〈特別研究課題〉

機能性高分子・繊維充填型ニードルを応用した
精密室内環境測定助 成 研 究 者

豊橋技術科学大学

神野清勝

機能性高分子･繊維充填型ニードルを応用した精密室内環境測定
神野 清勝（豊橋技術科学大学第5工学系）

Novel Needle-Type Sample Preparation Device Packed with
Polymeric and Fibrous Materials for the Analysis of Various
Volatile Compounds in In-Room Environments
Kiyokatsu Jinno(School of Materials Science, Toyohashi University of Technology)

Chapter 1
Analysis of Volatile Organic Solvents by
Polymer-Packed Sample Preparation Device

1.1 Abstract
A novel in-needle extraction device has been developed for the preconcentration of gaseous organic
compounds prior to the determination in gas chromatography (GC). As the extraction medium, acopolymer of methacrylic acid and ethylene glycol dimethacrylate was synthesized. Based on the
results in the preliminary experiments, the desorption conditions such as desorption temperature andtime have been optimized along with the evaluation of the extraction efficiency. The storage
performance of the needle extraction device was also studied. The results clearly demonstrated theexcellent extraction performance for typical organic solvents and also suggested the future possibility
such as in the applications for the analysis of working environments.

− 1 −1.2 Introduction
Miniaturization of sample preparation process has been recently focused, especially in separation
science and the related research fields, because the down-sizing could be one of the most promisingsolution to realize the recent requirements such as improved selectivity and sensitivity, and also lowcost and environmentally-friendly features [1-4]. On-line coupling of the novel miniaturized sample
preparation methods to the corresponding microscale separation system was also studied in order toensure the effective hyphenation between these techniques [3]. As a miniaturized sample preparation
method in liquid chromatography (LC), in-tube solid-phase microextraction (in-tube SPME) was
developed, where a section of open-tubular column in gas chromatography (GC) was introduced as theextraction medium [5-10]. Several other miniaturized sample preparation processes for the subsequent
LC separation have been proposed such as wire-in-tube SPME [11], fiber-in-tube solid-phase extraction(fiber-in-tube SPE) [12-16] and liquid-phase microextraction (LPME) [17-19], and the successful on-line
coupling of these sample preparation and separation techniques has been demonstrated assummarized in some recent review articles [3,20,21].
For the GC analysis of volatile organic compounds, solvent-less microscale sample preparation
methods have been developed [22-25]. SPME is one of the most successful examples having attractive
features over traditional sample preparation methods with a large amount of organic solvents [22,23],
however, it requires a careful handling during the extraction and desorption processes, where theexposed fused-silica rod coated with polymeric materials is fragile. Needle-type microextraction device
is alternative sample preparation device [26-34]. Recent studies showed that the needle-type microscale
sample preparation possesses the most of the advantageous features of the SPME, but without theabove disadvantage, for the preconcentration of volatile organic compounds prior to the GC separation.
Compared to the SPME, a wide variety of the extraction media could be used and easy to handle
during the extraction and desorption processes that will be an attractive feature for automation and online coupling to typical GC instruments, although a continuous flow of the gaseous sample through theextraction needle should be supplied during the sampling.
In this work, a novel in-needle sample preparation device [34] was introduced for the GC analysis ofseveral organic solvents commonly used in typical chemical laboratory. Because of a wider selectivity
for both polar and non-polar analytes, a copolymer of methacrylic acid and ethylene glycol
dimethacrylate, typically employed as the material for molecularly imprinted polymers (MIPs) [35,36],
was synthesized to prepare the extraction medium instead of other polymeric materials such aspolystyrene-divinylbenzene (PS-DVB) and polydimethylsiloxane (PDMS). A relatively easier synthetic
procedure is another advantageous feature of the present method. The polymeric beads were packed
into a section of a specially prepared needle. During the sampling of gaseous sample mixtures avacuum sampling device was attached to the needle extractor, while a desired volume of the samples
could be passed through the needle. The extraction needle was then transferred to the heated GC
injection port for the thermal desorption, and the simultaneous injection to the GC column was made.
The extraction performance of the polymer-packed needle extractor has been evaluated. Taking into

− 2 −account the applications including the working environment analysis, the storage power of the needle
device for the extracted analytes under the room temperature was also studied along with theconsideration to the repeatability for run-to-run and the reproducibility for needle-to-needle.

1.3 Experimental
Reagents
All reagents, solvents and sample solutes were of analytical grade and purchased either from Kishida
Chemical, Osaka, Japan or Tokyo Kasei Kogyo, Tokyo, Japan unless otherwise specified. Water was
purified by a Milli-Q Water Purification System (Millipore, Tokyo, Japan).

