Gas chromatography and liquid chromatography coupled to mass spectrometry for the determination of fluorotelomer olefins, fluorotelomer alcohols, perfluoroalkyl sulfonamides and sulfonamido-ethanols in water.

In this work, the suitability of gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the multi-class determination of different families of neutral per- and polyfluoroalkyl substances (PFASs), such as fluorotelomer olefins (FTOs), alcohols (FTOHs) and fluorooctanesulfonamides (FOSAs) and sulfonamido-ethanols (FOSEs), was investigated and compared. Regarding GC-MS, the use of a semi-polar GC column (DB-624, 6%-cyanopropilphenyl 94%-dimethyl polysiloxane) allowed the adequate separation of all the compounds while chemical ionisation (CI) of positive ions as ionisation technique provided the best responses. Concerning UHPLC-MS/MS, atmospheric pressure chemical ionisation (APCI) and photoionisation (APPI) sources allowed the ionisation of all studied neutral PFASs, including FTOs for the first time. High vaporizer temperatures (450 °C) and acetonitrile/water mobile phase mixtures were required to favour the ionisation of FTOs, with adequate ionisation for FTOHs, FOSAs and FOSEs. The chromatographic separation, performed on a totally porous column (Luna C18), allowed the successful separation of the four families of neutral PFASs. After comparing the performance of the studied methods, the highest detectability was achieved using UHPLC-APCI-MS/MS and it was chosen in combination with a solid-phase extraction (SPE) procedure for the analysis of neutral PFASs in water samples. The whole method provided low limits of detection (0.003-6 µg L-1), good precision (RSD < 9%) and trueness (relative error < 10%). The methodology was applied to the analysis of river water samples and the presence of some neutral PFASs were detected (8:2 FTO) and quantified (4:2 FTOH and N-EtFOSA) at low concentration levels (ng L-1).

Impact of biological filtrations for organic micropollutants and polyfluoroalkyl substances removal from secondary effluent.

The impact of biological activated carbon (BAC), sand filtration (SF) and biological aerated filter (BAF) for removal of the selected organic micropollutants and polyfluoroalkyl substances (PFASs) from secondary effluent was studied. BAC led to greater removal of dissolved organic carbon (43%) than BAF (30%) which in turn was greater than SF (24%). All biological filtration systems could effectively remove most of the selected organic micropollutants, and there was a greater removal of these micropollutants by BAC (76-98%) than BAF (70-92%) or SF (68-90%). It was found that all treatment was effective for removal of the hydrophobic (log D > 3.2) and readily biodegradable organic micropollutants. The major mechanism for the removal of these molecules was biodegradation by the micro-organism and sorption by the biofilm. Compared to organic micropollutants removal, there was a lower removal of PFASs by all treatments, and BAF and SF had a considerably lower removal than BAC treatment. The better removal for all molecule types by BAC was due to additional adsorption capacity by the activated carbon. This study demonstrated that the BAC process was most effective in removing organic micropollutants present in the secondary effluent.

Spontaneous resolution of Julia-Kocienski intermediates facilitates phase separation to produce Z- and E-monofluoroalkenes.

The monofluoroalkene motif is important in drug development as it serves as a peptide bond isostere and is found in a number of biologically active compounds with various pharmacological activities. Direct olefination of carbonyl compound is a straightforward way to prepare monofluoroalkenes; however, these methods often result in a mixture of Z- and E-isomers that cannot be easily separated. We discovered a unique spontaneous resolving reaction that simultaneously addresses the problems in the synthesis and separation of Z- and E-monofluoroalkenes. The reaction is accompanied by a highly efficient spontaneous kinetic resolution and phase labeling of monofluoroalkene precursors which allows the separation of Z- and E-monofluoroalkenes by liquid-liquid extraction. The application of the method is demonstrated by the synthesis and separation of potential anticancer agents, which are inseparable by HPLC.

Rapid residue analysis of oxathiapiprolin and its metabolites in typical Chinese soil, water, and sediments by a modified quick, easy, cheap, effective, rugged, and safe method with ultra high performance liquid chromatography and tandem mass spectrometry.

