Method development of total oxidizable precursor …1274106/FULLTEXT01.pdfs-1 (2) Although the...

School of Science and Technology Analytical Science Programme in Chemistry with a focus on Forensics

Bachelor thesis 15hp

Method development of total oxidizable precursor assay for perfluoroalkyl acid

precursors in domestic sludge

Lydia Soumlderlund

Supervisor Leo Yeung

Examinator Anna Kaumlrrman

Date 2018-01-21

Project in Chemistry 15 hp School of Science and Technology Oumlrebro University

Abstract Per- and polyfluoroalkyl substances (PFASs) are persistent organic pollutants used in industrial applications and are globally distributed in the environment A group of PFASs that are difficult to measure with todayrsquos method are perfluoroalkyl acid precursors (PFAA precursors) that when degraded serves as indirect sources of PFAAs This study has optimized a previously developed method for quantification of PFAA precursors in soil through total oxidizable precursor assay (TOP assay) under alkaline conditions to be applicable on sewage sludge To achieve and maintain an alkaline environment during the entire oxidative treatment several parameters were tested concentrations of NaOH persulfate and sample additional clean-up with graphitized non-porous carbon and reaction time Solid phase extraction-weak anion exchange (SPE-WAX) was used for clean-up and separation of analytes and LC-MSMS was used for quantification The optimal conditions with the highest levels of PFAAs detected was obtained with 133 M NaOH 60 mM persulfate 357 gL sludge with a reaction time of 6 hours The use of graphitized non-porous carbon reduced matrix effects on oxidative conversion resulting in a higher pH as well as a higher degree of oxidation but with some analyte loss

Keywords Total oxidizable precursor assay (TOP assay) Perfluoroalkyl substances (PFASs) Perfluoroalkyl acids (PFAAs) Sewage sludge Oxidative conversion Organofluorine


Table of Content

Abstract 2

Introduction 4

Aims and Limitations 4

Background 5

Polyfluoroalkyl andor perfluoroalkyl substances (PFASs) and oxidative conversion 5

Total oxidizable precursor assay (TOP assay) 6

PFAA precursors 6

Sewage Sludge 7

Method 8

Materials 8

Stock testing sample 8

Graphitized non-porous carbon treatment 8

Total oxidizable precursor (TOP) assay 8

Solid phase extraction 8

LC-MSMS analysis 9

Results 10

pH after reaction 10

Oxidative Transformation 11

Relative standard deviation 12

Recovery 13

Discussion 14

pH 14

Graphitized non-porous carbonrsquos effect on target compounds 14


Conclusion 16

References 17


Introduction Poly- and perfluoroalkyl substances (PFASs) are anthropogenic compounds where one or more of the hydrogen atoms have been substituted with fluoride atoms giving them properties useful for water repellence and tension lowering Since the 1950rsquos industries have used PFASs in a wide range of applications resulting in a global emission of these compounds While we can analyse more than 70 PFASs with current methods many of them remain not studied because of unknown identity and the availability of authentic standards leaving a large part of the organofluorine unidentified To overcome this issue a new method total oxidizable precursor assay (TOP assay) that transforms precursor compounds into detectable PFASs via oxidative treatment have been developed for assessing the amount of PFAS precursor in a sample1

Aims and Limitations The aim of current study was to develop a method for the analysis of PFAA precursors in sewage sludge by oxidative conversion and the method was initially based on a published method for soil Parameters tested in current investigation included concentrations of NaOH and persulfate graphitized non-porous carbon as an additional clean-up method before reaction reaction time and concentrationsamounts of sample (table 2) The goal was to obtain a pH of ge 12 during the entire reaction time and to qualitative evaluate the changes in levels of PFAA and PFAA precursors

For every batch of reaction a negative control sample without the oxidizing reagent was also prepared for contamination check Positive and negative control samples containing 62 FTSA a PFCA precursor was prepared and analyzed

Solid Phase Extraction ndash Weak Anion Exchange (SPE-WAX) cartridge was used as a clean-up and separation step for the analysis Recoveries of the SPE on selected PFASs were also evaluated in the samples Levels of PFASs in the samples were analyzed with LC-MSMS

The target compounds included PFCAs C4-C14 C16 C18 (PFBA PFPeA PFHxA PFHpA PFOA PFNA PFDA PFUnDA PFDoDA PFTrDA PFTDA PFHxDA and PFOcDA) PFSAs C4-C10 C12 (PFBS PFPeS PFHxS PFHpS PFOS PFNS PFDS and PFDoDS) and FTSAs C4-C8 (42 FTSA 62 FTSA 82 FTSA) Table 1 shows the abbreviations mentioned above


Background Polyfluoroalkyl andor perfluoroalkyl substances (PFASs) and oxidative conversion Polyfluoroalkyl- and perfluoroalkyl substances (PFASs) are compounds that consist of a hydrophilic functional group attached to a carbon chain where the hydrogen atoms are partially or totally substituted with fluorine atoms2 This structure gives properties of a surfactant hydrophobic and tension lowering which makes them suitable components in a wide range of applications such as paint grease proof materials coatings and aqueous film forming foams (AFFF) for firefighting3 PFASs are divided into numerous families of which the most prominent compounds belong to the perfluoroalkyl acids (PFAAs)23 (table 1) PFAAs a family that have earned great attention in research and media consist just like the other PFASs of a fluorinated carbon chain but with an acidic functional group attached to its terminal end such as carboxylic acid (for PFCAs) or sulfonic acid (for PFSAs)

Table 1 List of the targeted PFASrsquos abbreviations names and their number of carbons

