This paper was presented at the American Chemical Society Fall meeting in Philadelphia, PA on the Environmental Chemistry Division program track in a symposium titled: Recent Advances in Remdeiation Strategies & Technologies for the Cleanup of Hazardous Waste Sites. This talk discusses headspace screening of VOC’s in soil and water samples that can be done in the field using a GC/PID headspace method for rapid detection.

1. Headspace GC/PID for on-site Screening of
Soil and Water at Hazardous Waste Sites
Dr. Jack Driscoll, ACSF & Jennifer Maclachlan
PID Analyzers, LLC, Sandwich, MA
ACS National Meeting, Philadelphia, ENVR Track
Wednesday August 24, 2016

2. Introduction
• Headspace screening of VOC’s in soil and water samples in the
laboratories is a common practice to prevent high level samples
from contaminating the GC/MS. The screening of soil and water
samples can be done in the field using headspace
• Photoionization detection (PID) is a common technique that has
been in used for more than 30 years. This is then coordinated with
laboratory GC/MS samples. With some of the new easy to use
instrumentation available like the battery operated Model 312
portable GC, it is now possible to obtain laboratory quality data in
the field.
• This could speed up the processing of samples once the
contaminants have been identified and reduce the number of
samples sent to the laboratory. The Model 312 can detect low ppb
levels of most contaminants including TCE and PCE. It will run for 6-
8 hours on the batteries and can accommodate 30M capillary
columns that are easily interchangeable. The general purpose
column is a 30M x 0.53 mm x 3 micron film methyl silicone column
that separated based on boiling point. The thick film column will
also separate gases as well as volatile liquids. This is an ideal tool to
help clean up hazardous waste sites more rapidly.

3. What is Headspace?
Solid Samples
• Head space is the gas
above the liquid or
solid sample that can
be efficiently
partitioned from the
sample. By using
similar preparation
techniques and
standards, the
approximate level of
contamination can be
determined.
Water Samples
• According to Henry’s law, the concentration
in the gas phase (headspace) at equilbrium is
proportional to the concentration in the
liquid (water) phase!
Henry’s law can be stated (at constant
temperature) that :
P = Kh C
• where:
P= the partial pressure of the solute in the
gas above the solution,
C=the concentration of the solute, and
Kh=a constant with the dimensions of
pressure divided by concentration.
The constant, known as the Henry’s law constant,
depends on the solvent, the solute, and the
temperature. Used for EPA method 8260

4. How can it be measured in the Field?
Model 102 PID- total VOC’s
GC312 Portable GC- VOC specific
Model 102
VOC
collection
Soil- weigh 5-50
g in 250 mL
beaker
Water- collect
125 mL in 250
mL beaker
Need larger
sample for this
analyzer
Model 312 GC
40 mL VOA vial- fill
to brim,
remove 10 cc and
inject 1 cc
Into the injection
port
Check soil portion

5. Model 102 PID Precision Total VOC’s
Gases in the Lab
Measurements 10 ppm
10 ppm ISOB Cylinder Bag Headspace
N/A 12.9 123
N/A 12.9 123
N/A 13 122
N/A 13 123
N/A 12.9 124
N/A 12.9 123
N/A 12.8 124
N/A 12.9 125
N/A 12.8 123
N/A 12.8 125
Avg N/A 12.89 123.5
SD N/A 0.073 0.972
CV% N/A 0.57 0.79
Measurements 100 ppm
100ppm Cylinder Bag Headspace
99.1 99.8 960
96.5 100 940
100.1 97.9 968
100.1 98.1 916
100.4 98.3 1001
101.5 98.1 1001
100.5 98.3 998
99.8 98.2 994
100 98.1 992
100 98 987
Avg 99.4 99.4 975.7
SD 1.98 1.98 29.15
CV% 1.99 1.99 2.99

6. Simple Headspace Equipment
Headspace Equipment Headspace Description
• Oven with heater, thermocouple
and temperature controller set
to 60oC
• Battery for field operations
• 250 mL beaker & aluminum foil
or Saran wrap
• Aluminum cups
• Balance to weigh soil or water
samples

7. Comparison of Total
VOC Headspace
Methods
Only get one reading per sample which is
about 50 cc or 30% of the headspace for
water and about 20% for the solid samples
The red line for typical HS drops by about
20 % after the first sample
By recirculating the sample, the decrease
is reduced

