PHOTOMETRIC DETERMINATION OF TRACE AMOUNTS OF PHENOL IN WATER AFTER ITS ENRICHMENT WITH ACTIVE CARBON

Trace amounts of phenol in water were enriched by adsorption on active carbon (graininess ≤80 μm) in an acetate buffer medium of pH 6.The enriched phenol was desorbed from active carbon with 50 g·L-1 NaOH solution.The alkaline solution was adjusted to pH 4 with phosphoric acid,and phenol was separated by distillation.An aliquot of the distillate was taken and reacted with 4-amino-antipyrine and potassium ferricyanide in an ammoniacal buffer to give an orange-reddish colored complex,the absorbance of which was measured at the wavelength of 510 nm using a reagent blank as reference solution.Calibration curve was prepared with standard phenol solutions in the concentration range of 0.5 to 12.5 μg per 52.5 mL of the colored solution.Detection limit of this method was 2.9×10-6g·L-1.In the analysis of 4 water samples for their phenol contents by this method,RSD′s (n=7) found were in the range of 3.5%-4.7%,and recoveries in the range from 92%-107%.