A sensitive and effective method for the simultaneous determination of residues from a new fungicide, oxathiapiprolin, and its metabolites (IN-E8S72 and IN-WR791) in soil, water, and sediment, was developed using ultra high performance liquid chromatography with tandem mass spectrometry. Three compounds were extracted from water, soil, and sediment by using acetonitrile and different proportions of formic acid aqueous solution (1% v/v for water; 2% v/v for soil; and sediment), and were cleaned with octadecylsilane. The target compounds were determined within 5 min using an electrospray ionization source in the positive mode for oxathiapiprolin and in the negative mode for the two metabolites. The limits of quantification for all the three compounds were 0.1 µg/kg in water and 1 µg/kg in soil and sediment. Recovery studies were performed using three spiked levels (0.1, 1, and 10 µg/kg for water; 1, 10, and 50 µg/kg for soil and sediment). The overall average recoveries ranged from 64.8 to 112.7% with all intra- and interday relative standard deviation values below 19.4 and 19.1%, respectively. The method validation confirmed that the proposed method was convenient and reliable for determining residual oxathiapiprolin and its metabolites in soil, water, and sediments.

Structure of a putative fluorinated natural product from Streptomyces sp. TC1.

Fluorine-containing natural products are extremely rare. The recent report on the isolation and biological activity of the bacterial secondary metabolite 3-(3,5-di-tert-butyl-4-fluorophenyl)propionic acid was thus highly remarkable. The compound contained the first aromatic fluorine substituent known to date in any natural product. The promise to discover an enzyme capable of aromatic fluorination in the producing strain Streptomyces sp. TC1 prompted our immediate interest. A close inspection of the originally reported analytical data of the fluoro metabolite revealed inconsistencies that triggered us to validate the reported structure. The results of these efforts are presented in this communication.

Total synthesis of a reported fluorometabolite from Streptomyces sp. TC1 indicates an incorrect assignment. The isolated compound did not contain fluorine.

3,5-Di-tert-butyl-4-fluorophenylpropionic acid (1) was recently reported as a natural product from Streptomyces sp. TC1. This was a notable disclosure because fluorinated natural products are exceedingly rare, and in this case it suggested that the bacterium had the capacity to mediate an enzymatic aryl fluorination reaction. However, a synthesis of the putative metabolite 1 demonstrates that the spectroscopic data are inconsistent with the proposed structure. There is no evidence that the isolated compound contained a fluorine atom.

A dual-channel gas chromatography method for the quantitation of low and high concentrations of NF3 and CF4 to study membrane separation of the two compounds.

A dual-channel gas chromatographic method is described in this paper that can be conveniently used for quantitation of NF3/CF4 mixtures with a thermal conductivity detector (TCD) on one channel for the quantitation of high-concentrations, and a pulsed discharge helium ionization detector (PDHID) on a second channel for the quantitation of low concentrations. It is shown that adequate separation is achieved on both channels with this dual single-column setup in which column switching as used for NF3/CF4 analysis in industrial chromatographic methods are not required, thus yielding an effective analysis method for laboratory-scale investigations. In addition, the use of packed columns with purified divinylbenzene-styrene co-polymers as the sole stationary phase yields satisfactory resolution between NF3 and CF4 at isothermal conditions of 30°C, with elution times of less than 8min on the TCD channel and less than 4min on the PDHID channel. Consequently, this method allows for reliable, straight-forward quantitation of NF3/CF4 mixtures, which is necessary when studying the commercially important problem of NF3 and CF4 separation by different methods. Therefore, the applicability of the method to studying membrane separation of NF3 and CF4 is briefly discussed and illustrated, for which the dual-channel setup is especially beneficial.

Use of on-site bioreactors to estimate the biotransformation rate of N-ethyl perfluorooctane sulfonamidoethanol (N-EtFOSE) during activated sludge treatment.

Accurate rates are needed for models that predict the fate of xenobiotic chemicals and impact of inhibitors at full-scale wastewater treatment plants. On-site rates for aerobic biotransformation of N-ethyl perfluorooctane sulfonamidoethanol (N-EtFOSE), a fluorinated repellent, were determined by continuously pumping mixed liquor from an aeration basin into two well-mixed acrylic bioreactors (4-L) operated in parallel. Known masses of N-EtFOSE and bromide were continuously added to the reactors. Reactor effluents were then monitored for bromide, N-EtFOSE, and metabolites of N-EtFOSE. Of the six transformation products reported in batch studies, only N-ethyl perfluorooctane sulfonamido acetate (N-EtFOSAA) was detected in the effluents. Bromide addition to the reactors enabled rate estimates despite variations in flow rate. Pseudo-second order rate coefficients for the N-EtFOSE biotransformation to N-EtFOSAA, predicted using a dynamic model of the reactor system, were k=2.0 and 2.4Lg(-1)VSSd(-1) for the two reactors, which are slower than the rates previously obtained using batch reactors. Given the relatively slow rate of N-EtFOSE transformation, its sorption and volatilization may be important in wastewater processes. The methodology used in this study should be suitable for similar on-site rate assessments with other contaminants or inhibitors.