Preparation of Standard Samples
Standard gas samples were prepared with two-step or three-step dilution of each organic solvent.
First an appropriate amount of the organic solvent was injected into a vacuum glass vessel of 1.0 L
volume to prepare the corresponding gas sample of 10 µg/mL, where N2 gas was used for the dilution
after vaporizing the organic solvent in the vessel. Next, 10 mL of the above gas sample was injected toa gas sampling bag (Tedlar Bag; GL Sciences, Tokyo Japan) of 1.0 L volume followed by the dilution
process with N2 (990 mL) therein, resulting the gas sample of 100 ng/mL. In the case of the standard
sample having lower concentration, a similar process was carried out once more. The standard
samples containing two or more organic solvents were also prepared in a similar manner.

Synthesis of Polymer-Based Extraction Medium
First, 15 g of poly(vinyl alcohol) having a degree of polymerization of 500 were dissolved into 500 mLof water at 50℃, and then sodium chloride (15 g) was also dissolved. To the solution, the mixture ofmethacrylic acid (2.58 g; 0.03 mol), ethylene glycol dimethacrylate (29.7 g; 0.15 mol), di-n-butyl
phthalate (27.44 g) and azobisisobutyronitrile (0.52 g) was added drop wise over about 3 min, while thesolution was kept at 50℃. Next, the solution was subject to the temperature-programmed heating at
the rate of 1.0℃/min to 85℃. The polymerization reaction was initiated at about 80 ℃. In order toensure the successful polymerization, the temperature of the reaction mixture was maintained at 85 ℃
for 1 h with vigorous stirring. After the polymerization reaction was completed, the resulting beads ofthe copolymer was sequentially washed with hot water, acetone, water and acetone (for five timeseach), and let dried at the room temperature.
The polymer-beads were sieved to obtain the spherical beads having the diameter between 150 and
180 µm. The specific surface area (SSA) measured by the nitrogen adsorption method was 390 m2/g.
The beads were packed into the specially designed needle (85 mm x 0.5 mm I.D., 0.7 mm O.D.) as
illustrated in Figure 1, where a section of about 30 mm length was packed with the copolymer beads.
To place the beads in the appropriate position in the needle, a small amount of a heat-resistant polymer
fiber [37,38] was also packed at the both end of the packed section. The typical amount of beads packed
in the needle is about 2 mg.

− 3 −Figure 1. Illustration of the in-needle sample preparation device

Extraction Procedure
The needle was attached to a commercially-available vacuum sampling device (Komyo Rikagaku
Kogyo, Tokyo, Japan). For the extraction process the needle was inserted into the gas sampling bag
containing the standard sample, while the sample gas was introduced to the vacuum sampling device
via the extraction needle. Typical sampling volume was 50 mL, and it takes about 6 min to complete
the sampling with the vacuum sampling device. After the extraction, the needle was attached to a
injection syringe (1.0 mL) containing N2 gas, and inserted to the injection port of the GC. The
desorption and injection were made simultaneously by injecting the N2 through the needle at theheated injection port, where the needle was heated for several seconds before the N2 injection. The
desorption temperature, the desorption time and the volume of the N2 has been optimized as described
below.

GC Measurements
An Agilent 6890N gas chromatograph (Yokogawa Analytical Systems, Musashino, Japan) with asplit/splitless injection port and a flame ionization detector (FID) was used for all the GC
measurements. All the injections were made by split mode with the ratio of 25:1. As the carrier gas, N2
was used, and the carrier gas and air were supplied from the respective gas cylinders through the
cartridge packed with molecular sieve. For the GC separation, a fused-silica column having apoly(ethylene glycol) coating, HR-20M (30 m x 0.25 mm I.D., d f = 0.5 µm; Shinwa Chemical, Kyoto,
Japan) was employed with an appropriate preconditioning before the use. Typical injection anddetection temperatures were 200 and 220 ℃, respectively. The other separation conditions such as
carrier gas flowrate, column head pressure, and temperature programs were determined by the resultsof preliminary experiments for each samples. All GC measurements were done at least three times,
and the relative standard deviations (RSDs) for the retention times were less than 1.0%. The datacollection was made with Borwin Chromatography Data Handling Software (Jasco, Tokyo, Japan)
running on a personal computer.

