Oo

AB

a

ARR1A

KSIS

1

ioieca

d

0d

J. of Supercritical Fluids 62 (2012) 123– 134

Contents lists available at SciVerse ScienceDirect

The Journal of Supercritical Fluids

jou rn al h om epage: www.elsev ier .com/ locate /supf lu

ptimization of variables on the supercritical fluid extraction of high-boilingrganic compounds in house-dust

thanasios Papadopoulos ∗

iomolecular Physics Laboratory, IRRP, NCSR “Demokritos”, Aghia Paraskevi, 15310 Attiki, Greece

r t i c l e i n f o

rticle history:eceived 19 May 2011eceived in revised form5 November 2011ccepted 16 November 2011

eywords:FE-CO2

ndoor dustorbent material

a b s t r a c t

Epidemiological and clinical studies in the recent years have shown that the importance of the indoorair quality to human health should not be underestimated. The assessment of indoor quality requiresefficient and reliable methods producing useful information particularly on that related to indoor dust.A significant task in designing mitigation or prevention measures is to identify firstly the classes of com-pounds that are present in house dust and secondly obtain their contribution in the samples particularlythat of low-volatile or non-volatile organic compounds, for which sparse data is available. Extraction ofhouse dust can be used as a screening method for high boiling organic compounds in the indoor envi-ronment. Most published work so far, on organic compounds of low volatility and on particulate organicmatter has been focused on a few classes of compounds of known toxicity. However, the absence ofknowledge on other possibly present classes of compounds could be crucial in determining the extentof exposure. To override this lack of knowledge, the present study introduces a new method based onsupercritical fluid extraction (SFE) to detect the classes of the low-volatile or non-volatile organic com-

pounds that are present in the house-dust samples. The application of the particular method of SFE withCO2 can help to extract and analyze a broad range of low volatile organic compounds in dust of indoorenvironments, which can lead effectively to a more complete characterization. The particular extrac-tion/analytical method for organics in house dust has been set up consisting of a two step supercriticalfluid extraction (SFE) with CO2 and CO2 + 5% of methanol, collection of the extracts on ODS trap, elutionof the extracted compounds with methanol and n-hexane and GC/MS analysis of the eluates.

. Introduction

Whereas indoor exposure to volatile organic pollution has beenntensely investigated, quality and concentrations of semi-volatilerganic compounds (SVOCs) and particulate organic matter (POM)n the indoor environment have been analyzed only to a limitedxtent. Most published work so far has been focused on a fewlasses of compounds of known toxicity, such as pesticides [1,2]nd polynuclear aromatic hydrocarbons (PAHs) [3,4].

No systematic survey study of SVOCs and POM has been madeue to a number of reasons such as:

(i) SVOCs in the indoor environment are partially in the vapourphase and partially adsorbed as POM, to particles (which may

be suspended or settled dust) or to indoor surfaces.

(ii) Exposure to these compounds does not exclusively and maynot even predominantly occur via inhalation. Ingestion of, and

∗ Tel.: +30 210 6503915.E-mail address: thapap@rrp.demokritos.gr

896-8446/$ – see front matter © 2011 Elsevier B.V. All rights reserved.oi:10.1016/j.supflu.2011.11.013

© 2011 Elsevier B.V. All rights reserved.

skin contact with house dust can be primary routes of exposurefor small children to pesticides [5–7], lead [8] and allergens [9].

(iii) Survey analysis of SVOCs and POM in air requires sampling ofboth vapours and particles from large air volumes. Establishedmethods for the extraction of the organic compounds from sor-bents and filters and their subsequent separation are complexand time consuming [10].

For the reasons (i)–(iii), analysis of air samples may not be themost appropriate screening method for high boiling organic com-pounds in the indoor environment, which may be of concern tohuman health. House dust, however, is an easily accessible envi-ronmental matrix with information on human indoor exposureto organic pollutants of low- or non-volatility. House dust can beboth a vector for the transfer of pollutants from sources to peo-ple and a reservoir for the accumulation of pollutants. Dust maycontain pollutants released from activities and materials in thehome or carried in from road dust, soil or work sites outdoor

[11]. Organics with low vapour pressure and/or high polarity areexpected to partition more to dust than to air, making house dusta potential reservoir of e.g. pesticides, PAHs and phthalates. Inaddition, there is an increasing trend to substitute volatile organic

1 critica

cbop

opis

(

(

ipcp

Cfthn

•

••

e

2

ogTita

2

Sdsswct1

te7si

24 A. Papadopoulos / J. of Super

ompounds as additives of indoor materials and products by higheroiling less volatile compounds that may be sorbed on house dustr indoor surfaces rather than contributing to vapour phase airollution.

In view of the observed and suspected impact of house dustn human health and well-being and, in particular, in view of theotentially high exposure and increased susceptibility of infants

ndoors, the current study aimed at developing a more rapid andimplified method for:

1) The detection of a wide range of organic compounds in indoordust, based on a survey analysis approach.

2) Obtaining the contribution, in terms of ranges of the con-centration values, of the low-volatile or non-volatile organiccompounds in the samples.

Due to the high number of compounds expected to be foundn house-dust, the method introduced here relies on the selectivere-separation process, so that the identified compounds can beategorised into fractions, depending on their molecular mass andolarity for a complete characterization.

