Analysis of Perfluoroalkyl Carboxylates and Perfluoroalkyl Sulfonates in Environmental Water by In-Port Arylation Gas Chromatography-Electron Impact Ionization-Mass Spectrometry

doi:10.21203/rs.3.rs-3886080/v1

Download PDF

Research Article

Analysis of Perfluoroalkyl Carboxylates and Perfluoroalkyl Sulfonates in Environmental Water by In-Port Arylation Gas Chromatography-Electron Impact Ionization-Mass Spectrometry

https://doi.org/10.21203/rs.3.rs-3886080/v1

This work is licensed under a CC BY 4.0 License

You are reading this latest preprint version

Per- and polyfluoroalkyl substances (PFASs) are persistent environmental pollutants that have been used for various purposes. Although PFASs can pollute the environment in a variety of areas related to use, storage, and disposal of their products, there are insufficient data on the extent of PFASs pollution outside industrialized countries with their manufacturing facilities. Most of analyses depend on high-cost liquid chromatography-tandem mass spectrometry. In this study, we established a method to analyze anionic PFASs using gas chromatography-electron impact ionization-mass spectrometry with in-port arylation by diaryl iodonium. Extraction of PFASs from water samples was performed using solid phase extraction with reverse phase sorbent. Fourteen PFAS compounds could be detected from spiked water samples, and the detection limit ranged from 3.1 to 8.1 ng L^− 1. Using this method, we analyzed groundwater samples from Okinawa Island, Japan, and detected PFASs up to a total concentration of 1.9 µg L^− 1. This method uses relatively inexpensive analytical equipment, hence it can possibly enable surveys on PFAS contaminations in a wide range of regions and opportunities.

Per-and polyfluoroalkyl substances (PFAS)

GC-MS

in-port derivatization

groundwater

environmental analysis

Okinawa

Per- and polyfluoroalkyl substances (PFASs) have been used over the past decades in a variety of applications including surfactants, surface protectors and in aqueous film-forming foams (AFFF). Since PFASs are persistent and some of them are bioaccumulative and toxic, they have recently attracted attention as environmental pollutants. Since 2009, several types of PFASs have been added to the Stockholm Convention on the Persistent Organic Pollutants list (SSC 2020).

Remarkable accumulation of PFASs in the environment and in the human body has been reported from early on in relation to PFAS manufacturing facilities (Boulanger et al. 2004, Oliaei et al. 2013). On the other hand, there are other diverse and important sources such as wastewater treatment plants (WWTPs) and aqueous film forming foams (AFFFs) for firefighting operations (Kurwadkar et al. 2022). Hence, it was pointed out by Kärrman et al. (2006), which reported the same level of PFASs in human serum in Australia as in European countries, that environmental contamination by PFASs is a common problem worldwide. This indicates an importance that information on the contamination status of PFASs should be collected not only in the areas surrounding their manufacturing facilities, but also in less industrialized countries. However, Hanssen et al. (2010), who measured PFASs in human serum in South Africa, noted the lack of analytical data in the southern hemisphere compared to the northern hemisphere. Similarly, the lack of data in developing regions, including the African continent, is a major concern from the viewpoint of assessing the situation of the global PFASs pollution (Kurwadkar et al. 2022) and considering countermeasures in each country (Ssebugeree et al. 2020). It has been pointed out that monitoring programs targeting trace hazardous substances in developed countries are rapidly developing and analytical techniques are advancing, but such analytical measurements require expensive equipment and facilities (Whylie et al. 2003). For this reason, monitoring necessary to understand the state of the environmental pollution and the fate of pollutants is not easy in developing countries with limited analytical capacities (Sindiku et al. 2013). It is important not only to improve the precision and sensitivity of the analysis method for trace amounts of hazardous substances, but also to reduce the cost and make it simple.