1.4 Results and Discussion
Optimization of Desorption Conditions
For the optimization of desorption conditions, D (%) has been defined as the following equation:− 4 −Peak area in the 1st desorption
D (%) = ───────────────────── × 100
Total peak area in the 1st and 2nd desorption
where the D (%) was calculated based on the ratio of the peak area obtained in the 1st desorption to
the total peak area obtained as the sum of the peak area in the 1st and 2nd desorption. The definitionof the above equation was derived from the results in the preliminary experiments, in which thedesorption of more than 99.99% of the analytes was made in the first two desorption for the sequential
desorption process for more than three times. That means, the quantitative desorption could be
evaluated based on the above equation.
The effect of desorption temperature was studied by setting the temperature of the GC injection port
between 150 and 230℃. For the optimization of desorption conditions, the extraction conditions weretentatively determined based on the preliminary experiments, however, the validity of those conditions
have been confirmed as described below. As found in Figure 2, the desorption for these two typicalorganic compounds was almost quantitatively made at about 180 ℃, however, at the same time, apartial decomposition of the copolymer at the temperature of higher than 220 ℃ was also found,although more systematic investigations should be needed to precisely evaluate the thermal stability of
the copolymer by the thermogravimetric analysis (TGA). In addition, the extraction power wasmaintained in the repeated use, typically more than 100 times with the desorption temperature at lower
than 210 ℃. This is quite consistent with the above observation for the partial decomposition of thecopolymer started at about 220℃. Therefore, the desorption temperature of 200 ℃ was used in thefollowing experiments.

Figure 2. Optimization of the desorption temperature. Extraction conditions: desorption time, 10 sec; injection volume of N2,
0.5 mL. Chromatographic conditions: column head pressure, 50 kPa; column temperature 150 ℃ (isothermal).
Other conditions are in the text.

− 5 −The optimization of the desorption time, that is the preheating time of the needle at the injection port
before injecting the desorption gas, was carried out as shown in Figure 3. The results showed thatnearly perfect desorption was obtained with the desorption time of 7 s. However, a slight peakbroadening, especially for the analytes eluted earlier, was found in the preliminary experiments if thedesorption time was more than 10 s. A longer preheating time is also not desirable in terms of theanalysis time, therefore, the desorption time of 10 s was chosen as the optimum value and used in all
the experiments below.
Similar optimization for the volume of the desorption gas was conducted. The results summarized in
Figure 4, indicating that more than 0.4 mL of the N2 gas is necessary for the complete desorption of
the analytes. Even a larger volume could be injected to conventional packed column, the volume of 0.5
mL was determined as the optimum volume for split injection to the typical open-tubular capillarycolumn used in this work.

Figure 3. Effect of the desorption time. Conditions:desorption temperature, 200 ℃; injection volumeof N2, 0.5 mL. Other conditions are the same as in
Figure 2.

Figure 4. Evaluation of the optimum N 2 volume for thedesorption. Desorption temperature and time,
200 ℃ and 10 sec, respectively. Other conditions
are the same as in Figure 2.

Evaluation of Preconcentration Performance
Taking into account the concentration of the standard gas sample of 100 ng/mL each and thesampling volume of 50 mL, the total amount of these organic compounds should be 5 μg each, if
assuming the complete extraction. Table 1 summarize the linear calibration ranges and thecorresponding correlation factors for each sample probes. The data clearly demonstrated the practicalextraction power for the quantification of typical gaseous organic compounds in the laboratory,
although the extraction for more complex sample mixtures should be further studied.
On successful optimization of the desorption conditions, the extraction efficiency was evaluated. A
standard gas sample containing 5 ng/mL each of four typical organic solvents, hexane, acetone, ethyl
acetate and toluene was prepared, and 50 mL of the sample was extracted with the needle extraction− 6 −Table 1. Linear range of the calibration curve and the correlation coefficients.

device, while another sample containing 500 ng/mL each was also prepared for the direct injection of
0.5 mL volume. Figure 5 shows the comparison of the needle extraction with the direct injection, andthe obtained peak area data were summarized in Table 2. Compared to the direct injection of 0.5 mL
sample, the extracted sample generates relatively sharp peak shape, suggesting the extraction wasmade at short section of the extraction medium and desorbed quickly during the desorption gas
injection of even the same volume. The quantitative extraction by the needle device could be
confirmed in Table 2, because the total amount of each analyte is the same in these two standard
samples.
Reproducible and repeatable extraction could be one of the most important requirements as an
extraction technique, especially in the case of multiple and multipoint sampling for environmental
analysis. In Table 3, the RSDs for run-to-run (n=5) and needle-to-needle (n=5) measurements weretabulated. Although the RSDs for needle-to-needle were somewhat larger than that of run-to-run, as
expected, these data demonstrated that the needle extraction will offer a good repeatability andreproducibility.

Figure 5. Chromatograms with (A) and without (B) the sample preconcentration by the needle extraction device. Column
temperature was programmed from 80 ℃ to 160 ℃ at the rate of 10 ℃/min. Other conditions are the same as in
Table 1. Peaks: (a) hexane; (b) acetone; (c) ethyl acetate; and (d) toluene.

− 7 −Table 2. Comparison of the peak area obtained with the needle extraction and the direct injection.

