原子吸光分析法によるカテコールの間接定量

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Indirect determination of catechol by atomic absorption spectrophotometry has been attempted. Catechol reacts with cupric ion to produce a yellowish 2 : 1 ratio chelate at pH 10.0, which is extractable with chloroform in the presence of capriquat, tri-n-octylmethylammonium chloride. Therefore, catechol may be determined indirectly, if the copper in the organic phase is measured by atomic absorption spectrophotometry. Measurements were carried out with a Hitachi Model 207 atomic absorption spectrophotometer, equipped with a premix type burner, using air and acetylene fuels and a hollow cathode lamp. The atomic absorption spectrophotometric conditions are: wavelength, 3247 Å; lamp current, 15 mA; slit width, 0.18 mm; air flow rate, 13.0 l/min and acetylene flow rate, 2.5 l/min. The determination procedure is: One ml of 1.0×10-3 M aqueous catechol solution and 1.0 ml of 5.0×10-3 M aqueous cupric chloride solution were added to 5.0 ml of Britton-Robinson buffer solution of pH 10.0 with mixing. After standing for 5 minutes, 10.0 ml of 1.0×10-3 M capriquat chloroform solution was added. The mixture was shaken well for 5 minutes and was centrifuged at 3000 rpm for 5 minutes. After separation, 5.0 ml of organic phase was transfered into a test tube and was made to 10.0 ml with methanol. The amount of copper was determined by atomic absorption spectrophotometry using a reagent blank as refference. As the suitable pH range was found to be 9.8?10.2, the buffer solution of pH 10.0 was used. The used concentrations of cupric chloride and capriquat were 5 and 10 times of catechol, respectively. The periods of reaction and shaking were both 5 minutes. According to the continuous variation method, the molar ratio of chelate {catechol-Cu(II)-capriquat} in organic phase was found to be 2 : 1 : 2. A linear relationship was shown between the absorbance and the catechol concentration in the range of 11.0176.2 μg/ml. The standard deviation and coefficient of variation were 0.31 and 0.71% respectively, and the recovery of catechol was 100.1 %, according to the back-extraction with 1 N HCl. The effect of diverse ions was examined(Table II, Table III). From these results, it has been found that this atomic absorption spectrophotometry is applicable to the quantitative determination of catechol.

原子吸光分析法によるカテコールの間接定量

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