Sampling and sample-preparation strategies
based on solid-phase microextraction for
analysis of indoor air

Jacek A. Koziel*, Inman Novak
Texas A&M University Agricultural Research and Extension Center, 6500 Amarillo Blvd. West, Amarillo,
TX 79106, USA

Applications of solid-phase microextraction (SPME)
to the sampling and analysis of volatile organic
compounds in indoor air are reviewed, including a
summary of quantification methods, coatings, com-
pounds, concentrations, sampling locations and
times, and detection limits. Strategies for on-site and
off-site sampling and analysis, advantages and
challenges associated with SPME for air sampling
are discussed. # 2002 Published by Elsevier Science
B.V. All rights reserved.

Keywords:

Air sampling; Environmental analysis; Gas chromato-

graphy; Indoor air; Solid-phase microextraction; Volatile organic

compounds

1. Introduction

1.1. SPME resources

SPME is an extraction technology that com-

bines sampling and sample preparation. Since it
conception, SPME has been widely used for
research applications in pharmaceutical, food,
aroma, forensic, environmental and physico-
chemical properties. Three books on SPME
summarize the theory, applications and many
practical considerations [1–3]. Several SPME
review articles include: new trends [4]; the evo-
lution of the technology [5]; a promising technique
for sample preparation [6]; trends in determination

of organic pollutants in environmental samples
[7]; biomedical analysis [8]; headspace for
analysis of biological fluids and samples [9]; and,
microextraction of drugs [10]. This journal has
published several SPME reviews [7,11], includ-
ing applications to chemical analysis of live bio-
logical

samples

[12].

SPME

manufacturer

application guides [13] and several Internet-
based literature databases [14] attempt to gauge
and to follow the wealth and breadth of SPME-
based publications.

1.2. Indoor air quality

In the past four decades, an increased aware-

ness of the indoor air quality (IAQ) in both
occupational and residential settings and its
impact on human health has encouraged the
development of new air-sampling methods.
Major indicators of IAQ include volatile organic
compounds (VOCs), particulates, CO, CO

2

,

NO

x

, SO

x

, ozone, environmental tobacco

smoke, radon, and biological agents. The
assessment of IAQ is challenged by the
presence of multiple sources, compounds,
interactions with building materials, the effects
of ventilation and occupant activities, and the
highly variable, and often low, concentrations of
analytes

[15,16].

The

sampling/analysis

approach has to be adjusted to the individual
case and optimize the choice of target pollu-
tants,

appropriate

sampling

and

analysis

method, budget and number of samples,
sampling

locations,

sampling

times

and

duration, and sample-preservation and custody
protocols [17].

0165-9936/02/$ - see front matter

# 2002 Published by Elsevier Science B.V. All rights reserved.

P I I : S 0 1 6 5 - 9 9 3 6 ( 0 2 ) 0 1 2 0 4 - 9

840

trends in analytical chemistry, vol. 21, no. 12, 2002

*Corresponding

author.

Tel.:

+1

(806)

677-5619;

Fax: [phone].

E-mail: [e-mail]

1.3. Indoor air sampling

Sampling and sample-preparation strategy are

the major part of an IAQ assessment. The
strategy considers:

(1) type of effect, e.g. acute vs. chronic;
(2) patterns of occupant or worker exposure;
(3) pollutant type and potential health risks;
(4) pollutant sources;
(5) applicable regulations (for occupational air);
(6) applicable sampling/analysis methods;
(7) site selection;
(8) the number of samples and their statistical

significance; and,

(9) budgetary, site access, and logistical limitations [17].

The relatively small air volume in IA makes

it difficult to sample without disturbing the
sampled microenvironments. For this reason,
some outdoor air-sampling methods are not
suitable for IA.

IA samplers can be personal, portable and

stationary. Samplers can also be classified as
analyzers (for real-time monitoring) and collectors
(for time-weighted average (TWA) or long-term
monitoring).

Sampling methods may be passive or active.

