Indirect determination of phenols by atomic absorption spectrophotometry

Abstract

The analysis of phenols were attempted by the use of atomic absorption spectrophotometry (AAS) for research of indirect determination of organic compound by AAS.
The phenols were determined by AAS and satisfactory results were obtained. The following compounds were investigated: phenol, ο-cresol, m-cresol, p-cresol, p-ethylphenol, ο-isopropylphenol, ο-sec-butylphenol, 3, 4-xylenol, 3, 5-xylenol, ο-aminophenol, ο-chlorophenol, p-chlorophenol, p-hydroxyphenylacetic acid, ο-hydroxybenzoic acid, m-hydroxybenzoic acid, p-hydroxybenzoic acid, propyl-p-hydroxybenzoate, p-nitrophenol, α-naphthol, β-naphthol and α-nitroso-β- naphthol. To prepare the sample solutions, the phenol was dissolved in water, and the other phenols in methyl alcohol.
The recomended procedures are as follows: Methyl alcohol was eliminated by evaporater when it was used as the solvent, and 3 ml of water was added (but in phenol, 1 ml of the phenol solution was added to 2 ml of water). To this solution were added 1 ml of 1.73 N acetic acid and 1 ml of 40.64 mg/ml sodium cobalt nitrite, and the solution was heated on a water bath for 5 minutes at 100°C. After the solution had been cooled, the cobalt-complex containing phenols was extracted with 10 ml of MIBK. The extracted solution was centrifuged and was subjected to AAS.
Since the measurement of cobalt was influenced by the concentrations of acetic acid and cobalt ion, the concentration of acetic acid was kept at 0.141.00 N, and the molar ratios cobalt ion/phenols were kept over 1.89 at measurements of both the sample and the calibration.
Those compounds did not interfere with the phenol determination which are K⁺, Ca²⁺, Mg²⁺, Pb²⁺ and Zn²⁺ even in about 8 times the phenol concentration, Ni²⁺ and Al³⁺ in about 16 times, ephedrine in about 10 times, benzoine in about 15 times, benzoic acid in about 20 times, and nitrobenzene in about 80 times, but Cu²⁺ and Fe³⁺ in about 0.08 times, and aniline in about 5 times interfered with the phenol determination. The interference of metal ion and aniline on the determination of phenol except phenol were successfully eliminated by the extraction of phenols from the acidic aqueous solution into chloroform.
The calibration curve were linear over the rangs 0.102.00 mg of phenol, 2.5014.28 mg of ο-cresol, 2.357.28 mg of m-cresol, 1.527.00 mg of p-cresol, 1.4541.50 mg of p-ethylphenol, 0.996.00 mg of ο-iso-propylphenol, 1.0012.50 mg of ο-sec-butylphenol, 1.243.00 mg of 3, 4-xylenol, 1.404.30 mg of 3, 5-xylenol, 0.7711.15 mg of ο-aminophenol, 2.139.00mg of ο-chlorophenol, 0.505.20 mg of p-chlorophenol, 0.805.08 mg of p-hydroxyphenylacetic acid, 20.51 mg of ο-hydroxybenzoic acid, 5.5223.00 mg of m-hydroxybenzoic acid, 2.5816.10 mg of p-hydroxybenzoic acid, 0.111.58 mg of propyl-p-hydroxybenzoate, 2.7212.40 mg of p-nitrophenol, 0.040.70 mg of α-naphthol, 0.051.53 mg of β-naphtol, and 0.160.38 mg of α-nitroso-β-naphthol in 10 ml of MIBK each. Per cent recovery of phenols ranged from 94.5 to 104.5%.
It has been found that this method is very easy and simple in the procedure and is satisfactory applicable to the quantitative determination of phenols.