Assessment of Potential Accumulation of Trifluoroacetate in Terminal Lakes.

Trifluoroacetate (TFA) is the anionic form of the shortest perfluorocarboxylic acid (PFCA) and is ubiquitous in the environment at concentrations that are typically much higher than those of other PFCAs. As a stable and nonvolatile anion, it is expected to accumulate in terminal lakes in endorheic basins. This research sampled eight terminal lakes in the Western United States to determine the degree to which TFA is concentrating in these lakes and compare the data to samples collected from three of these lakes 25 years ago. The first observation was that three of the six terminal lakes sampled had higher TFA concentrations than their input streams, while the last two lakes lacked surface water inputs at the sampling time. The TFA concentrations in Mono Lake effectively remained constant over 25 years despite the input stream concentrations increasing 6.5-fold. In contrast, Pyramid Lake concentrations increased approximately the expected amount based on a simplistic analysis of input flows and concentrations. An additional observation was that lakes in basins with agricultural activity appeared to have higher TFA concentrations, which suggests an agricultural input.

Hydrothermal Destruction and Defluorination of Trifluoroacetic Acid (TFA).

Per- and polyfluoroalkyl substances (PFAS) have received increased attention due to their environmental prevalence and threat to public health. Trifluoroacetic acid (TFA) is an ultrashort-chain PFAS and the simplest perfluorocarboxylic acid (PFCA). While the US EPA does not currently regulate TFA, its chemical similarity to other PFCAs and its simple molecular structure make it a suitable model compound for studying the transformation of PFAS. We show that hydrothermal processing in compressed liquid water transforms TFA at relatively mild conditions (T = 150-250 °C, P < 30 MPa), initially yielding gaseous products, such as CHF3 and CO2, that naturally aspirate from the solution. Alkali amendment (e.g., NaOH) promotes the mineralization of CHF3, yielding dissolved fluoride, formate, and carbonate species as final products. Fluorine and carbon balances are closed using Raman spectroscopy and fluoride ion selective electrode measurements for experiments performed at alkaline conditions, where gas yields are negligible. Qualitative FTIR gas analysis allows for establishing the transformation pathways; however, the F-balance could not be quantitatively closed for experiments without NaOH amendment. The kinetics of TFA transformation under hydrothermal conditions are measured, showing little to no dependency on NaOH concentration, indicating that the thermal decarboxylation is a rate-limiting step. A proposed TFA transformation mechanism motivates additional work to generalize the hydrothermal reaction pathways to other PFCAs.

Application of a robust MALDI mass spectrometry approach for bee pollen investigation.

Pollen collected by pollinators can be used as a marker of the foraging behavior as well as indicate the botanical species present in each environment. Pollen intake is essential for pollinators' health and survival. During the foraging activity, some pollinators, such as honeybees, manipulate the collected pollen mixing it with salivary secretions and nectar (corbicular pollen) changing the pollen chemical profile. Different tools have been developed for the identification of the botanical origin of pollen, based on microscopy, spectrometry, or molecular markers. However, up to date, corbicular pollen has never been investigated. In our work, corbicular pollen from 5 regions with different climate conditions was collected during spring. Pollens were identified with microscopy-based techniques, and then analyzed in MALDI-MS. Four different chemical extraction solutions and two physical disruption methods were tested to achieve a MALDI-MS effective protocol. The best performance was obtained using a sonication disruption method after extraction with acetic acid or trifluoroacetic acid. Therefore, we propose a new rapid and reliable methodology for the identification of the botanical origin of the corbicular pollens using MALDI-MS. This new approach opens to a wide range of environmental studies spanning from plant biodiversity to ecosystem trophic interactions.

Elevated Levels of Ultrashort- and Short-Chain Perfluoroalkyl Acids in US Homes and People.