Conventional air-sampling methods use a wide
variety of real-time analyzers, passive samplers,
whole air samplers and sorbent tubes. Inexpen-
sive multi-analyte analysis of residential IA
combining direct (instantaneous, real-time) and
integrated (long-term, TWA) is still in its
infancy.

SPME is well suited to IAQ assessment.

SPME has several qualities that are superior to
conventional methods. This review attempts to
summarize applications of SPME to VOCs in
occupational and residential IA, as reported in
recent years. Types of sample and sample-
preparation strategies based on SPME are iden-
tified and illustrated with references. Sampling
locations, sampling times, SPME coatings,
detected

compounds,

concentrations,

and

method

detection

limits

are

summarized.

Advantages and limitations of SPME-based
methods for IA sampling and analysis are also
discussed.

2. SPME

2.1. General characteristics

The original SPME design comprised poly-

mer-coated fused silica fiber housed inside a
needle [1–3]. Other SPME geometries and
phases have also evolved and are described
elsewhere [1–5].

SPME is a solvent-less sampling/extraction

and pre-concentration of analytes and is based
on partitioning between the polymeric phase
and the sample matrix. There are currently eight
SPME coatings commercially available. The
most popular for air sampling include poly-
dimethyl siloxane (PDMS), PDMS/divinyl-
benzene (DVB) and Carboxen/PDMS. The
PDMS coating is a non-porous, viscous liquid-
like polymeric phase, while the latter two can be
considered predominantly porous polymeric
phases. Extraction of analytes on PDMS is via
absorption, while it is adsorption for PDMS/
DVB and is likely to be capillary condensation
for Carboxen/PDMS. Although all analytes in
air will partition with the polymeric phase, each
coating has a different sensitivity and can be
used to provide selective air sampling, as was
demonstrated for on-fiber derivatization of
formaldehyde [18,19].

2.2. Sampling time and sampling modes

Typically, the sampling time is determined by

detector sensitivity and quantification require-
ments. Sampling times for SPME can range
from a few seconds to days for assessment of
short-term and long-term exposures, respec-
tively. Occupational exposures for gaseous pol-
lutants, such as threshold limit value (TLV),
recommended exposure limit (REL), and per-
missible exposure limit (PEL) are typically
defined in 8-hr intervals. Occupational short-
term exposure limits (STEL) are based on a
15-min TWA concentrations. The ‘‘immediately
dangerous to life and health’’ levels reflect an
instantaneous concentration. The occupational
thresholds can in some cases serve as surrogate
reference, although there are no regulations for

trends in analytical chemistry, vol. 21, no. 12, 2002

841

residential IA in the USA. SPME-fiber position
with the reference to the needle can be either
‘‘exposed’’ with the fiber outside the needle or
‘‘retracted’’ with the fiber inside the needle
(Fig. 1). The latter lends itself to long-term
sampling, while the former is used for spot
sampling. Selection of the sampling time and the
sampling mode is crucial for quantification.

2.3. Quantification with SPME

Quantification with SPME is complicated by

its variable sensitivity to all analytes and coating
types, and the effects of sampling time, air
temperature, relative humidity and air velocity.

2.3.1. Liquid (absorptive) coatings

For liquid (absorptive) coatings, such as

PDMS, sampling is typically conducted until
a partitioning equilibrium is reached between
target analytes in air and the SPME coating. The
main challenge is establishing the value of the
partitioning coefficient (K

fg

) for an individual

analyte and then adjusting it for the actual field-
sampling temperature and pressure. The values
of K

fg

can be determined through a series of

experiments involving the sampling of standard
gases or from their physicochemical properties
[20].

A more elegant way to establish the values of

K

fg

is based on the use of the linear temperature-

programmed retention index (LTPRI) system

first developed by Martos and Pawliszyn [20].
The LTPRI system is based on the chromato-
graphic

retention

of

n-alkanes.

A

linear

relationship allows for the determination of K

fg

at 25

C as a function of the LTPRI [20]. No

calibration is needed, and values of the K

fg

can

be established using chromatographic retention
times only. This approach was tested on the
standard gas mixture of 29 isoparaffinic and 33
aromatic compounds in air [21]. To date, the
LTPRI approach has been used for quantifica-
tion of VOCs in few applications involving real
IA [22,23].

