Introduction to PCB Congeners Presented by Jamie Fox
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Purpose • To provide general information on PCB’s. • To describe the analytical methods. • To describe uncommon terms. • Example Reports • To answer your questions.
What are PCB’s? • Aroclors are a mixture of PCB’s numbered by type and percent chlorine content (i.e. 1242 is 42% chlorine) • PCB’s are a group of 209 polychlorinated biphenyl congeners. Commonly referred to by a numbering system. • 12 PCB’s (WHO list) are distinguished as a sub-group. These are considered to be the most toxic. They are the ones whose toxicity is defined. • Totals are reported by homolog group, e.g. Total Mono PCB’s, Totals Di PCB’s, etc. and Total PCB Congeners.
What are PCBs? 209 Mono-Deca PCB Congeners Polychlorinated Biphenyl (10 substitution positions) 3’ 3 2 2’ 4’ 4 5’ 5 Cln 6’ 6 Cln
What are PCBs? • PCB-77 • PCB-81 • PCB-105 • PCB-114 • PCB-118 • PCB-123 • PCB-126 • PCB-156 • PCB-157 • PCB-167 • PCB-169 • PCB-189 The Twelve Toxic Congeners
The PCB Problem • Manufactured in US from 1929 to 70’s for transformers, capacitors, paints, caulk, etc. • Ubiquitous and persistent in the environment • Neuroendocrine disruptor, teratogen, likely carcinogen • Contaminated sites everywhere—Great Lakes, Hudson River, Newtown Creek
Aroclor Method Method 8082 is historically the most common analytical method for measuring PCB’s. • GC/ECD • Uses fingerprinting method • Common RL is low ppb • Least expensive
PCB Homolog Method Method 680 is commonly used in conjunction with pesticide analysis. • GC/LRMS SIM • Measures by homolog group • Common RL is mid ppt
PCB Congener Method Method 1668 can be used for Clean Water Act (CWA) compliance (e.g., NPDES permits, TMDL studies, CBC). • Versions A, B*, and C exist. Versions A and C are very similar and of primary concern. • Existing studies use version A. • Version C has tighter QA/QC limits, causing about 5-20% more failures • Common RL is low ppq * Version B was largely ignored by laboratory and regulators due to disagreements over QA/QC requirements, too loose in some areas, too tight in others.
TMDL • TMDL = Total Maximum Daily Load • Section 303(d) of CWA • Used to study impacted waterways • Calculates allowable pollutant discharge limits that ensures water quality standards are met • Example: Delaware River • Delaware River Basin Commission • Virginia DEQ
Individual Congeners • Verify weathering of Aroclors • Due to “fingerprint” nature of Method 8082, PCBs may still be present • Weathering may result in Aroclor ND’s that would be detected as individual congeners • Congener specific analysis has been used for source identification based on industrial process
Bioaccumulation • Tissue analysis often requires low detection limits • Human health concerns drive PCB regulatory limits lower than traditional analytical method RLs
Isotope Dilution What do we do with the 13C labeled congeners? (PCBs and Dioxins) Act as surrogates and internal standards for the native congeners at each step in the preparation and analysis: • Extraction Standards (ES) just before the extraction. • Cleanup Standards (CS) just before the fractionation. • Injection Standards (JS) just before the injection.
Isotope Dilution Extraction Standards (ES) When? Extraction Standards are introduced inside the sample matrix before the extraction step. Why? • Used to measure the overall extraction and fractionation efficiency • Used in the qualitative and quantitative characterizations of native congeners
Isotope Dilution Cleanup Standards (CS) When? Cleanup Standards are introduced to the sample after extraction but prior to the cleanup step (when applicable.) Why? • Used to measure the efficiency associated with the fractionation step alone.
Isotope Dilution Injection Standards (JS) When? • Injection Standards are introduced to the sample after cleanup but prior to injection. Why? • They act as internal standards to determine the recoveries of the Extraction and Cleanup Standards. • Provide a measurement of injection efficiency useful to the analyst.
High Resolution Mass Spectrometry How high is high? Well, it’s 10000 Resolving Power! The ability to zoom in on a mass spectrum and tell the differences between masses that are very close in weight.
High Resolution Mass Spectrometry 100ppm 5% line
Sample specific Estimated Detection Limit (EDL) • Not the same as a Method Detection Limit (MDL) • The concentration of a given analyte required to produce a signal with a peak height of at least 2.5 times the background signal level. • Used for blanks, not for samples as the method is written
Toxic Equivalency Quotient (TEQ) • Simplest means of reporting a sample’s toxicity, one number! • TEQ is a sum based on the concentration of the toxic PCB congeners and their relative toxicity to 2,3,7,8-TCDD. • Important client decisions include: • the choice of Toxic Equivalency Factors (TEFs) • treatment of non-detects • the use of EMPCs or not
Thank you! Jamie Fox 505-307-3770 email@example.com www.capefearanalytical.com