A Study of Preparation and Performance of a Dichlorvos Electrochemical Sensor Based on Molecularly Imprinted Technique

A new dichlorvos molecularly imprinted electrochemical sensor was prepared. The sensitive membrane sensor was fabricated by electro-polymerizing on an Au electrode surface using o-aminophenol as a monomer and dichlorvos as a template. The 5 mmol/L K₃[Fe(CN)₆] containing 0.1 mol/L KCl was used as the test background solution, while cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to study the properties of the senor. The changes of oxidation peak current versus dichlorvos concentration showed linearity in the range of 0.12–0.42 µmol/L (R ² = 0.9432) and 0.45–15 µmol/L (R ² = 0.9516) with a detection limit of 0.06 µmol/L (S/N = 3). Moreover, the selectivity and repeatability properties of the dichlorvos electrochemical sensor were examined. Results showed that the senor had excellent repeatability (RSD = 3.92%, n = 5), good selectivity to the dichlorvos in detection, and only a ten minute response time. Organophosphorus insecticides have some response signals in the detections.     

Synthesis and Performance of Novel Sulfonate Gemini Surfactant with Trialkyl Chains

A new type of sulfonate gemini surfactant with three lipophilic alkyl chains (3C₁₀-DS) was synthesized, and the structure of the product was confirmed by using the infrared spectrum and mass spectrum. Its critical micelle concentration (CMC) is 0.41 mmol/L, one order of magnitude lower than those of convectional (single-chain) surfactants, and the minimum surface tension is 27.6 mN/m. The interfacial tension (IFT) between the compound system of 3C₁₀-DS and petroleum sulfonate (PS) and the simulated oil reaches ultra-low levels (10^?3 mN/m), and there exists significant synergistic effect between 3C₁₀-DS and PS. The compound flooding system consisting of polymer and the mixture of 3C₁₀-DS and PS can effectively improve oil recovery for high-medium permeability cores and have a good application prospect in enhancing oil recovery.     

Validation of an HPLC Analytical Method for Determination of Pancuronium Bromide in Pharmaceutical Injections

Abstract

Pancuronium bromide is used with general anesthesia in surgery for muscle relaxation and as an aid to intubation. A high performance liquid chromatographic method was fully validated for the quantitative determination of pancuronium bromide in pharmaceutical injectable solutions. The analytical method was performed on an amino column (Luna® 150 mm × 4.6 mm, 5 µm). The mobile phase was composed of acetonitrile:water containing 50 mmol L^?1 of 1-octane sulfonic acid sodium salt (20:80 v/v) with a flow rate of 1.0 mL min^?1 and ultraviolet (UV) detection at 210 nm. The proposed analytical method was compared with that described in the British Pharmacopoeia.     

Cyclodextrin-Modified Gold Nanoparticle Capillary Electrochromatography with Online Sample Stacking for Simultaneous and Sensitive Determination of Aminobenzoic Acid Isomers

A newly-developed method of complete separation and sensitive determination of o-, m-, and p-aminobenzoic acid isomers was achieved by combining open-tubular columns for capillary electrochromatography (OT-CEC) and online sample stacking. In this study, spherical gold nanoparticles were modified by a covalent attachment of mono-6-thio-β-cyclodextrin, and OT-CEC was formed by immobilizing cyclodextrin-modified gold nanoparticles (CD-AuNP) on prederivatized 3-mercaptopropyl-trimethoxysilane fused-silica capillaries. Based on the theory of moving chemical reaction boundary, effects of several important factors such as the pH and concentration of running buffer and the conditions of stacking analytes were optimized. The optimized separations were carried out in 58 mmol/L HAc buffer at pH 3.0 using a capillary coated with CD-AuNP, while the optimized concentration was carried out in 50 mmol/L disodium hydrogen phosphate (pH 9.5). The linear ranges for m-, p-, and o-aminobenzoic acid were from 5.0 × 10⁻⁴–0.1, 5.0 × 10⁻⁴–0.1 and 1.0 × 10⁻⁴–0.1 mmol/L, respectively. And the detection limits (S/N = 3) were as low as 8.22 × 10⁻⁵, 8.21 × 10⁻⁵, and 3.76 × 10⁻⁵ mmol/L for m-, p-, and o-aminobenzoic acid, respectively. The run-to-run, day-to-day, and column-to-column reproducibilities of migration time were satisfactory with relative standard deviation values of less than 4.5 % in all cases. This method was successfully used in determining procaine hydrochloride injection sample with recoveries in the range of 96.1–106.6 % and relative standard deviations less than 5.0 %.