The method is based on supercritical fluid extraction (SFE) withO2 that is increasingly applied to extract organic trace compoundsrom environmental samples. SFE offers a number of characteristicshat appeared particularly promising for the analysis of organics inouse dust. Compared to Soxhlet extraction, the “classical” alter-ative, SFE offers the following:

a non toxic solvent without any difficulty of disposal (use of CO2as supercritical fluid);much shorter times to achieve quantitative extraction;an easy and fast way of pre-separation of extracted compoundsby collecting the extracts on supports with different sorptioncharacteristics.

It must be mentioned that only small amounts of house dust,asily collectable, are needed for the proposed analysis.

. Materials and methods

The survey analysis, performed initially to detect a wide range ofrganic compounds in a sample, was semi-quantitative, as the mainoal was to describe qualitatively the organic content of house dust.he quantitative data analysis, carried out as a subsequent step, wasntended to provide the order of magnitude of the concentrations ofhe compounds under investigation. A description of the samplingnd extraction approach is provided in the following section.

.1. Instrumentation and extraction method

House dust samples were collected by means of the High Volumemall surface Sampler (HVS3 Cascade Stack Sampling Systems)eveloped by the Environmental Protection Agency (EPA US). Theurface dust enters the system through the nozzle. The nozzle ispecially designed to move across a floor with little resistance,hile still maintaining a sufficient seal to collect a sample. A

yclone collected particles greater than 5 �m. The collected par-icles were sieved to remove those with diameters larger than06 �m.

The dust samples (0.5 g) were placed in a thimble, i.e. ahick-walled stainless steel tube. The thimble was placed in the

xtraction chamber of the HP supercritical fluid extractor (HP680T). The supercritical fluid passed through the thimble and sub-equently through an adjustable nozzle where it was depressurizednto a trap, i.e. a cartridge containing an adsorbent. CO2 or CO2

l Fluids 62 (2012) 123– 134

modified with methanol have been used as the supercritical fluids.The extracted compounds were collected in an absorbing material,while CO2 was vented. The semi-volatile and non-volatile extractedcompounds were rinsed off the trap by solvents and were col-lected in automatic sampler vials. An aliquot of each rinsing fractionwas injected on-column to the gas chromatograph (HP 5890 SeriesII plus) equipped with mass spectrometry (HP 5972 Series II). Anon-polar general purpose column (OV1, Mega, Capillary columnslaboratory, Via Plinio 29, Legnano MI, Italy) with a phase thick-ness of 0.1–0.15 �m, internal diameter 0.2 mm and 25 m lengthwas used. Because of the different polarities of the extracted com-pounds, in some cases, the hydrophilic fractions were analyzed bya carbowax polar column (Mega-Acid, Mega, Capillary columns lab-oratory, Via Plinio 29, Legnano MI, Italy) with a phase thickness of0.1–0.15 �m and internal diameter 0.2 mm. The GC temperatureprograms were designed as follows:

(a) OV1 column: 10 ◦C/min from 50 to 320 ◦C.(b) Mega-acid column: 10 ◦C/min from 50 to 250 ◦C.

3. Results

The above described SFE method was optimized by testing var-ious combinations of extraction and elution parameters:

(i) the supercritical fluid (CO2) pressure and composition,(ii) the trap material,

(iii) the rinsing solvents.

The extraction process was computer controlled. For eachextraction programme, a method had to be created for the datasystem that specified the number and duration of the extractionsteps, pressure and composition of the extraction fluids duringthe steps, the rinsing steps and solvents. A detailed discussion ofthe testing of these parameters is provided below. The methodwas applied in a number of real indoor samples for validationpurposes successfully. However, for the scope of the currentpaper, the discussion of the results of a randomly picked sam-ple was sufficient to present the method, as any sample wasfound to comprise organic compounds mostly available in indoordust.

3.1. Selection of supercritical fluid compositions and pressure

To optimize the pre-separation process, it was decided to inves-tigate the effect of performing several successive extraction steps,using CO2 of different densities, as well as adding methanol asa polar modifier. Higher CO2 densities result in the extractionof higher molecular weight compounds as well as compounds ofhigher hydrophilicity. A polar modifier is added to extract veryhydrophilic compounds which could not be extracted using pure(lipophilic) CO2.

In Fig. 1, the results of four consecutive extractions of the samehouse dust sample are reported, using CO2 of three different den-sities and adding 5% of methanol as a modifier to the extractionfluid. The figure shows that there is no efficient pre-separationbetween extractions with CO2 densities of 0.25 g/ml and 0.50 g/mland between extractions with a CO2 density of 0.90 g/ml withand without the addition of methanol. All compounds extractedin Fig. 1A would have also been extracted in Fig. 1B without adding

complexity to the chromatogram. Similarly, compounds extractedin Fig. 1C would have been extracted in Fig. 1D. Therefore, the twoextraction steps of CO2 densities of 0.50 g/ml and 0.90 g/ml with theaddition of methanol (omitting the extractions with CO2 densities

A. Papadopoulos / J. of Supercritical Fluids 62 (2012) 123– 134 125

Fig. 1. Chromatograms of four successive extractions of the same house dust sample with supercritical CO2 of increasing density (A–C) and the addition of methanol (D).Extracted compounds have been trapped on an ODS trap and rinsed off with n-hexane. 1, 1,2-benzenedicarboxylic acid, butyl 2-methylpropyl ester; 2, 1,2-benzenedicarboxylica e; 8, 1a cosane1 oic ac

os

3

mp

hTlt

a

cid, dibutyl ester; 3, eicosane; 4, heneicosane; 5, docosane; 6, tricosane; 7, tetracosancid; 11, dodecanoic acid; 12, tetradecanoic acid; 13, hexadecanoic acid; 14, penta8, octacosane; 19, nonacosane; 20, triacontane; 21, hentriacontane; 22, octadecan

f 0.25 g/ml and 0.90 g/ml) would have resulted in sufficient pre-eparation, regarding the extraction fluid.

