i TECH MAG Vol 2 (2020) 38-40

i TECH MAG
DOI: http://doi.org/10.26480/itechmag.02.2020.38.40

ISSN: 2710-5873 (Online)
CODEN: ITMNBHRESEARCH ARTICLE

OPTIMIZATION OF SOLVENT FOR THE EXTRACTION OF PERFLUOROOCTANOICACID(PFOA) FROM A POLYTETRAFLUOROETHYLENE RESIN
Koji Furukawaa*, Makoto Hashimotoa, Hiromu Motozawaa, Satoshi Kanecoba Mie Prefecture Environmental Conservation Agency, Tsu, Mie 510-0304, Japan.
b Department of Chemistry for Materials, Graduate School of Engineering, Mie University, Tsu, Mie 514-8507, Japan.

*Corresponding Author E-mail: furukawa1@mec.or.jp
This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction
in any medium, provided the original work is properly cited.
ARTICLE DETAILSABSTRACT

Article History:

The optimization of the extraction conditions of perfluorooctanoic acid (PFOA) from a polytetrafluoroethylene(PTFE) fine resin powder was investigated in this work. A PTFE resin containing a high concentration of PFOA
was used for the optimization. From the optimization results, the effective extraction solvents were determined
to be methanol and acetone, and their PFOA‒analyzed concentrations were 9840 ng/g and 9520 ng/g withrelative standard deviation (RSD) values of 4.1% and 2.6%, respectively, based on three measurements.
Conversely, the PFOA could not be extracted using hexane as the solvent. The reproducibility of the PFOA analysis
in PTFE fine resin powder by the extraction with methanol was investigated. As a result, the recovery for the
spiked PFOA in the PTFE resin was 108±6% (N=5). Conclusively, the developed method for the extraction of PFOA
in the PTFE fine resin powder was considered satisfactory.

Received 27 October 2020
Accepted 28 November 2020
Available online 09 December2020

KEYWORDSPFOA, PTFE resin, LC/MS/MS, Extraction, Optimization.

1. INTRODUCTION
In recent years, perfluorinated organic compounds (PFCs), such as
perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS),
have been widely used as water repellents, fire extinguishers,
fluoropolymer processing, and surfactants. PFCs accumulate in theenvironment due to their low degradability; consequently, they causesignificant environmental pollution, which is attracting global concern(Olsen et al., 2003; Saito et al., 2004; Olsen et al., 2007; Haukas et al., 2007;
Dreyer et al., 2009; Takagi et al., 2012). Therefore, the regulation andcontrol of PFCs globally are highly necessary. In particular, PFOA wasofficially added to the persistent organic pollutants Convention in 2019
(Stockholm Convention On Persistent Organic Pollutants, United Nations
Nations Unies, 2019) and the Registration, Evaluation, Authorization, andRestriction of Chemicals (REACH) regulation. The standard concentrationof PFOA and its salts was set to a very low level of 25 ng/g, due to therevision of the restricted substances in Annex XVII in July 2020 (European
Chemicals Agency, ANNEX XVII TO REACH–Conditions of restriction).
Thus far, PFOA has been applied as an auxiliary agent or surfactant in the
fabrication of fluoroplastics, including polytetrafluoroethylene (PTFE).
Additionally, PFOA may be detected in the by-products obtained fromPTFE resin owing to the scission of the main chain under exposure toradiation. Therefore, the determination of the PFOA content in eachproduct and the evaluation of the satisfaction degree of the regulation
value for the products are imperative.
So far, the determination of the PFOA content from bulk samples
containing PTFE polymers, packaging materials and textiles usingpressurized liquid extraction (PLE) have been reported (Larsen et al.,2005; Gang et al., 2009; Gang et al., 2009). Also, the determination of the
PFOA content from particulate activated carbon has been reported, andthe CEN/TS 15968:2010 method for the determination of PFOS in coatedand impregnated solid particles has been presented by the European
Committee for Standardization (Comite Europeen de Normalisation, 2010;
Takemine et al., 2013). However, there is little information on the
optimization of solvents, which have been extensively studied from polar

to non-polar solvents, for the extraction conditions of PFOA from products
such as PTFE resins. In this study, we investigate the optimization of theextraction conditions of PFOA from a PTFE fine resin powder and therelationship between the extraction solvent and the PFOA efficiency todevelop a standard analysis method for PFOA.