Many PFASs such as perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkyl sulfonic acids (PFSAs) are anionic substances and are generally analyzed using liquid chromatography with tandem mass spectrometry (LC-MS/MS). However, the equipment for LC-MS/MS is more expensive than general-purpose gas chromatography-single quadrupole mass spectrometer (GC-MS). In addition some branched isomers of perfluorooctane sulfonate (PFOS), one of the most important PFASs detected in the environment and the human body, were difficult to separately quantify by PFOS-specific product ions due to co-elution in LC. Therefore, analysis methods using GC-MS by derivatization have been investigated. Langlois et al. (2007) performed a qualitative separation analysis of PFOS isomers by esterification of PFASs with iso-propanol and analysis by high-resolution GC-MS. Hu et al. (2020) used single quadrupole GC-MS mainly to simplify the analytical method, and quantified PFCAs of about ng ml^− 1 in water samples by iso-butylation. Alzaga et al. (2004) analyzed PFCAs by negative chemical ionization (NCI)-MS using an in-port derivatization reaction with tetrabutylammonium in the GC injector. In addition, Chu & Letcher (2009) also butylated 11 PFOS isomers by similar in-port derivatization and analyzed with GC-NCI-MS. Furthermore, Harada et al. (2020) showed that in-port arylation GC-NCI-MS with diaryl iodonium salt enables separation and sensitive quantification of linear and branched PFOS isomers. They further analyzed 23 kinds of PFASs in serum after separating isomers, and also suggested the possibility of analysis by in-port arylation GC-electron impact ionization (EI)-MS.

The purpose of this study is to establish a method of the simultaneous analysis of PFCAs and PFSAs expanding the applicability of commonly used GC-EI-single quadrupole MS (qMS). With the developed method, an attempt was made to analyze the groundwater sample in Okinawa, Japan where PFAS contamination by AFFFs occurred.

PFAC-EPA533PAR mixed standard solution of PFCAs and PFSAs was purchased from Wellington Laboratories (Guelph, ON, Canada) and diluted with methanol to prepare standard solutions of each concentration. Bis(4-tert-butylphenyl) iodonium hexafluorophosphate (BtBPI) was obtained from Tokyo Chemical Industry Co., Ltd. (Tokyo, Japan). BtBPI powder was washed with hexane and dissolved in acetone to prepare a 0.5% (w/v) solution. InertSep PLS-3 (6 cc, 200 mg, 60 µm) solid phase extraction cartridges comprised of styrene-divinylbenzene methacrylate copolymer with nitrogen-containing polar group were obtained from GL-Science Inc. (Tokyo, Japan). Other reagents and solvents were obtained from Fujifilm Wako Pure Chemical Co., Ltd. (Osaka, Japan).

Extraction of PFASs from water samples was performed referring to the method of Hayashi (2010), who used PLS-3 solid phase cartridge for the analysis of PFOA and PFOS in river waters by LC-MS. The advantage of the use of reverse phase extraction to that of ion-exchange extraction is the fact that the smaller amount of salts are left in the dried eluent. PFASs in excess salts would be insoluble in the organic solvent for the derivatization reagent and may lower the recovery rates of GC-MS analysis. The cartridge was conditioned by passage of 20 mL of methanol, and then 10 mL of purified water. Fifty mL of a diluted standard solution or ground water sample was loaded on the cartridge at a flow rate of 5 mL per minute. The cartridge was washed with 5 mL of purified water, and dried by passing nitrogen gas. The target compounds were eluted with 5 mL of methanol, and concentrated to dryness at 60℃ under gentle nitrogen flow. The dried sample was dissolved with 50 µL of methanol, and 50 µL of BtBPI solution was added. The solution was transferred to a GC vial for the following GC-MS analysis.

