These volatile compounds can be present in the air and water environment and can be transformed into highly persistent perfluoroalkyl carboxylic acids. Gas chromatography with mass spectrometry was employed for the detection and quantification of the analytes. The absolute instrumental limits of detection were in the range of 0. The volatile PFASs were shown to readily partition into the air rather than into water. Consequently, large losses in the amount of PFASs were observed when these were spiked into the water.
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These volatile compounds can be present in the air and water environment and can be transformed into highly persistent perfluoroalkyl carboxylic acids. Gas chromatography with mass spectrometry was employed for the detection and quantification of the analytes. The absolute instrumental limits of detection were in the range of 0. The volatile PFASs were shown to readily partition into the air rather than into water.
Consequently, large losses in the amount of PFASs were observed when these were spiked into the water. The interest in determining the different poly- and perfluorinated alkyl substances PFASs in the environment has increased rapidly in recent years.
These compounds have been labeled as pollutants due to their various harmful effects that spring from their unique properties, such as their low degradability. Perfluoroalkyl carboxylic acids PFCAs and perfluoroalkane sulfonic acids PFSAs , particularly their C 8 homologues perfluorooctanoic acid PFOA and perfluorooctane sulfonic acid PFOS , have been the subject of many studies—their occurrence, fate, and distribution in different samples and environmental compartments [ 1 ]; their biodegradability and bioaccumulation [ 2 , 3 ]; and their toxicities to different organisms [ 4 , 5 ].
In controlling these substances, there is a need to identify their possible sources. One potential source is the physico-chemical and biological transformation of other PFASs [ 6 — 8 ]. It involves first, a UV-catalyzed radical reaction of trifluoromethyl iodide producing perfluoroalkyl iodides PFAI of varying number of carbon atoms [ 1 , 9 ]. The unreacted species in the synthesis of PFASs can be released into the environment during the manufacturing process as part of the industrial waste.
A survey of the area around a fluorochemical manufacturing plant in China revealed high concentrations of even numbered carbon PFAIs and FTIs in the air. The study also showed that these precursor compounds are easily volatilized and only the longer chains are detected in the soil samples [ 10 ]. The unreacted species are also present in the final products as residuals.
For example, in a study by Dinglasan-Panlilio and Mabury, all the fluorinated materials tested contained unbound fluorinated alcohols at a level between 0. The authors suggested that the residuals can be potential sources of FTOHs released into the environment [ 11 ]. Given the pivotal role of the volatile PFASs in the synthesis of the majority of the other PFASs, the detection and quantification of these compounds would be important in accounting the sources of PFASs in the environment [ 6 , 12 , 13 ].
In spite of this, volatile PFASs except the FTOHs are not usually measured in environmental samples as indicated by the limited availability of literature sources [ 10 , 14 — 16 ]. Another challenge in the measurement of the abovementioned compounds is their high volatility and extremely low water solubility, making it difficult to prepare aqueous standard solutions. Thus, if volatile PFASs are also to be determined, then a separate method needs to be developed.
Other problems that can arise in measuring volatile PFASs include their handling. Analyte separation was done using gas chromatography GC while MS with electron ionization EI ion source was utilized to detect and quantify the analytes.
Anal Bioanal Chem. We also report on the difficulty we encountered in assessing the accuracy more specifically, trueness of the method for WWTP influents and effluents. A pseudo-partitioning experiment, made possible using the developed method, was done to verify the initial inferences.
Two sets of calibration solutions were prepared. The air and water samples were collected from different industrial and municipal WWTP in the Netherlands and in Germany. The air sampling set-ups were directly placed above the compartments where the influent enters the WWTP. The sampling of influent, air and effluent was scheduled in such a way that there was correspondence in the collected samples i.
The cartridge was attached to a membrane pump with a low-volume flow controller and a silica moisture trap. The final volume of the air that was passed through the cartridge was recorded.
The set-up was placed over the coarse waste filtration area where the influent enters the WWTP. The flask was then sealed with a stopper with two openings connected to a SPE cartridge with enrichment control standard and to an air source. The water samples were passed through immediately after spiking into the conditioned SPE cartridges using the SPE-manifold that was connected to a vacuum. The flow of water was maintained at 0.
The cartridges were first brought to room temperature. The injector and the oven parameters were initially developed. The quantifier and qualifier ions were chosen for each analyte based on the criteria of high ion intensity and uniqueness [ 17 ].
Standard perfluorotributylamine was used to tune the MS. Data processing was done using the Qual browser of the Xcalibur software ver. During method development, peak identification was carried out by comparison with the mass spectra and retention times of single standards and with the NIST mass spectral library ver. The pseudo-partitioning experiment set-up consisted of two 4-L bottles bottle 1 and bottle 2.
A known volume of the methanolic volatile PFASs solution was added into the water while the tip of the pipet was submerged intentionally into the water. After equilibration, the water was pushed toward bottle 2 by introducing air in bottle 1 via aeration pump 1. The connection was promptly closed to prevent transfer of gas from bottle 1 to bottle 2. The gases including the volatile PFASs that partitioned into the air in bottle 1 were forced through SPE cartridge 1 using air pumped in by aeration pump 1.
