Understanding Volatile Organic Compounds

Apr 18, 2025

Analysis of Volatile Organic Compounds - Pre-seminar Material

Speaker

  • Mr. Tim Wong

Curriculum Link

  • Hong Kong Accreditation Service
  • Builds on knowledge from DSE curriculum:
    • Chemistry: Topics V, XI & XV
    • Combined Science (Chemistry): Topic V

Introduction to VOCs

  • Volatile Organic Compounds (VOCs) are organic compounds with high vapor pressure (low boiling point) at room temperature.
  • Common air pollutants found in:
    • Car exhausts
    • Paints
    • Coatings
    • Solvents
    • New furnishings
    • Office equipment

Effects of VOCs

  • Adverse health effects:
    • Allergies
    • Skin and respiratory irritations
    • Headache
    • Immune effects
  • Precursors to photochemical smog, reducing visibility
  • Definitions of VOCs may vary by country

Examples of VOCs

  • Formaldehyde (methanal)
    • Chemical Formula: HCHO
    • Boiling Point: -19°C
    • Sources: Adhesives and paints
  • Methane
    • Chemical Formula: CH4
    • Boiling Point: -160°C
    • Sources: Biological wastes
  • Benzene
    • Chemical Formula: C6H6
    • Boiling Point: 80°C
    • Sources: Solvents

Analysis of VOCs

  • Techniques used:
    • Chromatography
    • Mass Spectrometry

Chromatography

  • Separates mixtures of chemicals
  • Common techniques:
    • Gas Chromatography (GC)
    • Liquid Chromatography (LC)

Paper Chromatography Experiment

  • Separation of ink components
  • Phases:
    • Mobile phase: Solvent (ethanol)
    • Stationary phase: Water on chromatographic paper
  • GC vs LC:
    • GC mobile phase: Gas
    • LC mobile phase: Liquid

Mass Spectrometry

  • Often coupled with GC or LC for compound identification
  • Process:
    • Bombardment of molecules with electron beam
    • Formation of molecular ion (M)
    • Fragmentation into smaller ions
    • Detection by MS

Seminar Topics

  • Definitions of VOCs
  • Sources of VOCs
  • Hazards associated with VOCs
  • Sampling and analytical methods
  • Accreditation

Glossary

  • Volatile organic compound (VOC)
  • Gas chromatography (GC)
  • Liquid chromatography (LC)
  • High-performance liquid chromatography (HPLC)
  • Paper chromatography
  • Mobile phase
  • Stationary phase
  • Carrier gas
  • Polar molecule
  • Photochemical smog
  • Visibility

External Resources

View note source

https://learn.hkmooc.hk/asset-v1:HKVU+COSAS+2021_Q4_R1+type@[email protected]