2. EXPERIMENTAL
2.1 Reagents and chemicals
A mixed standard solution of PFC-MXA (2 µg/mL), manufactured by
Wellington Laboratories, was used as the PFOA standard solution.
Immediately before use, the standard solution was diluted with methanol
in six steps so that the concentrations of the PFOA solution were in therange of 0.050–2.0 ng/mL. A standard solution of MPFOA (PFOA-13C4
internal standard, 50 µg/mL), purchased from Wellington Laboratories,
was used by the PFOA-13C4 internal standard solution. The PFOA-13C4
internal standard solution was diluted with methanol to a concentrationof 1.0 ng/mL immediately before use. A portion (100 μL) of the PFOA-13C4
internal standard solution was added to 1 mL of the PFOA standard
solution, and a nitrogen stream was supplied to adjust the volume to 1 mL
to obtain the standard solution for the calibration curve. Methanol,
toluene, and hexane (residual pesticide test grade) were obtained from
Kanto Chemical Co. Acetonitrile and formic acid (LC/MS analytical grade)were obtained from Kanto Chemical Co. Acetone (residual pesticide test
grade) and ammonium acetate (special reagent grade) were manufactured
by Fuji Film Wako Pure Chemical Co. Mill-Q water was used for theexperiments. PTFE resin powders (A) and (B) containing relatively highand low concentrations of PFOA were purchased from an anonymouscompany. The obtained PTFE resin powders were freeze-pulverized intofine particles, which were filtered through a 500 µm mesh before use.
2.2 Determination of the optimal organic extraction solvent
The extraction of PFOA from a PTFE resin powder (A) was performed withreference to CEN/TS 15968:2010 (Comite Europeen de Normalisation,2010). Approximately 0.5 g of the PTFE powder (A) was weighed in a 50

Cite The Article: Koji Furukawa, Makoto Hashimoto, Hiromu Motozawa, Satoshi Kaneco(2020).Optimization Of Solvent For Th Extra ction Of Perfluorooctanoic
Acid(PFOA) From A Polytetrafluoroethylene Resin. i Tech Mag, Vol 2: 38-40.

i TECH MAG Vol 2 (2020) 38-40
mL centrifuge tube, and 50 mL of an organic solvent was added for the
extraction of PFOA from PTFE. Next, the suspension was subjected toultrasonic irradiation at 60 °C for 2 h for the extraction. The extraction
temperature of 60 °C was sourced from the CEN/TS 15968:2010 method.
A different temperature of 20 °C was also tested to examine the effect ofrelatively low temperatures. After the extraction, 25 µL of each extract wasadded to 1 mL of the PFOA-13C4 internal standard solution (1 ng/mL) in a
Spitz tube (10 mL). Thereafter, the solution was adjusted to 10 mL withmethanol to obtain an analytical solution, which was subjected to liquid
chromatography with tandem mass spectrometry (LC/MS/MS) analysis.
2.3 Recovery Test
To evaluate the precision of the developed method, a recovery test was
performed with the PTFE fine resin powder (B) containing the PFOA in a
relatively low concentration. The PTFE resin powder (approximately 0.5g) was weighed into a 50 mL centrifuge tube, and 250 µL of the PFOA
standard solution (100 pg/µL) and 50 mL of methanol were added.
Subsequently, the suspension was sonicated for 2 h at 60 °C for the
extraction. After the extraction, a 1 mL portion of the extraction methanol
was added to 100 µL of the PFOA-13C4 internal standard solution (1ng/mL) in Spitz tubes (10 mL). Afterward, the solution was evaporated todryness under a mild nitrogen stream at room temperature. Finally, theresidue was dissolved in 1.0 mL of methanol. The sample was subjected to
LC/MS/MS analysis. The recovery test data were the average values
obtained with more than five samples.