Decyl-perfluorinated magnetic mesoporous microspheres for extraction and analysis perfluorinated compounds in water using ultrahigh-performance liquid chromatography-mass spectrometry.

In this work, the interior-walls decyl-perfluorinated functionalized magnetic mesoporous microspheres (F(17)-Fe(3)O(4)@mSiO(2)) were synthesized for the first time, and applied as adsorbents to extract and concentrate perfluorinated compounds (PFCs) from water samples. The fluorous functionalized interior pore-walls contributed to the high-selective preconcentration of PFCs due to fluorous affinity; and abundant silanol groups on the exterior surface of microspheres contributed to the good dispersibility in water sample. Four kinds of PFCs were selected as model analytes, including perfluorooctanoic acid, perfluorononanoic acid, perfluorododecanoic acid, and perfluorooctane sulphonate. In addition, UHPLC-ESI/MS/MS was introduced to the fast and sensitive detection of the analytes after sample pretreatment. Important parameters of the extraction procedure were optimized, including salinity, eluting solvent, the amount of F(17)-Fe(3)O(4)@mSiO(2) microspheres, and extraction time. The optimized procedure took only 10 min to extract analytes with high recoveries and merely 800-µL acetonitrile to elute analytes from the magnetic adsorbents. Validation experiments showed good linearity (0.994-0.998), precision (2.6-7.6%), high recovery (93.4-105.7%) of the proposed method, and the limits of detection were from 0.008 to 0.125 µg/L. The F(17)-Fe(3)O(4)@mSiO(2) magnetic microspheres have the advantages of great dispersibility in aqueous solution, high specificity of extraction, large surface area, and efficient separation ability. The results showed that the proposed method based on F(17)-Fe(3)O(4)@mSiO(2) microspheres is a simple, fast, and sensitive tool for the analysis of PFCs in water sample.

Ultra trace determination of fluorobenzoic acids in tap and reservoir water using solid-phase extraction and gas chromatography-mass spectrometry.

A method for the ultra trace analysis of 21 fluorobenzoic acids (FBAs) via GC-MS based on solid-phase extraction (SPE) and derivatization with BF3·MeOH is described. All fluorobenzoic acids were enriched and determined simultaneously. Solid-phase extraction on hydrophilic-lipophilic-balanced reversed-phase cartridges containing a poly(divinylbenzene-co-N-vinylpyrrolidone) polymer allowed a 250-fold enrichment of the acids if 100mL sample volume is used with extraction efficiencies between 71% and 94%. The method enables the determination of fluorobenzoic acid methyl esters (FBAMEs) down to the range of 6-44 ng L(-1) combined with a fast and easy sample-preparation (pH-adjusting prior to SPE and derivatization within 24 h at 64 °C directly in the vial). It uses low amounts of chemicals and is adaptable to larger and smaller sample volumes. Simultaneous extraction and determination of 21 fluorinated aromatic acids in reservoir samples with high salinity confirmed the applicability and reproducibility of the method.

A simplified synthesis of the hypoxia imaging agent 2-(2-Nitro-1H-imidazol-1-yl)-N-(2,2,3,3,3-[(18)F]pentafluoropropyl)-acetamide ([18F]EF5).