     

Cyclodextrin-Modified Gold Nanoparticle Capillary Electrochromatography with Online Sample Stacking for Simultaneous and Sensitive Determination of Aminobenzoic Acid Isomers

A newly-developed method of complete separation and sensitive determination of o-, m-, and p-aminobenzoic acid isomers was achieved by combining open-tubular columns for capillary electrochromatography (OT-CEC) and online sample stacking. In this study, spherical gold nanoparticles were modified by a covalent attachment of mono-6-thio-β-cyclodextrin, and OT-CEC was formed by immobilizing cyclodextrin-modified gold nanoparticles (CD-AuNP) on prederivatized 3-mercaptopropyl-trimethoxysilane fused-silica capillaries. Based on the theory of moving chemical reaction boundary, effects of several important factors such as the pH and concentration of running buffer and the conditions of stacking analytes were optimized. The optimized separations were carried out in 58 mmol/L HAc buffer at pH 3.0 using a capillary coated with CD-AuNP, while the optimized concentration was carried out in 50 mmol/L disodium hydrogen phosphate (pH 9.5). The linear ranges for m-, p-, and o-aminobenzoic acid were from 5.0 × 10^?4–0.1, 5.0 × 10^?4–0.1 and 1.0 × 10^?4–0.1 mmol/L, respectively. And the detection limits (S/N = 3) were as low as 8.22 × 10^?5, 8.21 × 10^?5, and 3.76 × 10^?5 mmol/L for m-, p-, and o-aminobenzoic acid, respectively. The run-to-run, day-to-day, and column-to-column reproducibilities of migration time were satisfactory with relative standard deviation values of less than 4.5 % in all cases. This method was successfully used in determining procaine hydrochloride injection sample with recoveries in the range of 96.1–106.6 % and relative standard deviations less than 5.0 %.     

Sulfobutylated Lignosulfonate with Ultrahigh Sulfonation Degree and Its Dispersion Property in Low-Rank Coal-Water Slurry

Using a simple method, we developed a new family of alkyl sulfonic acid modified lignosulfonate (ASLSs) with simultaneously improved sulfonation degrees and molecular weights via one step. Direct sulfonation occurred on both phenolic and alcoholic hydroxyl groups of alkali lignin raw material with 1,4-butylenesulfone used as sulfonation agent. A sulfonation degree of 3.86 mmol/g had been achieved which presents as one of the highest sulfonation degrees among those of reported LSs, to date. ¹H-NMR and Fourier transform infrared spectroscopy measurements confirmed the efficient sulfonation. Furthermore, the dispersion properties were investigated in low-rank coal-water slurry (CWS). ASLS3 showed better viscosity-reduction effect than naphthalene sulfonate formaldehyde condensate (FDN) in CWS with dosages from 0.6% to 1.0 wt%. ASLS3 had the similar sulfonation degree with FDN; however, the large steric hindrance, soft long alkyl chain-C₄H₈-SO₃H, and their efficient anchoring effect of ASLSs contributed to their improved dispersion properties.     

Gamma-irradiation of cellulose nanocrystals (CNCs): investigation of physicochemical and antioxidant properties

Gamma irradiation is a common process mostly used for sterilization against bacteria growth. However, when the process is applied to a material, physical and chemical changes may alter its integrity and behaviour. The aim of this study was to observe the effect of γ-irradiation on the surface chemistry of CNCs. The carbonyl content (both carboxylic acid and aldehyde functionalities) was followed to investigate the influence of the irradiation dose. Thermal stability, wettability and antioxidant properties were also measured. Conductometric titration showed that the carboxylic acid groups content (COOH) was increased from 43 mmol COOH kg^?1 CNCs for native CNCs to 631 mmol COOH kg^?1 CNCs when a dose of 80 kGy was applied. These changes were confirmed by FTIR and fluorescence spectroscopy. At high irradiation doses, a significant decrease of approximately 30% was observed in the cellulose degree of polymerization while the aldehyde groups content was increased to 379 mmol CHO kg^?1 CNCs due to the cleavage of glycosidic linkages. These physicochemical changes led to enhanced antioxidant properties of CNCs.     