Abbreviation Name Carbon chain length PFSA Perfluorosulfonic acid PFBS Perfluorobutane sulfonic acid 4 PFPeS Perfluoropentane sulfonic acid 5 PFHxS Perflurohexane sulfonic acid 6 PFHpS Perfluoroheptane sulfonic acid 7 PFOS Perfluorooctane sulfonic acid 8 PFNS Perfluorononane sulfonic acid 9 PFDS Perfluorodecane sulfonic acid 10 PFDoS Perfluorododecane sulfonic acid 12 PFCA Perfluorocarboxylic acid PFBA Perfluorobutanoic acid 4 PFPeA Perfluoropentanoic acid 5 PFHxA Perfluorohexanoic acid 6 PFHpA Perfluoroheptanoic acid 7 PFOA Perfluorooctanoic acid 8 PFNA Perfluorononanoic acid 9 PFDA Perfluorodecanoic acid 10 PFUnDA Perfluoroundecanoic acid 11 PFDoDA Perfluorododecanoic acid 12 PFTrDA Perfluorotridecanoic acid 13 PFTDA Perfluorotetradecanoic acid 14 FTSA Fluorotelomer sulfonic acid 42 FTSA 42 Fluorotelomer sulfonic acid 4 62 FTSA 62 Fluorotelomer sulfonic acid 6 82 FTSA 82 Fluorotelomer sulfonic acid 8


In the 1950rsquos industries began taking advantage of the unique characteristics of these substances in numerous applications but the effects of PFAS emission to the environment were not studied until the early 2000rsquos4 That study showed a global distribution of PFAS in animal tissues and potential accumulation to higher trophic levels Further research found that high doses of PFAS could be lethal to newborn rodents that PFASs could act as tumour inducing and immunotoxic agents in the body5 that they can be transferred to the fetus during pregnancy6 and to infants through lactation7

These findings suggesting that PFASs are potentially hazardous to human health persistent to degradation and bioaccumulative have raised concern among scientists and general population After the voluntary phase out of PFOS and PFOA the European Union started to take action and restricted the use of certain PFAS compounds in 20068 Subsequently the interests on this topic have grown and more than 400 scientific articles about it are published every year2

Total oxidizable precursor assay (TOP assay) The most studied source of PFAS is direct emission which involves release of the substances from products containing PFAS industries and waste water treatment plants However PFAS can also enter the environment indirectly by oxidative transformation of other polyfluorinated compounds forming perfluoroalkyl acids (PFAAs)2 These polyfluorinated compounds such as 62 FTSA and FOSA are referred to as PFAA precursors29 (see details below) One way to analyze them is to mimic the oxidation process in a procedure called total oxidizable precursor assay (TOP assay) which have worked successfully in various matrices (eg water and soil)10 The method uses hydroxyl radicals formed by thermolysis of persulfate under alkaline conditions to transform PFAA precursors into PFAA of corresponding chain length In previous experiments with urban runoff water the PFCA levels increased with a median of 69 after undergoing oxidative treatment1

Demonstrated in earlier experiments the reaction rate of the persulfate radicals to hydroxyl radicals transformation is 1 times 107 times faster under alkaline (eq 2) than acidic (eq 1) conditions11 Addition of NaOH in the absence of persulfate during heating however have previously not shown to affect the precursor levels1 Therefore pH is an important factor when conducting TOP assay and maintaining a pH of 12 or above is required to assure a consistent degree of transformation between batches

All pH 1198781198781198781198784minus + 1198671198672119878119878 rarr 11987811987811987811987842minus + 119878119878119867119867 + 119867119867+ k lt 60 M-1 s-1 (1)

Alkaline pH 1198781198781198781198784minus + 119878119878119867119867minus rarr 11987811987811987811987842minus + 119878119878119867119867 k = 7 times 107 M-1 s-1 (2)

Although the technique is a promising tool when examining PFAS precursors there are various limitations that currently makes it a qualitative method such as insufficient knowledge about the oxidation processrsquos efficiency with the presence of organic contaminants in the matrix Mixed results as a consequence of partial oxidation of some PFASs and a need for evaluation of the method for several PFAS precursor compounds are some of the issues that the method struggles with Therefore the results of this experiment were evaluated mainly qualitatively12

PFAA precursors PFAA precursors refer to any compound that could degrade and give rise to PFAAs (PFSAs or PFCAs) For example compounds that degrade to PFSAs are typically constructed of a PFSA unit connected to another functional group such as an amide Commonly used industrial precursors are N-ethylperfluoro-octanesulfonamide (EtFOSA) N-ethylperfluorooctane-sulfonamidoethanol (EtFOSE) N-methylperfluorooctansulfonamide (MeFOSA) and N-methylperfluorooctanesulfonamidoethanol (MeFOSE)9

62 fluorotelomer sulfonic acid (62 FTSA) is one of the main components of aqueous film forming foam (AFFF) for firefighting13 and can if environmentally degraded contribute to emission of


PFCAs Studies have shown that some microorganisms have the ability to through desulfonation and oxidation transform 62 FTSA into PFCAs1314

Sewage Sludge Sewage sludge is a waste product from waste water treatment plants (WWTP) It is composed of organic matter chemicals and all sorts of things that are flushed down the toilet Because of the high nutrition value the agriculture industry is reusing it as a fertilizer for fields and forests15

However WWTPs have been considered sources of PFASs release to the environment16 Recent studies have detected large quantities of PFASs in sewage sludge from Swedish WWTPs where the majority was of unidentified kind17 As there are some evidence for uptake of PFAS in plants the use of sewage sludge as a fertilizer may result in an accumulation of PFASs in foodstuff18 Therefore it is of great interest to analyse sewage sludge in the attempt to fully understand the toxicity and bioaccumulation effects of PFASs Further evaluating the levels of PFAA precursors is a vital step in future investigations and risk assessments of PFASs in order to avoid underestimation of the total PFASs that humans and the environment are potentially exposed to

