3,4,4',5-Tetrachlorobiphenyl (PCB-81): Properties & Uses

3,4,4',5-Tetrachlorobiphenyl is a coplanar, dioxin-like polychlorinated biphenyl congener (PCB-81) widely used as an analytical reference standard and research tool for studying aryl hydrocarbon receptor (AhR) activation, environmental contamination, and toxicological endpoints.

Common Name / Congener Code

PCB-81

CAS Number

70362-50-4

Molecular Formula

C₁₂H₆Cl₄

Molecular Weight

291.99 g/mol

Classification

Dioxin-like coplanar PCB; AhR agonist

Primary Research Use

Analytical reference standard, toxicology, environmental monitoring

Aladdin SKU

T1539622

What Is 3,4,4',5-Tetrachlorobiphenyl (PCB-81)?

3,4,4',5-Tetrachlorobiphenyl, designated PCB-81 under the Ballschmiter–Zell numbering system, is one of 209 possible polychlorinated biphenyl (PCB) congeners. It carries four chlorine substituents at the 3, 4, 4', and 5 positions of the biphenyl scaffold, a substitution pattern that enforces near-coplanarity of the two phenyl rings.

This coplanar geometry is toxicologically significant: it allows PCB-81 to bind the aryl hydrocarbon receptor (AhR), triggering downstream gene expression cascades analogous to—though weaker than—those induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). PCB-81 is therefore classified as a dioxin-like PCB and is assigned a WHO Toxic Equivalency Factor (TEF).

Industrially, PCBs were produced as complex mixtures (e.g., Aroclor, Clophen) until bans took effect in most countries during the late 1970s–1980s. PCB-81 persists in environmental matrices including sediments, soil, fish tissue, and human serum, making it a target analyte in regulatory environmental monitoring programmes.

Key Physical and Chemical Properties

Understanding the physicochemical properties of PCB-81 is essential for correct handling, storage, and analytical method development.

• Molecular formula: C₁₂H₆Cl₄
• Molecular weight: 291.99 g/mol
• CAS number: 70362-50-4
• Appearance: Typically a white to off-white crystalline solid at room temperature
• Solubility: Poorly soluble in water; soluble in common organic solvents such as hexane, dichloromethane, acetone, and methanol
• Stability: Chemically stable under normal laboratory conditions; resistant to hydrolysis and photodegradation compared to lower-chlorinated congeners, though UV exposure should be minimised during analytical work
• Log K_ow: High (estimated >5), indicating strong lipophilicity and potential for bioaccumulation

Stock solutions are commonly prepared in isooctane, hexane, or nonane for GC-based analytical applications, and in DMSO for cell-based bioassays.

Research Applications and Toxicological Relevance

PCB-81 serves multiple roles in contemporary life-science and environmental research:

1. Analytical reference standard: Used to calibrate GC-ECD, GC-MS, and GC-MS/MS methods for quantifying PCBs in environmental samples (water, sediment, biota) and biological matrices (blood, adipose tissue). High-purity certified reference materials are required for regulatory compliance work under programmes such as EU Water Framework Directive monitoring or US EPA methods.
2. AhR biology and mechanistic toxicology: PCB-81 is employed in cell-based reporter-gene assays (e.g., CALUX, DR-LIPO) and receptor-binding studies to characterise AhR ligand potency relative to TCDD. It is assigned a WHO-TEF, enabling its contribution to total dioxin toxic equivalents (TEQ) to be calculated in risk assessment.
3. Bioaccumulation and ecotoxicology studies: Researchers use PCB-81 dosing solutions to investigate uptake, distribution, metabolism, and elimination in fish, invertebrates, and mammalian models, informing environmental risk assessments.
4. Mixture toxicology: As a component of commercial PCB mixtures, PCB-81 is used to reconstruct environmental mixtures in the laboratory to study combined exposures and potential synergistic or antagonistic interactions with other halogenated compounds.

Safe Handling, Storage, and Regulatory Considerations

Hazard classification: PCBs, including PCB-81, are persistent organic pollutants (POPs) listed under the Stockholm Convention. They are classified as potentially carcinogenic and are subject to strict regulatory controls in most jurisdictions. Users must consult the Safety Data Sheet (SDS) provided with the product before use.

Personal protective equipment: Work with PCB-81 in a well-ventilated fume hood. Wear appropriate chemical-resistant gloves (e.g., nitrile, >0.1 mm thickness), a laboratory coat, and eye protection. Avoid generating aerosols or dusts from solid material.

Storage: Store in a tightly sealed container away from heat, light, and incompatible materials (strong oxidisers). Refrigerated storage (2–8 °C) in amber vials is recommended to maintain solution stability. Follow institutional guidelines for controlled substance storage where applicable.

