Analytical procedure for the determination of very volatile organic compounds (C3–C6) in indoor air
Analytical procedure for the determination of very volatile organic compounds (C3-C6) in indoor air
Alexandra Schieweck 0
Jan Gunschera 0
Deniz Varol 0
Tunga Salthammer 0
0 Department of Material Analysis and Indoor Chemistry, Fraunhofer Wilhelm-Klauditz-Institut , Bienroder Weg 54E, 38108 Braunschweig , Germany
The substance group of very volatile organic compounds (VVOCs) is moving into the focus of indoor air analysis, facing ongoing regulations at international and European levels targeting on indoor air quality and human health. However, there exists at present no validated analysis for the identification and quantification of VVOCs in indoor air. Therefore, the present study targeted on the development of an analytical method in order to sample the maximum possible quantity of VVOCs in indoor air on solid sorbents with subsequent analysis by thermal desorption and coupled gas chromatography/mass spectrometry (TDS-GC/ MS). For this purpose, it was necessary to investigate the performance of available sorbents and to optimize the parameters of GC/MS analysis. Stainless steel tubes filled with Carbograph 5TD were applied successfully for low-volume sampling (2-4 l) with minimal breakthrough (< 1%). With the developed method, VVOCs between C3 and C6 of different volatility and polarity can be detected even in trace quantities with low limits of quantitation (LOQ; 1-3 μg m−3). Limitations occur for low molecular weight compounds ≤C3, especially for polar substances, such as carboxylic acids and for some aldehydes and alcohols. Consequently, established methods for the quantification of these compounds in indoor air cannot be fully substituted yet. At least three different analytical techniques are needed to cover the large spectrum of relevant VVOCs in indoor air. In addition, unexpected reaction products might occur and need to be taken into account to avoid misinterpretation of chromatographic signals.
VVOC; Indoor air; Analysis; Gas chromatography; Mass spectrometry; Thermal desorption
Determination of indoor air quality has become of increasing
importance against the background of potential adverse effects
on human health and well-being due to airborne pollutants [
Specific measurement of chemical substances plays a role in
many fields of indoor-related research such as sick building
], microbial contamination [
], bioeffluents [
odor evaluation [
], and indoor chemistry [
significance of material emission testing has just recently been
outlined by the European Union (EU) Construction Products
Regulation (CPR) which defines six basic requirements for
construction works (BRCW) [
]. The third basic requirement
(BRCW 3) is dedicated to the aspects of hygiene, health, and
environment and, therein, points out the protection of the health
of building occupants and users as one main target of
construction work. Among other things, the Bgiving-off of toxic gases^
and Bthe emissions of dangerous substances, volatile organic
compounds (VOC), greenhouse gases or dangerous particles into
indoor or outdoor air^ are included. This applies not only to
buildings, but also as basic requirement to single materials,
products, and furnishing contained in them. Thus, the limitation and
prevention of airborne pollutants in indoor environments are
explicitly identified and are consequently main conditions
regarding the possible release of volatile substances from materials.
The measurement of pollutants indoors has been
standardized at the international level in the last decades. The main
important standard can be found within the ISO 16000 series
targeting on the analysis of organic chemicals in emission test
chambers and indoor air [
]. On the European level, the
performance of chamber emission testing of products used
indoors as well as the analysis of organic emissions is
harmonized on the basis of EN 16516 [
]. The standard only
defines the procedure for testing and chemical analysis, but no
harmonized strategy exists so far regarding the evaluation of
measured material emissions. In the meantime, national and
product-related procedures have been developed in different
European countries [
]. Within the European Collaborative
Action BUrban Air, Indoor Environment and Human
Exposure^, criteria for a harmonized testing procedure and a
scheme for a uniform and reproducible health-related
evaluation of emissions from building products for indoor use have
been derived [
]. The criteria cover VOCs and carbonyl
compounds, including formaldehyde . The evaluation is
based on the derivation of the so-called LCI (Lowest
concentration of interest) levels above which, according to best
professional judgment, the pollutant may have some effect on
people in the indoor environment [
]. The European work
on harmonized EU-LCI values considered in a first stage just
VOCs, but with the important note that very volatile organic
compounds (VVOCs) should be addressed in the future. In
2013, EU-LCI values for few VVOCs have been published,
namely for formaldehyde, acetaldehyde, butanal, and
pentanal. With status as of December 2016, the derivation of some
other VVOCs is pending (propanal and 2-propanone).
Speaking of VVOCs is linked to the problem that in
contrast to VOCs there exists so far neither a uniform definition of
the term BVVOC^ nor a reliable and robust analytical method
for the identification and quantification of many very volatile
substances. Salthammer [
] has recently outlined the
difficulties and inconsistencies when comparing the different
approaches for classifying VVOCs. The European standard EN
] defines VVOCs as those substances, which elute
before n-hexane on a slightly polar gas chromatographic
column (5%/95% phenyl-/methylpolysiloxane). However, the
standard also offers a normative annex listing noncarcinogenic
and carcinogenic VOCs in addition to the analytical window
of VOCs (n-hexane to n-hexadecane). This includes also
substances, which can be defined as VVOCs due to their number
of carbon atoms (<C6), irrespective of whether they are eluting
from the gas chromatographic column before or after
Diverse measurement techniques for the analysis of
atmospheric VOC species in outdoor air, including very volatiles
such as acetaldehyde, isoprene, and 1,3-butadiene, already
]. The difficulty of retaining very volatiles on solid
sorbent tubes when sampling at ambient temperatures can be
overcome by collecting whole air samples to pre-evacuated
and passivated stainless steel canisters [
]. The method is
described in the US EPA Compendium Methods TO-14 and
] as well as in ASTM D5466-15 . Even
though the canister sampling technique offers short sampling
times, long storage periods of up to 30 days, and low detection
limits (1 μg m−3), there are several drawbacks. These relate to
the repeatability of taken samples which restricts the
application of TO-15 to polar substances and organic compounds less
volatile than n-octane [
]. Condensation, matrix, and sink
effects as well as the undesired loss of target substances
through the canister walls or during the transfer of the air
sample to the analytical device are not totally excluded [
In addition, the cleaning and preparation of canisters is
extensive and their handling is difficult, and especially
timeweighted-average (TWA) samples need a relatively complex
]. Moreover, measurement campaigns on-site
would require the transport of some dozen canisters.