As TOP assay has not been tested on sewage sludge before this report initially adopted a method developed for soil and groundwater10 and optimized it from there


Method Materials Potassium peroxodisulfate (K2S2O 990) and ammonium acetate (C2H7NO2 990) were purchased from Sigma Aldrich Sodium hydroxide pellets (NaOH laboratory reagent grade) methanol (CH3OH HPLC grade) ammonia solution (NH4OH 25 analytical reagent grade) were purchased from Fisher Scientific

All plastic containers and SPE equipment were sonicated with MilliQ-water and detergent and then with ethanol followed by a rinse with methanol before use

Stock testing sample A stock testing sample was prepared by extracting 15 g of domestic sludge (standard reference material (SRM) 2781 from National Institute of Standards and Technology) in 12 ml of 02 M NaOH in methanol in a 50 ml PP tube The solution was homogenized by vortex followed by sonication for 30 min After sonication 18 ml of methanol was added the tube was vortexed again and centrifuged for 10 min at 6000 rpm the mixture was divided into a supernatant and a pellet The supernatant was transferred to a new 50 ml tube and 12 ml of methanol was added to the remaining pellet The centrifugation and transfer of supernatant procedure was repeated once and the final volume of the supernatant was adjusted to 42 ml using methanol Thereafter the stock testing sample was divided into subsamples displayed in table 2 the subsamples in respective PP tubes were evaporated to dryness with nitrogen gas When the samples were completely dry 5 ml of MilliQ-water was used for resuspension Following NaOH MilliQ-water and potassium persulfate were added to each sample to obtain the proportions shown in table 2 and the tubes were filled up to 15 ml with MilliQ-water

Graphitized non-porous carbon treatment Before the evaporation some subsamples were subjected to graphitized non-porous carbon (GNPC) clean-up using a 1 ml Supelcleantrade ENVI-Carbtrade 1ml100mg (Supelco) cartridge Initially the cartridge was rinsed with 1 ml of methanol 3 times before loading the sample The entire sample was loaded and collected another 1 ml of methanol was added to eluate any analyte residues

Total oxidizable precursor (TOP) assay The samples were incubated in a water bath at 85degC for either 6h or 10h When finished the samples were placed in an ice bath to stop the reaction The pH of the reaction solution was measured and then adjusted to pH 4 using concentrated hydrochloric acid before clean-up using solid phase extraction-weak anion exchange

Table 2 The parameters that were tested in the reaction

[NaOH] Sample [Persulfate] GNPC Reaction time 0125 M 1785 mg 60 mM With 6 hours 133 M 357 mg 600 mM Without 10 hours

5355 mg 1071 mg

Solid phase extraction After reaction all samples were treated with solid phase extraction-weak anion exchange (Oasis SPE-WAX Waters Corporation) First the SPE cartridge was conditioned with 4 ml of 01 NH4OH in methanol 4 ml of methanol and 4 ml of MilliQ-water Second the sample was loaded and the cartridge washed with 20 ml of 001 NH4OH followed by 30 ml of MilliQ-water to remove any inorganic fluorine Finally 4 ml of acetate buffer was added and the cartridge was centrifugated at


3000 rpm for 2 min and then dried under vacuum for approximately 30 min After that the analytes were eluted in two fractions with 4 ml methanol for fraction 1 (fraction containing neutral and cationic compounds) and 4 ml of 01 NH4OH in methanol for fraction 2 (fraction containing anionic compounds) The sample volume was concentrated to 05 ml under a gentle flow of nitrogen gas

LC-MSMS analysis After the concentration step the samples were transferred to LC vials for instrumental analysis with the following combinations of mobile phase and standards mobile phase (02 M ammonium acetate in MilliQ-water) and recovery standard in the proportions samplemobile phase 8020 for fraction 1 and 4060 for fraction 2

The instrument used for analysis was an Acquity UPLC system coupled to a XEVO TQ-S (Waters Co Milford USA) triple quadrupole mass spectrometer operated in negative ionization mode using electrospray ionization The analytes were separated in a 100 mm C18 BEH column (17 microm 21 mm) using a gradient elution of mobile phase A (2mM ammonium acetate in a water and methanol mixture (7030)) and B (2mM ammonium acetate in methanol)

The levels of PFCA PFSA and FTSAs were quantified using internal standards that where added prior to analysis LOD was calculated according to eq 3 and LOQ to eq 4 All reported values are above LOQ

119871119871119871119871119871119871 = 119898119898119898119898119898119898119898119898119887119887119887119887119887119887119887119887119887119887 119887119887119886119886119886119886119887119887 + 3 times 119904119904119904119904119898119898119898119898119904119904119898119898119904119904119904119904 119904119904119898119898119889119889119889119889119898119898119904119904119889119889119871119871119898119898119887119887119887119887119887119887119887119887119887119887 119887119887119886119886119886119886119887119887 (3)

119871119871119871119871119871119871 = 1198711198711198711198711198711198713

times 10 (4)

The LOD and LOQ values were calculated from the values of 7 blank replicates for samples treated with graphitized non-porous carbon and 2 blank replicates for blanks not treated with graphitized non-porous carbon


Results pH after reaction The first trials tested the lower sodium hydroxide concentration (0125 M) along with different amount of persulfate (60 mM and 600 mM) and the effect of graphitized non-porous carbon (GNPC) clean-up All samples resulted in an undesired pH and therefore the concentration of sodium hydroxide was increased in the next trials In combination with the higher NaOH concentration (133 M) four different sample amounts were tested with further subparameters Using a sample amount of 1071 mg resulted in an undesired pH in all test both with high and low concentration of persulfate However an improvement from pH 1 to pH 7 could be observed when using GNPC By reason of crystals observed in the sample when using 600 mM persulfate the experiment proceeded with 60 mM persulfate Three lower sample amounts with 5355 mg as the highest were tested and all three successfully obtained a high pH during a 6 hour reaction time both with and without GNPC An additional test using the parameters 133 M NaOH 5355 mg sample 60 mM persulfate Additionally one 5355 mg GNPC treated sample was tested with a reaction time of 10 hours instead of 6 The prolonged reaction resulted in a decrease in pH from 12 to 7

