Monitoring Analysis of Perfluoroalkyl Substances and F-53B in Bottled Water, Tea and Juice Samples by LC-MS/MS

Abstract

Monitoring analysis of 14 per- and polyfluoroalkyl substances (PFAS), 9-chlorohexadecafluoro-3-oxanonane-1-sulfonate (F-53B) and dodecafluoro-3H-4,8-dioxanonanoate (ADONA) in bottled drinking water, tea and juice samples was performed using LC coupled with tandem mass spectrometry (LC-MS/MS) and solid-phase extraction (SPE). In the electrospray negative ion mode, the limit of detection and limit of quantification (LOQ) values were 0.1 to 0.8 ng/mL and 0.2 to 1.6 ng/mL, respectively. The calibration curves were linear from LOQ to 50 ng/mL (r² > 0.999). The SPE procedure (Presep PFC-II) was utilized for sample preparation and recovery rates for three standards (35, 70 and 140 ng/L) were 80.4–118.8% with relative standard deviation (RSD) ≤ 0.6%. Using the developed method, various samples (n = 54) from Japanese markets were investigated for PFAS and F-53B contamination, and values below the LOQ were observed. It is concluded that for monitoring products in the Japanese market, our method represents a significant improvement over complex techniques for the quantification of PFAS and related compounds from various foods.

Introduction

In the past years, per- and polyfluoroalkyl substances (PFAS), mainly perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), have been investigated with respect to environmental contamination and human exposure risk assessment.¹⁾ Several thousand PFAS-related compounds have been manufactured and are continuously being detected in environmental samples.²⁾ For example, the novel PFAS compound 9-chlorohexadecafluoro-3-oxanonane-1-sulfonate (F-53B) has shown an increased presence in emissions from Chinese industry and has resulted in environmental contamination.^3,4) The renewed appearance of PFAS compounds constitutes a major pollutant concern because of their persistence in the environment, e.g., in river water, soil, air, wildlife and the food chain. In regard to human health risks, while direct exposure by means of their use in products (packaging, paper products, oil-repellents, cookware and food processing equipment) can be easily phased out by modification of chemical processes, exposure driven by PFAS contamination in the food chain and groundwater can persist over an extended period.⁵⁾ Thus, it is very important to monitor the daily intake of PFAS in the general public by using total diet studies (TDS).^6–8) In the first stage of exposure assessment, investigation of drinking water (Group 14, G14 in TDS) is the current approach to assess health effects.^9–12) Indeed, in 2020, the Japanese Ministry of Health, Labour and Welfare established a provisional target value (50 ng/L) of combined PFOS and PFOA in tap water.¹³⁾ However, individual regions or countries will have unique situations and guidelines and/or risk assessments need to be conducted using region-specific analytical data (drinking, bottled and tap waters).^14–16) Nevertheless, a significant challenge for monitoring analysis of PFAS by Japanese researchers is the lack of reliable results for drinking water.

Comprehensive studies concerning PFOS and PFOA provide important information on human health as well as reveal exposure levels by dietary intake. A previous report utilized a gas chromatographic technique for the separation and quantitation of PFOS and PFOA in packaging materials and textiles.¹⁷⁾ Similarly, a relatively useful, sensitive and selective assay for PFAS, including PFOS and PFOA, involves LC-MS or tandem mass spectrometry (LC-MS/MS).^18–20) LC-MS/MS techniques have been used to evaluate several PFAS varieties in drinking water.^21–23) Unfortunately, previous methods were unsuccessful in determining PFAS limits and were burdened by cumbersome preparation methods. Thus, in the present study, monitoring analysis of fourteen PFAS, F-53B and dodecafluoro-3H-4,8-dioxanonanoate (ADONA) in drinking water, tea and juice samples was assessed using LC-MS/MS and solid-phase extraction (SPE) for application to establishing preliminary TDS.