Table 3. Relative standard deviations (RSDs) of the peak area for the run-to-run and needle-to-needle measurements.

Table 4. Storage performance of the needle extraction device for various organic solvents over 7 days at room temperature.

Storage Performance of the Needle Extractor
As a gas sampling device, the storage performance will be an advantageous feature, especially forthe multipoint sampling at the same time. To evaluate the storage performance of the needle
extraction device, the needle was stored up to 7 days at the room temperature, with the PTFE caps at
both ends of the needle, after the sampling. The results are summarized in Table 4, where therecovery (%) was calculated on the basis of the immediate quantification by the needle extraction. The
excellent storage power of the needle extraction device was shown. The stability of aromatic solutes
for the long storage time, more than 3 days, might be improved further by changing the chemical
structure of the copolymer.

− 8 −1.5 Conclusions
Miniaturized sample preparation with in-needle extraction device has been successfully developed
for the sample preparation of volatile organic solvents. The specially designed needle was packed withporous beads of the polymeric material that showed the excellent performance for the extraction and asuitable thermal stability for typical analysis in GC. The extracted analytes were quantitatively
desorbed by simply passing N2 at the heated injection port in GC. The extracted samples could bedetermined even after the storage at the room temperature for several days.
More extensive work is currently underway in our laboratory including, the coupling of the needle
extraction device to the polymer-coated fiber-packed capillary columns with a higher sample loading
capacity, the design and synthesis of the novel polymeric extraction medium, and also the applicationsof the in-needle extraction technique to the in-room environmental analysis.

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− 9 −

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Chapter 2
Analysis of Volatile Aldehydes with Simultaneous Derivatization/Preconcentration
by Fiber-Packed Sample Preparation Device

2.1 Abstract
Novel in-needle sample preparation device has been developed for the determination of volatile
aldehydes in gaseous samples. The needle device is designed for the gas chromatographic (GC)
analysis of aldehydes and ketones commonly found in typical in-house environments. In order toprepare the extraction device, a bundle of the polymer-coated filaments was longitudinally packed intoa specially-designed needle. Introducing the derivatization reaction with 2,4-dinitrophenylhydrazine(NDPH) in the needle, the aldehydes and ketones were derivatized to be the corresponding
hydrazones and simultaneously extracted in the extraction needle. The reproducible preparation of
the extraction needle was established along with the repeatable derivatization/extraction that ensure
the successful determination of aldehydes. The storage performance of the extraction needle was also
evaluated at the room temperature for three days. The results demonstrated the successful− 10 −

applications of the fiber-packed extraction device for the sample preparation of gaseous sample ofaldehydes, and the future possibility of the extraction device for the analysis of the in-houseenvironments.

2.2 Introduction
Miniaturized sample preparation techniques have been increasingly studied in the research field ofseparation science due to the promising possibility to meet the recent requirements such as enhanced
sensitivity and selectivity, and more economical and ecological features [1-3]. The effective hyphenationof the miniaturized sample preparation to microscale separation methods was also investigated,allowing the successful on-line coupling of these techniques without disadvantages that typically foundin an off-line multistep process for the analysis of complex sample mixtures [3]. For the liquid-phaseseparation methods such as liquid chromatography (LC) and capillary electrophoresis (CE), various
types of novel sample preparation techniques have been reported, where most of the publications weremainly focused on the increased sensitivity and selectivity of the target analytes with a speciallydesigned concentration process [4-10]. Downsizing the sample preparation it could make possible toobtain the enhanced mass sensitivity and reduce the sample size, although the suitable optimization of
the hyphenated system should be considered.
As the sample preparation designed for the analysis of volatile compounds in gas chromatography(GC), solid-phase microextraction (SPME) [11,12] is one of the successful approaches with several
attractive features over traditional sample preparation techniques that require a significant amount oforganic solvent in the procedure. A wide variety of the SPME applications have been developed,
however, conventional SPME requires a careful handling during the extraction and desorption
processes, because the exposed fused-silica rod with polymeric coating is somewhat fragile.
Alternative sample preparation techniques were developed with a needle-shaped extraction device [13-19].
It has been shown from the recent studies that the needle-type microscale sample preparation has themost of the advantages of the conventional SPME, but without the above disadvantage for thepreconcentration of volatile organic compounds prior to the analysis in GC. For the needle-type
extraction, a continuous flow of the gaseous sample through the extraction needle should be supplied
during the sampling process, however, a wide variety of the extraction media can be employed andeasy to handle during the extraction and desorption processes, which must be additional attractive
features for the automation and on-line coupling to typical GC instruments.
Introducing the synthetic fibers as extraction medium, novel miniaturized sample preparation has
been developed, where several hundreds of the polymeric filaments were longitudinally packed into a
short capillary to prepare the extraction cartridge [20-26]. The method, so-called fiber-in-tube solid-phaseextraction (FIT-SPE), was successfully applied to the sample preparation of complex sample mixtures,
especially in LC [20-25]. Using the FIT-SPE technique, a trace amount of analytes could be extracted onto
the surface of the fine filaments in the extraction capillary by simply passing the aqueous sample
solution into the extraction tube. The extracted analytes are desorbed by pumping a small amount of− 11 −