Per- and polyfluoroalkyl substances (PFAS) make up a large group of fluorinated organic compounds extensively used in consumer products and industrial applications. Perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), the two perfluoroalkyl acids (PFAAs) with 8 carbons in their structure, have been phased out on a global scale because of their high environmental persistence and toxicity. As a result, shorter-chain PFAAs with less than 8 carbons in their structure are being used as their replacements and are now widely detected in the environment, raising concerns about their effects on human health. In this study, 47 PFAAs and their precursors were measured in paired samples of dust and drinking water collected from residential homes in Indiana, United States, and in blood and urine samples collected from the residents of these homes. Ultrashort- (with 2 or 3 carbons [C2-C3]) and short-chain (with 4-7 carbons [C4-C7]) PFAAs were the most abundant in all four matrices and constituted on average 69-100% of the total PFAA concentrations. Specifically, trifluoroacetic acid (TFA, C2) and perfluoropropanoic acid (PFPrA, C3) were the predominant PFAAs in most of the samples. Significant positive correlations (n = 81; r = 0.23-0.42; p < 0.05) were found between TFA, perfluorobutanoic acid (PFBA, C4), and perfluoroheptanoic acid (PFHpA, C7) concentrations in dust or water and those in serum, suggesting dust ingestion and/or drinking water consumption as important exposure pathways for these compounds. This study demonstrates that ultrashort- and short-chain PFAAs are now abundant in the indoor environment and in humans and warrants further research on potential adverse health effects of these exposures.

Developed rapid and simple RP-HPLC method for simultaneous separation and quantification of bovine milk protein fractions and their genetic variants.

The aim was to develop a reliable rapid reversed-phase high-performance liquid chromatography (RP-HPLC) method to simultaneously determine the main bovine milk protein fractions, including their genetic variants. Compared to the previous studies, our method is able to separate the main protein fractions within 20 min of total run time. The method validation consisted of testing repeatability, reproducibility linearity, repeatability, and accuracy. The procedure was developed using raw individual, bulk, and commercially available heat-treated cow milk samples. The RSD of peak areas ranged from 1.43 to 3.16% within analytical day and from 3.29 to 6.70% across analytical days. The method can be applied to investigate both raw and heat-treated milk samples.

Increases in Trifluoroacetate Concentrations in Surface Waters over Two Decades.

Trifluoroacetate (TFA) is a persistent perfluorinated alkanoic acid anion that has many anthropogenic sources, with fluorocarbon refrigerants being a major one. After an initial burst of research in the late 1990s and early 2000s, research on this ubiquitous pollutant declined as atmospheric emissions of the precursor compounds grew rapidly. Thus, there is little contemporaneous information about the concentrations of TFA in the environment and how they have changed over time. This research determined the change in TFA concentrations in streams by resampling a transect that was originally sampled in 1998. The transect was designed to determine the regional distribution of TFA both upwind and downwind of major metropolitan areas in Northern California as well as a set of globally remote sites in Alaska. The results showed that TFA concentrations increased by an average of 6-fold over the intervening 23 years, which resulted in a median concentration of 180 ng/L (range 21.3-2790). The highest concentrations were found in streams immediately downwind of the San Francisco Bay Area, while substantially lower concentrations were found in the upwind, regionally remote, and globally remote sites. The C3 to C5 perfluorinated alkanoic acids were also investigated, but they were rarely detected with this methodology.

Benzothiazole Pyrazoline: Acid-Switchable Absorption and Fluorescence of Photoinduced Electron Transfer (PET).