.2. Selection of trap material

The selection of the appropriate combination of a sorbent (trap)aterial and eluting (rinsing) solvents is required to optimize the

re-separation.On a lipophilic sorbent, elution should first be made with a

ydrophilic solvent, essentially to elute all hydrophilic compounds.hen, an elution with a lipophilic solvent follows to elute the

ipophilic compounds, which are more strongly absorbed on thisype of sorbent.

Similarly, good pre-separation is expected to be obtained when hydrophilic sorbent and strong lipophilic solvent are used. The

,2-benzenedicarboxylic acid, bis(2-ethylhexyl) ester; 9, nonanoic acid; 10, decanoic; 15, hexacosane; 16, tetracosane, 2,6,10,15,19,23-hexamethyl-; 17, heptacosane;

id.

sequence of the elution solvents should obviously be the inverseof the one described for a lipophilic sorbent. In this study, threesorbents were tested as follows:

• From experience gained with adsorbing materials, which havealso been extensively used for other techniques such as liquidchromatography, ODS (octadecyl chains bonded to silica spheres)was chosen as an appropriate lipophilic adsorbent [12,13].

• “DIOL”, a diol-ester (Pentan-1,3-diol diisobutyrate 2,2,4-trimethyl-), also bonded to silica spheres, was used as anexample of a hydrophilic adsorbent [14].

• In addition, stainless steel spheres were taken into consideration,

the characteristics of which were less clear [15].

The difference between the use of ODS and stainless steel spheretraps was mostly marked for the first fraction (lowest CO2 density),

126 A. Papadopoulos / J. of Supercritical Fluids 62 (2012) 123– 134

Fig. 2. Chromatograms of two samples (A and B) of the same house dust extracted twice, (1) with CO2 of 0.25 g/ml density and (2) with CO2 of 0.50 g/ml density. Extracts of sam-ple A were collected on a stainless steel trap and those of sample B on an ODS trap. Both traps were rinsed with n-hexane after each extraction. 1, 1,2-benzenedicarboxylic acid,b ne; 4a cid; 12t acosa

wtstp(

pfieau

utyl 2-methylpropyl ester; 2, 1,2-benzenedicarboxylic acid, dibutyl ester; 3, eicosacid, bis(2-ethylhexyl) ester; 9, nonanoic acid; 10, decanoic acid; 11, dodecanoic aetracosane, 2,6,10,15,19,23-hexamethyl-; 17, heptacosane; 18, octacosane; 19, non

hich was more abundant on the ODS trap with its higher adsorp-ion capacity and strength (vapourization appeared to occur fromtainless steel spheres for low molecular weight compounds). Onhe other hand, the stainless steel spheres were effective for trap-ing compounds with higher molecular weight and lower volatilityFig. 2).

Because of the polar nature of the DIOL trap material, the appro-riate sequence of solvents for achieving good pre-separation was

rstly to rinse with hexane and subsequently with methanol forach extraction step. Even in that case, the selective pre-separationchieved (Fig. 3), was not as satisfactory as that accomplishedsing the ODS trap: n-hexane was eluted from the hydrophilic

, heneicosane; 5, docosane; 6, tricosane; 7, tetracosane; 8, 1,2-benzenedicarboxylic, tetradecanoic acid; 13, hexadecanoic acid; 14, pentacosane; 15, hexacosane; 16,ne; 20, triacontane; 21, hentriacontane.

sorbent compounds that had both lipophilic and hydrophilic char-acteristics, such as phthalates (Fig. 3A and C) but the elution wasincomplete. The remaining quantities of those compounds retainedin the trap, were eluted with methanol (Fig. 3B and D).

3.3. Selection of rinsing solvents

The rinsing solvents tested were the following three com-

pounds:

• Methanol (a typical hydrophilic solvent).• n-Hexane (a classical lipophilic solvent).

A. Papadopoulos / J. of Supercritical Fluids 62 (2012) 123– 134 127

Fig. 3. Chromatograms of two successive extractions of the same house dust sample and two rinses (hexane and methanol) of the “DIOL” trap after each extraction. 1,1,2-benzenedicarboxylic acid, dibutylester; 2, hexadecanoic acid; 3, docosane; 4, tricosane; 5, tetracosane; 6, pentacosane; 7, 1,2-benzenedicarboxylic acid, bis(2-ethylhexyl)ester; 8, hexacosane; 9, heptacosane; 10, octacosane; 11, tetracosane, 2,6,10,15,19,23-hexamethyl-; 12, nonacosane; 13, triacontane; 14, hentriacontane; 15, nonanoica d; 20,m id; 255

•

wraovfia

cid; 16, decanoic acid; 17, dodecanoic acid; 18, 3-nonanone; 19, tetradecanoic aciethyl ester; 22, hexadecanoic acid; 23, heptadecanoic acid; 24, 9-octadecenoic ac

-cholestene-3-ol (3.beta.)-.