although the reason could not be elucidated (Takemine et al., 2013). Thismay be attributed to the low affinity between acetonitrile and PFOA.
In the case of methanol containing 1% formic acid, recommended by the
Ministry of Environment, the concentration of the extracted PFOA was
8781 ng g‒1 with an RSD of 3.8% (N=3) (Waste Management andRecycling Department, 2011). For methanol with 5% formic acid, theconcentration was 8668 ng/g with an RSD of 3.8% (N=3), and with 10%
formic acid, it was 8845 ng/g with an RSD of 4.2% (N=3). The
concentration was approximately 10% lower than that extracted withmethanol only. We expect that the relatively low pH due to the addition of
formic acid increases the extraction efficiency of PFOA due to the decreasein the dissociation of PFOA. However, the result suggested that thephysical factors: the formic acid mixture and pH, had little influence on theextraction efficiency of PFOA. Consequently, the formic acid concentration
did not noticeably affect the extraction efficiency of PFOA. This may
suggest that the inclusion of trace water in the extract weakens the affinity
between the extract and the PTFE particle surface, accounting for themoderately negative effect on the extraction efficiency of PFOA, due to thehydrophobicity of the PTFE powder surface.

2.4 Analysis of PFOA by LC/MS/MS
The LC section of an Agilent 1260 HPLC and the MS/MS section of a Sciex
QTRAP5500 were utilized for the LC/MS/MS measurement in this study(Furukawa et al., 2009). The separation column was an InertSustain C18(2.1 × 150 mm, 3 µm: GL Sciences Inc.), and the column temperature was
40 °C. The mobile phases for the gradient measurement were A: 55% + B:
45% (0 min) and A: 5% + B: 95% (13 min), with an aqueous solution of A:
0.5 mM ammonium acetate containing 0.1% formic acid and B:
acetonitrile. The flow rate was 0.2 mL min‒1, and the injection volume was
20 µL. For the MS/MS operating conditions, the negative ESI mode was
employed, and the multiple reaction monitoring (MRM) transitions werefrom m/z 413 to m/z 169 for the quantitative ion of PFOA and m/z 417 tom/z 372 for the quantitative ion of PFOA-13C4 (internal standard).

3. RESULTS AND DISCUSSION
It was described in the previous work that the pressurized liquid
extraction (PLE) of PFOA was used for the analysis of the PFOA content in
the bulk samples containing PTFE polymers, packaging materials andtextiles (Larsen et al., 2005; Gang et al., 2009). Although intensive
conditions using PLE for the determination of PFOA were needed for bulk
samples (sample size: more than 500 µm), little information on mild
extraction conditions of PFOA has been reported for the fine PTFE powder.
Hence, the optimization of the extraction of PFOA from a PTFE fine resin
powder under mild conditions was studied for the determination of PFOA
using LC/MS/MS. To optimize the extraction conditions of PFOA from thePTFE fine resin powder, the effects of the organic solvent and temperatureon the extraction efficiency were investigated. First, suitable organic
solvents were explored for the extraction of PFOA from the PTFE fine resin
powder (A).
Various organic media such as methanol; methanol containing 1%, 5%,
and 10% formic acid; acetone; acetonitrile; toluene; and hexane were
evaluated for the extraction. Figure 1 shows the effect of the organic
solvent on the concentration of the PFOA extracted from the PTFE resin
powder. As shown in Figure 1, methanol was the most effective solvent for
the extraction of PFOA, and the analyzed concentration was 9840 ng/gwith a relative standard deviation (RSD) of 4.1% (N=3). Methanol was
adopted as the extraction organic solvent in the CEN/TS 15968 procedure(Comite Europeen de Normalisation, 2010). When acetone was used as theextractant, the PFOA‒extracted concentration was 9520 ng/g with an RSDof 2.6% (N=3). The result was similar to that obtained with methanol.
The trends were in good agreement with the results on the efficiency of
PFOA extraction from granular activated carbon (Takemine et al., 2013).
Conversely, in the case of toluene, the concentration of PFOA was 3280
ng/g with an RSD of 34.3% (N=3), and the values were significantly lower
than those observed for methanol and acetone. Furthermore, theextraction of PFOA using hexane was difficult. Since the structure of PFOA
has a hydrophilic carboxylic acid group, a polar organic solvent may beeffective for its extraction from PTFE. However, when acetonitrile wasused, the concentration of PFOA was considerably low (5950 ng/g with an
RSD of 5.1% (N=3)). Similar results have been reported by Takemine,

