Objective

1
Objective

• Finish with VOCs
• Prepare for the field measurements on Friday

2
VOCs in Buildings

• Sources
• Fate
• Effects
• Measurement

3
VOC
Volatile Organic Compounds (VOCs)

• What is a VOC?
• Organic C, H
• affinity for gas phase, significant
  evaporation rate
• Tb lt 260 oC
• Thousands (reduce list to 50 to 100)
• What is TVOC?

4
Categories

• Odor-causing
• Irritating
• SBS fatigue, eyes, headaches, upper resp., etc
• Other skin irritation, asthma, MCS
• Toxic/Hazardous
• Carcinogen
• Teratogen
• Neurotoxin, etc.
• Reactive
• Generally w/ ozone

5
Representative Examples

• Benzene
• Toluene
• Ethylbenzene
• Xylenes (all isomers)
• Trimethylbenzenes (all isomers)
• Dichlorobenzenes (not all isomers created equal)
• Tetrachloroethene (PERC)
• Chloroform (a THM)
• 4-Phenylcyclohexene (4-PCH)
• Styrene
• Terpenes (limonene, pinene, etc.)
• Formaldehyde (HCHO) often not classified as a
  VOC

BTEX
6
Relative Exposure to VOCs

• Exposure (I/O) 3 x 18 x 0.4 22
• indoor contribution gt 95 (most volatile HAPs,
  etc.)

7
Some Important Sources

• Building materials and furnishing (wood,
  adhesives, gyp board)
• Flooring materials (carpet, vinyl flooring, wood)
• Architectural coatings (paints, varnishes, waxes,
  etc.)
• Consumer products (cleaners, detergents,
  fresheners, personal, etc.)
• Combustion sources (ETS, candles, gas stoves,
  space heaters)
• Electronics (computers, photocopiers, printers,
  TVs/VCRs)
• Heating of particulate matter
• Soil vapor intrusion
• Drinking water
• Mold (MVOCs)
• People

8
Measurement Issues

• Objective(s)
• Required detection limits
• (Real-time) vs. (collect and analyze)
• Non-specific vs. species specific (speciated)
• Grab versus integrated
• Interferences
• Preservation requirements
• Quality assurance requirements
• EPA/OSHA/NIOSH methods exist?
• Cost/Budget

Measurement Method
9
Sample Collection Methods

• Real-time (field) measurement/analysis
• generally sensor (mostly FID, PID)
• some separation (w/ GC) sensor
• Also colorimetric tubes (general MDL gt 1 ppm)
• Collect for analysis
• whole-volume samplers (canisters, bags)
• concentration samplers (sorbents, SPME)
• either case preservation and analysis in
  laboratory

10
Canisters

• Whole volume
• Grab versus integrated
• EPA Methods TO-14 / 15
• Benefits
• Inert/impermeable
• Experience
• Multiple analyses
• Drawbacks
• bulky
• cleaning
• Scratch
• Ozone / Sample stability

1 15 L
http//www.skcinc.com
400 mL
11
Tedlar Bags

• Whole volume
• Tedlar polyvinylfluoride
• Pump to collect (unlike cans)
• Issues
• Benefits
• inert / impervious (like cans)
• repeat samples (like cans)
• lighter than cans
• lower initial cost than cans
• Drawbacks
• not as reuseable as cans
• tearing
• cleaning
• stability with some compounds

http//www.essvial.com/products/airsample.html
0.5 100 L
12
Sorbent Sampling

• VOC adsorbs to solid adsorbent
• Passive sampling
• Similar to ozone badge
• Integrated sample over 24 hours, etc.
• Indoor, personal, outdoor
• Active Sampling
• Pump through packed tube
• Collect mass over known volume
• C m/V
• Short-term vs. integrated
• More control, but more difficult

http//www.aerotechpk.com/
http//www.sisweb.com/index/referenc/resin10.htm
13
Sorbent Tubes

• EPA Method
• Various sorbents can be used
• Note VOC types/ranges
• Some issues
• Method detection limit, precision, accuracy
• Sample preservation
• Breakthrough volume
• Artifact formation (especially via ozone)
• Sorbent pre-conditioning / breakdown over time
• Use of multi-sorbent beds
• Focus on Tenax-TA