Cellulose hydrolysis catalyzed by highly acidic lignin-derived carbonaceous catalyst synthesized via hydrothermal carbonization

Acidic carbonaceous solids were synthesized from mass pine alkali lignin via hydrothermal carbonization followed by sulfonation. Hydrothermal carbonization of lignin in the presence of acrylic acid (LAHC-SO₃H) provided many more carboxylic groups than that in the absence of acrylic acid, allowing subsequent sulfonation to produce a highly active and stable catalyst for cellulose hydrolysis in the [BMIM]Cl-H₂O solvent system. The hydrochar and catalyst were characterized using field emission scanning electron microscopy, X-ray diffractometer, X-ray photoelectron spectroscopy, thermal gravimetric analysis, Fourier transform infrared spectrometer, Brunauer–Emmett–Teller and acid–base titration. Results showed that a high acid content of 5.48 mmol/g, including carboxylic group (2.85 mmol/g), phenolic hydroxyl group (1.05 mmol/g) and sulfonic acid group (1.58 mmol/g), contributed significantly to the highly efficient hydrolysis of cellulose. Further, it was found that addition of trace water in [BMIM]Cl was favorable to cellulose hydrolysis. The highest yield (75.4%) of total reducing sugar (TRS) obtained in [BMIM]Cl-H₂O at a mass ratio of 100:1 was more than twice that (36.1%) achieved in [BMIM]Cl without water; the corresponding reaction conditions were 50 mg of microcrystalline cellulose, 30 mg of catalyst, 1.0 g of [BMIM]Cl, 10 mg of H₂O, reaction temperature of 130 °C and reaction time of 2 h. Furthermore, the TRS yield with 5 cycles for LAHC-SO₃H was higher than 68.1%, and the catalytic activity of catalyst could be fully recovered (74.0% of TRS yield) easily by regeneration.     

Solubilization of Terfenadine,Riboflavin, and Sudan III by Aqueous Multi-basic Organic Acids

ABSTRACT

The aqueous solubility of terfenadine, riboflavin, and Sudan III (water-insoluble compounds) was enhanced by the addition of multi-basic organic acids, including citric, glutaric, malic, malonic, and tartaric acids. The variations of physical properties (density, viscosity, electrical conductivity, pH, and surface tension) against acid concentration (0–3.6 M at 25°C) were measured in order to explore possible mechanisms of solubility enhancement. Apart from the partial molar volumes, the measured physical properties varied nonlinearly with acid concentration. Glutaric acid contributes to solubility enhancement of terfenadine and Sudan III more than citric acid, with the latter slightly more effective towards riboflavin. Tartaric acid is the least effective, while malic and malonic acids occupy an intermediate position. Among the organic acids examined, only glutaric acid solutions exhibit significant surface activity, which lends itself to solubility enhancement of the three hydrophobic drugs (interfacial packing of 55 ± 3 Å² at the air–water interface, critical aggregate concentrations (CAC) at 1.8 ± 0.4 M). In contrast, all five organic acid solutions of terfenadine demonstrate more effective lowering of the surface tension of water, with the terfenadinium acid salts exhibiting interfacial packing of 108 ± 9 Å² at the air–water interface. On the other hand, organic acid solutions of riboflavin and Sudan III exhibited essentially no surface activity, aside from the intrinsic contribution of the organic acids themselves. Thus, self-association of glutaric acid contributes to the solubility enhancement of the three hydrophobic drugs. This combined with the surface activity of terfenadinium acid salts explains the higher tendency of glutaric acid to solubilize terfenadine. Mixed micellization of terfenadinium glutarate and glutaric acid occurs with an interfacial packing of 166 ± 18 Å² at the air–water interface. The corresponding CAC were estimated at 3.1 ± 0.2 mM for terfenadinium glutarate and 8.0 ± 0.4 mM for glutaric acid. Intermolecular hydrogen bonding with the extensive hydroxyl group network of riboflavin reflects the higher affinity of citric acid than glutaric acid towards riboflavin. The variability in solubility enhancement exhibited by tartaric, malic, and malonic acids appears to be a result of the interplay between several factors including intra- vs. inter-molecular hydrogen bonding, slight organic acid surface activity, and acid hydration.     