A similar approach for establishing values of

K

fg

for the PDMS fiber coating was developed

by Bartelt [24]. He introduced a ‘‘calibration
factor’’, which is a surrogate equivalent of the
product of the K

fg

for the individual analyte and

the fiber-coating volume. Bartelt and Zilkowski
proposed a semi-empirical model for the cali-
bration factor as a function of LTPRI, sampling
temperature and a functional group [25]. The
functional groups include n-alkanes, esters,
ketones, aldehydes, alcohols, carboxylic acids,
amines and others [24]. This model was
developed based on sampling from moving air
streams with 71 standard gases and is applicable
to

both

equilibrium

and

non-equilibrium

conditions [25,26]. To date, no field applications
of this approach have been reported.

2.3.2. Solid (adsorptive) SPME coatings

Solid (adsorptive) SPME coatings are typically

more efficient in the sampling of highly volatile
organic

compounds

and

VOCs

[1,2,27].

Naturally, these coatings should be preferred
in some applications, particularly where short
sampling times are required.

In the past, quantification with solid SPME

coatings was often complicated by non-linear
extractions [27]. A possible solution based on
very short sampling times and extractions con-
trolled by diffusion through the boundary layer
(thickness ) surrounding the fiber was pro-
posed by Koziel et al. [28]. Constant extraction
conditions are maintained by exposing the fiber
to fast-moving air at constant velocity. The
main challenge in this method is establishing

Fig. 1. Schematic of sampling with exposed (for spot
sampling) and retracted (for TWA sampling) SPME fibers.
n

f

=amount of an analyte; K

fg

=air/coating partition coeffi-

cient (at equilibrium); V

f

=coating volume; C

g

=concentration

of analyte in air; D

g

=gas-phase molecular diffusion coeffi-

cient; A=needle opening area; Z=diffusion path length; and,
t=sampling time.

842

trends in analytical chemistry, vol. 21, no. 12, 2002

as a function of fiber-coating dimensions, dif-
fusion coefficients, air velocity, air temperature
and air viscosity. This approach was originally
developed

for

standard

gas

mixtures

of

benzene, toluene, xylenes and ethylbenzene
(BTEX) in air and later field tested in occu-
pational IA surveys [29].

2.3.3. On-fiber derivatization

On-fiber derivatization allows for very effi-

cient

extraction

of

formaldehyde

from

IA [18,19]. The derivatizing agent, water-soluble
o-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine
(PFBHA), is first doped in excess on the
PDMS/DVB 65-mm coating using headspace

Fig. 2. Strategies for SPME-based sampling and sample preparation for indoor air.

trends in analytical chemistry, vol. 21, no. 12, 2002

843

extraction immediately before exposing the fiber
to air. Formaldehyde in air reacts with the
PFBHA forming a stable derivative (PFBHA-
HCHO oxime). The on-fiber reaction is the
rate-controlling step and the amount of oxime
formed is proportional to the formaldehyde
concentration. This method has reported detec-
tion limits of less than 5 ppbv, well below the
current occupational TLVs. This on-fiber deri-
vatization method was tested in several IA
locations using 10-min. spot sampling and 8-hr
TWA sampling modes [19]. Martos

and

Pawliszyn suggested that the same approach
could be used for sampling and analysis of
acetaldehyde and other airborne aldehydes [18].

Velikonja et al. presented a similar approach

for the determination of formaldehyde [30].
This method used doping of PDMS 7-mm fiber
via

direct extraction of dinitrophenylhydrazine

(DNPH) or acetylacetone derivatizing agents.
Doping was followed by sampling of formalde-
hyde from vial headspaces. Limited field appli-
cations to the interior of new furniture have
been reported [30]. However, method detection
limits of approximately 140 ppbv were too high
to detect concentrations in a room with new
furniture.