8. Qualitative Analysis of Soils by Headspace in the Field
Qualitative Analysis total VOC’s via 102 PID
Qualitative Analysis Total VOC’s in Soil via PID
Qualitative Analysis of Soils
Weigh 5 g of soil into an Al weighing boat
Place into 250 mL beaker, cover and heat to 60oC for 15
min.
Cool to ambient and measure the headspace with the 102

9. Precision of Lab and field HS Sand Samples
Laboratory Prep Samples
ppm VOC
Lab Prep 30
33
27
35
27
Avg 30.4
SD 3.6
CV % 11.8
Field Samples
ppm VOC 1st set ppm VOC 2nd set
233 328
217 376
242 297
228 327
303 253
329
196
192
avg 242.5 316.2
SD 49.0 45.26
cv% 20.21 14.31

10. Other Screening Applications for Headspace
Applications
• In addition to soils, there are other
applications for headspace of solids below:
• Quality control for materials
• Treated paper
• Tape- residual solvents
• Pharmaceuticals residual solvents
• Food- cereals (additives like honey…)
• Polymers
• Residual monomers in polymer sample
• Acetaldehyde in PET
• Forensics
• Arson sample screening for accelerants
Materials
food
arson
plastics tape

11. Qualitative Headspace of Water Samples
• A 250 mL covered beaker is
filled to 100 mL with a water
sample
• It is heated to 60oC for 30
minutes, then cooled to
ambient T
• Headspace measurements are
made with the Model 102 using
• Direct measurement
• Direct with built in Headspace
software
Model 102 PID
Method

12. Total VOC’s in Water
by HS with 102 PID
Gasoline in water
Gasoline 971
930
815
832
Avg ppm 887
SD 65.41
CV % ppm 7.37
Acetone in water
Acetone 226
208
230
196
238
187
Avg ppm 212.75
SD 21.67
CV % 10.19
145
120
130
120
Avg ppm 128.75
SD 10.23
CV % 7.95Each sample represents a separate run
Acetone in water samples

13. Headspace Technique for Water Sampling with GC Analysis
Description of Headspace Technique
• Water samples are collected in a 40 mL EPA VOA vial. Ten ml of sample
is removed with a syringe, the vial is allowed to equilibrate, then a one
ml headspace sample is removed and injected into the GC for analysis
of CH4. Now, according to Henry’s law, the concentration in the gas
phase is proportional to the concentration in the liquid phase and the
gas sample is injected into the GC.
Henry’s law can be stated (at constant temperature) as :
P = Kh C
• where:
P= the partial pressure of the solute in the gas above the solution,
C=the concentration of the solute, and
Kh=a constant with the dimensions of pressure divided by
concentration.
The constant, known as the Henry’s law constant, depends on the
solvent, the solute, and the temperature.
Photo of VOA vials & VOC Headspace
13

14. Model GC 312 Portable GC Precision
Acetone 10 ppm
10.5
10.7
9.9
9.8
10.2
10.1
9.9
10.2
10.1
10.4
Avg 9.2
SD 0.29
CV% 3.11
Gasoline 500 ppb
521
535
515
540
501
511
523
534
511
515
Avg 520.6
SD 12.47
CV% 2.40
Each result represents a separately prepared sample

15. Portable GC312/PID Chromatogram for VOC Static
Headspace at Low ppb Levels of VOC’s

16. Static Headspace Water Sample by GC
Results (ppb) Chromatogram of HS water sample

17. Are headspace in field comparable to purge & trap lab results?
Aromatic hydrocarbons- Comparing static
headspace and purge & trap Linearity of Static Head Space
Using the static headspace and the purge & trap, the
difference between the two methods is not statistically
significant

18. Detection Limits
Total VOC’s (102)
• Head- space
soils/plastics/foods
/Arson
• Low to sub ppm
• Head space- water
• Low to sub ppm
Specific VOC’s (GC312)
• Head space
• Soils, Monomers,
Foods, Arson …
• Low ppb
• Water
• Low ppb

19. Summary
• Headspace PID (Model 102) is a
rapid qualitative method for total
VOC’s (low to high ppm Levels) in
water, soils, plastics, foods, arson
samples etc.
• It can be easily run in the field, near
process or in the laboratory
• It can be used at cleanup sites, by
first responders
• to determine the extent of
contamination at sites or for
screening high contamination soil or
water samples for GC/MS to prevent
overloading and subsequent shut
down
• Headspace GC (Model GC312 PID)
can provide quantitative lab quality
data in the field at low ppb levels.
Specific components can be
identified in the field or later back in
the laboratory.