Synthesis of mesoporous SnO2 nanomaterials with selective gas-sensing properties

Using SBA-15/KIT-5/KIT-6 as the hard templates, the mesoporous SnO₂ nanomaterials with different structures were synthesized by nanocasting. X-ray diffraction, transmission electron microscopy, and nitrogen adsorption isotherms were used to testify their structure characteristics. These mesoporous SnO₂ nanomaterials showed high specific surface areas (57–96 m² g^?1) and pore volume (0.17–0.27 cm³ g^?1). The nanopore of these templates makes the nanosize particle of the final mesoporous SnO₂ nanomaterials (4–9 nm) at last. The sensing properties of acetone, ethyl alcohol and methyl alcohol were investigated. The response of SnO₂-15, SnO₂-5, and SnO₂-6 are 17.0, 19.5, and 16.1, respectively as the concentration of ethyl alcohol on 200 ppm. The sensitivity of SnO₂-5 is 28.2 as the concentration of acetone was increased to 200 ppm. With the large surface area, high pore volume, and nanosized particles (close to 2 L = 6 nm of SnO₂), the SnO₂-5 show four fold enhancement in sensitivity compared to commercial SnO₂ powder and low detection limit (even at 200 ppb). The surface area and particle size play a significant party in the gas response. With the large surface area and smallest particle size, SnO₂-5 shows the highest sensitivity of all. These mesoporous nanomaterials show well potential application on the gas response.     

Synthesis and characteristics of hyperbranched polymer with phosphonic acid groups for high-temperature fuel cells

Two different molecular weight hyperbranched polymers (HBP(L)-(PA)₂ and HBP(H)-(PA)₂) with two phosphonic acid groups as a functional group at the periphery and a low molecular weight hyperbranched polymer (HBP(L)-(PA)₂-Ac) with both two phosphonic acid groups and an acryloyl group as a cross-linker at the periphery were successfully synthesized as thermally stable proton-conducting electrolytes. A cross-linked electrolyte membrane (CL-HBP(L)-(PA)₂) was prepared by thermal polymerization of the HBP(L)-(PA)₂-Ac using benzoyl peroxide. Ionic conductivities of the HBP(L)-(PA)₂, the HBP(H)-(PA)₂, and the CL-HBP(L)-(PA)₂ under dry condition and their thermal properties were investigated, and also, the effect of the phosphonic acid group number on them was discussed. Ionic conductivities of the HBP(L)-(PA)₂ and the HBP(H)-(PA)₂ were found to be 1.5?×?10^?5 S cm^?1 at 150 °C and 3.6?×?10^?6 S cm^?1 at 143 °C, respectively, under dry condition, and showed the Vogel–Tamman–Fulcher type temperature dependence. The hyperbranched polymers and the cross-linked electrolyte membrane were thermally stable up to 300 °C, and the cross-linked electrolyte membrane (CL-HBP-(PA)₂) had suitable thermal stability as an electrolyte membrane for the high-temperature fuel cells under dry condition. Fuel cell measurement using a single membrane electrode assembly cell with the cross-linked membrane was performed.     

Isolation of Chlorogenic Acid from <Emphasis Type="Italic">Flaveria bidentis</Emphasis> (L.) Kuntze by CCC and Synthesis of Chlorogenic Acid-Intercalated Layered Double Hydroxide

Preparative counter-current chromatography (CCC) was successfully used for isolation and purification of chlorogenic acid from Flaveria bidentis (L.) Kuntze with a solvent system composed of ethyl acetate–methanol–water at a volume ratio of 50:1:50, v/v. Using a preparative unit of the CCC centrifuge, about 800 mg of the crude extract was separated, yielding 3.2 mg of chlorogenic acid at a purity of 92.0%. The blood pressure lowering and antivirus chlorogenic acid (C₁₆H₁₈O₉) was intercalated into magnesium–aluminum–layered double hydroxides, which was used as host materials for drug-LDH host-guest supermolecular structures by anion exchange under a nitrogen atmosphere. Chlorogenic acid–LDH is a functional and effective drug. The product chlorogenic acid–LDH has been characterized by powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR), thermogravimetric analysis (TGA) and scanning electron micrographs (SEM). The X-ray diffraction patterns of NO₃ ^? form of LDH and chlorogenic acid–LDH were compared, and the basal d spacing value of NO₃ ^?-LDH layer was 8.75 Å (2θ = 10.100°); however, the basal reflection (003) of chlorogenic acid–LDH shifts to lower 2θ (for 003 reflection: 2θ = 5.119°) that is expanded to 17.25 Å, indicating the intercalation of chlorogenic acid into the interlayer of Mg–Al-LDH. Thermogravimetric analysis showed that chlorogenic acid stability had improved, and scanning electron micrographs showed that the morphology of the chlorogenic acid–LDH was irregular masses of distinctly thicker flakes, which was similar to the morphology of NO₃ ^? form of LDH.     