Analysis by in-port arylation of PFASs was performed according to the method of Harada et al. (2020). Sample in GC vial was injected into a GC-qMS (QP-2010, Shimadzu Corporation) with a DB-5MS capillary column (30 m length, 0.32 mm i.d., 0.25 µm film thickness). Injection volume was 1 µL, and the inlet temperature was maintained at 300°C. Ultra-pure helium gas (> 99.9999%) was used as the carrier gas, and the flow rate was 1.5 mL/min. The oven temperature was held at 70°C for 1 minute and ramped at 7°C/min to 170°C, and 30°C/min to 260°C and held for 5 minutes. The interface temperature was 280°C. EI of MS was performed with an electron energy of 70 eV and the ion source temperature was 200°C. In order to avoid the influence of by-products from in-port arylation on the ion source, the BtBPI solution diluted 100-fold with acetone was analyzed in advance to know the elution time of the by-products, and the detector filament was turned off during their elution time. Monitor ions for quantification and qualification of target substances were selected with reference to the study by Harada et al. (2020) (Table 1). Standard solutions diluted in methanol with five different concentrations were analyzed with the above described method to prepare the calibration curves for the target substances.

Groundwater samples were collected at five sites in an area of Okinawa Island, Japan (Fig. 1), where PFASs contaminations in groundwater and river water have been reported (Shiokawa & Tamaki, 2017). Spring waters were directly collected at sites A, C, D, and E, while another sample in a channel that drainage spring water in the area to the coast was collected at site B. Samples were filled in polypropylene bottles, transported to the laboratory, and then stored refrigerated until analysis. A 50 mL groundwater sample was adjusted to pH 4 with 2% formic acid, and subjected to the extraction described above.

1) Analysis of PFASs by in-port arylation GC-EI-MS

Diluted standard solutions of PFASs were analyzed by GC-EI-MS with in-port arylation, and the peaks for each monitor ion appeared in the same order of retention times as reported by Harada et al. (2020) (Table 1). The analysis of serially diluted standard solutions gave a good linear relationship (r ≥ 0.995) between the amount of substance injected into the GC (1.6–25 pg) and the detected peak area of each monitor ion for all target substances. In addition, the elutes from solid-phase extraction of purified water spiked with standard solution were analyzed by the same method, and the standard deviation of measured concentrations (n = 8) for each PFAS was multiplied by the Student’s t-value corresponding to the 99% confidence level to calculate the method detection limit (MDL), which resulted in 3.1–8.1 ng L^− 1 (Table 2). No peaks for PFASs were detected for the elute of solid-phase extraction of purified water blank, and the recovery rate of each substance was 83–107%. The slightly lower recovery rate of PFBA (83%) compared to the other substances may be attributed to its shorter carbon chain, however, PLS-3 cartridge showed satisfactory recoveries for all the substances under acidic condition.

Alzaga et al. (2004) established the analytical method of PFCAs in water samples using in-port butylation GC-NCI-MS with tetrabutylammonium, which gave 20–100 ng L^− 1 of MDLs for PFCAs. The method of the present study with arylation could achieve better sensitivity using GC-EI-qMS, which is more commonly installed in wide range of laboratories than GC-NCI-MS and LC-MS/MS.

2) Groundwater analysis

Groundwater samples were solid-phase extracted and analyzed by in-port arylation GC-EI-MS. All the analyzed substances except PFDA, PFUnDA, PFDoDA were detected in the samples, and the total concentration of PFASs detected was up to 1.9 µg L^− 1 (Table 3). In the same area as the present study, the local government measured PFOS, PFHxS, and PFOA in groundwater at 46 sites using LC-MS/MS from July to September 2022, and the maximum concentration of each substance was 1.8, 0.9, and 0.32 µg L^− 1, respectively (Okinawa Prefectural Government, 2022). The concentrations of these substances detected in the present study were comparable to these values, and the sum of the concentrations of PFOS and PFOA for each sample exceeded Japanese provisional guideline value for environmental standards (0.05 µg L^− 1), confirming the environmental pollution in this area. Furthermore, it has been revealed that the drainage with several hundred ng L^− 1 of PFASs is discharged directly into the coastal water of Okinawa Island at site B. Okinawa is surrounded by fringing coral reefs, which support rich and highly productive coral ecosystems and serve as the foundation of coastal fishery and tourism industries (Roberts et al. 2002). Further extensive contamination surveys and studies of impacts on coral reef organisms and ecosystems in this area are required.