Experimental

Reagents and Chemicals

Fourteen PFAS, F-53B and ADONA and stable isotope standards were obtained from Wellington Laboratories, Inc. (Guelph, ON, Canada), FUJIFILM Wako Pure Chemical Corporation (Osaka, Japan), Fluorochem Ltd. (Hadfield, U.K.), Tokyo Chemical Industry Co., Ltd. (Tokyo, Japan), Cambridge Isotope Laboratories, Inc. (Tewksbury, MA, U.S.A.), and Sigma-Aldrich Co. (St. Louis, MO, U.S.A.). Methanol, formic acid (FA), ammonium acetate and acetonitrile were obtained from FUJIFILM Wako Pure Chemical Corporation. The 28% ammonia solution was obtained from Sigma-Aldrich Co. Purified water was used for the mobile phase and sample preparation and was obtained from a PURELAB Flex 5 system (ELGA, London, U.K.). In addition, all experimental water was filtered using an InertSep Slim-J AC (400 mg) from GL Sciences Inc. (Tokyo, Japan). Stock solutions of analytes (500 µg/L) were adjusted using methanol and stored at −80 °C. Bottled water, tea and juice samples were purchased from Japanese markets in 2019–2020.

LC-MS/MS Equipment and Condition

The LC system was a Waters Acquity H Class Plus (Waters Co., Milford, MA, U.S.A.). Reversed-phase (RP) analysis was performed via an InertSustain C₈ column (3 µm, 2.1 × 100 mm, GL Sciences Inc., Tokyo, Japan) at 40 °C. The injection volume was 10 µL. The mobile phase, consisting of solvent A (20 mmol/L ammonium acetate in water) and solvent B (methanol), was delivered at a flow rate of 0.2 mL/min. The gradient elution was as follows: 55% solvent B at 0 min, 55% solvent B at 3 min, 58% solvent B at 6 min, 90% solvent B at 11 min, 98% solvent B at 15 min, 98% solvent B at 18 min, 55% solvent B at 18.1 min, and 55% solvent B at 20 min. A Waters Xevo TQD triple quadrupole mass spectrometer was operated with the electrospray ionization (ESI) source in negative mode. The ionization source conditions were as follows: capillary voltage of 2.0 kV, extractor voltage of 3 V, RF lens voltage of 2.5 V, source temperature of 150 °C, and desolvation temperature of 400 °C. The cone and desolvation gas flows were 50 and 800 L/h, respectively, which were obtained using a nitrogen source (N₂ Supplier Model 24S, Anest Iwata Co., Yokohama, Japan). Detailed selected reaction monitoring (SRM) transitions are shown in Table 1.

Table 1. Analytical Information and MS/MS Conditions for PFAS, F-53B and ADONA

Formula	Abbreviated name	Molecular mass	CAS	Precursor ion (m/z)	Cone voltage (V)	Product ion (m/z)	Collision energy (eV)	Internal standard	LOD (ng/mL)	LOQ (ng/mL)
C4F9-COOH	PFPeA	264.05	2706-90-3	263	20	219	10	13C5-PFHxA	0.4	0.8
C5F11-COOH	PFHxA	314.05	307-24-4	313	20	269	10	13C5-PFHxA	0.4	0.8
C6F13-COOH	PFHpA	364.06	375-85-9	363	20	319	10	13C5-PFHxA	0.4	0.8
C7F15-COOH	PFOA	414.07	335-67-1	413	20	369	10	13C6-PFOA	0.1	0.2
C8F17-COOH	PFNA	464.08	375-95-1	463	25	419	10	13C7-PFUdA	0.8	1.6
C9F19-COOH	PFDA	514.08	335-76-2	513	25	469	10	13C7-PFUdA	0.1	0.2
C10F21-COOH	PFUdA	564.09	2058-94-8	563	25	519	10	13C7-PFUdA	0.1	0.2
C4F9-SO3H	PFBS	300.10	375-73-5	299	55	80	30	13C3-PFHxS	0.1	0.2
C5F11-SO3H	PFPeS	350.11	2706-91-4	349	55	80	35	13C3-PFHxS	0.1	0.2
C6F13-SO3H	PFHxS	400.12	355-46-4	399	60	80	40	13C3-PFHxS	0.1	0.2
C7F15-SO3H	PFHpS	450.12	375-92-8	449	65	80	45	13C3-PFHxS	0.1	0.2
C8F17-SO3H	PFOS	500.13	1763-23-1	499	65	80	50	13C8-PFOS	0.1	0.2
C9F19-SO3H	PFNS	550.14	98789-57-2	549	60	80	50	13C8-PFOS	0.1	0.2
C10F21-SO3H	PFDS	600.15	335-77-3	599	65	80	50	13C8-PFOS	0.1	0.2
CF3OC3F6OCFHCF2-COOH	ADONA	400.05	958445-44-8	377	25	251	10	13C5-PFHxA	0.1	0.2
CClF2C5F10OC2F4-SO3H	F-53B	570.67	73606-19-6	531	50	351	25	13C8-PFOS	0.1	0.2

