A linear calibration graph was obtained for 0.1-1 µM-Co, the detection limit was 0.034 µM (2 ng/ml), and the RSD (n = 10) for 0.68 µM-Co was 0.6%. Mn(II), Cu(II), Zn(II) and Cr(II) interfered; masking agents for these metals are discussed.