Spectrophotometric Determination of Cobalt with Phenylfluorone in the Presence of Zephiramine and Sodium Nitrite

Abstract

Phenylfluorone reacts with cobalt in the presence of zephiramine and sodium nitrite to form a blue water-soluble chelate. The absorption maximum was found at 645 nm and its absorbance was constant in the pH region 4.55-5.O. The molar absorptivity is 4.8 x 10⁴ at 645 nm and the sensitivity is 0.0012 Co μg/cm² for log (I₀/I) (absorbance) = 0.001. This complex formation was applied to the determination of a microamount of cobalt. The calibration curve prepared at 645 nm was linear for the cobalt concentration up to 2.0 μg/ml.
The composition ratio of cobalt to phenylfluorone in the complex was estimated to be 1 to 2 in the presence of both zephiramine and sodium nitrite.