INTRODUCTION: [(18)F]EF5 is a validated marker for PET imaging of tumor hypoxia. It is prepared by reacting a trifluoroallyl precursor with carrier-added [(18)F]F(2) gas in trifluoroacetic acid (TFA) solvent. We report here an improved radiosynthesis and purification of [(18)F]EF5 by utilizing an electroformed nickel (Ni) target for [(18)F]F(2) production, and Oasis® HLB cartridges for on-line solid phase extraction of [(18)F]EF5 prior to HPLC purification. METHODS: [(18)F]F(2) was produced by deuteron bombardment of neon plus F(2) in an Ni target, and bubbled through the radiolabelling precursor solution. Purification was achieved by extracting the contents of the crude reaction mixture onto Oasis HLB cartridges, and subsequently eluted onto a semi-preparative HPLC column for further separation. Purified [(18)F]EF5 was evaluated in small animal PET studies using HCT116 tumor xenografts in nude mice. RESULTS: The electroformed Ni target enabled recovery of >75% of the radioactivity from the cyclotron target, resulting in 16.2 ± 2.2 GBq (438 ± 58 mCi) of [(18)F]F(2) available for the synthesis. Use of Oasis cartridges yielded a less complex mixture for purification. On average, 1140 ± 200 MBq (30.8 ± 5.4 mCi) of [(18)F]EF5 were collected at EOS. Small animal PET imaging studies showed specific retention of [(18)F]EF5 in tumors, with tumor-to-muscle ratios of 2.7 ± 0.3 at about 160 min after injection. CONCLUSION: A simple procedure has been developed for the routine synthesis of [(18)F]EF5 in amounts and purity required for clinical studies. This new method avoids the need for TFA evaporation and also enables facile automation of the synthesis using commercially available radiosynthesis modules.

Improved characterization of gas-particle partitioning for per- and polyfluoroalkyl substances in the atmosphere using annular diffusion denuder samplers.

Gas-phase perfluoroalkyl carboxylic acids (PFCAs) sorb strongly on filter material (i.e., GFF, QFF) used in conventional high volume air samplers, which results in an overestimation of the particle-phase concentration. In this study, we investigated an improved technique for measuring the gas-particle partitioning of per- and polyfluoroalkyl substances (PFASs) using an annular diffusion denuder sampler. Samples were analyzed for 7 PFAS classes [i.e., PFCAs, perfluoroalkane sulfonic acids (PFSAs), fluorotelomer alcohols (FTOHs), fluorotelomer methacrylates (FTMACs), fluorotelomer acrylates (FTACs), perfluorooctane sulfonamides (FOSAs), and perfluorooctane sulfonamidoethanols (FOSEs)]. The measured particulate associated fraction (Φ') using the diffusion denuder sampler generally followed the trend FTACs (0%) < FTOHs (~8%) < FOSAs (~21%) < PFSAs (~29%) < FOSEs (~66%), whereas the Φ' of the C(8)-C(18) PFCAs increased with carbon chain length, and ranged from 6% to 100%. The ionizability of some PFASs, when associated with particles, is an important consideration when calculating the gas-particle partitioning coefficient as both ionic and neutral forms can be present in the particles. Here we differentiate between a gas-particle partitioning coefficient for neutral species, K(p), and one that accounts for both ionic and neutral species of a compound, K(p)'. The measured K(p)' for PFSAs and PFCAs was 4-5 log units higher compared to the interpolated K(p) for the neutral form only. The measured K(p)' can be corrected (to apply to the neutral form only) with knowledge of the pK(a) of the chemical and the pH of the condensed medium ("wet" particle or aqueous aerosol). The denuder-based sampling of PFASs has yielded a robust data set that demonstrates the importance of atmospheric pH and chemical pK(a) values in determining gas-particle partitioning of PFASs.

Sorption of fluorinated herbicides to plant biomass-derived biochars as a function of molecular structure.

Biochars produced at different heat treatment temperatures (HTT) are molecularly distinct and thus expected to show variable sorbent characteristics. We investigated the difference in sorption behavior of norflurazon (NORO) and fluridone (FLUN) to biochars from wood and grass feedstocks produced at different HTT. Amorphous biochars (HTT=400°C) exhibited the highest sorption parameter (K(OC)) for the two herbicides, emphasizing the importance of amorphous structural arrangement of aromatic moieties in these chars. Negative correlation between biochar aromaticity and isotherm nonlinearity (n) suggests that the n values were related mainly to total aromatic C content, not to that in the individual phases. Sorption of FLUN and NORO to low-temperature biochars (HTT=400°C) was about 1100 times and 6400 times greater, respectively, than a sediment sample, confirming that applications of low-temperature biochars to arable soils may reduce the mobility of FLUN and NORO, thus preventing unwanted herbicide leaching and subsequent contamination of sensitive water bodies.

Isolation and structure elucidation of major alkaline degradant of ezetimibe.