PFOS showed the highest concentrations among detected PFASs for all the groundwater samples in the present study, followed by PFHxS. PFOS and PFHxS were the most commonly used among the PFASs for fire extinguishing agents before they were banned (Moody et al. 2002). As Okinawa is an island without any manufacturing facilities for PFAS products, it is likely that the use or disposal of PFAS products, mostly fire extinguishing agents, is the origin of groundwater contamination. Munoz et al. (2017) analyzed PFASs in environmental waters in French volcanic islands located in the tropics, and reported several hundred ng L^− 1 of PFASs in the groundwaters from specific monitoring sites. Though PFOS and other PFSAs occupied the major proportion of PFASs in the samples from some of these sites, on the other hand, the samples from the rest of these sites were dominated by short-chain (C₄-C₇) PFCAs and 6:2 FTSA which suggested spills of AFFF with precursors of 6:2 FTSA produced after ban of PFOS and other ‘legacy’ PFASs. The low proportions (10–19%) of short-chain PFCAs in total PFASs commonly observed for the groundwaters in the present study suggested that historical spill events of AFFF with PFOS should be the major source of PFAS contamination of the environment in this area. Contamination of river waters from this same area as the present study by PFASs were once reported by Shiokawa & Tamaki (2017), pointing out the possibility of the adjacent U.S. military facilities as the source, according to their analyses using LC-MS/MS. The PFASs detected in groundwater in the present study might also be originated from U.S. military facilities, where spills of POPs, including PCBs and DDTs, in the past and current environmental contamination had been reported (Yoshinaga et al.1978, Tashiro et al. 2021).

In industrial areas of developed countries, analytical results of surface waters and groundwaters with PFASs exceeding µg L^− 1 levels have often been reported (Kurwadkar et al. 2022) and used to determine the location of sources and the fate of pollutants have been investigated (e.g., Moody et al. 2002, Saito et al. 2004). On the other hand, among the analysis results of PFASs in environmental water, mainly river water, of developing countries without PFASs product manufacturing facilities, PFAS contaminations caused by the use, storage, and/or dumping of products have been reported with concentrations up to several hundreds of ng L^− 1 (Ssebugere et al. 2020). The analysis of PFASs in environmental water by in-port arylation with GC-EI-qMS demonstrated in the present study can be applied to investigate the state of contamination especially in such relatively highly contaminated areas.

In the present study, we developed a method for analyzing PFASs using single quadrupole GC-EI-MS by solid-phase extraction and in-port arylation with diaryl iodonium salt. As a result, it was shown that fourteen compounds of PFCAs and PFSAs, which are important in the assessment of environmental pollution, can be analyzed in the concentration range of several ng L^− 1 in water.

The occurrence of PFASs in groundwater in an area of Okinawa Island was detected, and their emission to the coastal water was discovered by analyzing samples using this method. Additionally, the composition of the detected PFASs suggested that the historical spill events of AFFF should be the major source of PFAS contamination of the environment in this area. These results indicated the need for more extensive pollution surveys in Okinawa Island and the surrounding marine ecosystem.

Single quadruple GC-EI-MS has widely been introduced in many research institutes worldwide including in developing countries because of its relatively low cost. It is expected that the similar method as demonstrated in the present study may also be developed for the analysis of a wide range of samples with relatively high contaminant concentrations, such as food, biological samples, and waste, expanding the usage of common GC-EI-MS equipment for surveillances of PFASs as an urgent environmental concern worldwide.

Ethical Approval

Not applicable.

Consent to Participate

Not applicable.

Consent to Publish

Not applicable.

Competing Interests

The authors have no relevant financial or non-financial interests to disclose.

Funding

Kouji H. Harada received a support from the Takagi Fund for Citizen Science (No. 226-002).

Authors Contributions

All authors contributed to the study conception and design. The methods for analysis were developed by Kouji H. Harada and Yutaka Tashiro. Sample collection and analysis were performed by Yutaka Tashiro, Takanori Ikehara and Takuma Ito. The first draft of the manuscript was written by Yutaka Tashiro and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.