Acid-responsive fluorescent compounds were prepared by introducing an ortho-hydroxyphenyl to pyrazoline with a benzothiazole backbone. These compounds demonstrated normal fluorescence photoinduced electron transfer (PET) under neutral conditions but the addition of trifluoroacetic acid showed an arctic blue fluorescence, we verified that a protonation process of nitrogen in the thiazole ring which weakened the ability of thiazole to donate electrons to the pyrazoline and changed the photoinduced electron transfer led to photoinduced electron transfer (PET), which was the mechanism of the fluorescence quenching phenomenon under strongly acidic conditions. The photophysical properties of Benzothiazole pyrazoline exhibited blue emission at 421 nm in aqueous DMSO. The blue shift in the emission was switched by acid in DMSO, showing the compound's distinct fluorescence peak at 554 nm. To investigate solvatochromism, eight different solvents were used. The red-shift emission observed in enhancing the polarity of solvents and emission in DMSO suggested the conformation of the molecule which led to the intramolecular charge transfer by color and emission changes. Furthermore, the probe was also applied using the High-performance liquid chromatography (HPLC) with a UV detector to determine the trifluoroacetic acid in water samples. Interestingly, the method was found to be linear over the range of 10.0 µg L-1 to 250.0 µg L-1 (0.999). Under the optimum condition, the separation of trifluoroacetic acid was achieved in 20 min with the LOD of 1.3 µg L-1 and LOQ of 5.1 µg L-1. This proposed method also showed satisfactory results when applied for the analysis of trifluoroacetic acid in a water sample.

TFA-mediated synthesis of functionalized pyrano[2,3-c]pyrazoles from pyrazol-3-ones, active carbonyl compounds and tert-BuOH.

Functionalized pyrano[2,3-c]pyrazoles were synthesized from 2,4-dihydro-3H-pyrazol-3-ones, active carbonyl compounds and tert-BuOH in the presence of trifluoroacetic acid at 65 °C. These reactions are proceeded by acid catalyzed generation of isobutylene from tert-BuOH for LUMOdiene-controlled inverse [4 + 2] cycloaddition reaction with in situ-generated vinylidenepyrazolones.

Bruceine A induces cell growth inhibition and apoptosis through PFKFB4/GSK3ß signaling in pancreatic cancer.

Pancreatic cancer is one of the most aggressive cancers with a poor prognosis and 5-year low survival rate. In the present study, we report that bruceine A, a quassinoid found in Brucea javanica (L.) Merr. has a strong antitumor activity against human pancreatic cancer cells both in vitro and in vivo. Human proteome microarray reveals that 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 4 (PFKFB4) is the candidate target of bruceine A and both fluorescence measurement and microscale thermophoresis suggest bruceine A binds to PFKFB4. Bruceine A suppresses glycolysis by inhibiting PFKFB4, leading to cell cycle arrest and apoptosis in MIA PaCa-2 cells. Furthermore, glycogen synthase kinase-3 ß (GSK3ß) is identified as a downstream target of PFKFB4 and an PFKFB4-interacting protein. Moreover, bruceine A induces cell growth inhibition and apoptosis through GSK3ß, which is dysregulated in pancreatic cancer and closely related to the prognosis. In all, these findings suggest that bruceine A inhibits human pancreatic cancer cell growth via PFKFB4/GSK3ß-mediated glycolysis, and it may serve as a potent agent for curing human pancreatic cancer.

Levels and Seasonal Trends of C1-C4 Perfluoroalkyl Acids and the Discovery of Trifluoromethane Sulfonic Acid in Surface Snow in the Arctic.

C1-C4 perfluoroalkyl acids (PFAAs) are highly persistent chemicals that have been found in the environment. To date, much uncertainty still exists about their sources and fate. The importance of the atmospheric degradation of volatile precursors to C1-C4 PFAAs were investigated by studying their distribution and seasonal variation in remote Arctic locations. C1-C4 PFAAs were measured in surface snow on the island of Spitsbergen in the Norwegian Arctic during January-August 2019. Trifluoroacetic acid (TFA), perfluoropropanoic acid (PFPrA), perfluorobutanoic acid (PFBA), and trifluoromethane sulfonic acid (TFMS) were detected in most samples, including samples collected at locations presumably receiving PFAA input solely from long-range processes. The flux of TFA, PFPrA, PFBA, and TFMS per precipitation event was in the ranges of 22-1800, 0.79-16, 0.19-170, and 1.5-57 ng/m2, respectively. A positive correlation between the flux of TFA, PFPrA, and PFBA with downward short-wave solar radiation was observed. No correlation was observed between the flux of TFMS and solar radiation. These findings suggest that atmospheric transport of volatile precursors and their subsequent degradation plays a major role in the global distribution of C2-C4 perfluoroalkyl carboxylic acids and their consequential deposition in Arctic environments. The discovery of TFMS in surface snow at these remote Arctic locations suggests that TFMS is globally distributed. However, the transport mechanism to the Arctic environment remains unknown.