solvents in a similar manner and are simultaneously transferred to the injection loop of LC system forthe subsequent chromatographic separation. Several advantageous features can be found with the FIT
format such as: an increased surface area of the extraction medium and a reduced pressure drop
through the extraction capillary.
On the basis of the above successful applications of synthetic fine fibrous materials as the medium
for the sample preparation in liquid phase separations, a novel in-needle sample preparation device wasdeveloped in this work, which is designed for the GC analysis of aldehydes and ketones commonly
found in typical in-house environments. Simultaneous derivatization with 2,4-dinitrophenylhydrazine(DNPH) was made during the sampling process of the gaseous sample, and the derivatized analytes
were desorbed by passing a small amount of organic solvent through the extraction needle in theheated GC injection port. The basic extraction performance of the fiber-packed needle extractor has
been evaluated along with the optimization of several experimental parameters on the derivatization,
extraction and desorption. Taking into account the applications including the in-house environment
analysis, the storage power of the needle device for the extracted analytes under the room temperature
was also studied.

2.3 Experimental
Reagents
All reagents, solvents and sample solutes were of analytical grade and purchased either from Wako
Pure Chemical Industries, Osaka, Japan or Tokyo Kasei Kogyo, Tokyo, Japan unless otherwise
specified. Water was purified by a Milli-Q Water Purification System (Millipore, Tokyo, Japan).

Preparation of Standard Samples
Standard gas samples were typically prepared with two-step or three-step dilution of each sample
solute. First an appropriate amount of the solute was injected into a vacuum glass vessel of 1.0 L
volume to prepare the corresponding gas sample of about 2.0-3.0 mg/L, where N2 gas was used for the
dilution after vaporizing the organic solvent in the vessel. Next, 10 mL of the above gas sample wasinjected to a gas sampling bag (Tedlar Bag; GL Sciences) of 1.0 L volume followed by the dilution
process with N2 (0.99 L) therein, resulting the gas sample concentration of about 20-30 µg/L.
In the case of the standard sample having lower concentration, a similar process was carried out
once more. The standard samples containing two or more samples were also prepared in a similarmanner. For the preparation of formaldehyde gas sample, a home-made vaporizer was used, in which
solid paraformaldehyde was vaporized to generate the gaseous standard sample followed by a similar
multi-step dilution process as described above.

Polymer Coating onto the Filaments
Prior to the packing process into the needle-shaped device, the polymer-coated filaments have been
prepared as the same procedure as previously described [27-32], where the coating treatment was made in− 12 −

a conventional fused-silica capillary of 1 m length packed with a bundle of the filaments. A bundle offilaments (166± 2 filaments) was longitudinally packed into the fused-silica capillary of 0.32 mm i.d.
To ensure the reproducible preparation of fiber-packed capillary, the total number of packed-filaments
was precisely counted before and after the packing process. As the coating material for the
preparation of polymer-coated filaments, HR-1, 100%-methyl-polysiloxane (Shinwa Chemical Industries,
Kyoto, Japan) was employed.
First, a fiber-packed capillary was connected to the pressure-proof vessel containing 10 mL ofacetone and washed with the solvent pumped by N2 gas at the pressure of 500 kPa. After the same
volumes of the following solvents; water, acetone and chloroform, were pumped in the similar manner,
the capillary was allowed to dry at room temperature for about 2 h using N2 gas flow. Second, thecapillary was subject to heating in a GC oven with the flow of N 2 gas. The temperature wasprogrammed from room temperature to 300 ℃ at 2 ℃/min and then held for about 10 h. Next, thesolution of the coating material (typically 3%) in n-hexane containing a cross-linking reagent (0.8% to
the polymer), benzoyl peroxide, was pumped through the packed capillary. After the total volume ofthe polymer solution (0.5 mL) was pumped, the N2 flow was maintained for more than 5 h. Then, thecolumn was installed in the GC oven again and the programmed heating was carried out as follows:from 40 ℃ to 300℃ at 0.5℃/min and then hold for more than 48 h to ensure the complete reaction.
The successful polymer-coating treatments were confirmed by the separation of a standard sample
containing three n-alkanes, n-dodecane, n-tetradecane and n-hexadecane on the polymer-coated fiberpacked capillary as a GC column [28], and the relative standard deviations (RSDs) for the retention
factors were less than 2.0% on three capillaries separately prepared with the same coating, where theaverage values of the retention factors for three consecutive runs on each capillary were used for the
calculation. The RSDs for multiple injection onto the same capillary were less than 1.5% (n=3) for all
the capillaries studied.