The air and the volatile compounds including the PFASs that were bubbled out were forced through cartridge 2. GC is a fitting method to separate and determine highly volatile compounds. The GC method was optimized in terms of the column oven temperature and the injection system. The final oven program consisted of multiple steps with different rates of temperature ramping that allowed better separation of the different PFASs.
The leak decreased the injection repeatability and method sensitivity for FTO and PFHxI, which were the most volatile from among the analytes. In splitless injection, however, the peaks from the early eluting analytes were broader resulting to a slight decrease in sensitivity. Overall, splitless injection had better performance characteristics. All the PFASs in the study were ionized using EI; however, the ion counts of the molecular ions radical cation were very low.
This fragment was detected in all the PFASs that were analyzed albeit in varying relative ion count. Another way to reduce fragmentation was to employ chemical ionization as an alternative method. The results from these chemical ionization techniques were compared to that of EI. The peaks in the chromatogram were identified using various means that included 1 comparison of the EI-mass spectrum of the unknown peak and the EI-mass spectrum of the compound that appeared when the mass spectral database using the NIST library similarity search function was performed; 2 comparison of retention times and EI-mass spectra of the standard mix and the single standard solutions; 3 comparison of the mass spectra from EI, PCI, and ECNI; and 4 evaluation of the fragmentation patterns in the EI-, PCI-, and ECNI-mass spectra versus the chemical structure of each compound.
Two or three ions with the most intense signals were chosen for the quantification and qualification of the analytes.
However, the quantification were done using ions that are not common to both. At a concentration below this limit, either the qualifier ion or the quantifier ion, or both are non-detectable. Five sets of mixed calibration standards were prepared and analyzed. The sensitivity of the method to all analytes was good as indicated by high slope values.
The coefficients of determination for both calibration solution series with and without internal standard were greater than 0. The area ratio of the analyte to the IS was more repeatable than when only the area of the analyte was used and therefore, in all quantitative work, the internal standard was used.
The absolute instrumental LODs were between 0. Three techniques were investigated: 1 volatilization of the analyte using the set-up shown in Fig. The losses could be due to the desorption of the volatile compounds from the SPE material by the methanol vapor at a short instance. The third method used to study the efficiency of HLB was by enrichment of fortified water samples. The method developed for air was applied to the analysis of the air above the influent in an industrial and a municipal WWTP.
The actual volumes of air were calculated and used in the determination of analyte concentration. None of the analytes was detected in the air above the municipal WWTP influent. The non-detection of the volatile PFASs in the municipal waste is expected because these compounds are not the final products themselves.
They could be present in domestic products as synthetic residues. Their entry into the water system and their fate in the municipal WWTP are less likely due to their extremely low solubility in water and high volatility. FTOs were also detected at this location but in lesser concentration, whereas none of the other volatile compounds were detected. More losses are expected if the influent is subjected to aeration and heating.
The compounds detected reflect the nature of the industrial activity in the vicinity. The fortified water was then passed through the HLB cartridge. The recoveries were similarly low. This is due to the highly hydrophobic and very volatile nature of these compounds. This makes calculation of percent recovery and evaluation of analytical trueness impossible. Also, the control standard added to the water before enrichment cannot correct for any error related to the sample preparation and the measurement because the magnitudes of losses due to partitioning and matrix effect for each compound are not proportional.
One way to assess and control the quality of measurements of the volatile PFASs in water samples is to add enrichment control standards into the water samples. The area ratio of the enrichment control standard to the GC injection control standard can then be calculated from the chromatograms. The area ratios of the control standards can be plotted in a control chart with estimated warning and critical limits.
Even with losses due to partitioning, when the enrichment process is strictly controlled, the precision of the method can be improved. The results for influents and effluents can be taken as acceptable if the ratio of the control standards falls within the control limits.
In implementing the method, the influent and effluent samples were always spiked with the control standards just prior to enrichment. This limits the losses due to fast partitioning into the headspace. It is assumed that the amount of the enrichment control standards that remained will be within the control limits in any of the water samples when the procedure is repeated uniformly to all samples. When the amount of the control standards relative to the GC injection IS was outside the control limits indicated by the area ratios , the result was reviewed or the analysis repeated.
It can be noted that this step is a qualitative assessment and has no implication in the calculation of the concentration of volatiles present in the water samples.
The method developed for water samples was used in the analysis of influents and effluents from a municipal and an industrial WWTP.
The compounds were not detected in the municipal wastewater samples. In the parallel study, the FTOHs were also not detected in the municipal wastewater samples.
This is consistent with the results of the analysis of industrial WWTP air. No analyte was detected in the wastewater effluents.
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We'd like to understand how you use our websites in order to improve them. Register your interest. Objectives: To assess the health effects of hexamethylenetetramine HMT on the airways and the skin of workers in the chemical industry. Methods: A cross-sectional study was performed with 17 employees of a HMT-producing chemical plant and 16 control subjects from the plant. Anamnestic data, total and specific IgE to four environmental allergens, lung function and bronchial responsiveness to methacholine were assessed by standard procedures. Results: A high number of exposed subjects and controls reported symptoms during the previous year