Quantification of VOCs using the TWA-

sampling mode with retracted SPME fiber was
first described by Martos and Pawliszyn [31].

The distance between the fiber opening and the
fiber tip serves as the diffusion barrier/path.
The sampling rate is much reduced compared
to the exposed fiber mode, allowing for sig-
nificant extension of the sampling time. TWA
sampling is non-equilibrium sampling, since the
SPME sorbent cannot be affected by saturation
throughout the sampling session for quantifica-
tion purposes. The diffusion path-length can be
reduced or increased, providing flexibility in
extending or reducing the sampling time in the
field. Thus, the use of SPME devices for TWA
sampling presents the potential user with flex-
ibility in choosing a time appropriate for both
short-term and long-term sampling.

A commercial SPME holder can be modified

for TWA sampling by adding additional notches
for precise retraction of the SPME fibers (Fig. 1)
[22]. The use of TWA sampling for VOCs in IA
applications has been demonstrated in several
publications [22,23,31-33] and there has been one
on on-fiber derivatization of formaldehyde [19].

3. Applications to indoor air

3.1. Historical perspective

SPME evolved from initial applications to

direct extractions from aqueous samples to

Table 1
Summary of SPME applications to air sampling of laboratory air

Location

Sampling
time (min)

SPME coating

GC
detector

Analytes

Reported (range of)
concentrations

Method
Detection
Limit (MDL)

Environmental
conditions

Ref.

Laboratory 15 min

100-mm PDMS MS

11 VOCs
identified

N/A

N/A

T=24.5

C

RH=54%

[54]

Organics
laboratory

35 min

95-mm PDMS

MS

Dichloromethane N/A

N/A

N/A

[55]

Organics
laboratory

20 min

100-mm PDMS MS

5 chlorinated
VOCs
Toluene

26-420 ng/L

0.05-2 ppb
0.2 ppb

N/A

[56]

Laboratory 60 min

100-mm
PDMS,
C18-bonded,
silica-coated
multifibers

MS

N/A

N/A

< 1 ppb

N/A
N/A

[57]

844

trends in analytical chemistry, vol. 21, no. 12, 2002

Table 2
Summary of SPME applications to off site indoor air sampling followed by analysis in a laboratory

Location

Sampling time
(min)

SPME coating

GC
detector

Analytes

Measured
concentrations

Method
Detection
Limit
(MDL)

Comments

Environmental
conditions

Ref.

Laminated
particle board
Hair gel

20-60 sec

65-mm PDMS/
DVB

FID

Formaldehyde

640 ppb

4.6 ppb

HCHO derivatized
with PFBHA

N/A

[18]

Acrolein

72000 ppb

N/A

n-Valeraldehyde

45000 ppb

N/A

6 residential/
occupational
sites

10 min-
8 hr (TWA)

65-mm
PDMS/DVB

FID

Formaldehyde

11-376 ppb

1 ppb

HCHO derivatized
with PFBHA and
collocated w/
NIOSH-2451

T=19.5-28.5

C

RH=34-76%

[19]

Indoor area of
an industry

5-30 min

100-mm PDMS

PID

Styrene

56-130 mg/L

N/A

Spot and TWA
sampling

T=23

C

RH=25%

[20]

House,
apartment,
industrial
shops

10 min-
7 hrs (TWA)

65-mm
PDMS/DVB,
100-mm PDMS

FID

Formaldehyde
TVOCs
(C8-C12 range)

11-90 ppb
0.5-28 mg/m

3

1 ppb
N/A

HCHO derivatized
with PFBHA and
collocated w/
NIOSH-2451

N/A

[22]

Technological
laboratories

30-840 min

100-mm PDMS

FID

Acetone

1.76 mg/m

3

N/A

T=27-33

C

[23]

n-alkanes
(C5 to C15)

0.01-12.86
mg/m

3

N/A

RH=N/A

Chloroform
TEX

0.60-1.37
mg/m

3

N/A

0.12-22.27
mg/m

3

N/A

Vehicle and
mechanical
shops

30 sec

65-mm
PDMS/DVB

FID

BTEX

BDL- 249 ppb

2-18 ppb

Use of forced air
for quantitative
screening
Collocated with
NIOSH-1501
method

N/A

[29]