This might be some of the reasons why most studies have
focused on the development of solid sorbent-based methods
allowing the application of known analytical steps without the
need of additional equipment. The use of porous solid
materials for sampling indoor air has become a kind of convention,
especially for trapping airborne organic vapors, as it has
several main advantages and overcomes serious disadvantages of
liquid absorbents [
]. In addition, solid sorbent tubes are
easy to store, carry, and transport and are reusable for a
specific service life. ASTM D6196-15  offers an extensive
guide for air sampling with solid sorbents.
Tenax TA® is a widespread polymer sorbent
recommended for retaining VOCs according to ISO 16000-6. It allows the
detection and quantification of nearly the most relevant
nonpolar and slightly polar substances in the analytical window
between n-hexane (C6) and n-hexadecane (C16) in one single
step. The standard refers to a nonpolar GC column and
highlights that the specified method is in principle also suitable for
the determination of some VVOCs if appropriate sorbents and
adequate gas chromatographic conditions are chosen [
However, more detailed specifications are left open.
Irrespective of the fact that compounds which might be
classified as VVOCs are already collected to a specific extent
when sampling indoor air on Tenax TA®, this polymer
sorbent is too weak for polar substances. Hence, the
quantification of target analytes which are more volatile than n-hexane is
afflicted with errors [
]. Most studies have therefore
investigated graphitized carbon blacks (GCB) and carbon molecular
sieves (CMS) as these were introduced as highly sorptive
alternatives for retaining reactive or low-boiling hydrocarbons
in indoor air while being largely hydrophobic [24–26].
Carbotrap X (20/40 mesh) was found to allow the
quantitative determination of low-boiling, reactive
hydrocarbons, such as 1,3-butadiene or isoprene with no significant
losses of the analytes . Carbograph 5 was also proven
to be able to sample low-boiling carbonyl compounds [26,
27]. Dettmer et al.  compared both GCBs regarding
their adsorption potential of low molecular weight
oxygenated substances in gaseous samples. Recovery rates
of the analytes were higher for Carbograph 5, despite of the
higher specific surface area of Carbotrap X. The recovery
might be influenced by relative humidity and the presence
of ozone or nitrogen oxides as discussed for the significant
losses of reactive light hydrocarbons on CMS .
Adsorption of CMS is based on nonspecific interactions
with several reaction processes taking place on the
adsorbent surface, e.g., the decomposition of α-pinene and
sabinene and a dimerization of 1,3-butadiene leading to
4-vinylcyclohexene on Carboxen 569 [25, 28, 29]. Ribes
et al.  combined GCB and CMS adsorbers in a
multisorbent tube in order to analyze a broad range of
VOCs in air, targeting especially on isocyanate species.
The developed method, based on TDS-GC/MS, allowed
also the detection of some small molecular weight
compounds, but without carrying out a validation for VVOC
analysis or any differentiation of VVOCs from VOCs.
Gallego et al.  found significant differences between
the concentrations obtained from this multibed tube and
common Tenax TA® tubes regarding VVOCs with boiling
points between 56 and 100 °C and vapor pressures (20 °C)
ranging from 4 to 47 kPa. The same was observed for
alcohols and chlorinated compounds resulting in higher
concentrations obtained by using the multibed tube
compared to a Tenax TA® tube. The authors assume that Tenax
TA® is not suitable for adsorbing VVOCs due to a
displacement of the adsorbed volatile and polar compounds
for nonpolar high molecular weight substances, as
previously reported [28, 32, 33]. However, this study included
just a small range of ten substances defined as VVOCs by
boiling point and vapor pressure. In addition, standard
deviations from measuring data obtained by indoor air
sampling were quite high for most VVOCs when using Tenax
TA® as sorbent. Breakthrough volumes for multisorbent
bed tubes were low with the exception of ethanol,
2propanone, dichloromethane, and 2-propanol at high
sampling volumes over 40 l. According to Woolfenden [
], tubes containing Tenax TA® backed up by a GCB
followed by a CMS should be able to retain
C3-hydrocarbons up to long-chained alkanes. However, when handling
CMS, water management becomes an important issue [
]. Brown and Crump [
] determined the breakthrough
volume of six VVOCs (mainly C4–C6 alkanes) on such a
multisorbent tube resulting in sample volumes of at least
Facing the current approaches and challenges, the aim of
the present study was to develop an analytical procedure to
measure concentrations of VVOCs in indoor air. For this
purpose, it was necessary to determine the performance of
different solid sorbents for their sorption/desorption capacities of
VVOCs, to develop a suitable GC/MS method, and to
consider already established techniques.
Materials and methods
Sorbent selection and conditioning
The selection of sorbent materials was based on their chemical
and physical material properties as well as on previous studies.
As the target substances to be investigated within this study are
very volatile organics with low boiling points, mainly medium
and strong sorbent media of different mesh sizes were selected.