Waste disposal: PCB-containing waste must be disposed of as hazardous chemical waste in compliance with local, national, and international regulations. Do not pour down the drain. Incineration at a licensed high-temperature facility is the accepted disposal route for PCB waste.

Regulatory status: PCBs are banned from new manufacture and use in most countries. Research use of reference-grade material is generally permitted under exemption provisions, but investigators must verify applicable national regulations and institutional biosafety/chemical-safety requirements.

Ordering, Specifications, and Quality

Aladdin Scientific offers 3,4,4',5-Tetrachlorobiphenyl (PCB-81) under SKU T1539622. Key ordering and quality considerations include:

• Purity: Confirm the certificate of analysis (CoA) for purity grade and analytical traceability before use in quantitative or regulatory work. High-purity (≥98%) material is recommended for reference standard applications.
• Available formats: Contact Aladdin Scientific for current stock information regarding solid form and solution concentrations. Custom concentrations may be available upon request.
• Documentation: A CoA and SDS are available for each lot. For regulatory submissions, certified reference material documentation may be required; consult the Aladdin Scientific technical support team.
• Shipping: PCB-containing compounds are subject to hazardous-materials shipping regulations (IATA, IMDG, DOT). Orders will be packaged and labelled in compliance with applicable dangerous-goods regulations. Check import permit requirements in your country before ordering.
• Returns: Due to the hazardous nature of PCB compounds, returns may be subject to restrictions. Please contact customer service before initiating a return.

Frequently asked questions

What is the WHO Toxic Equivalency Factor (TEF) assigned to PCB-81?

PCB-81 is classified as a dioxin-like PCB and has been assigned a WHO-TEF value used in human health and ecological risk assessments to calculate total dioxin toxic equivalents (TEQ). The specific numerical TEF value should be confirmed against the most current WHO guidance document, as values have been revised across different assessment years (1994, 1998, 2005).

What solvents are recommended for preparing PCB-81 stock solutions?

For GC-based analytical methods, PCB-81 stock solutions are typically prepared in isooctane, hexane, or nonane, as these solvents are compatible with GC injectors and produce minimal background interference. For cell-based bioassays requiring aqueous delivery, DMSO is the preferred vehicle solvent; the final DMSO concentration in cell culture media should be kept below 0.1% (v/v) to avoid solvent-related cytotoxicity. Verify solubility limits and carrier compatibility with your specific assay conditions.

Is a special permit required to purchase or use PCB-81 for research purposes?

Regulatory requirements vary by country and institution. In many jurisdictions, PCBs are classified as restricted substances under environmental legislation (e.g., the Stockholm Convention, EU POPs Regulation, US TSCA), but research and analytical use of reference-grade quantities is generally permitted under specific exemptions. Researchers should consult their institutional chemical-safety officer and verify applicable national import, handling, and waste-disposal regulations before ordering.

How should PCB-81 solutions be stored to ensure stability?

PCB-81 solutions should be stored in tightly sealed amber (light-protected) glass vials at 2–8 °C, away from heat sources and strong oxidisers. Organic solvent solutions in isooctane or hexane are generally stable for extended periods when stored correctly. Avoid repeated freeze-thaw cycles. Always check the certificate of analysis for the manufacturer's recommended storage conditions and shelf life for the specific lot.

Can PCB-81 be detected by GC-ECD and what are typical chromatographic considerations?

Yes, PCB-81 is readily detectable by gas chromatography with electron-capture detection (GC-ECD), which is highly sensitive to halogenated compounds. Capillary columns with nonpolar to mid-polarity stationary phases (e.g., DB-5, DB-XLB) are commonly used. Dual-column confirmation and, ideally, GC-MS or GC-MS/MS are recommended for unambiguous congener identification, as co-elution of PCB congeners can occur on a single column. Use of isotopically labelled internal standards (e.g., ¹³C₁₂-PCB-81) is best practice for quantitative work.

References

1. Van den Berg M, et al. WHO/TEF re-evaluation of human and mammalian toxic equivalency factors for dioxins and dioxin-like compounds. Toxicological Sciences, 2006.
2. Ballschmiter K, Zell M. Analysis of polychlorinated biphenyls (PCB) by glass capillary gas chromatography. Fresenius Z Anal Chem, 1980.
3. Stockholm Convention on Persistent Organic Pollutants. United Nations Environment Programme (UNEP). http://www.pops.int
4. US EPA. Method 1668C: Chlorinated Biphenyl Congeners in Water, Soil, Sediment, Biosolids, and Tissue by HRGC/HRMS. US Environmental Protection Agency.

Products are supplied for research and development use only. Not for use in humans, animals, diagnosis, or therapy.