Room with
new & old
furniture

1 min

7-mm PDMS

ECD

Formaldehyde

1.3 mg/m

3

0.17 mg/m

3

HCHO found in
interior of new
furniture

T=23-24

C

RH=N/A

[30]

Unidentified
industrial site

7 hr

65-mm
PDMS/DVB

FID

Formaldehyde

57- 152 ppb

12.5 ppb

HCHO derivatized
with PFBHA
Co-located with
NIOSH-2451. TWA
sampling

T=23

C

RH=25%

[31]

(continued)

trends

in
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12,

2002

845

Table 2 (continued)

Location

Sampling time
(min)

SPME coating

GC
detector

Analytes

Measured
concentrations

Method
Detection
Limit
(MDL)

Comments

Environmental
conditions

Ref.

Home/garage

120-

60-mm PDMS/
DVB

FID

n-alkanes
(C7-C12)

ND-0.78 mg/L

N/A

TWA sampling
collocated with
NIOSH-1550 method

N/A

[32]

Classroom,

210 min

grinding shop

Computer,
polymer
laboratories,
mailroom

75 min
10 min

100-mm PDMS,
PDMS/DVB(65)

FID

n-alkanes
(C5, C6, C12)
Formaldehyde

0.70-878 ppb
8.3 ppb

N/A

Spot/TWA sampling
collocated with
NIOSH-1550
method; HCHO
derivatized with PFBHA

N/A

[33]

Underground
parking lot

4 min

180-mm

MS

BTEX

4-33 ppb

1-10 ppb

Novel PDMS fiber
design

N/A

[45]

PDMS

n-Hexane

357 ppb

N/A

i-Octane

8 ppb

N/A

Organic
laboratory,
lilac bush

3 min

100-mm PDMS,
PDMS/DVB (65)
Carboxen/PDMS

FID

N/A

N/A

N/A

Commercial and novel
field samplers tested
for sample retention

N/A

[53]

Living room,
bedroom, and
laboratory air

15 min

100-mm PDMS

MS

BTEX

0.19-71.05
mg/m

3

0.002
mg/m

3

T=18-25

C

[58]

Chlorobenzene

2.15-18.65
mg/m

3

0.002
mg/m

3

RH=35.5-56%

n-Decane

0.05-3.84
mg/m

3

0.005
mg/m

3

TVOCs

1.8-63.9
mg/m

3

N/A

Indoor
swimming
pool

5 min

100-mm PDMS

MS

Trichloromethane

1.4-2.9 ppb

0.02 ppb

T=N/A

[59]

Tetrachloromethane

0.7-0.35 ppb

0.02 ppb

RH=N/A

Trichloroethylene

0.11-0.15 ppb

0.02 ppb

BTEX=benzene, toluene, ethylbenzene, and xylenes; TEX=toluene, ethylbenzene, and xylenes; ND=no detectable amounts; BDL=below detection limits.

846

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chemistry,

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2002

Table 3
Summary of SPME applications to sample preparation in conventional air-analysis methods, where the SPME was used only as a pre-concentrating device is in the
laboratory

Location

Sampling
time (min)

SPME
coating

GC
detector

Analytes

Measured
(range of)
concentrations

Method
Detection
Limit (MDL)

Comments

Environmental
conditions

Ref.