The mesh size indirectly determines the particle size and,
hence, the specific surface area of the solid sorbent. Among
other parameters, the surface area is one important factor
describing the sorbent strength of the material. According to
Woolfenden , the mesh size within the 30–80 range does
not play a critical role regarding selection of solid sorbents as
the analyte retention volume will remain constant. Patil and
] investigated Tenax TA® of different mesh sizes
for sampling volatile organic species in workplace air. No
significant effects on adsorption and desorption in dependence of
the particle size were found. Materials chosen in the presented
study comprised the GCBs Carbotrap (20/40 mesh,
SigmaAldrich), Carbopack X (40/60 mesh, Sigma-Aldrich), and
Carbograph 5TD (20/40 mesh, Markes International Ltd.) as
well as the CMS Carbosieve S-III (60/60 mesh, Supelco),
Carboxen 569 (20/45 mesh, Supelco), and Carboxen 1000
(80/100 mesh, Supelco). Table 1 gives an overview of their
relevant properties. For further information on GCBs and
CMS, please refer to the literature [
24, 28, 35
In order to prepare single-bed tubes, ~ 300 mg of the
selected sorbents were placed in stainless steel desorption tubes
(Markes International Ltd., 89 mm length, 6.4 mm O.D.)
between glass wool end plugs. Initial conditioning of freshly
packed tubes was performed at 300 °C for 3 h in total, whereas
heating was done at different stages during preparation of the
tubes. Before each use, all tubes were conditioned for 115 min
at a maximum temperature of 300 °C under a helium flow.
After conditioning, tubes were immediately sealed using
Swagelok brass end caps fitted with PTFE ferrules and stored
in closed metal boxes. Sampled tubes were desorbed and
analyzed immediately after finishing the tests in order to avoid
analyte losses due to storage time .
Target substances used in this study were selected based on
the elution time before n-hexane on a nonpolar or slightly
polar GC column. They can therefore not be determined by
the procedure given for VOCs (C6–C16) in ISO 16000-6
]. Table 2 summarizes the selected organic compounds
and their specific properties. Chemicals were purchased
from Sigma-Aldrich with purities of ≥ 99%. Absolute
grade methanol used for the preparation of the standard
solution was supplied by Sigma-Aldrich.
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The standard solution was prepared as mixture of all selected
VVOCs (see Table 2) by weighing 10 mg of each substance
into a glass flask, which was filled up with 10 ml methanol to
obtain a standard concentration of 1 mg ml−1 of each
Analysis of VVOCs
Analysis of target substances designated as VVOCs was
performed by automatic thermal desorption (TD-100, Markes
International Ltd.) with subsequent capillary gas
chromatography (Agilent 7890A) coupled with a mass spectrometry
detector (Agilent 5975C). Conditions for thermal desorption
were used as follows: prepurge 3 min at a flow rate of
50 ml min−1, primary desorption at 300 °C for 6 min with a
flow rate of 20 ml min−1, no inlet split, cold trap low 25 °C,
pretrap fire purge 3 min at 50 ml min−1, trap heating rate
40 °C s−1, cold trap high at 300 °C for 6 min, outlet split
10 ml min−1, and flow path temperature at 200 °C. The cold
trap contained quartz wool/Carbograph 1TD (40/60 mesh)
and Carboxen 1000 (80/100 mesh) with a ratio of 1:4.
The GC was fitted with a fused silica capillary column of
medium polarity (DB 624, 60 m, 0.32 mm, 1.8 μm, Agilent
(J&W); composition 6%/94% c yanopropylphenyl/
dimethylpolysiloxane). The column oven temperature was
initially 30 °C for 6 min, increased in a first step to 40 °C at a rate
of 1 °C min−1, in a second step to 70 °C at a rate of 5 °C min−1,
and maintained after a third increasing rate of 20 °C min−1 at
240 °C for 10 min (40.5 min run). The GC was operated in
scan mode with a mass range of 20–450 amu, MS source
temperature 230 °C, and quadrupole temperature 150 °C.
Data were processed using ChemStation® software mass
spectral library. Qualifying was based on PBM library search
]. Mass spectra and retention data were compared with
those of reference compounds. All identified substances were
quantified using their own response factors.
The limit of detection xLOD and limit of quantitation xLOQ
for each target analyte were calculated from the linear
calibration curve y = a ∙ x + b. Calculation was based on
the approach given by Einax et al. [
] with reference to
DIN 32645 [
uu 1 1 x
xLOD ¼ sx0∙t f ;αtm þ n þ Q
sx0 is the standard deviation of the method, tf; α is the t
value for f degrees of freedom and an error probability α, and k
is a conventional factor to weigh the uncertainty of the result
and is usually set to k = 3 for an uncertainty of 33.3% [
A one-sided t -test was applied for f = n − 2 and α = 0.01 as
significance level (99%). n is the number of calibration points
xi, and m is the number of samples measured of each
concentration xn − xn + 1. x2 is the square of the arithmetic mean of the
content of all calibration samples and Qx is the sum of
quadratic deviations of x. The limit of quantitation xLOQ was
obtained from Eq. (2).
uu 1 1 xLOQ−x
xLOQ ¼ k sx0 t f ;αtm þ n þ
Equation (2) is recursive starting with xLOQ = k ∙ xLOD .
The standard deviation of the method sx0 is calculated
from Eq. (3).
sy, x is the residual standard deviation of the calibration
measurement values, and b is the slope of the linear calibration
Limits of detection xLOD and limits of quantitation xLOQ
obtained for each VVOC target analyte are discussed at the
end of the method development part. Calculation details are
given in the BLimits of detection and limits of quantitation^
Experimental results and discussion
Gas chromatographic selectivity for target analytes
An aliquot of 1 μl of the standard solution was injected on
three tubes of each adsorbent media including Tenax TA®.
Directly after injection, the tubes were analyzed by TDS-GC/
MS as described in the BAnalysis of VVOCs^ section. As
shown in Fig. 1a, a VVOC substance mixture, injected on
Tenax TA®, cannot be sufficiently separated on a nonpolar
gas chromatographic column according to ISO 16000-6 [
The target analytes elute in a narrow window, most of them are
co-eluting or overlapping. Modifications of the complete
analytical setup are necessary in order to obtain bell-shaped
peaks (Gaussian curves) and a satisfying separation. Needed
changes cover both the thermal desorption and gas
chromatographic system and, in particular, the cooling trap, the GC
column, and the temperature programs.