Removal of 63Ni and 57Co from aqueous solution using antimony doped tin dioxide–polyacrylonitrile (Sb doped SnO2–PAN) composite ion-exchangers

Tin dioxide and its antimony doped counterpart were synthesized using traditional sol–gel procedure. The metal oxides were then turned into composites by mixing them with polyacrylonitrile (PAN) and composite spheres ready for use in traditional column applications were obtained. The characterization of materials was investigated by X-ray diffraction, scanning electron microscopy–energy dispersive X-ray, surface area, point of zero charge and thermal analyses. Static batch experiments showed that the antimony doped tin dioxide–PAN (Sb doped SnO₂–PAN) is an effective material for nickel removal and the composite maintains its good metal uptake properties in dynamic column conditions. The composite showed a high nickel uptake capacity of 9 mmol/g in 0.1 M NaNO₃ solution. It was observed that the ion exchange kinetics of antimony doped tin dioxide (Sb doped SnO₂) was remarkably fast for ⁵⁷Co and ⁶³Ni ions but turning the material into PAN composite significantly decreased the materials kinetic properties.     

Synthesis of Cinnamyl Alcohol from Cinnamaldehyde with Bacillus stearothermophilus Alcohol Dehydrogenase as the Isolated Enzyme and in Recombinant E. coli Cells

The synthesis of the aroma chemical cinnamyl alcohol (CMO) by means of enzymatic reduction of cinnamaldehyde (CMA) was investigated using NADH-dependent alcohol dehydrogenase from Bacillus stearothermophilus both as an isolated enzyme, and in recombinant Escherichia coli whole cells. The influence of parameters such as reaction time and cofactor, substrate, co-substrate 2-propanol and biocatalyst concentrations on the bioreduction reaction was investigated and an efficient and sustainable one-phase system developed. The reduction of CMA (0.5 g/L, 3.8 mmol/L) by the isolated enzyme occurred in 3 h at 50 °C with 97 % conversion, and yielded high purity CMO (≥98 %) with a yield of 88 % and a productivity of 50 g/g_enzyme. The reduction of 12.5 g/L (94 mmol/L) CMA by whole cells in 6 h, at 37 °C and no requirement of external cofactor occurred with 97 % conversion, 82 % yield of 98 % pure alcohol and a productivity of 34 mg/g_{wet cell weight}. The results demonstrate the microbial system as a practical and efficient method for larger-scale synthesis of CMO.     

Rheological properties and enhanced oil recovery performance of a novel sulfonate polyacrylamide

A novel hydrosoluble sulfonate copolymer (SPAM) containing sulfonic acid groups was synthesized under mild conditions with Acrylamide (AM), 2-(Dimethylamino) ethyl methacrylate (DMAEMA) and 2-methyl-2-[(1-oxo-2-propenyl)amino]-1-propane sulfonic acid (AMPS) as monomers by segmentation initiation with 2,2'-azobis[2-methylpropionamidine] dihydrochloride and redox initiation system, respectively. The structures of copolymers were characterized by infrared (IR) spectroscopy, ¹H NMR spectroscopy and thermogravimetric analysis. The rheological properties of the copolymer solution at different shear rate, temperature and salt concentration were investigated. The shear-tolerance, temperature-tolerance and salt-tolerance of the novel synthetic hydrosoluble sulfonate copolymer are improved remarkably compared with partially hydrolyzed polyacrylamide (HPAM). The synthetic copolymer solution possesses a higher viscosity retention rate (53.3%) than HPAM (35.3%) at the total salinity of 20000 mg/L when temperature changed from 30°C to 99°C. The enhanced oil recovery (EOR) of the synthetic copolymer was performed by core flood, and the EOR degree of the synthetic copolymer in the 20000 mg/L salt solution at 80°C was better than that of HPAM. Compared with HPAM flooding, the EOR with the synthetic copolymer flooding was increased by 6.8% at 80°C.     