Figure 1. Miniaturized sample preparation device prepared with polymer-coated fibrous material.

Preparation of the Extraction Needle
For the preparation of the extraction needle, a bundle of the polymer-coated filaments was taken out
from the capillary, and packed into the specially-designed needle [19] (85 mm x 0.5 mm i.d., 0.7 mm o.d.)
as illustrated in Figure 1, where a section of about 20 mm length was packed with the filaments, andone end of the packed section was positioned just before the side hole of the needle. The number of− 13 −

filaments packed was 830, and the corresponding RSD (n=5) was less than 1.5%.
In order to ensure the parallel alignment of all the polymer-coated filaments in the needle, thepacking process (Figure 2) was carried out [24,32]: (1) insert an appropriate length of poly(vinylidene
fluoride) (PVF) fishing line (25 µm o.d.) as the first guide fiber (line (a) in Figure 2) into the needle,
while the guide fiber should have an extra length to form a loop at the outside of the needle; and (2)then the second PVF guide fiber (line (b) in Figure 2) is inserted into the loop of the first guide fiber;(3-4) pull the first guide fiber from the other end of the needle, resulting another loop of the second
guide fiber; (5) the bundle of the filaments (40 mm length for 20 mm packed section) to be packed isinserted into the loop of the second guide fiber, where the front-end of the bundle should beappropriately bended to make sure the smooth introduction; (6) pull the second guide fiber from theside hole of the needle with careful attention to produce the uniform introduction of the bundle; andfinally (7) carefully pull out the second guide fiber, followed by the attachment of the syringe
connector to the resulting polymer-coated fiber-packed needle as depicted in Figure 1.

Figure 2. Packing procedure of the polymer-coated filaments into the needle-type extraction device. Two lines indicated as (a)and (b) are the guide fibers for the packing process.

GC-MS Measurements
An Agilent 6890N gas chromatograph (Yokogawa Analytical Systems, Musashino, Japan) with asplit/splitless injection port and a HP 5972A mass selective detector (MSD) was used for all the GC
measurements. All the injections were made by split mode with the typical ratio of 5:1. As the carriergas, helium was used. For the GC separation, a fused-silica column having a PDMS coating, DB-1 (15m x 0.25 mm i.d., d f = 0.25 µm; J&W Scientific, Folsom, CA, USA) was employed with an appropriate
preconditioning before the use. The mass spectrometer was operated either total ion monitoring mode

− 14 −

(TIM) or selected ion monitoring mode (SIM) with electron impact ionization. The ionization voltage
was 70eV. The other separation conditions such as carrier gas flowrate, column head pressure, andtemperature programs were determined by the results of preliminary experiments for each samples.
All GC measurements were done at least three times, and the RSDs for the retention times were lessthan 1.0%. The data collection was made with Borwin Chromatography Data Handling Software (Jasco,Tokyo, Japan) running on a personal computer.

2.4 Results and Discussion
Simultaneous Derivatization and Extraction of Aldehydes
For the derivatization of aldehydes, the most well-known specific reaction of carbonyl compoundswith DNPH resulting the corresponding hydrazones [33-41] was used. Figure 3 shows the reaction
scheme of the DNPH derivatization, where aldehydes and ketones quantitatively react with DNPH toform the derivatives. Except for formaldehydes, it has been demonstrated that the formation of E- andZ-stereoisomers could be expected for the aldehydes as well as asymmetric ketones, although theisomerization was also reported in several specific conditions [36-41].

Figure 3. Scheme of the derivatization reaction for aldehydes and ketones with DNPH.

On the basis of the preliminary experiments for the derivatization in the needle extraction device, an
acetonitrile solution (0.1 mg/mL) of DNPH hydrochloric acid salt was employed as the derivatization
reagent as found in Figure 4. Prior to the sample gas introduction, the DNPH solution was pumped
through the polymer-coated fiber-packed needle at about 16 µL/min for 4 min, and then the remaining
solution was vented by passing N2 of 1 mL. The needle was attached to a commercially-available
vacuum sampling device [19] (Komyo Rikagaku Kogyo, Tokyo, Japan). For the extraction process, theneedle was inserted into the gas sampling bag containing the standard sample, while the sample gas
was introduced to the vacuum sampling device via the extraction needle with the derivatization reagent
therein. Typical sampling volume was 50 mL, and it takes about 8 min to complete the sampling withthe vacuum sampling device, where the RSD (n=5) for the sampling time was less than 1.0% on thesame needle, although the RSD for needle-to-needle was somewhat larger, about 3.3% regarding fiveneedles separately prepared. The completion of the gas sampling for each run was confirmed by theindicator equipped in the vacuum sampling device.