Headspace of
sewage tank

20 min

95-mm PDMS

ECD

6 chlorinated VOCs,
toluene

122-1959 ng/L

0.01-0.9 ppb Air sample collected

in SUMMA canisters

T=25

C

RH=25%

[56]

Gas-treatment
facility

10 min

100-mm PDMS

FID

BTEX

BDL- 189 mg/m

3

0.1 mg/m

3

Air samples collected
using Tedlar bags

T=23

C

RH=N/A

[60]

Smoking/non-
smoking rooms,
inside/outside of
laboratory bench,
car interior

30 min-
24 hr

75-mm Carboxen
PDMS

FID

BTEX

BDL- 70.0 mg/m

3

0.36-2.02
mg/m

3

SPME was used to
sample the headspace
of the solvent extraction
of charcoal tubes and
pads

T= 10-60

C

RH=N/A

[61]

Industrial area
(indoor/outdoor
not specified)

10 min

100-mm PDMS

MS,
CI, EI

14-Aromatic HCs

N/A

67 ng

SPME was used to
extract VOCs from
headspace of sorbent
tube adsorbent placed
in a sealed vial

T=100

C

RH=N/A

[62]

5-Chlorinated VOCs N/A

67 ng

8-Ketones

N/A

67 ng

4-Oxygenated VOCs N/A

67 ng

3-VOCs

N/A

67 ng

BTEX=benzene, toluene, ethylbenzene, and xylenes; BDL=below detection limits.

trends

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chemistry,

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847

headspace extractions, standard gases, spot
sampling of laboratory air, and eventually to
field air sampling [1–5]. Several studies using
headspace extractions could provide an insight
(coating

and

analytical

method

selection,

method detection limits, effects of temperature
or sampling time) to the development of
methods for VOCs that are important to IAQ.
Extractions of specific groups of VOCs from
vial headspaces include volatile amines [34],
ammonia and methylamine [35], volatile fatty
acids [36,37], and aromatic and halogenated
VOCs [38–40].

Studies with standard gases provided impor-

tant SPME characteristics including those listed
for headspace extraction and others, such as
humidity, air velocity, and sample-preservation
time. Specific groups of VOCs involving gas
standards and SPME include: sulfur VOCs
[41,42]; formaldehyde [18]; benzene, toluene,
ethylbenzene, xylenes (BTEX) [27,28,43–45],
isoparaffins and aromatic VOCs [21], halogen-
ated VOCs [43–45], n-alkanes, esters, ketones,
aldehydes, alcohols, carboxylic acids, amines
[24–26,46], and n-alkanes [32,47].

Several research articles involving SPME

sampling from moving/dynamic standard gas
samples

are

also

available

[18,20,21,24–

26,28,46,48,49]. In addition, SPME has also
been used to sample human breath [50,51], and
bovine breath [52].

Another important characteristic for field

applications, i.e. the retention of air samples on
SPME fiber coatings, has been researched
[22,41,49,53].

Comparison of novel SPME-based field

samplers with a commercial SPME field
sampler has also been described [53].

3.2. Strategies

To date, several strategies have been used in

applications of SPME to sampling and analysis
of IA (Fig. 2).

The first strategy is to use SPME for test

sampling of laboratory air (Table 1). Several
authors report sampling laboratory air [54–57].
In this case, no sample preservation is needed,

Table

4

Summary

of

SPME

applications

where

fi

eld

SPME

sampling

was

combined

with

on-site

analysis

with

a

portable

GC

Location

Sampling

time

(min)

SPME

coating

GC

detector

Analytes

Reported

(range

of)

concentrations

Method

Detection

Limit

(MDL)

Comments

Environmental

Ref.

Paint,

grinding,

carpenter,

and

vehicle

shops

1

min

65-

m

m

PDMS/DVB

Mobile

GC/PID

BTEX

Hexane

BDL-953

ppb

BDL-468

ppb

1.3-1.9

ppb

8.6

ppb

Collocated

sampling

with

the

NIOSH-1501

method

T=N/A

RH=N/A

[22]

Garage,

hall,

of

fi

ce,

solvent

storage

1

min

65-

m

m

PDMS/DVB

Mobile

GC/PID

BTEX

Hexane

BDL-573

ppb

BDL-575

ppb

1.3-1.9

ppb

8.6

ppb

Collocated

sampling

with

the

NIOSH-1501

method

T=N/A

RH=N/A

[27]

Living

room,

kitchen,

bedroom

1

min

65-

m

m

PDMS/DVB

Mobile

GC/PID

Toluene

24.1-35.8

ppb

1.3

ppb

Collocated

sampling

with

the

NIOSH-1501

method

T=35-40

C

RH=N/A

[33]

BTEX=benzene,

toluene,

ethylbenzene,

and

xylenes;

BDL=below

detection

limits.

