Pace Analytical routinely runs analysis of Polychlorinated Biphenyls by Gas Chromatography with Electron Capture Detection for Aroclors. This method determines and quantifies PCB Aroclors as outlined in the following methods: EPA method 508, 608, EPA SW-846 Method 8082, Webb-McCall, and AOAC 970.52, 983.21.
EPA SW-846 Method 8082 is equivalent to AOAC method 970.52: Determination and Quantification of PCBs by Aroclors.
The following Aroclors are routinely detected and analyzed for:
Pace’s basic Aroclor analysis is done by Gas Chromatography (GC)/ Electron Capture Detection (ECD). The GC/ECD is routinely equipped with a high-resolution fused-silica capillary chromatographic column. The primary column is DB-1 column (30 m, 0.25 mm i.d., 0.25 um thickness; J&W Company) and the secondary column for dual column confirmation analysis is a DB-5(30 m, 0.25 mm i.d., 0.25 um thickness; J&W Company). The analysis time per injection is 30 minutes or less which gives the best chromatographic separation of PCB congener groups for the quantification of Aroclors. For each Aroclor, five peaks have been selected to quantify the amount of that Aroclor. The peaks selected from the multi-component Aroclor formulations were based on maximizing the separation for each Aroclor (i.e., minimizing peak overlap). Consideration is also given to selecting peaks that normally do not have problems with co-elution with interfering peaks or possible co-elution with organochlorine pesticides. The determined area of the five peaks selected for calibration is processed by the data workstation as a group, combining the area for calculation of the calibration factors.
Pace employs a five-point initial calibration for each of the Aroclor with two calibration ranges. The first is for high level samples (soils, caulk, DNAPL, PCB oil): the curve ranges from 0.100 to 1.000 PPM and a second for low level samples (Water, Air). This later curve ranges from 0.005 to 0.100 PPM. With either of these calibrations, the RSD is ≤20% for the relative response factors and the Correlation Coefficient R must be >0.99 from Linear Regression analysis determinations.
PACE High Level Calibration Curve
PACE Low Level Calibration Curve
1.000 PPM or 1000 PPB
0.100 PPM or 100 PPB
0.500 PPM or 500 PPB
0.050 PPM or 50 PPB
0.250 PPM or 250 PPB
0.020 PPM or 20 PPB
0.200 PPM or 200 PPB
0.010 PPM or 10 PPB
0.100 PPM or 100 PPB
0.005 PPM or 5 PPB
Although described in SW-846 Method 8082 when PCBs are to be quantitatively determined as Aroclors, the initial calibration consists of only two Aroclors, Aroclor 1016 and Aroclor 1260 which includes many of the peaks represented in the other five Aroclor mixtures. Thus, such a standard may be used to demonstrate the linearity of the detector and that a sample does not contain peaks that represent any one of the Aroclors. This standard can also be used to determine the concentrations of either Aroclor 1016 or Aroclor 1260, should they be present in a sample. Therefore, an initial five-point calibration is performed routinely using the mixture of Aroclors 1016 and 1260 only. Standards of the other five Aroclors may be necessary for pattern recognition. These standards can also be used to determine a single-point calibration factor for each Aroclor, assuming that the Aroclor 1016/1260 mixture above has been used to verify the detector response. Many labs run this calibration and quantification for samples and report the best match to Aroclor 1016 or 1260. This is fundamentally a screening method only, and it is not recommended for use in reporting PCB Aroclors other than 1016 and 1260. Pace’s PCB specialty laboratories rarely use this type of screening calibration for quantitative methodologies.
Positive identification of PCB Aroclors is based on comparison of retention time of the five selected quantitation peaks and major non-quantitation peaks for the unknown sample with retention time of reference standards for the specific Aroclor in question (continuing calibration verification standards).. Additionally, pattern recognition is used for comparison of unknown samples with reference standards for positive identification. Pace Analytical maintains a “reference library” for PCB Aroclors. Our library contains patterns for all 9 Aroclors mixtures as produced by Monsanto. Pace has technical mixes for Aroclor that were used together – for example, Aroclor 1242 and 1254. We have also built chromatograms for field (or real world) samples representative of the “weathering” process.