Determn. of polychlorinated bi:phenol(s) in oils - by decomposition and determn. of chloride by mercurimetry

摘要

The polychlorinated biphenyl (PCB) content of oils is measured by decomposing the PCB to form Cl ions, extracting the Cl ions, determining the Cl ion concn. by mercurimetry, and calculating the PCB content from the Cl ion concn. and the Cl content of PCB. Pref. the oil is diluted with a paraffinic or naphthenic hydrocarbon treated with a soln. of a polycyclic aromatic hydrocarbon in an inert polar solvent, treated with excess alkali metal dispersed in a paraffinic or naphthenic hydrocarbon, treated with a Cl-free aq. acid to remove excess alkali metal, and then decanted. The aq. phase is titrated with an aq. Hg(NO3)2 soln. at pH 1-4 in the presence of an indicator, and the resulting Cl ion concn. (in ppm) is multiplied by 100/T, where T is the estimated Cl content of PCB. Interference from reducing agents in the titration is eliminated by pretreating the aq. phase with an oxidising agent, esp. H2O2. The Cl content due to PCB may be determined by chromatography, the oil on a polar adsorbent, eluting the oil with a 5-10C aliphatic hydrocarbon, removing the solvent from the eluate, and measuring the Cl content of the eluate.