After adjustment of these parameters, the gas
chromatographic separation of target analytes can be significantly
improved, even though the analytes were injected again on a
Tenax TA® tube (see Fig. 1a). The use of a stronger adsorbent
material, which is more convenient for low-boiling
substances, leads in a second step to an increased
analyteadsorbent interaction and, thus, to a further improvement.
Especially concerning the tested GCB adsorbent media, the
gas chromatographic separation achieved is satisfactory and
the analytical window is broadened. As can be seen in Fig. 1b,
Fig. 1 a Gas chromatographic (GC) separation of a VVOC standard
solution injected on and thermally desorbed of Tenax TA® on a
nonpolar GC column (black plot; DB 5, 60 m × 0.25 mm × 0.25 μm)
a n d o n a m e d i u m p o l a r G C c o l u m n ( r e d p l o t ; D B 6 2 4 ,
60 m × 0.32 mm × 1.8 μm). Total ion chromatogram (TIC). b Gas
chromatographic (GC) separation of a VVOC standard solution injected
on and thermally desorbed of Carbotrap (black plot), Carbopack X (green
plot), Carbograph 5TD (red plot), and Tenax TA® (gray plot). Medium
polar GC column (DB 624, 60 m × 0.32 mm × 1.8 μm). Total ion
chromatogram (TIC). c Gas chromatographic (GC) separation of a
VVOC standard solution injected on and thermally desorbed of the
CMS Carboxen 569 (black plot) and the GCB Carbograph 5TD (red
plot). Medium polar GC column (DB 624, 60 m × 0.32 mm × 1.8 μm).
Total ion chromatogram (TIC). b and c Detector was switched off in the
retention window of methanol (4.00–5.30 min), which was used as
solvent for the standard solution
response and separation performance of VVOC analytes on a
medium polar GC column are the best after thermal desorption
from Carbograph 5TD in comparison to other GCB
adsorbents. Gas chromatographic separation in dependence of the
solid sorbent decreased in the following order: Carbograph
5TD > Carbopack X > Carbotrap > Tenax TA®. When using
CMS as sorbent bed, neither exploitable peak forms nor a
sufficient separation of single peaks could be obtained.
Retention times of target analytes were strongly shifted
compared to those obtained when applying GCBs (see Fig. 1c).
Regardless of the chosen sorbent, both formic acid and acetic
acid eluted with a strong tailing. Moreover, the signal of
formic acid can hardly be distinguished from the background.
This finding shows that neither the investigated solid sorbents
nor the analytical procedure is appropriate for detecting formic
acid and acetic acid. It is therefore recommended to analyze
both substances by ion chromatography after trapping on
pretreated silica gel-filled cartridges as recently standardized
in VDI 4301-7 [
]. After elution with sodium carbonate
solution, the compounds are separated on an anion separation
column coupled with a conductivity detector. The method
allows a much more precise determination of C1–C2
carboxylic acids in indoor air as by the use of Tenax TA® and
subsequent analysis by TDS-GC/MS as it is currently common
practice (see Fig. 2).
Adsorption performance for target analytes
The adsorption performance of different adsorbent materials
for selected target analytes can be described by recovery rates.
Again, an aliquot of 1 μl of the standard solution was injected
on three tubes of each solid sorbent including Tenax TA®.
Target analytes have to be equally well adsorbed by the
sorbent bed and desorbed again in the subsequent thermal
desorption step. The recovery rates were calculated by
standardizing the arithmetic mean of the peak areas of each adsorbent
media to the arithmetic mean of Tenax TA® obtained by triple
measurements. Tenax TA® was chosen as reference even
Fig. 2 Comparison of formic acid and acetic acid concentrations obtained
by active sampling on Tenax TA® (TDS-GC/MS) and on silica gel (IC)
during chamber emission testing of a building product over 28 days
though the authors are aware that it is not suitable for
VVOCs. The arithmetic mean of each target analyte obtained
by Tenax TA® was set to 1. Sorbents more suitable for
retaining VVOCs are characterized by calculated data higher
than 1. Values lower than 1 can be traced back either to weaker
adsorption performances or to a very strong adsorption which
impedes the desorption process (see Fig. 3).
Recovery rates for CMS were below 1. As an exception,
2propanone, methyl acetate, and acetaldehyde were both well
adsorbed and desorbed. Carboxen 569 was also able to sample
methacroleine, chloropropane, methyl vinyl ketone, and
3methylpentane with recovery values between 0.9 and 1.
Fig. 3 Recovery of selected target analytes on tested solid adsorbents in
relation to recovery rates on Tenax TA®. Results are standardized to
Tenax TA® = 1
Most of those substances which have been adsorbed well on
CMS sorbents were low molecular weight substances with
two and three carbon atoms, even though not all small
molecules were adsorbed and desorbed equally well. Results for
formic acid were again poor. Recovery of 3-methylpentane on
Carboxen 569 was satisfying, although this is a C6 compound
with a relatively high molecular weight (86.2 g mol−1).
The tested GCB adsorbent materials showed good
recoveries for nearly all target analytes. The best adsorption
performances were achieved by using Carbopack X and
Carbograph 5TD, respectively, which were superior to
Carbotrap. The lowest recovery rates were found for ethanol
and 2-methylpropanal even though these two substances
differ regarding the number of carbon atoms and physical
characteristics. Furthermore, recovery rates for n-butanal were
not superior to Tenax TA®. For all sorbents tested, recoveries
higher than 3.5 were found for 2-propanol, which cannot be
The results indicate that GCB-filled tubes are able to adsorb
a broad range of low molecular substances (C3–C6) with some
limitations concerning alcohols and aldehydes. For
compounds ≤C3, CMS appear to be the better sampling media.