14
Tenax-TA

• 2,6-diphenylene oxide polymer resin (porous)
• Specific area 35 m2/g
• Pore size 200 nm (average)
• Density 0.25 g/cm3
• Various mesh sizes (e.g., 60/80)
• Low affinity for water (good for high RH)
• Non-polar VOCs (Tb gt 100 oC) polar (Tb gt 150
  oC)
• Artifacts w/ O3 benzaldehyde, phenol,
  acetophenone

15
Gas Chromatography (GC)

• Goal separate compounds
• Use capillary column
• Properties of column
• Properties of chemical
• Thermal program of GC oven
• Temporal passage to a detector
• analyze peaks
• analyze molecular fragments (MS)

16
Gas Chromatography (GC)
http//www.chromatography-online.org/GC/Modern-GC/
rs2.html
17
Figure 5 Chromatogram of Tenax-sampling in a
show case (sample volume 1l) - iaq.dk/iap/iaq2003/
posters/hahn5.gif
Blue slides www.sisweb.com/art/referenc/aap54
18
GC Issues

• Type of injection?
• Need to cryofocus?
• Type of column?
• Type of detector?
• If MS, model of detection
• Temperature programs
• Instrument calibration / response

19
Detectors

• Flame ionization detector (FID)
• Photoionization detector (PID)
• Electron capture detector (ECD)
• Mass spectrometer (MS)
• These are primary detectors for VOCs in indoor
  air
• Specific uses vary considerably

Non-specific or speciated (w/ GC)
w/ speciated (w/ GC)
20
Flame Ionization Detectors (FID)

• Relatively simple system ?
• Ions formed migrate to plate
• Generate current
• Detection typical to pg/s
• Benefits
• Rugged, low cost, workhorse
• Linear response over wide range
• Insensitive to H2O, CO2, SO2, CO, NOx ..
• Drawbacks
• No identification
• Lower response if not simple HC
• Destructive

www.chem.agilent.com
21
Photoionization Detectors (PID)

• UV light ionizes VOCs --- R hv ? R e-
• Collected by electrodes current
• VOCs with different ionization potentials
• Benefits
• Simple to use
• Sample non-destructive (relatively)
• Drawbacks
• No identification
• Highly variable responses
• Not all VOCs detected
• Lamp burnout / contamination

http//www.chemistry.adelaide.edu.au/external/soc-
rel/content/pid.htm
22
Electron Capture Detectors (ECD)

• Low energy Beta emitter 63Ni
• e- attracted to positively charged electrode
  (anode)
• Molecules in sample absorb e- and reduce current
• effective halogens, nitrogen-containing
• Benefits
• 10-1,000 x more sensitive than FID
• femtogram/s ----- ppt levels
• Drawbacks
• More limited linear range than FID
• Radiological safety requirements
• O2 contamination issues
• Response strong function of T, P, flowrate

http//www.chemistry.adelaide.edu.au/external/soc-
rel/content/ecd.htm
23
Mass Spectrometer (MS)

• Bombard molecules w/ intense electron source
• Generate positive ion fragments
• Use fragment fingerprint to identify molecule
• Quantify amount of fragments to determine mass
• Most common MS quadrupole

24
Quadrupole MS

• Electron source
• Four rods (electromagnets)
• Applied Voltage
• DC/AC components
• Voltages fn(time)
• Affects trajectory
• Selective M/Z to detector

http//www.chemistry.adelaide.edu.au/external/soc-
rel/content/quadrupo.htm
25
Total Ion Chromatogram (TIC)
linalool
limonene
Mondello et al., J. of Chromatography A, 1067
235-243 (2005)
26
Summary

• VOCs important in indoor environments
• Many types of VOCs
• Different properties
• Different effects
• Different sample collection and analysis
  protocols
• Sampling and analysis protocols NOT TRIVIAL
• Many types of collection methods
• Many types of analysis methods / including
  detectors
• A lot of issues involved w/ sample/analysis
  decisions
• A lot can go wrong (difficult business)
• Cumbersome and costly -------- but really
  important

27
Field trip

• Friday afternoon
• 10800 Pecan Park Boulevard Suite 210. Austin, TX
  78750
• Measurement of
• Primarily IAQ parameters
• Prepare on Thursday
• Distribute duties
• Equipment assembly
• Packing and check out
• .