848

trends in analytical chemistry, vol. 21, no. 12, 2002

because sample analysis was performed within a
very short time following the sample collection.
Chemicals found included aromatic and chlori-
nated hydrocarbons. A summary of these
applications including locations, sampling time,
SPME coating, compounds detected and their
range of concentrations is presented in Table 1.

The second strategy is the use of SPME as a

field sampler followed by analysis in the labora-
tory [18–20,22,23,29–33,45,53,58,59] (Table 2).
In such cases, some means of sample preserva-
tion was used, such as novel field samplers, low
temperature, or selection of a SPME coating
with high affinity for a particular group of
analytes. Several researchers studied sample
preservation on SPME fibers [22,41,49,53,55].
However, relatively little is known about SPME-
sample stability.

The third strategy is to use SPME as a sample

pre-concentration device in the laboratory
[56,60–62] (Table 3). In this case, sampling is
conducted with conventional methods, such as
Summa canisters [56], Tedlar bags [60] or sor-
bent tubes [61,62]. SPME served only to extract
analytes from Tedlar bags, Summa canisters, or
the headspace of sorbent tube extracts to
enhance the method detection limits or to speed
up the extraction process.

Finally, SPME can also be used for field

sampling combined with on-site analysis with a
portable GC [22,27,33] (Table 4). This approach
allows for collection and fast analysis of multiple
samples in the field. This is likely to be the most
efficient use of SPME to result in high sample
throughput and low cost per sample. On-site
analysis allows for greater flexibility in conduct-
ing an IA survey. This is because it makes
possible spot and TWA sampling, on-site
investigations of leaks and sources [27]. The
number of samples that can be collected within
a given sampling period and the relatively low
cost of such sampling serves are advantages.
The lower sensitivity of a portable GC (as
compared to stationary, full-scale GC) can be
offset by the sensitivity of SPME.

SPME

offers

many

advantages

for

air

sampling. These relate to its high sensitivity and
precision, speed of extraction, wide range of

sampling times, applicability to a wide rage of
compounds, reusability, possibility of automa-
tion, and compatibility with conventional analy-
tical equipment. To date, SPME remains best
suited to a research setting in which sampling
and analysis are typically conducted by the same
person/team.

Some

of

the

disadvantages

include coating-quality issues [19,32], lack of
comprehensive

guides

to

quantification

methods, and the relative lack of field com-
parisons with conventional methods.

4. Summary and conclusions

SPME has great potential to be used for

sampling of VOCs in indoor and ambient air. It
is very sensitive, small, flexible as to the selec-
tion of sampling time and relatively inexpensive.
While SPME cannot replace some conventional
methods, it can provide a powerful alternative
or validation technique, particularly in research
settings. Quantification models exist and are
applicable to several types of coatings and
groups of VOCs. Some coating-quality issues
affect SPME performance and therefore its
wide acceptance by air-pollution practitioners.

There remain several unknowns in the use of

SPME for air sampling and analysis, and there
are many opportunities for research, including:

(1) the development of quantification models and their

comparison/validation with conventional methods
for a wide range of VOCs;

(2) determination of sensitivity to air temperature,

pressure, relative humidity, air or wind velocity, and
other environmental variables;

(3) comprehensive evaluation of sample-preservation

techniques for both commercial and prototype
SPME devices; and,

(4) standardization and dissemination of protocols for

SPME-based methods.

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Jacek Koziel is an assistant professor at the Texas Agricultural
Experiment Station, Texas A&M University in Amarillo, Texas,
USA. He uses SPME for characterization and assessment of
abatement strategies for odorous gases. Inman Novak is a senior-
year student at the Amarillo Area Center for Advanced Learning.

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trends in analytical chemistry, vol. 21, no. 12, 2002