Regarding the control samples containing 62 FTSA the results were similar to the SRM-tests 0125 M NaOH resulted in a low pH level as well as a 133 M NaOH with a reaction time of 10 hours However a combination of 133 M NaOH 60 mM persulfate and 6 hours reaction time resulted in pH 12

Figure 1 Flowchart of the combination of parameters test and their resulting pH


Oxidative Transformation The presented data are obtained from the samples with the parameters 133 M NaOH 60 mM persulfate 5355 mg sample and a reaction time of 6 hours

Figures 2-4 Mean concentration (pgg SRM) of PFCAs (figure 2) PFSAs (figure 3) and FTSAs (figure 4) in three replicates of SRM samples P positive (with persulfate) N negative (without persulfate) E with GNPC treatment

0

100000

200000

300000

400000

500000

600000

700000

800000

900000

1000000

1100000

PE NE P N

Conc (pgg)PFCAs in SRM

PFOcDA

PFHxDA

PFTDA

PFTrDA

PFDoDA

PFUnDA

PFDA

PFNA

PFOA

PFHpA

PFHxA

PFPeA

PFBA

0

150000

300000

450000

600000

750000

900000

1050000

1200000

1350000

1500000

PE NE P N

Conc (pgg)

PFSAs in SRM

PFDoDS

PFDS

PFNS

PFOS

PFHpS

PFHxS

PFPeS

PFBS

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

5500

6000

6500

7000

7500

PE NE P N

Conc (pgg)FTSAs in SRM

82 FTSA

62 FTSA

42 FTSA


Figure 5-7 The quantity of substance (nmol) of PFCAs (figure 5) PFSAs (figure 6) and FTSAs (figure 7) in the control samples PC positive control (with persulfate) NC negative control (without persulfate) E with GNPC treatment

Relative standard deviation Table 3 The relative standard deviation of the three replicates of every sample

Compound PE NE P N

PFBA 40 ltLOQ 27 73 PFPeA 52 ltLOQ 15 18 PFHxA 28 ltLOQ 16 19 PFHpA 20 5 17 16 PFOA 25 7 16 21 PFNA 24 4 20 14 PFDA 25 8 19 70 PFUnDA 28 ltLOQ 18 19 PFDoDA 23 8 33 ltLOQ PFTrDA 21 10 23 ltLOQ PFTDA 22 ltLOQ 39 ltLOQ PFHxDA 37 ltLOQ ltLOQ ltLOQ PFOcDA 73 ltLOQ 29 56

0

500

1000

1500

2000

2500

3000

PCE NCE PC NC

n (nmol)PFCA in control

PFOcDA

PFHxDA

PFTDA

PFTrDA

PFDoDA

PFUnDA

PFDA

PFNA

PFOA

PFHpA

PFHxA

PFPeA

PFBA

0

001

002

003

004

005

006

007

008

009

01

011

PCE NCE PC NC

n (nmol)PFSA in control

PFDoS

PFDS

PFNS

PFOS

PFHpS

PFHxS

PFPeS

PFBS

0

5

10

15

20

25

30

35

40

45

50

55

60

65

PCE NCE PC NC

n (nmol)FTSA in control

82 FTSA

62 FTSA

42 FTSA


PFBS 23 20 13 15 PFPeS ltLOQ ltLOQ 11 16 PFHxS 19 21 9 21 PFHpS 17 7 14 24 PFOS 18 10 9 21 PFNS 18 9 12 18 PFDS 25 9 12 17 PFDoDS ltLOQ ltLOQ ltLOQ ltLOQ

42 FTSA ltLOQ ltLOQ ltLOQ ltLOQ 62 FTSA ltLOQ 13 ltLOQ 23 82 FTSA ltLOQ 12 21 11

Recovery The recovery of the SPE was measured in some samples and ranged between 04-506 in the real samples 14-448 in the blanks and 14-996 in the FTSA controls Recovery of the 62 FTSA in the control samples however was about 900


Discussion pH As discussed in the background section pH is a vital parameter when conducting TOP assay and maintaining a pH of 12 during the entire reaction time is desired for even and reproducible results between batches Initially the parameters 0125 M NaOH 60 mM persulfate with GNPC reaction time of 6 hours were chosen according to a study on water and soil sample10 and applied on positive (with persulfate) and negative (without persulfate) triplicates of SRM and a control sample with a standard containing 62 FTSA However after reaction both the SRM and the control samples resulted in a pH 1 Thereafter additional tests with various concentrations of NaOH persulfate and sample were evaluated

Sample amount All tests with the initial sample amount (1071 mg) resulted in a low pH In the three trials testing the lower amounts of sample with 133 M NaOH and 60 mM persulfate however all three resulted in a pH of 12 suggesting that the reaction worked accordingly with le 5355 mg SRM in 15 ml MilliQ-water

Reaction time Parameters that were confirmed in to yield a pH of 12 were applied but with a reaction time of 10h instead of 6h However the pH level dropped to pH 7 in the SRM sample and 9 in the control sample when the reaction time was increased These results indicate that the matrix might not necessarily be the cause of a decrease in pH since the control sample did not contain any matrix A reason for the pH drop could be that all hydroxyl radicals were consumed during a prolonged reaction time and that higher concentration of NaOH would be required for such conditions although more comprehensive studies would be necessary to confirm that Further matrix effect meaning that the oxidant reacted with other chemicals could not be ruled out based on the current experiment In conclusion 133 M NaOH resulted in pH 12 when using a sample concentration of le 5355 mg in 15 ml MilliQ-water (357 gL) with a reaction time of 6 hours However when increasing the reaction time to 10h more NaOH is needed to maintain pH 12 during the entire reaction time