Rapid Identification between Two Fish Species Using UV-Vis Spectroscopy for Substitution Detection.

Fish species substitution and fraud has become a worldwide economic issue in the seafood industry. In this study, an ultraviolet-visible (UV-Vis) spectroscopy-based method was developed for the identification of fish samples. Sixty fish samples from twelve commonly consumed fish species in China were analyzed as models to testify the protocol. The obtained results show that UV-Vis spectroscopy combined with chemometric analysis, such as principal component analysis (PCA), can accurately distinguish two fish species by boiling fish tissue sample in trifluoroacetic acid (TFA) solution for 2 min and analyzing the resultant samples using a UV-Vis spectrometer. The developed strategy was successfully applied to the classification and identification of fish samples on the market. It is a promising strategy that can be applied to the classification and authenticity testing of closely related fish species in order to detect and recognize fish substitution.

Fe-O Clusters Anchored on Nodes of Metal-Organic Frameworks for Direct Methane Oxidation.

Direct methane oxidation into value-added organic oxygenates with high productivity under mild condition remains a great challenge. We show Fe-O clusters on nodes of metal-organic frameworks (MOFs) with tunable electronic state for direct methane oxidation into C1 organic oxygenates at 50 °C. The Fe-O clusters are grafted onto inorganic Zr6 nodes of UiO-66, while the organic terephthalic acid (H2 BDC) ligands of UiO-66 are partially substituted with monocarboxylic modulators of acetic acid (AA) or trifluoroacetic acid (TFA). Experiments and theoretical calculation disclose that the TFA group coordinated with Zr6 node of UiO-66 enhances the oxidation state of adjacent Fe-O cluster due to its electron-withdrawing ability, promotes the activation of C-H bond of methane, and increases its selective conversion, thus leading to the extraordinarily high C1 oxygenate yield of 4799 µmol gcat -1 h-1 with 97.9 % selectivity, circa 8 times higher than those modulated with AA.

Transition-metal-free intramolecular Friedel-Crafts reaction by alkene activation: A method for the synthesis of some novel xanthene derivatives.

In this work, new derivatives (substituted 9-methyl-9-arylxanthenes) of xanthene compounds (5a-l) of possible biological significance were synthesized by developing a new synthesis method. In order to obtain xanthene derivatives, the original alkene compounds to be used as the starting materials were synthesized in four steps using appropriate reactions. A cyclization reaction by intramolecular Friedel-Crafts alkylation was carried out in order to synthesize the desired xanthene derivatives using the alkenes as starting compounds. The intramolecular Friedel-Crafts reaction was catalyzed by trifluoroacetic acid (TFA) and provided some novel substituted 9-methyl-9-arylxanthenes with good yields at room temperature within 6-24 hours. As a result, an alkene compound was used for activation with TFA in the synthesis of xanthene through intramolecular Friedel-Crafts alkylation for the first time.

Challenges in the analytical determination of ultra-short-chain perfluoroalkyl acids and implications for environmental and human health.

