IMPROVEMENTS IN THE SEPARATION OF POLYCHLORINATED BIPHENYL CONGENERS BY HIGH-RESOLUTION GAS-CHROMATOGRAPHY - APPLICATION TO THE ANALYSIS OF 2 MINERAL-OILS AND POWDERED MILK

A comparative study of the separation of seven polychlorinated biphenyl (PCB) congeners (IUPAC Nos. 28, 52, 101, 118, 138, 153 and 180) and other important PCBs (31, 44, 61, 105, 128, 149, 156, 163, 170 and 186), selected on the basis of their toxicity and levels found in environmental and food samples, was performed using DB-5 and CP-Sil 8 CB (5% phenyl-95% methyl polysiloxane), DB-1701 (14% cyanopropylphenyl-86% methyl polysiloxane) and DB-17 (50% phenyl-50% methyl polysiloxane) fused-silica capillary columns in gas chromatography with electron-capture detection. The combination of DB-5 or CP-Sil 8 CB and DB-17 capillary columns allowed the separation and determination of PCB congeners 118-149, 138-163 and 153-105-132. Some of these congeners were determined in candidate reference materials, two waste mineral oils of different concentration levels and a milk powder, as part of an intercalibration exercise. The recoveries obtained for thirteen selected PCBs were > 90% in the three different samples. The concentrations of PCB congeners determined in the samples ranged between 0.086 and 2.054 mg kg(-1), 0.758 and 66.720 mg kg(-1) and 0.208 and 14.00 mu g kg(-1) for oil of low level, oil of high level and milk powder, respectively. The methods were validated by participation in several round-robin exercises and the results obtained were in good agreement (R.S.D. = 20-40%) for all participating laboratories (between 11 and 19).