Potassium persulfate No difference between a higher or lower concentration of NaOH could be observed both resulted in undesired pHs Besides crystals of precipitated persulfate were observed in the samples indicating that the reacting solution was saturated Therefore 60 mM persulfate was used instead of 600 mM in next trials In future experiment more thorough evaluations of the effect of persulfate concentration on the reaction is desirable to further optimize the reaction

Graphitized non-porous carbon (GNPC) Regarding the pH a test was conducted to see whether the use of GNPC could reduce any matrix effects of the pH Successfully the test confirmed that a raise of the pH from 1 to 7 could be seen when using the initial sample amount (1073 mg) along with 133 M NaOH and GNPC The use of GNPC can reduce the amount of other substances consuming the hydroxyl radicals yet a NaOH concentration of 133 M is still required to maintain the desired reaction

Graphitized non-porous carbonrsquos effect on target compounds SRM samples The levels of all detected compounds in the negative samples follow a similar trend with lower levels after GNPC treatment even for the precursors suggesting a recovery loss during GNPC clean-up Despite that the amount of PFCAs (figure 2) and PFSAs (figure 3) in the SRM samples were more prevalent in the positive GNPC treatment (PE) than in the positive without GNPC treatment (P) Additionally more precursor compounds were found to be transformed in PE than in P (figure 4) A possible explanation for this could be that the GNPC removes organic matter from the matrix that might also consume the hydroxyl radicals instead of the PFAA precursors


The PFCAs with the highest levels in both PE and P were the C5-C8 indicating that the precursors dominating the SRM sludge are of 8 or lower carbon chain length

The PFSAs were found in higher amounts than the PFCAs in the SRM in both the positive and negative samples In the samples without GNPC treatment the levels did not differ significantly between negative and positive experiments

Regarding the FTSAs slightly lower levels were found in the GNPC treated samples This strengthens the suggestion that GNPC treatment causes a loss of analytes Besides 82 FTSA were also found in the positive sample suggesting that the total amount of precursors was not fully oxidized

Control samples The PFCAs found in the control samples were mainly C4-C6 as expected since the precursor that were added have a six carbon backbone and some C7 contaminations (figure 5) In contrast to the SRM samples the levels of PFCAs were almost twice as high in the sample not treated with GNPC (PC) than in the one treated with GNPC (PCE) If the previous suggested explanation for this phenomenon is accurate an outcome like this would be logical since what reduced the levels in the positive SRM samples without GNPC (PE) was the matrix effects and not the absence of GNPC In this case where there is no matrix the yield is lower when treated with GNPC as seen in the negative SRM samples (figure 2 3 5 6)

Quantifiable amounts of PFSAs were only found in the negative control sample without GNPC treatment Accordingly PFSAs are not the main transformation products of FTSA 13 meaning that these compounds are likely to be contaminants or transformation products of contaminants

When comparing the levels of precursors and the transformation products they should relate to each other since the molar ration between FTSA and PFCA is 11 The levels of PFCAs found the in the samples were about 20 in PCE and 40 in PC times greater than the levels of FTSA in their corresponding negative samples

The FTSA found in the negative samples also exceed the amount that was initially added (0094 nmol) This can be explained by the very high recovery of the 62 FTSA found in the negative samples around 900 Also small amounts of impurities of 82 FTSA were found in the 62 FTSA standard used in the experiment

In conclusion while the pH was improved and the yields in the positive SRM samples better with GNPC treatment loss of analytes was observed in the negative SRM samples and the control samples Despite the favourable increased transformation to PFCAs an analyte loss is not desired in quantitative investigations and would have to be accounted for in some way As it is not possible to add internal standard before reaction more thorough rinse of the cartridge could be one way to improve the recovery

Relative standard deviation The relative standard deviation (RSD) (table 2) corresponds to the amount of the compound found in the sample in some extent Low levels resulted in a high RSD and higher in lower RSD with some exceptions (PFBA and PFPeA in the positive GNPC-treated samples) The negative samples have generally lower RSD than the positive indicating that there could be an inconsistency in the reaction For the PFSAs the opposite trend is observed in P and N where the RSD is lower in the positive samples than in the negative Still the differences between the PFSA levels in P and N and their RSD values are not significantly great


Conclusion To maintain a pH of ge 12 during a reaction time of 6h the most suitable combination of parameters are le 5355 mg in 15 ml (357 gL) 133 M NaOH and 60 mM persulfate When increasing the reaction time which might be required for a complete oxidation of the total amount of precursors a higher concentration of NaOH is needed to avoid the pH drop observed when increasing the reaction time Whether an increased reaction time yields a higher amount of PFCAs could not be validated in the current investigation and further studies are necessary

Moreover GNPCgives advantages in terms of reducing matrix components that by consuming the hydroxyl radicals could cause a decrease in pH In other words the use of GNPC could prevent a pH drop and thereby increase the efficiency of the oxidation although a loss of analyte was observed Further the consistency of the transformation to PFCAs resulted in RSD values of 20-73 with GNPC treatment and 15-39 without (table 3)


References

1 Houtz E F amp Sedlak D L Oxidative Conversion as a Means of Detecting Precursors to Perfluoroalkyl Acids in Urban Runoff Environ Sci Technol 46 9342ndash9349 (2012)

2 Buck R C et al Perfluoroalkyl and polyfluoroalkyl substances in the environment Terminology classification and origins Integr Environ Assess Manag 7 513ndash541 (2011)