Ultra-short-chain perfluoroalkyl acids have recently gained attention due to increasing environmental concentrations being observed. The most well-known ultra-short-chain perfluoroalkyl acid is trifluoroacetic acid (TFA) which has been studied since the 1990s. Potential sources and the fate of ultra-short-chain perfluoroalkyl acids other than TFA are not well studied and data reporting their environmental occurrence is scarce. The analytical determination of ultra-short-chain perfluoroalkyl acids is challenging due to their high polarity resulting in low retention using reversed-phase liquid chromatography. Furthermore, recent studies have reported varying extraction recoveries in water samples depending on the water matrix and different methods have been suggested to increase the extraction recovery. The present review gives an overview of the currently used analytical methods and summarizes the findings regarding potential analytical challenges. In addition, the current state of knowledge regarding TFA and other ultra-short-chain perfluoroalkyl acids, namely perfluoropropanoic acid, trifluoromethane sulfonic acid, perfluoroethane sulfonic acid, and perfluoropropane sulfonic acid' are reviewed. Both known and potential sources as well as environmental concentrations are summarized and discussed together with their fate and the environmental and human implications.

Human multidrug resistance protein 4 (MRP4) is a cellular efflux transporter for paracetamol glutathione and cysteine conjugates.

Paracetamol (acetaminophen, APAP) overdose is a leading cause of acute drug-induced liver failure. APAP hepatotoxicity is mediated by the reactive metabolite N-acetyl-p-benzoquinone imine (NAPQI). NAPQI is inactivated by conjugation with glutathione (GSH) to APAP-GSH, which is further converted into its cysteine derivative APAP-CYS. Before necrosis of hepatocytes occurs, APAP-CYS is measurable in plasma of the affected patient and it has been proposed as an early biomarker of acetaminophen toxicity. APAP-GSH and APAP-CYS can be extruded by hepatocytes, but the transporters involved are unknown. In this study we examined whether ATP-binding cassette (ABC) transporters play a role in the cellular efflux of APAP, APAP-GSH, and APAP-CYS. The ABC transport proteins P-gp/ABCB1, BSEP/ABCB11, BCRP/ABCG2, and MRP/ABCC1-5 were overexpressed in HEK293 cells and membrane vesicles were produced. Whereas P-gp, BSEP, MRP3, MRP5, and BCRP did not transport any of the compounds, uptake of APAP-GSH was found for MRP1, MRP2 and MRP4. APAP-CYS appeared to be a substrate of MRP4 and none of the ABC proteins transported APAP. The results suggest that the NAPQI metabolite APAP-CYS can be excreted into plasma by MRP4, where it could be a useful biomarker for APAP exposure and toxicity. Characterization of the cellular efflux of APAP-CYS is important for its development as a biomarker, because plasma concentrations might be influenced by drug-transporter interactions and upregulation of MRP4.

Preparative separation of flavone dimers from Dysosma versipellis by counter-current chromatography: Trifluoroacetic acid as a solvent system modifier.

The separation of natural products is grueling and time-consuming work with repeated isolations needed to obtain purified compounds. However, using counter-current chromatography, a unique liquid-liquid partition chromatography, constituents can usually be purified efficiently. During the separation of flavone dimers from Dysosma versipellis (Hance) by counter-current chromatography, the separation resolution and sample loading was impeded by the emulsification of the sample. By screening, trifluoroacetic acid was selected as the solvent modifier to eliminate the emulsification. Then, a quaternary solvent system of hexane/ethyl acetate/methanol/water (4:6:5:5 v/v/v/v) with trifluoroacetic acid at a low concentration of 0.5% v/v was used to purify the components from D. versipellis. Compared to that without trifluoroacetic acid, the separation resolution as well as the sample loading both increased greatly. In addition, flavone dimers in low concentrations could be enriched and purified at high sample loading. As a result, five podophyllotoxins and 11 flavonoids were purified and characterized by interpretation of spectroscopic data, in which two of eight flavone dimers were new and a known flavone dimer was first separated from this species.

Trifluoroacetic acid: Three times the fluoride, three times the toxicity?