Low molecular weight carbonyl compounds in air are
recommended to be analyzed according to ISO 16000-3 [
derivatization with 2,4-dinitrophenylhydrazine (DNPH) and
subsequent separation and detection by HPLC/UV.
Breakthrough and safe sampling volumes
For determining the breakthrough and the sampling
reproducibility, two sampling tubes of each adsorbent were connected
in series. The first tube was spiked with an aliquot of 1 μl of
the VVOC standard solution. The exit of the back-up tube was
connected with a calibrated sampling pump. The tube pairs
were subjected to three different flow rates and two sampling
volumes: (a) 50 ml min−1, 2 l; (b) 125 ml min−1, 2 l; and (c)
125 ml min−1, 4 l. Table 3 gives the arithmetic mean and the
average standard deviations of the breakthrough, obtained
by double measurements. Breakthrough is given as %
VVOC (target analyte) in the back-up tube. Sampling
reproducibility was evaluated by calculating the relative standard
deviation (%) of the duplicates. Table 3 does not include
data for Carboxen 1000, which was representatively tested
as CMS adsorbent. The thermal desorption and gas
chromatographic separation of target analytes was poor so that
the obtained chromatograms showed no sharp peak form
and could not be therefore evaluated, especially regarding
the back-up tube.
A breakthrough volume (BV) of < 5% is recommended
in order to ensure that no breakthrough occurred at that
sample volume [
]. Even though VVOCs directly injected
on Tenax TA® might be well thermally desorbed and
separated on a medium polar GC column (as described in the
BGas chromatographic selectivity for target analytes^
section), the adsorption performance drops significantly when
passing an air flow through the sorbent bed. The obtained
breakthrough volumes vary between 10 and 76%. For 13
out of 19 analytes, the breakthrough increases with
increasing flow rate and sampling volume, e.g., regarding
2methylpropanal, methacroleine, methyl vinyl ketone, vinyl
acetate, and 3-methylpentane. There are just few
compounds with a BV < 5% on Tenax TA®. The GCBs
Carbograph 5TD and Carbopack X showed a BV < 1% for
nearly all substances. Formic acid was not detected on the
back-up tubes of all GCB adsorbents due to the inadequate
analytical process (see BGas chromatographic selectivity for
target analytes^ section). Again, limitations occurred
regarding some low molecular alcohols and aldehydes such
as ethanol and acetaldehyde. 2-Methylpropanal could not be
detected on Carbograph 5TD at a flow rate of 50 ml min−1
(2 l) and 125 ml min−1 (2 l), but by increasing the sampling
volume (125 ml min−1, 4 l) with no breakthrough occurring.
There are just minor differences in the breakthrough data
o b t a i n e d f o r C a r b o g r a p h 5 T D a n d C a r b o p a c k X .
Nevertheless, Carbograph 5TD can be assessed as superior
in comparison to Carbopack X due to a better gas
chromatographic separation of the VVOC substance mixture. BVs on
Carbotrap are significantly worse than those on Carbopack
X and Carbograph 5TD, but better than those obtained on
Tenax TA®. Even though values are < 5% for some
analytes, high breakthrough (20–93%) occurs for alcohols
(1-/2-propanol, 2-methyl-1-propanol), 2-methylpropanal,
2-chloropropane, and methyl acetate.
In order to reduce the risk of analyte breakthrough, the save
sampling volume (SSV) for a specific analyte/sorbent
combination is defined as not more than 70% of the 5% BV [
Facing low BV, a SSV for VVOCs on Carbograph 5TD of 2–
4 l is recommended. As the total sampling volume is already
small, a further reduction to 1.4 and 2.8 l, respectively, is not
Calibration of the analytical method for quantitative
determination of VVOCs (C3–C6) in indoor air was performed for
the VVOC target analytes as liquid standards in methanol. A
low concentration range from 0.0005 to 0.005 mg ml−1 and a
high concentration range from 0.01 to 0.05 mg ml−1 were
chosen. n = 10 equidistant calibration points xi, and m = 3
samples of each concentration x01 to x10 were measured.
The individual working range for each target analyte was
set according to the linear sector of the calibration curve.
The lowest concentration could not be detected for all single
VVOCs. Thus, this lowest calibration point is in the range of
the limit of detection (LOD).
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Limits of detection and limits of quantitation
Limits of detection (LOD) and limits of quantitation (LOQ) of
each target analyte are summarized in Table 4. Calibration
ranges (μg ml−1) are varying in dependence of the specific
substance as calculation is based on the linear area of the
calibration curve. Calibration details are given in the
Electronic supplementary material (ESM). With a total
sampling volume of 4 l on Carbograph 5TD, the obtained LODs
are equal to or lower than 3 μg m−3. As outlined above, ISO
] is the preferred method for small aldehydes and
ketones. However, the detection and quantification of these
carbonyl compounds via thermal desorption with subsequent
GC/MS analysis is possible with LOQs between 3 and
5 μg m−3. LOQs are highest for some alcohols (1-propanol,
2-methyl-2-propanol) with 7 and 8 μg m−3. Lower LOD and
LOQ with 1 and 3 μg m−3 were surprisingly found for ethanol,
although recovery was poor (< 1, see Fig. 3), and
breakthrough volumes on Carbograph 5TD were high when
sampling 2 and 4 l with a flow rate of 125 ml min−1 (35.43 ±
8.49% and 35.32 ± 49.61%, see Table 3). Therefore, the
quantitative determination of ethanol in indoor air after sampling
on Carbograph 5TD must be carefully observed in the future.