3 Hutzinger O The handbook of environmental chemistry Fuel Oxygenates Handbook of Environmental Chemsitry2 (1980) doi101007b_10457

4 Giesy J P amp Kannan K Global Distribution of Perfluorooctane Sulfonate in Wildlife Environ Sci Technol 35 1339ndash1342 (2001)

5 Butenhoff J L amp Rodricks J V Human Health Risk Assessment of Perfluoroalkyl Acids Toxicological Effects of Perfluoroalkyl and Polyfluoroalkyl Substances by DeWitt Jamie C (2015) doi101007978-3-319-15518-0

6 Lau C et al Exposure to perfluorooctane sulfonate during pregnancy in rat and mouse II Postnatal evaluation Toxicol Sci 74 382ndash392 (2003)

7 Kaumlrrman A et al Exposure of perfluorinated chemicals through lactation Levels of matched human milk and serum and a temporal trend 1996-2004 in Sweden Environ Health Perspect 115 226ndash230 (2007)

8 Council of the European Union amp Parlament Directive 2006122ECOF perfluorooctane sulfonates Regulation 166ndash168 (2006)

9 Martin J W Asher B J Beesoon S Benskin J P amp Ross M S PFOS or PreFOS Are perfluorooctane sulfonate precursors (PreFOS) important determinants of human and environmental perfluorooctane sulfonate (PFOS) exposure J Environ Monit 12 1979 (2010)

10 Houtz E F Higgins C P Field J A amp Sedlak D L Persistence of perfluoroalkyl acid precursors in AFFF-impacted groundwater and soil Environ Sci Technol 47 8187ndash8195 (2013)

11 Lee Y C Lo S L Kuo J amp Lin Y L Persulfate oxidation of perfluorooctanoic acid under the temperatures of 20-40degC Chem Eng J 198ndash199 27ndash32 (2012)

12 Banzhaf S Filipovic M Lewis J Sparrenbom C J amp Barthel R A review of contamination of surface- ground- and drinking water in Sweden by perfluoroalkyl and polyfluoroalkyl substances (PFASs) Ambio 46 335ndash346 (2017)

13 Zhang S Lu X Wang N amp Buck R C Biotransformation potential of 62 fluorotelomer sulfonate (62 FTSA) in aerobic and anaerobic sediment Chemosphere 154 224ndash230 (2016)

14 Wang N et al 62 Fluorotelomer sulfonate aerobic biotransformation in activated sludge of waste water treatment plants Chemosphere 82 853ndash858 (2011)

15 Sundin A M (Naturvaringrdsverket) Anvaumlndningsmoumljligheter foumlr avloppsslam httpwwwnaturvardsverketseStod-i-miljoarbetet Available at httpwwwnaturvardsverketseStod-i-miljoarbetetVagledningarAvloppAvloppsslamAnvandningsmojligheter-for-avloppsslam (Accessed 6th October 2015)

16 Weinberg I Dreyer A amp Ebinghaus R Waste water treatment plants as sources of polyfluorinated compounds polybrominated diphenyl ethers and musk fragrances to ambient


air Environ Pollut 159 935ndash941 (2011)

17 Kaumlrrman A Yeung L Eriksson U amp Swedish National Environmental Protection Agency A pilot study on unidentified poly- and perfluoroalkyl substances (PFASs) in sewage in Sweden

18 Stahl T et al Carryover of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) from soil to plants Arch Environ Contam Toxicol 57 289ndash298 (2009)

Abstract

Introduction

Aims and Limitations

Background

Polyfluoroalkyl andor perfluoroalkyl substances (PFASs) and oxidative conversion

Total oxidizable precursor assay (TOP assay)

PFAA precursors

Sewage Sludge

Method

Materials

Stock testing sample

Graphitized non-porous carbon treatment

Total oxidizable precursor (TOP) assay

Solid phase extraction

LC-MSMS analysis

Results

pH after reaction

Oxidative Transformation

Relative standard deviation

Recovery

Discussion

pH

Graphitized non-porous carbonrsquos effect on target compounds


Conclusion

References


Abstract Per- and polyfluoroalkyl substances (PFASs) are persistent organic pollutants used in industrial applications and are globally distributed in the environment A group of PFASs that are difficult to measure with todayrsquos method are perfluoroalkyl acid precursors (PFAA precursors) that when degraded serves as indirect sources of PFAAs This study has optimized a previously developed method for quantification of PFAA precursors in soil through total oxidizable precursor assay (TOP assay) under alkaline conditions to be applicable on sewage sludge To achieve and maintain an alkaline environment during the entire oxidative treatment several parameters were tested concentrations of NaOH persulfate and sample additional clean-up with graphitized non-porous carbon and reaction time Solid phase extraction-weak anion exchange (SPE-WAX) was used for clean-up and separation of analytes and LC-MSMS was used for quantification The optimal conditions with the highest levels of PFAAs detected was obtained with 133 M NaOH 60 mM persulfate 357 gL sludge with a reaction time of 6 hours The use of graphitized non-porous carbon reduced matrix effects on oxidative conversion resulting in a higher pH as well as a higher degree of oxidation but with some analyte loss

Keywords Total oxidizable precursor assay (TOP assay) Perfluoroalkyl substances (PFASs) Perfluoroalkyl acids (PFAAs) Sewage sludge Oxidative conversion Organofluorine


Table of Content

Abstract 2

Introduction 4


Background 5



PFAA precursors 6

Sewage Sludge 7

Method 8

Materials 8





LC-MSMS analysis 9

Results 10




Recovery 13

Discussion 14

pH 14



Conclusion 16

References 17


































5355 mg 1071 mg







119871119871119871119871119871119871 = 119898119898119898119898119898119898119898119898119887119887119887119887119887119887119887119887119887119887 119887119887119886119886119886119886119887119887 + 3 times 119904119904119904119904119898119898119898119898119904119904119898119898119904119904119904119904 119904119904119898119898119889119889119889119889119898119898119904119904119889119889119871119871119898119898119887119887119887119887119887119887119887119887119887119887 119887119887119886119886119886119886119887119887 (3)