2-Propanol (a solvent more lipophilic than methanol, due to ashort aliphatic chain).

The investigation for the use of the appropriate rinsing solventsas performed using mainly the ODS trap. The application of two

inses of the extracts was considered from the collection trapsfter each extraction step, one with a polar solvent for the elution

f the hydrophilic compounds and another with an apolar sol-ent for the rinsing of the lipophilic compounds. The two solventsrst selected for testing were methanol, as a typical polar solventnd n-hexane as a typical apolar solvent. As shown in Fig. 4, only

1,2-benzenedicarboxylic acid, butyl 2-methylpropyl ester; 21, hexadecanoic acid,, octadecanoic acid; 26, 1,2-benzenedicarboxylic acid, butylphenylmethylester; 27,

oxygen containing compounds were eluted with methanol (seechromatograms in Fig. 4A and C), whereas n-hexane eluted onlyhydrocarbons (Fig. 4B and D). Furthermore, 2-propanol was testedas an alternative hydrophilic solvent, mainly to confirm the choiceof methanol. In fact (see Fig. 5), very few traces of compounds werestill retained after the elution with 2-propanol (see chromatogramsin Fig. 5A and C), since it eluted all hydrophilic and lipophilic com-

pounds due to its stronger lipophilic characteristics compared tothose of methanol. As a result, no separation of hydrophilic andlipophilic compounds occurred. It must also be mentioned thatadditional tests performed by the substitution of the hydrophilic

128 A. Papadopoulos / J. of Supercritical Fluids 62 (2012) 123– 134

Fig. 4. Chromatograms of two successive extractions of the same house dust sample and two rinses (methanol and hexane) of the ODS trap after each extraction. 1, ethanol;2-butoxy-; 2, nonanal; 3, nonanoic acid; 4, decanoic acid; 5, dodecanoic acid; 6, 1,2-benzenedicarboxylic acid, diethyl ester; 7, tetradecanoic acid; 8, 1,2-benzenedicarboxylicacid, butyl 2-methylpropyl ester; 9, 1-hexadecanol; 10, 1,2-benzenedicarboxylic acid, dibutyl ester; 11, hexadecanoic acid; 12, 1-octadecanol; 13, 1,2-benzenedicarboxylica ester;t nacost 3.beta

sn

4

4

t

cid, butyl phenylmethyl ester; 14, 1,2-benzenedicarboxylic acid, bis(2-ethylhexyl)etracosane, 2,6,10,15,19,23-hexamethyl-; 21, heptacosane; 22, octacosane; 23, noetratriacontane; 29, octadecanoic acid; 30, eicosanoic acid; 31, 5-cholestene-3-ol (

olvent (methanol) with a mixture of 30% methanol–70% water didot show any advantage over the use of pure methanol.

. Discussion

.1. Final selected analytical procedure

As a result of the tests described above (Sections 3.1–3.3),he combination of two extraction steps with two rinses of the

15, docosane; 16, tricosane; 17, tetracosane; 18, pentacosane; 19, hexacosane; 20,ane; 24, triacontane; 25, hentriacontane; 26, dotriacontane; 27, tritriacontane; 28,.)-.

extracts from the ODS collection trap was selected. The corre-sponding chromatograms are presented in Fig. 4. A schematicrepresentation of the extraction, trapping and elution steps isshown in Fig. 6. Using that method, a very satisfactory selectivepre-separation–fractionation was achieved:

- The hydrophilic compounds were rinsed with methanol, whereasthe lipophilic compounds were rinsed with n-hexane.

A. Papadopoulos / J. of Supercritical Fluids 62 (2012) 123– 134 129

Fig. 5. Chromatograms of two successive extractions of the same housedust sample and two rinses (propanol-2 and hexane) of the ODS trap after each extraction. 1, nonanoicacid; 2, decanoic acid; 3, dodecanoic acid; 4, tetradecanoic acid; 5, 1,2-benzenedicarboxylic acid, butyl 2-methylpropyl ester; 6, 1,2-benzenedicarboxylic acid, dibutylester;7, hexadecanoic acid; 8, heneicosane; 9, docosane; 10, tricosane; 11, tetracosane; 12, pentacosane; 13, 1,2-benzenedicarboxylic acid, bis(2-ethylhexyl) ester; 14, hexacosane;1 octad

-

4

ifrtf

th

5, tetracosane, 2,6,10,15,19,23-hexamethyl-; 16, heptacosane; 17, octacosane; 18,

Compounds of smaller molecular weight were extracted duringthe first extraction step, and the extraction of heavier compoundsoccurred during the next step (higher CO2 density).

.2. Semi-quantitative determination of extracted compounds

In view of the high expected number of the compounds to bedentified, the semi-quantitative analysis was deemed appropriateor the purpose of classifying the compounds in three concentrationanges. More detailed quantitation would have only complicatedhe interpretation. The three concentration ranges were defined as

ollows: ≥200 �g/g, 20–200 �g/g, <20 �g/g.