PFPeA; Perfluoropentanoic acid, PFHxA; Perfluorohexanoic acid, PFHpA; Perfluoroheptanoic acid, PFOA; Perfluorooctanoic acid, PFNA; Perfluorononanoic acid, PFDA; Perfluorodecanoic acid, PFUdA; Perfluoroundecanoic acid, PFBS; Perfluorobutanesulfonic acid, PFPeS; Perfluoropentanesulfonic acid, PFHxS; Perfluorohexanesulfonic acid, PFHpS; Perfluoroheptanesulfonic acid, PFOS, Perfluorooctanesulfonic acid, PFNS; Perfluorononanesulfonic acid, PFDS; Perfluorodecanesulfonic acid, ADONA; Dodecafluoro-3H-4,8-dioxanonanoate, F-53B; 9-chlorohexadecafluoro-3-oxanonane-1-sulfonate.

Sample Preparation

Drinking water and other samples were subjected to clean-up and concentration using a solid phase extraction (SPE) cartridge (Presep PFC-II: 60 mg/3 mL, FUJIFILM Wako Pure Chemical Corporation). The SPE cartridge was pre-conditioned with 5 mL of acetonitrile, followed by the addition of 5 mL of 1.0% FA in water/acetonitrile (70 : 30, v/v). The sample (35 mL) was combined with 50 µL of mixed stable isotope standard (100 ng/mL in methanol) and then 15 mL of 3.0% FA in acetonitrile was added. The mixture was centrifuged at 9894 × g for 10 min (High-speed Micro Centrifuge CF16RN, HITACHI Co., Tokyo, Japan). The sample solution (supernatant) was passed through the SPE cartridge, which was then washed with 5 mL of water/acetonitrile (70 : 30, v/v). The retained chemicals were eluted using 5 mL of 1.0% ammonium in acetonitrile based on 0.3 mL/min. The eluate was evaporated to dryness and redissolved in 500 µL of water/methanol (50 : 50, v/v).

Quantitative Procedure

Fixed concentrations of the standard solutions (limit of quantitation (LOQ) −50 ng/mL) were prepared by sequential dilutions of the stock solutions. The limit of detection (LOD) and LOQ values were evaluated based on the signal-to-noise ratio (S/N) obtained while detecting the concentration of analytes and were determined as S/N = 3 and S/N > 10, respectively. Calibration curves were constructed using seven analyte concentrations to evaluate linearity at each concentration by plotting the peak area ratio of the standard solutions based on MassLynx software (configuration; internal standard (y) vs. each concentration of the adjusted standard solution (x) based on curve type, linear; origin, exclude; weighting, 1/x; and axis tras, none).

For the quantitation of the analytes in the samples, a 70-fold dilution of the sample was preparation and analyzed by LC-MS/MS. Using the calibration curve, the quantities of the analytes in the samples were calculated as 1/70× concentration (calibration range from LOQ to 50 ng/mL) from the detected peak response. Thus, the lower limit of quantitation (LLOQ) was 1/70× LOQ. Reliable LLOQ values were determined to be 25 ng/L for PFNA, 15 ng/L for PFPeA, PFHxA, PFHpA, and 5 ng/L for other PFAS.

