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Exclusive GC Phase has Unique Selectivity for PCB Congeners

by Gary Stidsen, GC Columns Marketing Manager, Restek Corp.

click the image to enlarge Figure 1: Excellent separation and peak symmetry for PCBs in combined Aroclor® mixes: Rtx®-PCB column. Column: Rtx®-PCB 40 m, 0.18 mm ID, 0.18 μm (cat.# 41303); Sample: 0.3 ng Aroclor® 1242-1254-1262 in 1.0 μL hexane; Injection: splitless (hold 0.75 min.), 230 C, 4 mm single gooseneck inlet liner; Carrier: hydrogen, constant pressure, 40 cm/sec. @ 100 C; Oven Temperature: 100 C (hold 1 min.) to 200 C @ 30 C/min., to 320 C @ 2 C/min. (hold 1 min.); Detection: ECD, 330 C. GC_EV00768

Environmental “weathering”, and bioaccumulation effects, dictate that polychlorinated biphenyls now be reported as congeners, rather than as the original commercial mixes (e.g., Aroclor®, Clophen, Kaneclor, Phenoclor). Identifying and quantifying PCB congeners chromatographically is challenging, because there are 209 combinations in which chlorine atoms can be incorporated into the biphenyl structure, and many of these have very similar retention characteristics. Using (1) as a guide, we compiled a target list of 158 congeners that either are components of Aroclor® mixes at concentrations above 0.01% wt/wt or, if not detected in Aroclor® mixes, are concentrated in tissue (PCB 169). The list includes the seven European PCB congener indicator compounds (PCBs 28, 52, 101, 118, 138, 153, 180) and the 12 most toxic congeners (non-ortho PCBs 77, 81, 126, 169; mono-ortho PCBs 105, 114, 118, 123, 156, 157, 167, 189), according to the World Health Organization (2).

(insert image 1 here) Using a 40-meter Rtx®-PCB column and electron capture detection, we determined the retention time for each congener individually, then analyzed a composite of Aroclor® PCB mixes 1242, 1254, and 1262. Of the 158 target PCB congeners, all except PCB 169 were present in the composite, and of these 103 eluted singly, greatly simplifying identification and quantification (Figure 1; also can be viewed on line at www.restek.com). In a GC/MS analysis on the same 40 m × 0.18 mm ID × 0.18 μm column, or on a 30 m × 0.25 mm ID × 0.25 μm column, each of the European indicator compounds can be evaluated without interference from other congeners (3).

Produced through an advanced polymer technology and rigorous quality assurance measures, Rtx®-PCB columns conform to exacting standards and ensure highly reproducible column-to-column performance. Unique selectivity and low bleed make these the column of choice for PCBs, and a necessity for trace analysis.

1. Frame, G., J. Cochran, and S., Bowadt, Complete PCB Congener Distributions for 17 Aroclor Mixtures Determined by 3 HRGC Systems Optimized for Comprehensive, Quantitative, Congener-Specific Analysis J. High Res. Chromatogr. 19: 657-668, 1996.

2. Assessment of the health risk of dioxins: re-evaluation of the Tolerable Daily Intake (TDI) Executive Summary, WHO Consultation, May 25-29, 1998, Geneva Switzerland.

www.who.int/ipcs/publications/en/exe-sum-final.pdf

3. Stidsen, G., New GC Column for PCB Congeners or Aroclor® Mixes: Rtx®-PCB Restek Advantage 2005 v1: 13.