The application of polymeric adsorbents and molecular sieves
involves the risk of by-product formation. Hübschmann [
identified benzene and some benzene derivatives as
Table 4 Limits of detection
(LOD) and limits of quantitation
(LOQ) given in micrograms per
cubic meter for VVOC target
analytes after sampling on
Carbograph 5TD with a total
sampling volume of 4 l.
Calibration range depends on the
interfering components from Tenax, Porapak, and XAD-2/4.
It is also well known that Tenax decomposes in the presence
of nitrogen oxides, ozone, and other reactive compounds [
]. Another known artifact in GC analysis is the formation of
hemiacetals and acetals from carbonyl compounds in
methanolic solution, as described for 1,1-dimethoxycyclohexane
from cyclohexanone . In this study, 2-butenal, which
was not injected on the sorbent tubes as part of the
standard solution, and methyl acetate unexpectedly appeared
during some test series of different sorbents. The chemical
mechanism leading to methyl acetate is unclear. It can be
speculated that methyl acetate results from esterification,
because acetic acid was found in trace concentrations as
an impurity of carbon molecular sieves (CMS). As a
potential product from the aldol condensation reaction of two
acetaldehyde molecules, 2-butenal was identified (see ESM
for the reaction scheme), which occurred after thermal
desorption of CMS, GCBs, and Tenax TA® [
]. There is
also evidence for the formation of the hemiacetal
1methoxyethanol from acetaldehyde and methanol (see
ESM for the reaction scheme), but the acetal
1,1dimethoxyethane could not be identified. This is plausible
because acidic conditions are required for the formation of
acetals from hemiacetals [
]. The identification of the
above mentioned reaction products was unambiguous.
However, it was not possible to clearly assign if the
hemiacetal reaction takes place in the methanolic standard
solution or on the sorbent. In general, molecular sieves are
known and applied as active materials . The formation
Limit of detection
(LOD) [μg m−3]
Limit of quantitation
(LOQ) [μg m−3]
Fig. 4 Schematic overview of
available analytical methods for
the quantitative determination of a
large spectrum of relevant
VVOCs in indoor air
ISO 16000-6 (2012)
Tenax TA® / TDS-GC/MS
VDI 4301-7 (2017)
Silica gel / IC
Carboxylic acids C1-C2
Carbonyl compounds C1-C5
DNPH / HPLC-UV
ISO 16000-3 (2013)
of these by-products is not considered as a severe
disadvantage of the method but needs to be taken into account
to avoid misinterpretation of chromatographic signals.
By using Carbograph 5TD (20/40 mesh) as solid sorbent and a
medium polar GC column, it is possible to detect VVOCs
between C3 and C6 of different volatility and polarity even
in trace quantities. Limitations occur for some low molecular
weight compounds ≤C3, especially for polar substances, such
as carboxylic acids (formic acid, acetic acid) and some
aldehydes. At least three different analytical techniques are
therefore needed to cover the large spectrum of relevant VVOCs in
indoor air (see Fig. 4). This allows a significantly broadening
of the analytical spectrum ≤C6 beyond the C6–C16 window for
VOCs as defined by ISO 16000-6 [
]. Facing the definition of
VVOCs in EN 16516 [
], it is important to highlight that this
standard can only be applied to the specified GC column and
analytical setup. As soon as the setup is changed, the
definition is no longer valid. By using a medium polar GC column
as in this study, substances which can fall within the class of
VVOCs (regardless of the specific definition) will elute both
before and after n-hexane (RI 534.38), e.g., isoprene (RI
516.12), 2-propanone (RI 532.02), methacroleine (RI
607.79), and methyl vinyl ketone (RI 631.49) (For calculation
of retention indices and a list of retention indices of VVOC
target substances, please see ESM and [
]). However, some
of these substances are defined as VOCs according to EN
16516 (normative annex G), such as 2-methyl-2-propanol,
n-butanal, and 2-methyl-1-propanol. Therefore, irrespective
of any standard, a significant extension of the range of
detectable and quantifiable volatile organics in indoor air was
achieved in this study.
It is reasonable that VVOCs ≤C3 might need even stronger
adsorbent media due to their high volatility. It is, however, still
questionable if the entire range of VVOCs in indoor air C1–C6
can be determined by sampling on solid sorbents with
subsequent TDS-GC/MS analysis. When handling strong sorbent
media, not just water management but also the occurrence of
unexpected by-products has to be considered. Furthermore, a
reduction of the number of solid sorbents and analysis
currently needed to cover a broad spectrum of volatile organics
( V V O C s / V O C s ) i s d e s i r a b l e . T h e p e r f o r m a n c e o f
multisorbent tubes will be therefore further investigated.
Acknowledgements Thanks are due to A. Repp, N. Siwinski, J. Freitag,
and E. Uhde for analytical and technical support. The authors are also
very grateful to Ch. Fauck for drawing again a unique graphical abstract.
Funding information The presented study is part of a research project,
which is funded by the Federal Ministry of Food and Agriculture (BMEL)
through the Agency of Renewable Resources (FNR, #22008114).
Compliance with ethical standards
Conflict of interest The authors declare that they have no conflict of
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ed. Cincinnati: Center for Environmental Research Information,
Office of Research and Development; 1999.
U.S. Environmental Protection Agency. Compendium Method
TO15, Determination of volatile organic compounds (VOCs) in air
collected in specially-prepared canisters and analyzed by gas
chromatography/mass spectrometry (GC/MS). In: Compendium
of methods for the determination of toxic organic compounds in
ambient air. 2nd ed. Cincinnati: Center for Environmental Research
Information, Office of Research and Development; 1999.
ASTM D5466-15. Standard test method for determination of
volatile organic compounds in atmospheres (canister sampling
methodology). West Conshohocken: ASTM International; 2015.
Uhde E. Application of solid sorbents for the sampling of volatile
organic compounds in indoor air. In: Salthammer T, Uhde E,
editors. Organic indoor air pollutants. Occurrence, measurement,
evaluation. Weinheim: Wiley; 2009. p. 3–18.