Results and Discussion

LC-MS/MS Analysis of PFAS, F-53B and ADONA

Based on a previous study, we selected common PFAS with fluorocarbon chains from C₄ to C₁₀²⁴⁾ (Table 1). In addition, F-53B and ADONA were selected for development of the LC-MS/MS screening method.²⁵⁾ Pre-experimentally, we investigated the C₄ and C₁₀ fluorocarbon chain of PFAS for chromatographic separation, ESI-negative ionization, and sample preparation with SPE. The results indicated that the RP separation and SPE procedure for these PFAS were unfavorable for optimization because of their completely different polar solubility. Thus, in this study, fourteen PFAS, F-53B and ADONA compounds were concomitantly examined using various RP columns and ESI-negative mode. In addition, four branched-chain PFAS (PFNA, PFHxS, PFOS and PFNS) were observed to produce separate peaks when monitoring the same ion mode. Based on these results, the optimal LC-MS/MS condition and SRM chromatograms are shown in Table 1 and Fig. 1. MS/MS spectra and calibration curves are shown in Figs. S1–S3. The observed sensitivity and selectivity were deemed useful and suitable for monitoring analysis of PFAS, F-53B and ADONA.

Fig. 1. SRM Chromatograms for 14 PFAS, F-53B, ADONA and Internal Standards

a) PFPeA standard solution (50 ng/mL) in m/z 263 > 219. b) PFHxA standard solution (50 ng/mL) in m/z 313 > 269. c) PFHpA standard solution (50 ng/mL) in m/z 363 > 319. d) PFOA standard solution (50 ng/mL) in m/z 413 > 369. e) PFNA and ipPFNA standard solutions (50 ng/mL) in m/z 463 > 419. f) PFDA standard solution (50 ng/mL) in m/z 513 > 469. g) PFUdA standard solution (50 ng/mL) in m/z 563 > 519. h) PFBS standard solution (50 ng/mL) in m/z 299 > 80. i) PFPeS standard solution (50 ng/mL) in m/z 349 > 80. j) PFHxS standard solution (50 ng/mL) in m/z 399 > 80. k) PFHpS standard solution (50 ng/mL) in m/z 449 > 80. l) PFOS standard solution (50 ng/mL) in m/z 499 > 80. m) PFNS and ipPFNA standard solutions (50 ng/mL) in m/z 549 > 80. n) PFDS standard solution (50 ng/mL) in m/z 599 > 80. o) ADONA standard solution (50 ng/mL) in m/z 377 > 251. p) F-53B standard solution (50 ng/mL) in m/z 531 > 351. q) ¹³C₅-PFHxA stable isotope internal standard solution (50 ng/mL) in m/z 318 > 273. r) ¹³C₃-PFHxS stable isotope internal standard solution (50 ng/mL) in m/z 402 > 273. s) ¹³C₆-PFOA stable isotope internal standard solution (50 ng/mL) in m/z 421 > 376. t) ¹³C₈-PFOA stable isotope internal standard solution (50 ng/mL) in m/z 507 > 80. u) ¹³C₇-PFUdA stable isotope internal standard solution (50 ng/mL) in m/z 570 > 525.

Sample Preparation of PFAS, F-53B and ADONA in Water, Tea and Juice Samples Using SPE

The ultimate goal of the screening method is to determine human exposure to PFAS based on TDS from Japanese food samples. Thus, the use of various food materials in developing the procedure is expected to result in a robust and broadly applicable procedure.-Based on our preliminary study for complex food materials, a flow-through SPE procedure used acetonitrile. Solvent extraction from drinking water or similar samples is not an essential step with SPE. Based on the simple SPE procedure, sample preparation was investigated using experimental water and showed the ability to detect trace levels of PFNA. To suppress background contamination, the experimental water was filtered using an activated carbon filter (InertSep Slim-J AC).²⁶⁾ However, limited contamination of PFNA was observed throughout the SPE procedure. Thus, the LLOQ of PFNA was increased to 25 ng/L for certifiable quantitative determinations. In addition, reliable LLOQ values were established as 25 ng/L for PFPeA, PFHxA, PFHpA, and 15 ng/L for other PFAS. The recovery of analytes in bottled water, tea and juice were examined using the optimal SPE procedure, showing acceptable values of 92.8 ± 0.2 to 117.7 ± 0.1%, 81.7 ± 0.2 to 118.8 ± 0.5, and 80.4 ± 0.5 to 102.3 ± 0.3%, for three concentration levels (35, 70 and 140 ng/L, respectively) (Table 2). In the inter-day assay (n = 6, 3 d), the repeatability of absolute stable isotope standards in recovery test showed the RSD values of 4.4% (¹³C₅-PFHxA), 6.3% (¹³C₆-PFOA), 4.4% (¹³C₇-PFUdA), 6.9% (¹³C₃-PFHxS) and 6.7% (¹³C₈-PFOS), respectively. Typical SRM chromatograms of analytes in samples are shown in Fig. 2.