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Figure 4. Preconditioning of the extraction device, and subsequent sampling of gaseous samples and the desorption/injectionin the GC injector.

Optimization of the Basic Desorption Conditions
After the derivatization/extraction process, the needle was attached to a injection syringe containing
pure acetonitrile and N2 gas, and inserted to the injection port of the GC as illustrated in Figure 4. The
desorption and injection were made simultaneously by injecting acetonitrile and N2 through the needle
at the heated injection port. The injection was made immediately after the insertion of the needle tothe injector, since it has been confirmed that no preheating time was necessary for the effective
desorption under the optimized conditions for the desorption temperature and the volume of thesolvent injected as described below.
Taking into account the solubility of both DNPH hydrochloric acid salt and the resulting hydrazones
formed by the derivatization reaction with aldehydes, and also the required chromatographic
separation from the derivatives and unreacted DNPH, acetonitrile was chosen as the desorption
solvent, although a more suitable solvent could be found as an alternative. In the preliminary
experiments, it was found that the desorption was significantly insufficient without the desorption
solvent, that means the desorption could be made with a flow of heated solvent, but not successfullycompleted only with N2 gas flow through the heated needle.
The optimum volume of the desorption solvent was studied with the DNPH derivative of
propionaldehyde (PA) as a representative of the volatile aldehydes, where 50 mL of the standard gas
sample containing 23.7 µg/L (corresponds 10 v/v ppm at 25 ℃) was extracted with the needle
extraction device. Changing the volume of the desorption solvent, acetonitrile, the resulting− 16 −

chromatograms were monitored with the SIM mode set at m/z 238. The peak area for the PA-DNPH
derivative was calculated as the sum of the peak areas for E- and Z-isomers. As shown in Figure 5, an
optimum volume (about 30 µL) of the desorption solvent could be found. The peak area was decreased
with insufficient volume of the solvent. At the same time, however, the desorption efficiency was also
decreased with the solvent volume of more than 40 µL, possibly resulted by an instantaneoustemperature drop of the injector due to the vaporization of unusually large volume of acetonitrile in theinjector. Similar trend was observed for acetone, an representative of volatile ketones, as plotted in
Figure 5. The above interpretation was also supported by the fact that a certain amount of the carryover was found with the needle desorbed under those undesirable desorption conditions.

Figure 5. Optimization of the volume of desorption solvent.
Extraction conditions: desorption temperature,
170 ℃; sample gas concentration, 23.7 µg/L for
both PA and acetone (corresponding about 10 v/v
ppm). GC conditions: temperature program,
150 ℃ (1.0 min) to 220 ℃ at 10 ℃/min; column
head pressure, 80 kPa. Other conditions are in
the text.

Figure 6. Effect of the desorption temperature. Conditions:desorption solvent and the volume, acetonitrile (30µL). Other conditions are the same as in Figure 5.

The desorption temperature in the GC injector was also optimized. The plots in Figure 6 clearlysuggest the existence of the optimum desorption temperature about 170 ℃ for the desorption with 30µL of acetonitrile as the solvent. The insufficient desorption was observed both at lower and higher
desorption temperatures. The decreased desorption efficiency was attributed to the unsatisfactory
heating, because the carry-over was found at the lower desorption temperature. The drop of the peakareas at the higher temperature could be interpreted as the partial decomposition of the DNPH
derivatives under these excessively-heated conditions, although a more extensive studies should bescheduled for the thermal stability of these derivatized species.

Performance of the Needle Extraction Device
On the basis of the above successful optimization on the volume of desorption solvent and the− 17 −

temperature, resulting the practically complete desorption (more than 99.99%) at the first desorption,
the extraction performance was evaluated. The linear calibration ranges and the corresponding
correlation factors for the determination of several compounds are summarized in Table 1, in which
the DNPH derivatives of formaldehyde (FA), acetaldehyde (AA), and acetone was also tabulated.
The quantification was carried out with the SIM mode for the corresponding target ions: FA-DNPH(m/z: 210), AA-DNPH (m/z: 224), PA-DNPH (m/z: 238) and acetone-DNPH (m/z: 238). All theconcentrations were calculated as that of underivatized analytes in Table 1. Considering the sampled
gas volume of 50 mL and the concentration range found in typical in-house measurements, the dataclearly demonstrate the practical quantification range for these compounds with excellent correlation
coefficients. As an extraction technique, the repeatable and reproducible extraction could be one of
the requirements to ensure the determination, especially for the multiple and/or multipoint samplingin environmental analysis. The RSDs for run-to-run (n=5) and needle-to-needle (n=5) measurements
are shown in Table 2. The RSDs for needle-to-needle were slightly larger than that of run-to-run,however, these data indicate a good repeatability and reproducibility for the needle preparation
including the derivatization reaction in the needle.
Table 1. Linear range of the calibration curve and the correlation coefficients.