For semi-quantitation, usually the FID signal is integrated overhe GC peak of each detected substance. Since, in any case, GC–MSad to be used for the identification of the extracted compounds, an

ecanoic acid.

investigation was also carried out of whether similar performancecould have been obtained for semi-quantitation, by integrating theTotal Ion Current (TIC) signal of the MS instead of the FID signal.

A typical house dust sample was used for the analysis, compris-ing frequently occurring organics of the most important compoundclasses found indoors. The response of those compounds was mea-sured with both detectors. In Fig. 7, the responses of the twodetectors were plotted in counts per GC peak. Scales were setproportional to the sum of the GC peak areas and expressed incounts (arbitrary units depending on amplifier settings), as thatwas determined by integrating the FID and TIC signals. FID counts

were lower than TIC counts, as indicated in Fig. 7. On average, oneFID count corresponded to f = 3200 TIC counts. As shown in Fig. 7,for a semi-quantitative evaluation of the results, the FID and TICmeasurements showed very good consistency.

130 A. Papadopoulos / J. of Supercritical Fluids 62 (2012) 123– 134

appin

d[

�

wn

ctGptq

b

Fig. 6. Schematic representation of the extraction, tr

The average difference � of the FID and the TIC counts for the 24etected compounds was determined using the following equation16]:

= 200n

×n∑

i=1

CTICi

− f × CFIDi

CTICi

+ f × CFIDi

(%)

here CTIC and CFID were the TIC and FID counts, respectively, while represented the number of samples.

The relative average difference � between the FID and the TICounts was found to be 10%, confirming the suitability of bothhe TIC and FID signals for semi-quantitative measurements. SinceC–MS was employed for the identification of the extracted com-ounds, it was decided to use the TIC counts for the quantitation

o deduce the association between an identified compound and itsuantity.

As the house dust extracts include a variety of compoundselonging to different compound classes, it was necessary even for

g and elution steps of the final analytical procedure.

a semi-quantitative evaluation to apply different response factors,at least for some groups of compounds. Two standard solutionswere used in order to obtain response factors for most of the com-pound classes, to which the majority of the compounds detected inthe house dust extracts belonged. The two solutions used for thispurpose were:

(a) A mixture of 16 n-alkanes in the range C7–C44, diluted in hex-ane, the composition of which is given in Appendix A.

(b) A solution in methanol of some characteristic compounds thatare normally present in the methanol eluate (two phthalates,two alcohols and two acids):• Ethanol, 2-butoxy-,• 1-Hexadecanol,

• Dodecanoic acid,• 9-Octadecenoic acid (E)-,• 1,2-Benzenedicarboxylic acid, diethyl ester,• 1,2-Benzenedicarboxylic acid, bis(2-ethylhexyl) ester.

A. Papadopoulos / J. of Supercritical Fluids 62 (2012) 123– 134 131

Table 1Semi-quantitative analytical results for the four eluted fractions of a house dust sample for the different classes of identified compounds: Fraction no. 1: 1st extractionstep, rinsing solvent methanol, Fraction no. 2: 1st extraction step, rinsing solvent hexane, Fraction no. 3: 2nd extraction step, rinsing solvent methanol, Fraction no. 4: 2ndextraction step, rinsing solvent hexane.

Identified compounds Fraction no.

Hydrocarbons 1 2 3 4

Hexadecane, 2,6,10,14-tetramethyl- b

Eicosane b

Heneicosane b

Docosane b

Tricosane b

Tetracosane b

Tetracosane, 2,6,10,15,19,23-hexamethyl- b

Pentacosane b

Hexacosane b a

Heptacosane b a

Octacosane a b

Nonacosane b

Triacontane b

Hentriacontane b

Dotriacontane b

Tritriacontane b

Tetratriacontane b

Pentatriacontane b

Hexatriacontane b

Heptatriacontane b

2,6,10,14,18,22-Tetracosahexaene, 2,6,10,15,19,23-hexamethyl-, (all-E)- (Squalene) b

Identified compounds Fraction no.

Acids 1 2 3 4

Hexanoic acid a

Hexanoic acid, 2-ethyl- a

Heptanoic acid a

Octanoic acid a

Nonanoic acid b

Decanoic acid b

Undecanoic acid a

Dodecanoic acid b a

Tridecanoic acid a a

Tetradecanoic acid a c

Pentadecanoic acid b

Hexadecanoic acid c

Heptadecanoic acid b

Octadecanoic acid c

Eicosanoic acid b

9-Hexadecenoic acid a

9-Octadecenoic acid a c

Identified compounds Fraction no.

Aliphatic alcohols 1 2 3 4

Ethanol, 2-(2-butoxyethoxy)- a

Ethanol, 2-butoxy- a

Ethanol, 2-(hexadecyloxy)- a

1-Hexanol, 2-ethyl- a

1-Dodecanol a

1-Tetradecanol a

1-Hexadecanol b

1-Heptadecanol a

1-Octadecanol b a

1-Eicosanol

Identified compounds Fraction no.

Aromatic alcohols (phenols) 1 2 3 4

Phenol, 2,6-bis(1,1-dimethylethyl)-4-methyl- a

Phenol, 4-(1,1,3,3-tetramethylbutyl)- a

Phenol, nonyl- a

2,6-Di-tert-butyl-4-ethylphenol (Ionol 2) a

Octyl phenol isomer a

2,6-Di-tertbutyl-4-methoxymethyl phenol a

Identified compounds Fraction no.