This work presents the isolation and characterization of the alkaline degradant of Ezetimibe. Ezetimibe, a selective inhibitor of intestinal cholesterol absorption, was subjected to alkaline degradation. Ezetimibe was reacted with 0.1M methanolic sodium hydroxide solution for 10min at 80°C to yield alkaline degradant to an extent of 90% of initial amount of the drug taken. This degradant was detected by high performance liquid chromatography (HPLC) at relative retention time (RRT) of 1.48 with respect to Ezetimibe. HPLC method involved an isocratic elution on a Waters Symmetry C(8) 150mm×4.6mm, 5µm column using ammonium acetate buffer (pH 4.5, 50mM) - acetonitrile (50:50, v/v) as the mobile phase at a flow rate of 1.0mL/min and UV detection at 242nm. The degradant was isolated by preparative HPLC. Purity of the isolated solid was found to be more than 99%. Structure of alkaline degradant was confirmed by LC-MS, (1)H and (13)C NMR and IR spectroscopy. On the basis of spectral data, the structure of the degradant was confirmed as 5-(4-fluorophenyl)-2-[(4-fluorophenyl amino)-(4-hydroxyphenyl)methyl]-pent-4-enoic acid. The route for the formation of this degradant is also proposed. Determining the structures of degradation products arouse during stress testing can be useful for preclinical discovery efforts.

Assessment of removal efficiency of perfluorocompounds (PFCs) in a semiconductor fabrication plant by gas chromatography.

This study investigated a gas chromatographic (GC) method to assess the destruction or removal efficiency (DRE) of local scrubbers on five perfluorocompounds (PFCs), i.e., SF(6), NF(3), CF(4), C(2)F(6), and C(3)F(8), which are very potent greenhouse gases used in a semiconductor fabrication plant. Air samples taken at inlets and outlets of local scrubbers were analyzed by a self-constructed multi-column GC system equipped with thermal conductivity detection. Three packed columns were integrated into the heart-cut GC system to allow simultaneous analysis of the five target PFCs. The Porapak Q pre-column performs rough separation and cuts eluent groups to two analytical columns for optimal separation. The Molecular Sieve - 5A column separated NF(3), CF(4), and C(3)F(8) and the second Porapak Q separated SF(6) and C(2)F(6). Linearity was greater than 0.995 (R(2)) for the five PFCs, and the reproducibility was about 4% (relative standard deviation) for NF(3), and better than 0.5% for the other four PFCs. DRE for the combustion (CB) and electric-thermal types of local scrubbers was evaluated by taking into account the in-line dilution from air and fuel gases. Both flow and tracer methods were employed to deduce the dilution factors (DFs). For the tracer method, helium was employed as the tracer and injected upstream of the scrubbers and thus mixed with the exhaust gas. With this method, the DFs were determined to be in the range from 4.8 to 5.9 for the CB unit, significantly higher than the value of 3.3 based on the flow method. The DREs for the CB unit for C(3)F(8) were greater than 90% and between 40% and 50% for CF(4).

Spatial distribution of polyfluoroalkyl compounds in seawater of the German Bight.

The spatial distribution of polyfluoroalkyl compounds (PFCs) and their composition profile was investigated in 48 water samples collected from the German Bight. All samples were prepared by solid-phase extraction with Strata XAW cartridges and analysed using high performance liquid chromatography/negative electrospray ionisation-tandem mass spectrometry (HPLC/(-)ESI-MS/MS). Concentrations of various PFCs, including perfluorinated sulfonates (PFSAs), perfluorinated carboxylic acids (PFCAs), unsaturated fluorotelomercarboxylic acids, perfluoralkyl sulfonamide and sulfonamidoethanol, were quantified. The Sigma PFC concentration ranges from 9.36 ng L(-1) to 31.2 ng L(-1), while perfluorobutane sulfonate (PFBS, 3.38-17.7 ng L(-1)) and perfluorooctanoic acid (PFOA, 2.67-7.83 ng L(-1)) dominated. The rivers Elbe, Weser and Ems had a high influence on the distribution of most PFCs in the German Bight, with maximum PFC concentrations found in their estuaries, and concentrations decreasing with increasing distance from the coast. Conversely, PFBS had its maximum concentration not in the estuaries but in the western German Bight, which suggest an additional source, where PFBS was transported into the German Bight with the westerly current.