Acknowledgments

Authors are grateful to Mr. Minoru Minei for valuable technical advice. Dr. Gloria E. Luyo Acero is kindly acknowledged for editing a draft of this manuscript.

Alzaga R, Bayona JM (2004) Determination of perfluorocarboxylic acids in aqueous matrices by ion-pair solid-phase microextraction–in-port derivatization–gas chromatography–negative ion chemical ionization mass spectrometry. J Chromatogr A 1042:155–162. https://doi.org/10.1016/j.chroma.2004.05.015
Boulanger B, Vargo J, Schnoor JL, Hornbuckle KC (2004) Detection of perfluorooctane surfactants in Great Lakes water. Environ Sci Technol 38:4064–4070. https://doi.org/10.1021/ES0496975
Chu S, Letcher RJ (2009) Linear and branched perfluorooctane sulfonate isomers in technical product and environmental samples by in-port derivatization-gas chromatography-mass spectrometry. Anal Chem 81:4256-62. 10.1021/ac8027273. PMID: 19402680
Hanssen L, Röllin H, Odland JØ, Moe MK, Sandanger TM (2010) Perfluorinated compounds in maternal serum and cord blood from selected areas of South Africa: results of a pilot study. Environ Monit 12:1355–1361. https://doi.org/10.1039/B924420D
Harada KH, Fujii Y, Zhu J, Zheng B, Cao Y, Hitomi T (2020) Analysis of perfluorooctanesulfonate isomers and other perfluorinated alkyl acids in serum by in-port arylation gas chromatography negative chemical ionization–mass spectrometry. Environ Sci Technol Lett 7:259–265. https://doi.org/10.1021/acs.estlett.0c00133
Hayashi H (2010) Emerging contaminants and advanced water treatment system. Seikatsu Eisei 54:128–136 (in Japanese)
Hu Z, Li Q, Xu L, Zhang W, Zhang Y (2020) Determination of perfluoroalkyl carboxylic acids in environmental water samples by dispersive liquid–liquid microextraction with GC-MS analysis. J Liq Chromatogr Relat Technol 43:282–290. https://doi.org/10.1080/10826076.2020.1728311
Kärrman A (2006) Levels of 12 perfluorinated chemicals in pooled Australian serum, collected 2002 – 2003, in relation to age, gender, and region. Environ Sci Technol 40: 3742–3748. https://doi.org/10.1021/es060301u
Kurwadkar S, Dane J, Kanel SR, Nadagouda MN, Cawdrey RW, Ambade B, Struckhoff GC, Wilkin R (2022) Per- and polyfluoroalkyl substances in water and wastewater: A critical review of their global occurrence and distribution. Sci Total Environ 809:151003. https://doi.org/10.1016/j.scitotenv.2021.151003
Langlois I, Berger U, Zencak Z, Oehme M (2007) Mass spectral studies of perfluorooctane sulfonate derivatives separated by high-resolution gas chromatography. Rapid Communications in Mass Spectrometry: An International Journal Devoted to the Rapid Dissemination of Up‐to‐the‐Minute. Res Mass Spectrom 21:3547–3553. https://doi.org/10.1002/rcm.3241
Moody CA, Martin JW, Kwan WC, Muir DC, Mabury SA (2002) Monitoring perfluorinated surfactants in biota and surface water samples following an accidental release of fire-fighting foam into Etobicoke Creek. Environ Sci Technol 36:545–551. https://doi.org/10.1021/es011001+
Munoz G, Labadie P, Botta F, Lestremau F, Lopez B, Geneste E, Pardon P, Dévier MH, Budzinski H (2017) Occurrence survey and spatial distribution of perfluoroalkyl and polyfluoroalkyl surfactants in groundwater, surface water, and sediments from tropical environments. Sci Total Environ 607:243–252. https://doi.org/10.1016/j.scitotenv.2017.06.146