119871119871119871119871119871119871 = 1198711198711198711198711198711198713

times 10 (4)









0

100000

200000

300000

400000

500000

600000

700000

800000

900000

1000000

1100000

PE NE P N


PFOcDA

PFHxDA

PFTDA

PFTrDA

PFDoDA

PFUnDA

PFDA

PFNA

PFOA

PFHpA

PFHxA

PFPeA

PFBA

0

150000

300000

450000

600000

750000

900000

1050000

1200000

1350000

1500000

PE NE P N

Conc (pgg)

PFSAs in SRM

PFDoDS

PFDS

PFNS

PFOS

PFHpS

PFHxS

PFPeS

PFBS

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

5500

6000

6500

7000

7500

PE NE P N


82 FTSA

62 FTSA

42 FTSA




Compound PE NE P N


0

500

1000

1500

2000

2500

3000

PCE NCE PC NC


PFOcDA

PFHxDA

PFTDA

PFTrDA

PFDoDA

PFUnDA

PFDA

PFNA

PFOA

PFHpA

PFHxA

PFPeA

PFBA

0

001

002

003

004

005

006

007

008

009

01

011

PCE NCE PC NC


PFDoS

PFDS

PFNS

PFOS

PFHpS

PFHxS

PFPeS

PFBS

0

5

10

15

20

25

30

35

40

45

50

55

60

65

PCE NCE PC NC


82 FTSA

62 FTSA

42 FTSA


























References





















Abstract

Introduction


Background



PFAA precursors

Sewage Sludge

Method

Materials





LC-MSMS analysis

Results

pH after reaction



Recovery

Discussion

pH



Conclusion

References


Table of Content

Abstract 2

Introduction 4


Background 5



PFAA precursors 6

Sewage Sludge 7

Method 8

Materials 8





LC-MSMS analysis 9

Results 10




Recovery 13

Discussion 14

pH 14



Conclusion 16

References 17


































5355 mg 1071 mg







119871119871119871119871119871119871 = 119898119898119898119898119898119898119898119898119887119887119887119887119887119887119887119887119887119887 119887119887119886119886119886119886119887119887 + 3 times 119904119904119904119904119898119898119898119898119904119904119898119898119904119904119904119904 119904119904119898119898119889119889119889119889119898119898119904119904119889119889119871119871119898119898119887119887119887119887119887119887119887119887119887119887 119887119887119886119886119886119886119887119887 (3)

119871119871119871119871119871119871 = 1198711198711198711198711198711198713

times 10 (4)









0

100000

200000

300000

400000

500000

600000

700000

800000

900000

1000000

1100000

PE NE P N


PFOcDA

PFHxDA

PFTDA

PFTrDA

PFDoDA

PFUnDA

PFDA

PFNA

PFOA

PFHpA

PFHxA

PFPeA

PFBA

0

150000

300000

450000

600000

750000

900000

1050000

1200000

1350000

1500000

PE NE P N

Conc (pgg)

PFSAs in SRM

PFDoDS

PFDS

PFNS

PFOS

PFHpS

PFHxS

PFPeS

PFBS

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

5500

6000

6500

7000

7500

PE NE P N


82 FTSA

62 FTSA

42 FTSA




Compound PE NE P N


0

500

1000

1500

2000

2500

3000

PCE NCE PC NC


PFOcDA

PFHxDA

PFTDA

PFTrDA

PFDoDA

PFUnDA

PFDA

PFNA

PFOA

PFHpA

PFHxA

PFPeA

PFBA

0

001

002

003

004

005

006

007

008

009

01

011

PCE NCE PC NC


PFDoS

PFDS

PFNS

PFOS

PFHpS

PFHxS

PFPeS

PFBS

0

5

10

15

20

25

30

35

40

45

50

55

60

65

PCE NCE PC NC


82 FTSA

62 FTSA

42 FTSA


























References





















Abstract

Introduction


Background



PFAA precursors

Sewage Sludge

Method

Materials





LC-MSMS analysis

Results

pH after reaction



Recovery

Discussion

pH



Conclusion

References


































5355 mg 1071 mg







119871119871119871119871119871119871 = 119898119898119898119898119898119898119898119898119887119887119887119887119887119887119887119887119887119887 119887119887119886119886119886119886119887119887 + 3 times 119904119904119904119904119898119898119898119898119904119904119898119898119904119904119904119904 119904119904119898119898119889119889119889119889119898119898119904119904119889119889119871119871119898119898119887119887119887119887119887119887119887119887119887119887 119887119887119886119886119886119886119887119887 (3)

119871119871119871119871119871119871 = 1198711198711198711198711198711198713

times 10 (4)









0

100000

200000

300000

400000

500000

600000

700000

800000

900000

1000000

1100000

PE NE P N


PFOcDA

PFHxDA

PFTDA

PFTrDA

PFDoDA

PFUnDA

PFDA

PFNA

PFOA

PFHpA

PFHxA

PFPeA

PFBA

0

150000

300000

450000

600000

750000

900000

1050000

1200000

1350000

1500000

PE NE P N

Conc (pgg)