Table 2. Recovery Test for PFAS, F-53B and ADONA

Analytes	Recovery value ± S.D. (%), (n = 3)for bottled water			Recovery value ± S.D. (%), (n = 3)for tea			Recovery value ± S.D. (%), (n = 3)for orange juice
	35 ng/L	70 ng/L	140 ng/L	35 ng/L	70 ng/L	140 ng/L	35 ng/L	70 ng/L	140 ng/L
PFPeA	117.7 ± 0.1	97.0 ± 0.3	110.6 ± 0.2	102.7 ± 0.2	118.4 ± 0.2	118.8 ± 0.5	100.6 ± 0.2	93.8 ± 0.2	80.4 ± 0.5
PFHxA	103.7 ± 0.1	99.5 ± 0.3	102.0 ± 0.4	109.5 ± 0.1	94.4 ± 0.1	102.2 ± 0.4	101.2 ± 0.1	99.0 ± 0.1	98.3 ± 0.3
PFHpA	95.3 ± 0.1	102.6 ± 0.1	98.7 ± 0.1	114.5 ± 0.3	94.5 ± 0.5	105.0 ± 0.4	98.2 ± 0.1	99.8 ± 0.2	95.3 ± 0.3
PFOA	95.5 ± 0.1	101.7 ± 0.2	99.4 ± 0.1	106.6 ± 0.6	93.3 ± 0.3	103.0 ± 0.2	100.6 ± 0.1	97.9 ± 0.2	94.9 ± 0.2
PFNA	92.8 ± 0.2	93.8 ± 0.4	108.0 ± 0.1	83.2 ± 0.1	84.3 ± 0.2	94.2 ± 0.3	93.2 ± 0.1	95.1 ± 0.2	86.1 ± 0.3
PFDA	100.2 ± 0.1	101.0 ± 0.2	97.7 ± 0.2	99.5 ± 0.2	91.1 ± 0.1	102.0 ± 0.3	102.3 ± 0.1	99.3 ± 0.2	85.7 ± 0.1
PFUdA	99.4 ± 0.1	99.7 ± 0.1	101.0 ± 0.4	112.4 ± 0.1	101.5 ± 0.2	97.8 ± 0.3	99.7 ± 0.1	94.1 ± 0.2	96.1 ± 0.2
PFBS	96.5 ± 0.1	100.3 ± 0.1	101.5 ± 0.4	94.0 ± 0.1	91.7 ± 0.1	96.2 ± 0.4	97.3 ± 0.1	83.7 ± 0.3	89.7 ± 0.3
PFPeS	100.5 ± 0.2	98.4 ± 0.1	98.1 ± 0.2	99.3 ± 0.1	93.7 ± 0.1	98.7 ± 0.5	95.5 ± 0.1	99.5 ± 0.2	88.6 ± 0.3
PFHxS	94.7 ± 0.1	97.5 ± 0.2	96.2 ± 0.2	89.3 ± 0.2	90.9 ± 0.2	85.8 ± 0.1	93.0 ± 0.2	88.8 ± 0.2	94.6 ± 0.3
PFHpS	98.7 ± 0.2	102.8 ± 0.1	102.0 ± 0.5	104.4 ± 0.1	98.8 ± 0.1	95.9 ± 0.3	92.9 ± 0.1	93.3 ± 0.2	97.8 ± 0.2
PFOS	100.1 ± 0.1	99.6 ± 0.1	99.9 ± 0.1	100.0 ± 0.1	99.5 ± 0.1	97.7 ± 0.5	97.4 ± 0.1	100.2 ± 0.1	93.3 ± 0.3
PFNS	93.1 ± 0.1	98.8 ± 0.1	105.0 ± 0.3	107.1 ± 0.1	114.6 ± 0.1	101.1 ± 0.4	97.4 ± 0.1	98.1 ± 0.1	99.1 ± 0.2
PFDS	98.6 ± 0.1	98.5 ± 0.2	100.6 ± 0.2	110.5 ± 0.2	111.9 ± 0.1	99.0 ± 0.6	97.2 ± 0.1	99.2 ± 0.4	98.8 ± 0.2
ADONA	98.9 ± 0.1	100.9 ± 0.1	100.7 ± 0.1	90.7 ± 0.1	81.7 ± 0.2	94.3 ± 0.4	100.2 ± 0.1	102.3 ± 0.3	96.3 ± 0.3
F-53B	98.1 ± 0.1	105.1 ± 0.1	106.7 ± 0.1	100.7 ± 0.1	103.5 ± 0.2	97.9 ± 0.3	100.0 ± 0.1	100.3 ± 0.1	98.1 ± 0.2