PFOA extraction concentration (ng/g)
Figure 1: Relationship between the concentration of PFOA extracted fromPTFE powder resin (A) and the type of organic solvent used for the
extraction. With hexane as the extractant, the PFOA concentration was lessthan the limit of quantitation.
Next, the influence of temperature on the extraction of PFOA in PTFE wasinvestigated with methanol as the extractant. When the extraction
temperature was 20 °C, the concentration of PFOA was 8950 ng/g, which
was 9% lower than that obtained at 60 °C. After the first extraction, thesecond and third extractions were carried out for the same PTFE samples.
The analytical values were 560 ng/g, and values less than the limit ofquantitation were obtained for the second and third extractions. The
reproducibility of the PFOA analysis in PTFE resin powder by the
combination of extraction with methanol and LC/MS/MS was investigated.
In this study, the PTFE samples (B) were spiked with 50 ng/g PFOA toevaluate the recovery rate. The PFOA quantitation limit for this study was
1.0 ng/g.
Firstly, the PFOA content of the PTFE powder resin (B) was determined in
the extraction with methanol method at 60 °C, and the content value of
PFOA was 16 ng/g (N=2). Next, 50 ng/g PFOA was spiked into the PTFE
sample (B) to evaluate the recovery. As a result of the spike recovery test,
the average PFOA content in the spiked PTFE resin was 69.8±3.7 ng/g with
an RSD of 5.3% (N=5). The recovery for the spiked PFOA was 108±6%(N=5). The developed extraction method could be consideredsatisfactorily for the determination of PFOA in PTFE resin powder.

4. CONCLUSIONSIn this study, we examined the optimization of the extraction conditions of
PFOA from PTFE fine resin powder. It could be found from the result thatthe condition of extraction with methanol at 60°C was the most effective.
It was also found that when acetone was used as the extraction solvent, it
almost had the same performance as that obtained with methanol. This
result shows that the extraction using acetone can be applied into thedetermination of the PFOA content in the PTFE-contained grease, which
can not be mixed with methanol.

ACKNOWLEDGEMENTS
We would like to thank Ms. Nozomi Yasui and Ms. Haruka Sakaguchi for
helping us with the experiment.

Cite The Article: Koji Furukawa, Makoto Hashimoto, Hiromu Motozawa, Satoshi Kaneco(2020).Optimization Of Solvent For Th Extra ction Of Perfluorooctanoic
Acid(PFOA) From A Polytetrafluoroethylene Resin. i Tech Mag, Vol 2: 38-40.

i TECH MAG Vol 2 (2020) 38-40

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Cite The Article: Koji Furukawa, Makoto Hashimoto, Hiromu Motozawa, Satoshi Kaneco(2020).Optimization Of Solvent For Th Extra ction Of Perfluorooctanoic
Acid(PFOA) From A Polytetrafluoroethylene Resin. i Tech Mag, Vol 2: 38-40.