Fatty acid esters 1 2 3 4

Butanoic acid, hexyl ester a

Nonanoic acid, methyl ester a

Decanoic acid, methyl ester a

Dodecanoic acid, methyl ester a

132 A. Papadopoulos / J. of Supercritical Fluids 62 (2012) 123– 134

Table 1(continued)

Identified compounds Fraction no.

Fatty acid esters 1 2 3 4

Tridecanoic acid, methyl ester a a

Tetradecanoic acid, methyl ester a a

Pentadecanoic acid, methyl ester a a

Hexadecanoic acid, methyl ester b

Hexadecanoic acid, 1-methylethyl ester a

Hexadecanoic acid, butyl ester a

Heptadecanoic acid, methyl ester a

Octadecanoic acid, methyl ester b

Octadecanoic acid, butyl ester a a

Hexadecanoic acid, tetradecyl ester a

Hexadecanoic acid, hexadecyl ester b

Hexanedioic acid, dioctyl ester a

Hexadecanoic acid, octadecyl ester a

Octadecanoic acid, octadecyl ester a

9-Hexadecenoic acid, methyl ester a

9-Octadecenoic acid, methyl ester a

9-Hexadecenoic acid, hexadecyl ester a

9-Hexadecenoic acid, octadecyl ester, (Z)- b

9-Hexadecenoic acid, eicosyl ester, (Z)- b

Identified compounds Fraction no.

Phthalates 1 2 3 4

1,2-Benzenedicarboxylic acid, dimethyl ester a

1,2-Benzenedicarboxylic acid, diethyl ester a

1,2-Benzenedicarboxylic acid, butyl methyl ester a

1,2-Benzenedicarboxylic acid, dibutyl ester b

1,2-Benzenedicarboxylic acid, butyl 2-methylpropyl ester b

1,2-Benzenedicarboxylic acid, bis(2-methylpropyl) ester c

1,2-Benzenedicarboxylic acid, butyl octyl ester a

1,2-Benzenedicarboxylic acid, bis(2-ethylhexyl) ester c a a

1,2-Benzenedicarboxylic acid, dinonyl ester a

1,2-Benzenedicarboxylic acid, bis(3,5,5-trimethylhexyl) ester b

1,2-Benzenedicarboxylic acid, butyl phenylmethyl ester b

Identified compounds Fraction no.

Aldehydes, ketones 1 2 3 4

Octanal, 2-(phenylmethylene)- (Hexyl Cinnamic Aldehyde) a

Nonanal a

3-Nonanone b

Nonanal dimethyl acetal a

Decanal a

Hexadecanal a

Ethanone, 1-4-(1,1-dimethylethyl)-2,6-dimethyl-3,5-dinitrophenyl- (Musk ketone) a

Identified compounds Fraction no.

Various 1 2 3 4

5-cholestene-3-ol (3.beta.)- b

Cholest-5-en-3-one a

Benzene, (1-methylundecyl)- a

Benzene, (1-methyldodecyl)- a

Menthol a

Camphor a

Trisiloxane, 1,1,1,5,5,5-hexamethyl-3,3-bis[(trimethylsilyl)oxy]- a

Cyclotetrasiloxane, octamethyl- a

Cyclopentasiloxane, decamethyl- a

Cyclohexasiloxane, dodecamethyl- a

1,1,1,3,5,7,9,9,9-nonamethylpentasiloxane a

Caffeine a a

Pyridine, 3-(1-methyl-2-pyrrolidinyl)- (nicotine) a a

p,p′-DDD a

o,p′-DDT b

Lindane a

Methanone, (2-hydroxy-4-methoxyphenyl) phenyl b

Phenanthrene a

Fluoranthene a

Pyrene a

1,3-Isobenzofurandione a

Kauran-18-al, 17-(acetyloxy)-, (4.beta). a

Ergost-5-en-3-ol, (3.beta.)- a

Cyclopropanecarboxylic acid, 2,2-dimethyl-3-(2-methyl-1-propenyl)-, 2-methyl-4-oxo-3-(2-propenyl)-2-cyclopenten-1-yl ester (Allethrin) a

Propanoic acid, 2-methyl-, 1-(1,1-dimethyl ethyl)-2-methyl-1,3-propanediyl ester (TXiB) b

Ethanol, 2-butoxy-, phosphate (3:1) a

a <20 �g/g.b 20–200 �g/g.c ≥200 �g/g.

A. Papadopoulos / J. of Supercritica

242220181614121086420

700000

Pea k no

FID

cou

nts

FI D

0.000

2.250x10 9

TIC

cou

nts

TIC

Fig. 7. Comparison of TIC and FID counts for some of the most abundant peaksof the eluates of a house dust sample. The numbered peaks correspond to thefollowing substances: 1, nonanoic acid; 2, decanoic acid; 3, diethyl phthalate; 4,1-hexadecanol; 5, dodecanoic acid; 6, diisobutyl phthalate; 7, tridecanoic acid; 8,1-octadecanol; 9, tetradecanoic acid; 10, pentadecanoic acid; 11, branched hex-adecanoic acid; 12, hexadecanoic acid; 13, 9-hexadecenoic acid; 14, heptadecenoicacid; 15, octadecanoic acid; 16, 9-octadecenoic acid; 17, bis(2-ethylhexyl) phthalate;18, tetracosane; 19, pentacosane; 20, hexacosane; 21, tetracosane, 2,6,10,15,19,23-h

of

braafsti

faasvatBwwoan

tAhpbida

28

n-C32 8.14

examethyl-; 22, heptacosane; 23, octacosane; 24, nonacosane.

