水溶性ポルフィリンを利用するppbオーダーの銅の吸光光度法

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Water soluble porphyrin, α, β, γ, δ-tetraphenylporphine-trisulfonate(TPPS), was found to be very useful agent for both the direct spectrophotometric determination and the photomeric titration of copper(II). The soret bands of TPPS and Cu-TPPS complex at pH 2.5 were at the wavelength of 434 nm (ε=5.0×105) and at 413 nm(ε=4.76×105), respectively. For the determination of copper, the wavelength of 434 nm was used and the sensitivity of the method was 0.00013 μg Cu2+·cm-2 for A=0.001. Beers law was followed in the range 060 ng·ml-1. Among twenty-two metal ions examined, only zinc(II) seriously interfered with the determination. The selectivity of the method seems to be largely depend on the kinetic nature of the metal incorporation reaction of TPPS. The recomended procedure is to add 2.5 ml of 1 M acetate buffer solution(pH 4.0) and 5 ml of 1×10-5 M standard TPPS solution to an about 40 ml solution containing 0.33 μg of copper, followed by heating to boil for one minute and by cooling to room temperature, then to adjust pH to 2.5 with 1.5 ml of 1 M chloroacetic acid solution, to dilute to 50 ml and measure the absorbance(A) at 434 nm against water with 1 cm cells. Copper concentration is determined from the decrease in absorbance by complexation as follows: Cu(ng/ml)=130×(A0-A), where A0 is the absorbance of reagent blank.
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