ASTM D6196-15. Standard practice for choosing sorbents,
sampling parameters and thermal desorption analytical conditions for
monitoring volatile organic chemicals in air. West Conshohocken:
ASTM International; 2015.
Woolfenden E. Sorbent-based sampling methods for volatile and
semi-volatile organic compounds in air. Part 2: Sorbent selection
and other aspects of optimizing air monitoring methods. J
Chromatogr A. 2010;1217(16):2685–94. https://doi.org/10.1016/
Dettmer K, Knobloch T, Engewald W. Stability of reactive low
boiling hydrocarbons on carbon based adsorbents typically used
for adsorptive enchrichment and thermal desorption. Fresenius J
Anal Chem. 2000;366:70–8.
Brancaleoni E, Scovaventi M, Frattoni M, Mabilia R, Ciccioli P.
Novel family of multi-layer cartridges filled with a new carbon
adsorbent for the quantitative determination of volatile organic
compounds in the atmosphere. J Chromatogr A. 1999;845(1–2):
Dettmer K, Bittner T, Engewald W. Adsorptive enrichment and
thermal desorption of low-boiling oxygenated
compounds—possibilities and limitations. Chromatographia Suppl. 2001;53:S322–6.
Dettmer K, Engewald W. Adsorbent materials commonly used in
air analysis for adsorptive enrichment and thermal desorption of
volatile organic compounds. Anal Bioanal Chem. 2002;373(6):
Coeur C, Jacob V, Denis I, Foster P. Decomposition of α-pinene
and sabinene on solid sorbents, Tenax TA and Carboxen. J
Chromatogr A. 1997;786:185–7.
Ribes A, Carrera G, Gallego E, Roca X, Berenguer MA, Guardino
X. Development and validation of a method for air-quality and
nuisance odors monitoring of volatile organic compounds using
multi-sorbent adsorption and gas chromatography/mass
spectrometry thermal desorption system. J Chromatogr A. 2007;1140(1–2):
Gallego E, Roca FJ, Perales JF, Guardino X. Comparative study of
the adsorption performance of a multi-sorbent bed (Carbotrap,
Carbopack X, Carboxen 569) and a Tenax TA adsorbent tube for
the analysis of volatile organic compounds (VOCs). Talanta.
Camel V, Caude M. Trace enrichment methods for the
determination of organic pollutants in ambient air. J Chromatogr A.
Rothweiler H, Wäger PA, Schlatter C. Comparison of Tenax TA
and Carbotrap for sampling and analysis of volatile organic
compounds in air. Atmos Environ. 1991;25B(2):231–5.
Fastyn P, Kornacki W, Gierczak T, Gawłowski J, Niedzielski J.
Adsorption of water vapour from humid air by selected carbon
adsorbents. J Chromatogr A. 2005;1078(1–2):7–12. https://doi.
1. Logue JM , McKone TE , Sherman MH , Singer BC . Hazard assessment of chemical air contaminants measured in residences . Indoor Air . 2011 ; 21 ( 2 ): 92 - 109 . https://doi.org/10.1111/j.1600- 0668 . 2010 . 00683 .x.
2. Sahlberg B , Gunnbjörnsdottir M , Soon A , Jogi R , Gislason T , Wieslander G , et al. Airborne molds and bacteria, microbial volatile organic compounds (MVOC), plasticizers and formaldehyde in dwellings in three North European cities in relation to sick building syndrome (SBS) . Sci Total Environ . 2013 ; 444 : 433 - 40 . https://doi. org/10.1016/j.scitotenv. 2012 . 10 .114 .
3. Polizzi V , Adams A , Malysheva SV , De Saeger S , Van Peteghem C , Moretti A , et al. Identification of volatile markers for indoor fungal growth and chemotaxonomic classification of Aspergillus species . Fungal Biol . 2012 ; 116 ( 9 ): 941 - 53 . https://doi.org/10.1016/j.funbio. 2012 . 06 .001.
4. Tsushima S , Wargocki P , Tanabe S. Sensory evaluation and chemical analysis of exhaled and dermally emitted bioeffluents . Indoor Air . 2018 ; 28 ( 1 ): 146 - 63 . https://doi.org/10.1111/ina.12424.
5. Bartsch J , Uhde E , Salthammer T. Analysis of odour compounds from scented consumer products using gas chromatography-mass spectrometry and gas chromatography-olfactometry . Anal Chim Acta . 2016 ; 904 : 98 - 106 . https://doi.org/10.1016/j.aca. 2015 . 11 .031.
6. Morrison G . Chemical reactions among indoor pollutants . In: Lazaridis M , Colbeck I , editors. Human exposure to pollutants via dermal absorption and inhalation . Vol. 17 . Environmental pollution. Dordrecht: Springer; 2010 . p. 73 - 96 .
7. Regulation (EU) No 305/2011 of the European Parliament and of the Council of 9 March 2011 laying down harmonised conditions for the marketing of construction products and repealing Council Directive 89 /106/EEC.
8. ISO 16000 -6. Indoor air-Part 6: Determination of volatile organic compounds in indoor and test chamber air by active sampling on Tenax TA® sorbent, thermal desorption and gas chromatography using MS or MS-FID . Berlin: Beuth Verlag; 2012 .
9. ISO 16000 -9. Indoor air-Part 9: Determination of the emission of volatile organic compounds from building products and furnishing-emission test chamber method . Berlin: Beuth Verlag; 2008 .
10. ISO 16000- 11 . Indoor air-Part 11: Determination of the emission of volatile organic compounds from building products and furnishing-sampling, storage of samples and preparation of test specimens . Berlin: Beuth Verlag; 2006 .