Fig. 2. Typical SRM Chromatograms of Analytes in the Recovery Test

Concentration level: 140 ng/L of sample (bottled water) a) PFPeA in m/z 263 > 219 b) PFHxA in m/z 313 > 269 c) PFHpA in m/z 363 > 319 d) PFOA in m/z 413 > 369 e) PFNA in m/z 463 > 419 f) PFDA in m/z 513 > 469 g) PFUdA in m/z 563 > 519 h) PFBS in m/z 299 > 80 i) PFPeS in m/z 349 > 80 j) PFHxS in m/z 399 > 80 k) PFHpS in m/z 449 > 80 L) PFOS in m/z 499 > 80 m) PFNS in m/z 549 > 80 n) PFDS in m/z 599 > 80 o) ADONA in m/z 377 > 251 p) F-53B in m/z 531 > 351 q) ¹³C₅-PFHxA stable isotope internal standard in m/z 318 > 273 r) ¹³C₃-PFHxS stable isotope internal standard in m/z 402 > 273 s) ¹³C₆-PFOA stable isotope internal standard in m/z 421 > 376 t) ¹³C₈-PFOA stable isotope internal standard in m/z 507 > 80 u) ¹³C₇-PFUdA stable isotope internal standard in m/z 570 > 525

Monitoring Analysis of PFAS, F-53B and ADONA in Bottled Water, Tea and Juice from Japanese Markets

In the monitoring application, bottled water samples produced in Japan (n = 14) and abroad (n = 10) were obtained in 2019–2020 from Japanese markets and online, respectively. In addition, bottled tea (n = 12) and various juice (n = 18) samples were obtained from Japanese markets in 2020. Analysis of these samples indicated that PFAS, F-53B and ADONA were not detected (<LLOQ) in any of the samples. Thus, our evaluation of typical drinking samples from Japanese markets indicated that we were not able to detect contamination with PFAS, F-53B and ADONA in the samples studied.

Conclusion

We described the monitoring analysis of PFAS, F-53B and ADONA using a preliminary market-basket method based on LC-MS/MS and SPE, which can be used to monitor daily intake in drinking samples. The recovered values in bottled water, tea and juice were examined using a Presep PFC-II cartridge and showed acceptable values of 80.4 ± 0.5% to 118.8 ± 0.5% for the three added concentration levels (35, 70 and 140 ng/L). Our findings suggest that the LC-MS/MS and SPE methods described herein are appropriate for generating regulatory data pertaining to human exposure limits, and as a versatile screening assay for PFAS, F-53B and ADONA contamination in various food samples. In addition, it can be explicated to evaluate these contaminations based on a provisional target levels (50 ng/L) of combined PFOS and PFOA in tap water from Japanese guideline.¹³⁾

Acknowledgments

This work was supported by a Health Labor Sciences Research Grant from the Ministry of Health, Labour and Welfare, Japan.

Conflict of Interest

The authors declare no conflict of interest.

Supplementary Materials

The online version of this article contains supplementary materials.

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