Trifluoroacetic acid (TFAA) is a carboxylic acid, similar to acetic acid, used industrially and in laboratories. There is a paucity of data regarding exposure and the concern is that toxicity may mimic that of hydrofluoric acid (HF), causing electrolyte abnormalities, dysrhythmia, and cardiac arrest. We report a case of a 27-year-old male that presents with a dermal exposure to TFAA. His exam was remarkable for a 4% body surface area partial thickness burn to the right forearm. There were no initial electrolyte abnormalities or dysrhythmias and the patient was admitted to telemetry monitoring overnight. Serial laboratories were normal, dysrhythmias did not occur, and patient was ultimately discharged with routine burn care of the wound. Previously reported TFAA exposures are uncommon and tend to be very small body surface area chemical burns without clear systemic toxicity. HF as well as sodium and ammonium bifluorides have been shown to cause clinically significant electrolyte disturbances that can lead to dysrhythmias and fatalities. While TFAA may be structurally similar, it does not appear to have similar toxicity. This is an important difference in presentation and treatment that emergency physicians should be aware of as occupational exposures are likely to present to the emergency department.

C-F bond activation of trifluoroethanol and trifluoroacetic acid catalysed by the dimolybdate anion, [Mo2O6(F)]- †.

Two gas-phase catalytic cycles involving C-F bond activation of trifluoroethanol and trifluoroacetic acid were detected by multistage mass spectrometry experiments. A binuclear dimolybdate centre [Mo2O6(F)]- acts as the catalyst in each cycle. The first cycle, entered via the reaction of [Mo2O6(OH)]- with trifluoroethanol and elimination of water to form [Mo2O6(OCH2CF3)]-, proceeds via four steps: (1) oxidation of the alkoxo ligand and its elimination as aldehyde; (2) reaction of [Mo2O5(OH)]- with trifluoroethanol and elimination of water to form [Mo2O5(OCH2CF3)]; (3) decomposition of the alkoxo ligand via loss of 1,1 difluoroethene; and (4) reaction of [Mo2O6(F)]- with a second equivalent of trifluoroethanol to regenerate Mo2O6(OCH2CF3)]-. Steps (2) and (3) do not occur at room temperature and require collisional activation to proceed. The second cycle is entered via the reaction of [Mo2O6(OH)]- with trifluoroacetic acid and elimination of water to form [Mo2O6(O2CCF3)]- and involves two steps only: (1) fluoride transfer to a molybdenum centre to form [Mo2O6(F)]-; (2) reaction of [Mo2O6(F)]- with trifluoroacetic acid and loss of water to regenerate [Mo2O6(O2CCF3)]-. Comparisons are made with the chemistry of [Mo2O6(OH)]- reacting with acetic acid.

Enhancement of Power Conversion Efficiency of TiO2-Based Dye-Sensitized Solar Cells on Various Acid Treatment.

The surface modification of the TiO2 photoelectrode film is one of the promising ways to improve the photovoltaic performance of dye-sensitized solar cell (DSSC). In this work for the acid treatment of TiO2 powder, fluorine containing compounds such as trifluoroacetic acid was carried out to enhance the properties of photoanode. In order to investigate the effect of trifluoroacetyl group, the TiO2 nanopowders were also treated with different acids such as acetic acid, nitric acid, hydrochloric acid, and sulfuric acid and their properties were compared. The TiO2 powders treated with both acetic acid and TFA have possessed smooth surface morphologies as well as enhanced particle dispersions with reduced particle sizes. Photoelectrodes prepared for these two kinds of TiO2 powders accommodated high amounts of dye loading and exhibited excellent light transmittance (wavelength region of 400­600 nm). Electrochemical impedance spectroscopy analysis showed the smallest radius of the semicircle which indicates the enhanced rate of electron transport for the cell based photoelectrode with trifluoroacetic acid treated TiO2 powder. The solar cell from the untreated TiO2 film showed the power conversion efficiency of 8.86% and the highest efficiency of 9.51% was achieved by the cell fabricated from trifluoroacetic acid treated TiO2 film.