11. EN 16516. Construction products: assessment of release of dangerous substances-determination of emissions into indoor air . Berlin: Beuth Verlag; 2018 .
12. European Collaborative Action (ECA). Harmonisation of indoor material emissions labelling systems in the EU . Inventory of existing schemes , Report No 24 , Urban Air , Indoor Environment and Human Exposure . Luxembourg: Office for Official Publications of the European Communities; 2005 .
13. European Collaborative Action (ECA). Harmonisation framework for indoor products labelling schemes in the EU , Report No 27, U r b a n a i r, i n d o o r e n v i r o n m e n t a n d h u m a n e x p o s u r e . Luxembourg: Office for Official Publications of the European Communities; 2012 .
14. European Collaborative Action (ECA). Harmonisation framework for health based evaluation of indoor emissions from construction products in the European Union using the EU-LCI concept , Report No 29, Urban air , indoor environment and human exposure. Luxembourg: Office for Official Publications of the European Communities; 2013 .
15. Salthammer T. Very volatile organic compounds: an understudied class of indoor air pollutants . Indoor Air . 2016 ; 26 ( 1 ): 25 - 38 . https:// doi.org/10.1111/ina.12173.
16. Wang B , Zhao Y , Lan Z , Yao Y , Wang L , Sun H . Sampling methods of emerging organic contaminants in indoor air . Trends Anal Chem . 2016 ; 12 ( Supplement C ): 13 - 22 . https://doi.org/10.1016/j.teac. 2016 . 11 .001.
17. Koppmann R , editor. Volatile organic compounds in the atmosphere . Oxford: Blackwell; 2007 .
18. Woolfenden E . Sorbent-based sampling methods for volatile and semi-volatile organic compounds in air. Part 1: Sorbent-based air monitoring options . J Chromatogr A . 2010 ; 1217 ( 16 ): 2674 - 84 . https://doi.org/10.1016/j.chroma. 2009 . 12 .042 .
19. U.S. Environmental Protection Agency. Compendium Method TO14, The determination of volatile organic compounds (VOCs) in ambient air using SUMMA(R) passivated canister sampling and gas chromatographic analysis, In: Compendium of methods for the determination of toxic organic compounds in ambient air . 2nd
35. Fastyn P , Kornacki W , Kardas M , Gawłowski J , Niedzielski J . Adsorption of water vapour from humid air in carbon molecular sieves: Carbosieve S-III and Carboxens 569, 1000 and 1001 . Analyst . 2003 ; 128 ( 2 ): 198 - 203 . https://doi.org/10.1039/ B209296D .
36. Brown VM , Crump DR . An investigation into the performance of a multi-sorbent sampling tube for the measurement of VVOC and VOC emissions from products used indoors . Anal Methods . 2013 ; 5 ( 11 ): 2746 - 56 . https://doi.org/10.1039/C3AY40224J.
37. Patil SF , Lonkar ST . Thermal desorption-gas chromatography for the determination of benzene, aniline, nitrobenzene and chlorobenzene in workplace air . J Chromatogr . 1992 ; 600 : 344 - 51 .
38. Rumble J , editor. CRC handbook of chemistry and physics . 98th ed. Boca Raton: Taylor & Francis; 2017 .
39. McLafferty FW , Turecek F . Interpretation of mass spectra . Mill Valley: University Science Books; 1993 .
40. Einax JW , Zwanziger HW , Geiß S. Chemometrics in environmental analysis . Weinheim: Wiley; 1997 .
41. DIN 32645. Chemical analysis-decision limit, detection limit and determination limit under repeatability conditions-terms, methods, evaluation . Berlin: Beuth Verlag; 2008 .
42. VDI 4301-7. Measurement of indoor air pollution-measurement of carboxylic acids . Düsseldorf: Verein Deutscher Ingenieure (VDI) ; 2017 .
43. ISO 16000-3. Indoor air-Part 3: Determination of formaldehyde and other carbonyl compounds in indoor air and test chamber airactive sampling method . Berlin: Beuth Verlag; 2013 .
44. U.S. Environmental Protection Agency. Compendium Method TO17, Determination of volatile organic compounds (VOCs) in ambient air using active sampling onto sorbent tubes . In: Compendium of methods for the determination of toxic organic compounds in ambient air . 2nd ed. Cincinnati: Center for Environmental Research Information, Office of Research and Development; 1999 .
45. ISO 16017. Indoor, ambient and workplace air-sampling and analysis of volatile organic compounds by sorbent tube/thermal desorption/capillary gas chromatography-Part 1: Pumped sampling . Berlin: Beuth Verlag; 2001 .
46. Hübschmann H-J. Handbook of GC-MS. Weinheim: Wiley; 2015 .
47. Clausen PA , Wolkoff P . Degradation products of Tenax TA formed during sampling and thermal desorption analysis: indicators of reactive species indoors . Atmos Environ . 1997 ; 31 ( 5 ): 715 - 25 .
48. Klenø JG , Wolkoff P , Clausen PA , Wilkins CK , Pedersen T. Degradation of the adsorbent Tenax TA by nitrogen oxides, ozone, hydrogen peroxide, OH radical and limonene oxidation products . Environ Sci Technol . 2002 ; 36 : 4121 - 6 .
49. Uhde E , Salthammer T. Impact of reaction products from building materials and furnishings on indoor air quality-a review of recent advances in indoor chemistry . Atmos Environ . 2007 ; 41 ( 15 ): 3111 - 28 . https://doi.org/10.1016/j.atmosenv. 2006 . 05 .082.
50. Sykes P. A guidebook to mechanism in organic chemistry . 6th ed. Malaysia: Pearson Education Limited; 1986 .
51. van Den Dool H , Kratz PD . A generalization of the retention index system including linear temperature programmed gas-liquid partition chromatography . J Chrom A . 1963 ; 11 : 463 - 71 .