PFSAs in SRM

PFDoDS

PFDS

PFNS

PFOS

PFHpS

PFHxS

PFPeS

PFBS

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

5500

6000

6500

7000

7500

PE NE P N


82 FTSA

62 FTSA

42 FTSA




Compound PE NE P N


0

500

1000

1500

2000

2500

3000

PCE NCE PC NC


PFOcDA

PFHxDA

PFTDA

PFTrDA

PFDoDA

PFUnDA

PFDA

PFNA

PFOA

PFHpA

PFHxA

PFPeA

PFBA

0

001

002

003

004

005

006

007

008

009

01

011

PCE NCE PC NC


PFDoS

PFDS

PFNS

PFOS

PFHpS

PFHxS

PFPeS

PFBS

0

5

10

15

20

25

30

35

40

45

50

55

60

65

PCE NCE PC NC


82 FTSA

62 FTSA

42 FTSA


























References





















Abstract

Introduction


Background



PFAA precursors

Sewage Sludge

Method

Materials





LC-MSMS analysis

Results

pH after reaction



Recovery

Discussion

pH



Conclusion

References






119871119871119871119871119871119871 = 119898119898119898119898119898119898119898119898119887119887119887119887119887119887119887119887119887119887 119887119887119886119886119886119886119887119887 + 3 times 119904119904119904119904119898119898119898119898119904119904119898119898119904119904119904119904 119904119904119898119898119889119889119889119889119898119898119904119904119889119889119871119871119898119898119887119887119887119887119887119887119887119887119887119887 119887119887119886119886119886119886119887119887 (3)

119871119871119871119871119871119871 = 1198711198711198711198711198711198713

times 10 (4)









0

100000

200000

300000

400000

500000

600000

700000

800000

900000

1000000

1100000

PE NE P N


PFOcDA

PFHxDA

PFTDA

PFTrDA

PFDoDA

PFUnDA

PFDA

PFNA

PFOA

PFHpA

PFHxA

PFPeA

PFBA

0

150000

300000

450000

600000

750000

900000

1050000

1200000

1350000

1500000

PE NE P N

Conc (pgg)

PFSAs in SRM

PFDoDS

PFDS

PFNS

PFOS

PFHpS

PFHxS

PFPeS

PFBS

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

5500

6000

6500

7000

7500

PE NE P N


82 FTSA

62 FTSA

42 FTSA




Compound PE NE P N


0

500

1000

1500

2000

2500

3000

PCE NCE PC NC


PFOcDA

PFHxDA

PFTDA

PFTrDA

PFDoDA

PFUnDA

PFDA

PFNA

PFOA

PFHpA

PFHxA

PFPeA

PFBA

0

001

002

003

004

005

006

007

008

009

01

011

PCE NCE PC NC


PFDoS

PFDS

PFNS

PFOS

PFHpS

PFHxS

PFPeS

PFBS

0

5

10

15

20

25

30

35

40

45

50

55

60

65

PCE NCE PC NC


82 FTSA

62 FTSA

42 FTSA


























References





















Abstract

Introduction


Background



PFAA precursors

Sewage Sludge

Method

Materials





LC-MSMS analysis

Results

pH after reaction



Recovery

Discussion

pH



Conclusion

References








0

100000

200000

300000

400000

500000

600000

700000

800000

900000

1000000

1100000

PE NE P N


PFOcDA

PFHxDA

PFTDA

PFTrDA

PFDoDA

PFUnDA

PFDA

PFNA

PFOA

PFHpA

PFHxA

PFPeA

PFBA

0

150000

300000

450000

600000

750000

900000

1050000

1200000

1350000

1500000

PE NE P N

Conc (pgg)

PFSAs in SRM

PFDoDS

PFDS

PFNS

PFOS

PFHpS

PFHxS

PFPeS

PFBS

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

5500

6000

6500

7000

7500

PE NE P N


82 FTSA

62 FTSA

42 FTSA




Compound PE NE P N


0

500

1000

1500

2000

2500

3000

PCE NCE PC NC


PFOcDA

PFHxDA

PFTDA

PFTrDA

PFDoDA

PFUnDA

PFDA

PFNA

PFOA

PFHpA

PFHxA

PFPeA

PFBA

0

001

002

003

004

005

006

007

008

009

01

011

PCE NCE PC NC


PFDoS

PFDS

PFNS

PFOS

PFHpS

PFHxS

PFPeS

PFBS

0

5

10

15

20

25

30

35

40

45

50

55

60

65

PCE NCE PC NC


82 FTSA

62 FTSA

42 FTSA


























References





















Abstract

Introduction


Background



PFAA precursors

Sewage Sludge

Method

Materials





LC-MSMS analysis

Results

pH after reaction



Recovery

Discussion

pH



Conclusion

References




Compound PE NE P N


0

500

1000

1500

2000

2500

3000

PCE NCE PC NC


PFOcDA

PFHxDA

PFTDA

PFTrDA

PFDoDA

PFUnDA

PFDA

PFNA

PFOA

PFHpA

PFHxA

PFPeA

PFBA

0

001

002

003

004

005

006

007

008

009

01

011

PCE NCE PC NC


PFDoS

PFDS

PFNS

PFOS

PFHpS

PFHxS

PFPeS

PFBS

0

5

10

15

20

25

30

35

40

45

50

55

60

65

PCE NCE PC NC


82 FTSA

62 FTSA

42 FTSA


























References





















Abstract

Introduction


Background



PFAA precursors

Sewage Sludge

Method

Materials





LC-MSMS analysis

Results

pH after reaction



Recovery

Discussion

pH



Conclusion

References


























References





















Abstract

Introduction


Background



PFAA precursors

Sewage Sludge

Method

Materials





LC-MSMS analysis

Results

pH after reaction



Recovery

Discussion

pH



Conclusion

References





Abstract

Introduction


Background



PFAA precursors

Sewage Sludge

Method

Materials





LC-MSMS analysis

Results

pH after reaction



Recovery

Discussion

pH



Conclusion

References

Method development of total oxidizable precursor …1274106/FULLTEXT01.pdfs-1 (2) Although the...

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Transcript of Method development of total oxidizable precursor …1274106/FULLTEXT01.pdfs-1 (2) Although the...