Evaluating indole-related derivatives as precursors in the directed biosynthesis of diazepinomicin analogues.

The effectiveness of precursor-directed biosynthesis to generate diazepinomicin (1) analogues with varied ring-A substitutents was investigated by feeding commercially available, potential ring-A precursors such as fluorinated tryptophans, halogenated anthranilates, and various substituted indoles into growing actinomycete culture DPJ15 (genus Micromonospora). Two new monofluorinated diazepinomicin analogues (2 and 3) were identified and characterized by spectroscopic methods. Both derivatives showed modest antibacterial activity against the Gram-positive coccus Staphylococcus aureus with MIC values in the range 8-32 microg/mL.

A novel method to decompose two potent greenhouse gases: photoreduction of SF6 and SF5CF3 in the presence of propene.

SF5CF3 and SF6 are the most effective greenhouse gases on a per molecule basis in the atmosphere. Original laboratory trial for photoreduction of them by use of propene as a reactant was performed to develop a novel technique to destroy them. The highly reductive radicals produced during the photolysis of propene at 184.9 nm, such as .CH3, .C2H3, and .C3H5, could efficiently decompose SF6 and SF5CF3 to CH4, elemental sulfur and trace amounts of fluorinated organic compounds. It was further demonstrated that the destruction and removal efficiency (DRE) of SF5X (X represented F or CF3) was highly dependent on the initial propene-to-SF5X ratio. The addition of certain amounts of oxygen and water vapor not only enhanced the DRE but avoided the generation of deposits. In both systems, employment nitrogen as dilution gas lessened the DRE slightly. Given the advantage of less toxic products, the technique might contribute to SF5X remediation.

Microwave-assisted extraction of active pharmaceutical ingredient from solid dosage forms.

The microwave assisted extraction (MAE) technique has been evaluated for the extraction of active pharmaceutical ingredients (API) from various solid dosage forms. Using immediate release tablets of Compound A as a model, optimization of the extraction method with regards to extraction solvent composition, extraction time and temperature was briefly discussed. Complete recovery of Compound A was achieved when samples were extracted using acetonitrile as the extraction solvent under microwave heating at a constant cell temperature of 50 degrees C for 5 min. The optimized MAE method was applied for content uniformity (single tablet extraction) and potency (multiple tablets extraction) assays of release and stability samples of two products of Compound A (5 and 25mg dose strength) stored at various conditions. To further demonstrate the applicability of MAE, the instrumental extraction conditions (50 degrees C for 5 min) were adopted for the extraction of montelukast sodium (Singulair) from various solid dosage forms using methanol-water (75:25, v/v) as the extraction solvent. The MAE procedure demonstrated an extraction efficiency of 97.4-101.9% label claim with the greatest RSD at 1.4%. The results compare favorably with 97.6-102.3% label claim with the greatest RSD at 2.9% obtained with validated mechanical extraction procedures. The system is affordable, user-friendly and simple to operate and troubleshoot. Rapid extraction process (7 min/run) along with high throughput capacity (up to 23 samples simultaneously) would lead to reduced cycle time and thus increased productivity.

A new method for separating HFC-134a from gas mixtures using clathrate hydrate formation.

A new separation method using gas hydrate formation is proposed for separating HFC-134a from gas mixtures containing N2 and HFC-134a. The feasibility of this separation method was investigated from various points of view. First, to determine the mixed hydrate stability region, three-phase equilibria of hydrate (H), liquid water (Lw), and vapor (V) for HFC-134a + N2 + water mixtures with various HFC-134a vapor compositions were closely examined in the temperature and pressure ranges of 275-285 K and 0.1-2.7 MPa, respectively. Second, the compositions of the hydrate and vapor phases at a three-phase equilibrium state were analyzed for identical mixtures at 278.15 and 282.15 K to confirm the actual separation efficiency. Third, kinetic experiments were performed to monitor the composition change behavior of the vapor phase and to determine the time required for an equilibrium state to be reached. Furthermore, X-ray diffraction confirmed that the mixed HFC-134a + N2 hydrates were structure II. Through an overall investigation of the experimental results, it was verified that more than 99 mol % HFC-134a could be obtained from gas mixtures after hydrate formation and subsequent dissociation processes. Separation of HFC-134a using hydrate formation can be carried out at mild temperature and low-pressure ranges. No additive is needed to lower the hydrate formation pressure.