An analysis of these standard solutions resulted in the choicef four response factors. The response factors calculated were theollowing (area counts/�g):Response factor Area counts/�g

Hydrocarbons 2,100,000Phthalates 2,500,000Fatty acids 1,200,000Alcohols 1,550,000

The choice of response factors for the rest of the compounds wasased on their structure. The selection and the use of comparableesponse factors for the compounds not belonging to any of thebove mentioned classes was sufficient for the purpose of this work,s the four response factors did not differ by more than about aactor of two. Also, as already mentioned, the main objective of theurvey analysis was to qualitatively describe the organic content ofhe house dust, whereas the quantitative data analysis was simplyntended to provide the order of magnitude.

As a result of the procedure depicted in Fig. 6, four elutedractions were obtained. The semi-quantitative data of the GC/MSnalysis of the four eluted fractions is shown in Table 1. The sep-ration due to the different values of CO2 density was not asharp as that due to the different polarities of the rinsing sol-ents. The results yielded that only in exceptional cases compoundsppeared in both methanol and hexane elutes. For the analysis ofhe dust sample presented in Table 1 that occurred only for 1,2-enzenedicarboxylic acid, bis(2-ethylhexyl)ester. The quantity elutedith hexane was very small (less than 2%) compared to that elutedith methanol. It seemed that because of the high concentration

f the compound in the sample, traces remained in the trap evenfter the elutions with methanol. Those were finally eluted with-hexane.

The classes of compounds detected in rather high concentra-ions were fatty acids and their esters, n-alkanes, and phthalates.mong them, phthalates were of particular interest with regard touman health effects. Some have been shown to have estrogenicroperties (i.e. act as hormone disrupters) [17–19]. Associationsetween phthalate levels in house dust and allergic symptoms

n children have also been reported [20,21]. The compoundsetected in the highest concentration range were: tetradecanoiccid, hexadecanoic acid, octadecanoic acid, 9-octadecenoic acid,

l Fluids 62 (2012) 123– 134 133

1,2-benzenedicarboxylic acid, bis(2-methylpropyl) ester and 1,2-benzenedicarboxylic acid, bis(2-ethylhexyl) ester.

5. Conclusions

The method introduced in this work, based on SFE, was appliedfor the first time on house dust samples for the reliable detectionof a broad range of organic compounds of low or non-volatility,producing successfully qualitative and semi-quantitative charac-terization.

The most important variables considered for the SFE of housedust were the supercritical fluid (CO2) pressure and composition,the sorbent material and eluting solvents. Those were optimizedto obtain higher efficiencies, recoveries and pre-separation of theextracted compounds, allowing for an accurate and simple gaschromatographic analysis. As a result, the combination of twoextraction steps (the first with CO2 of 0.5 g/ml density and thesecond with CO2 of 0.9 g/ml density with the addition of 5% ofmethanol) and two rinses (the first with methanol and the secondn-hexane) of the extracts from an ODS collection trap was finallyselected for efficient analysis.

As the focus of the work was the comparative survey oflow/non volatile organic compounds in indoor dust along with therather high number of the identified compounds (over 120 dif-ferent compounds in the sample analyzed), the semi-quantitativeanalysis approach was found to be most suitable. Three con-centration ranges were selected for the classification of thecompounds (≥200 �g/g dust, 20–200 �g/g dust, and <20 �g/g dust).The method reapplied in additional dust samples collected fromother houses verified that the particular sample used for themethod development was typical and representative of a domesticindoor environment. The particular house dust extract was foundto include a variety of organic compounds belonging to differ-ent compound classes of importance to human health. The classesdetected in the higher concentrations ranges were fatty acids andtheir esters, n-alkanes, and phthalates. It is safe to conclude thatthe method presented here could be applied consistently and effi-ciently in detecting low- or non-volatile organic compounds aswell as obtaining their concentration ranges in dust samples fromdomestic environments.

Acknowledgements

The author would like to thank Dr. Knoppel and Professor M.I.Karayannis for their scientific advice and full support. This workwas partly carried out in the experimental laboratories of the Envi-ronment Institute of JRC, E.U. in Ispra, Italy.

Appendix A. Quantitative calibration Mix D2887 (Supelco),diluted in n-hexane

Compound Concentration (�g/ml)

n-C7 48.87n-C8 65.16n-C9 65.16n-C10 97.74n-C11 97.74n-C12 97.74n-C14 97.74n-C16 81.45n-C18 40.72n-C20 16.29n-C24 16.29n-C 8.14

n-C36 8.14n-C40 8.14n-C44 8.14

1 critica

R

[

[

[

[

[

[

[

[

[

[

[

34 A. Papadopoulos / J. of Super

eferences

[1] C. Garcia-Jares, J. Regueiro, R. Barro, T. Dagnac, M. Llompart, Analysis of indus-trial contaminants in indoor air. Part 2. Emergent contaminants and pesticides,J. Chromatography A 1216 (2009) 567–597.

[2] R.A. Rudel, L.J. Perovich, Endocrine disrupting chemicals in indoor and outdoorair, Atmospheric Environment 43 (2009) 170–181.