Okinawa Prefectural Government (2022) Results of survey on environmental PFAS residues in summer 2022. Okinawa Prefectural Government, Okinawa. (in Japanese)
Oliaei F, Kriens D, Weber R, Watson A (2013) PFOS and PFC releases and associated pollution from a PFC production plant in Minnesota (USA). Environ Sci Pollut Res 204:1977–1992. https://doi.org/10.1007/S11356-012-1275-4 2012
Roberts CM, McClean CJ, Veron JEN, Hawkins JP, Allen GR, McAllister DE, Mittermeier CG, Schueler FW, Spalding M, Wells F, Vynne FC, Werner TB (2002) Marine biodiversity hotspots and conservation priorities for tropical reefs. Science 295:1280–1284. https://doi.org/10.1126/science.1067728
Saito N, Harada K, Inoue K, Sasaki K, Yoshinaga T, Koizumi A (2004) Perfluorooctanoate and perfluorooctane sulfonate concentrations in surface water in Japan. J Occup Health 46:49–59. https://doi.org/10.1539/joh.46.49
Shiokawa A, Tamaki F (2017) The survey on environmental pollution of Perfluorinated compounds (PFCs) in rivers and the sea areas of Okinawa Island. Rep Okinawa Prefectural Inst Health Environ 51:33–48 (in Japanese)
Sindiku O, Orata F, Weber R, Osibanjo O (2013) Per- and polyfluoroalkyl substances in selected sewage sludge in Nigeria. Chemosphere 92:329–335. https://doi.org/10.1016/j.chemosphere.2013.04.010
SSC (Secretariat of the Stockholm Convention) (2020) Stockholm Convention on Persistent Organic Pollutants (POPs) Text and Annexes revised in 2019. SSC. Genève 10, Switzerland
Ssebugere P, Sillanpää M, Matovu H, Wang Z, Schramm KW, Omwoma S, Wanasolo W, Ngeno EC, Odongo S (2020) Environmental levels and human body burdens of per- and poly-fluoroalkyl substances in Africa: A critical review. Sci Total Environ 739:139913. https://doi.org/10.1016/j.scitotenv.2020.139913
Tashiro Y, Goto A, Kunisue T, Tanabe S (2021) Contamination of habu (Protobothrops flavoviridis) in Okinawa, Japan by persistent organochlorine chemicals. Environ Sci Pollut Res 28:1018–1028. https://doi.org/10.1007/s11356-020-10510-y
Whylie P, Albaiges J, Barra R, Bouwman H, Dyke P, Wania F, Wong M (2003) Regionally based assessment of persistent toxic substances. Global report. UNEP Chemicals / GEF. Geneva, Switzerland. Available from: http://www.chem.unep.ch
Yoshinaga A, Oyama M, Oshiro Z, Ikema S, Chibana Y, Sakugawa H, Shimoji K, Miyagi K, Takeuchi T, Takara T (1978) Survey results of drainages from U.S. military bases in 1977. Rep Okinawa Prefectural Inst Health Environ 12:44–51 (in Japanese)

Tables 1 to 3 are available in the Supplementary Files section.

Tables.xlsx

Download PDF

Editorial decision: Major Revision
22 May, 2024
Reviewers agreed at journal
12 Mar, 2024
Reviewers invited by journal
19 Feb, 2024
Editor assigned by journal
06 Feb, 2024
First submitted to journal
30 Jan, 2024

You are reading this latest preprint version

Analysis of Perfluoroalkyl Carboxylates and Perfluoroalkyl Sulfonates in Environmental Water by In-Port Arylation Gas Chromatography-Electron Impact Ionization-Mass Spectrometry

Status:

Version 1

Abstract

Figures

1. Introduction

2. Materials and Methods

3. Results and Discussion

1) Analysis of PFASs by in-port arylation GC-EI-MS

2) Groundwater analysis

4. Conclusion

Declarations

Ethical Approval

Competing Interests

Funding

Authors Contributions

Acknowledgments

References

Tables

Supplementary Files

Status:

Version 1