Table 2. Relative standard deviations (%) of the peak area for the run-to-run (n=5) and needle-to-needle (n=5)
measurements.

Figure 7 shows a typical separation of DNPH derivatives of three aldehydes that have been
derivatized and simultaneously extracted with the needle extraction device. The top chromatogram
was obtained by the TIM mode with the m/z range of between 200 and 250, while the otherchromatograms were extracted from the above TIM data set at the corresponding m/z number.
Introducing the time-programmed SIM mode as depicted in Figure 8A, the lowest quantification level
could be improved more. The estimated lowest quantification level for FA (50 mL sampling) was
improved to be less than few ng/L, because the determined concentration of FA in Figure 8A was 25− 18 −

ng/L (corresponds about 20 v/v ppb). Similar improvement was also confirmed for the determinationof acetone and methyl ethyl ketone (MEK) as found in Figure 8B. In addition, the linearity of thecalibration curve (Table 1) could be also extended with an increased sampling volume, it can be said
that the present method will be successfully applied to the FA determination in typical air samples.

Figure 7. Typical GC-MS separation of the aldehydes derivatives. Extraction conditions: desorption temperature, 170 ℃;
desorption solvent and the volume, acetonitrile (30 µL). Sample gas concentration: 0.6 µg/L for FA, 3.6 µg/L for
AA and 4.7 µg/L for PA, corresponding 0.5, 2.0 and 2.0 v/v ppm, respectively. GC conditions are the same as in
Figure 5. The peaks for FA-DNPH, AA-DNPH and PA-DNHP in TIM trace were assigned by the corresponding
extracted chromatograms at m/z: 210, 224 and 238, respectively.

Figure 8. Chromatograms for the separation of the DNHP derivatives of (A) aldehydes and (B) ketones with programmed SIM
mode. Peaks: (A) FA-DNPH (m/z: 210; 4.0-5.6 min; 25 ng/L as FA), AA-DNPH (m/z: 224; 5.6-6.6 min; 300
ng/L as AA) and PA-DNPH (m/z: 238; 6.6-8.0 min; 400 ng/L as PA), and (B) acetone-DNPH (m/z: 238; 5.0-7.4
min; 500 ng/L as acetone) and MEK-DNPH (m/z: 252; 7.4-9.0; 600 ng/L as MEK). The extraction and GC
conditions are the same as in Figure 5, except for the final temperature of 230 ℃ regarding the chromatogram in
Figure 8B. Other conditions are described in the text.

− 19 −

In Table 3, the storage performance of the needle extraction device was summarized, where therecovery (%) was calculated based on the immediate quantification. Up to three days after the
sampling, the needles were stored at the room temperature (about 24℃). During this storage period,
all the needles were sealed with the plugs manufactured by a small piece of polytetrafluoroethylene(PTFE). The excellent storage performance of the needle could be confirmed in Table 3, suggesting
the advantageous feature for the large number of sampling at the same time. The limit of detection(LOD) and the limit of quantification (LOQ) are summarized in Table 4. Although further optimization
should be carried out to improve the performance of the present approach, especially on the injection
conditions, these data clearly demonstrated the practical employment of the present method to thealdehydes determination in typical in-house environments.

Table 3. Storage performance of the needle extraction device for aldehydes at room temperature.

Table 4. Limits of detection (LOD) and quantification (LOQ).

2.5 Conclusions
Simultaneous derivatization/extraction for the volatile aldehydes was studied with the speciallydesigned needle extraction device packed with a bundle of polymer-coated filaments. Although some
additional studies regarding a more systematic optimization for extraction and determination
procedures might be necessary along with the additional investigations for the derivatization reaction
and the isomerization, the above results suggest the practical applicability of the method to theanalysis of volatile aldehydes in typical in-house air. On the basis of the excellent storage power of theneedle extraction device, the extracted samples could be determined even after the storage at theroom temperature for at least three days.

− 20 −

With the miniaturized needle-type extraction device, more extensive work is currently underway in
our laboratory including, the determination of volatile ketones in air samples, the coupling of theneedle extraction device to the polymer-coated fiber-packed capillary columns [27-32] with a higher
sample loading capacity, and the design and synthesis of the novel polymeric extraction medium basedon the surface derivatization reaction of the filaments [42] to be packed into the needle.

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