[3] R. Barro, J. Regueiro, M. Llompart, C. Garcia-Jares, Analysis of industrial contam-inants in indoor air. Part 1. Volatile organic compounds, carbonyl compounds,polycyclic aromatic hydrocarbons and polychlorinated biphenyls, J. Chro-matography A 1216 (2009) 540–566.

[4] H. Fromme, T. Lahrz, M. Piloty, H. Gebhardt, A. Oddoy, H. Ruden, Polycyclic aro-matic hydrocarbons inside and outside of apartments in an urban area, Scienceof the Total Environment 326 (2004) 143–149.

[5] S.E. Carozza, B. Li, Q. Wang, S. Horel, S. Cooper, Agricultural pesticides and riskof childhood cancers, International J. Hygiene and Environmental Health 212(2009) 186–195.

[6] M.-J. Lopez-Espinosa, E. Lopez-Navarrete, A. Rivas, M.F. Fernandez, M.s.Nogueras, C. Campoy, F. Olea-Serrano, P. Lardelli, N. Olea, Organochlorine pes-ticide exposure in children living in southern Spain, Environmental Research106 (2008) 1–6.

[7] Z. Chen, L. Robison, R. Giller, M. Krailo, M. Davis, S. Davies, X.-O. Shu, Environ-mental exposure to residential pesticides, chemicals, dusts, fumes, and metals,and risk of childhood germ cell tumours, International J. Hygiene and Environ-mental Health 209 (2006) 31–40.

[8] S.L. Dixon, J.W. Wilson, C.S. Clark, W.A. Galke, P.A. Succop, M. Chen, Effective-ness of lead-hazard control interventions on dust lead loadings: findings fromthe evaluation of the HUD Lead-based Paint Hazard Control Grant Program,Environmental Research 98 (2005) 303–314.

[9] S. Engelhart, T. Bieber, M. Exner, House dust mite allergen levels in German day-

care centers, International J. Hygiene and Environmental Health 205 (2002)453–457.

10] M. Oehme, H. Knöppel, Analysis of low volatile (>C15) and particle bound indoorpollutants: assessment of a sensitive method and first results, in: B. Seifert, et al.(Eds.), Indoor Air ‘87, vol. 1, Berlin, 1987, p. 210.

[

l Fluids 62 (2012) 123– 134

11] J.W. Roberts, W.T. Budd, M.G. Ruby, D.E. Camann, R.C. Fortmann, R.G. Lewis,L.A. Wallace, T.M. Spittler, Human exposure to pollutants in the floor dust ofhomes and offices, J. Exposure Analysis and Epidemiology 1 (1992) 127–146.

12] K. Hartonen, S. Bøwadt, S.B. Hawthorne, M.-L. Riekkola, Supercritical fluidextraction with solid-phase trapping of chlorinated and brominated pollutantsfrom sediment samples, J. Chromatography A 774 (1–2) (1997) 229–242.

13] S.J. Lehotay, A.V. García, Evaluation of different solid-phase traps for automatedcollection and clean-up in the analysis of multiple pesticides in fruits and veg-etables after supercritical fluid extraction, J. Chromatography A 765 (1) (1997)69–84.

14] I.W. Kim, H.S. Lee, Y.K. Lee, M.D. Jang, J.H. Park, Selectivity of amino-, cyano- anddiol-bonded silica in reversed-phase liquid chromatography, J. Chromatogra-phy A 915 (2001) 35–42.

15] P. Persson, Z. Barisic, A. Cohen, L. Thörneby, L. Gorton, Countercurrent supercrit-ical fluid extraction of phenolic compounds from aqueous matrices, AnalyticaChimica Acta 460 (2002) 1–12.

16] M.I. Karayiannis, Treatment, evaluation and presentation of analytical data,University of Ioannina, Editors Book, 1992 (in Greek).

17] T.M. Crisp, E.D. Dlegg, R.L. Cooper, W.P. Wood, D.G. Anderson, K.P. Baetcke, J.L.Hoffmann, M.S. Morrow, D.J. Rodier, J.E. Schaeffer, L.W. Touart, M.G. Zeeman,Y.M. Patel, Environmental endocrine disruption: an effect assessment and anal-ysis, Environmental Health Perspectives 106 (Suppl. 1) (1998) 11–56.

18] NRC National Research Council, Hormonally Active Agents in the Environment,National Academy Press, Washington, DC, 1999.

19] G. Rasier, J. Toppari, A.-S. Parent, J.-P. Bourguignon, Female sexual matura-tion and reproduction after prepubertal exposure to estrogens and endocrinedisrupting chemicals: a review of rodent and human data, Molecular CellEndocrinology 254–255 (2006) 187–201.

20] C.G. Bornehag, J. Sundell, C.J. Weschler, T. Sigsgaard, B. Lundgren, M. Hasselgren,L. Hägerhed-Engman, The association between asthma and allergic symptoms

in children and phthalates in house dust: a nested case–control study, Envi-ronmental Health Perspectives 112 (14) (2004) 1393–1397.

21] B. Kolarik, K. Naydenov, M. Larsson, C.G. Bornehag, J. Sundell, The associationbetween phthalates in dust and allergic diseases among Bulgarian children,Environmental Health Perspectives 116 (1) (2008) 98–103.