Clopyralid detection by using a molecularly imprinted electrochemical luminescence sensor based on the “gate-controlled” effect

A new strategy for trace analysis was proposed by preparing a molecularly imprinted polymer (MIP) sensor. The template molecules of clopyralid were determined based on “gate-controlled” electrochemiluminescence (ECL) measurement. A dense polymer film was electropolymerized on an electrode surface to fabricate the MIP–ECL sensor. The process of template elution and rebinding acted as a gate to control the flux of probes, which pass through the cavities and react on the electrode surface. ECL measurement was conducted in the luminol–H₂O₂ system. A linear relationship between ECL intensity and clopyralid concentrations in the range of 1?×?10^?9 mol/L to 8?×?10^?7 mol/L exists, and the detection limit was 3.7?×?10^?10 mol/L. The prepared sensor was used to detect clopyralid in vegetables. Recoveries of 97.9 % to 102.9 % were obtained. The sensor showed highly selective recognition, high sensitivity, good stability, and reproducibility for clopyralid detection.     

Radiosynthesis and biodistribution studies of [62Zn/62Cu]–plerixafor complex as a novel in vivo PET generator for chemokine receptor imaging

In order to develop a possible C-X-C chemokine receptor type 4 (CXCR4) imaging agent for oncological scintigraphy, [⁶²Zn]labeled 1,1′-[1,4-phenylenebis(methylene)]bis-1,4,8,11-tetraazacyclotetradecane ([⁶²Zn]-AMD3100) was prepared using in-house made [⁶²Zn]ZnCl₂ and AMD-3100 for 1 h at 50 °C (radiochemical purity: >97 % ITLC, >96 % HPLC, specific activity: 20–22 GBq/mmol) in acetate buffer. The complex showed highly hydrophilic properties (log P = ?1.114). Stability of the complex was checked in presence of human serum (37 °C) and in final formulation for 1 day. The biodistribution of the labeled compound in vital organs of wild-type Sprague–Dawdley rats were determined and compared with that of free Zn²⁺ cation up to 6 h. Co-incidence imaging of the complex was consistent with the distribution data up to 3 h. The complex can be a possible in vivo generator compound for PET imaging in CXCR4 positive tumors.     

Thermal properties of sulfonic acid group functionalized Brönsted acidic ionic liquids

Thermal decomposition onset temperatures have been measured for a total of 24 methylimidazolium, triethanolammonium, and pyridinium type sulfonic acid groups functionalized Brönsted acidic ionic liquids with Cl^?, Br^?, SO₄ ^2?, PO₄ ^3?, BF₄ ^? _, CH₃CO₂ ^?, and CH₃SO₃ ^? anions, using thermogravimetric analysis. Thermal stabilities of these sulfonic acid group functionalized ionic liquids decreases in the order, methylimidazolium > triethanolammonium > pyridinium. The methylimidazolium, pyridinium, and triethanolammonium ionic liquids investigated showed decomposition onset temperatures (air) in the 213–353, 167–240, and 230–307 °C ranges, respectively. Additionally, the decomposition temperatures of these ionic liquids are highly dependent on the nature of the anion.     

Interaction Between GMAC-m-CS and Surfactants: Surface Tension and Conductivity Methods

Glycidyl trimethyl ammonium chloride-modified chitosan (GMAC-m-CS) was synthesized through nucleophilic substitution of GMAC on CS in isopropanol dispersed system, which was characterized by FTIR and ¹H NMR methods. The interaction between GMAC-m-CS and surface active ILs ?1-dodecyl (tetradecyl and hexadecyl)-3-methylimidazolium bromide (C_nmimBr, n = 12, 14, 16) was studied by surface tension and conductivity methods. The amount of C_nmimBr adsorbed on GMAC-m-CS increases first with raising temperature, and then decreases, which reaches the largest amount at 30°C. The amount increases with the increase of alkyl chain length. The surface tension reducing capabilities of GMAC-m-CS/C_nmimBr systems increase with temperature, however, decrease with the increase of GMAC-m-CS concentration. The aggregation processes of C₁₄mimBr in solutions without GMAC-m-CS and with high concentration of GMAC-m-CS were entropy driven; however, it is enthalpy driven in solutions with low concentration of GMAC-m-CS. Based on the analysis of properties of GMAC-m-CS/C_nmimBr, the interaction model of GMAC-m-CS/ILs was proposed.     

Synthesis of 15-(4-[11C]methylphenyl)pentadecanoic acid (MePPA) via Stille cross-coupling reaction

For experimental studies by animal PET [¹¹C]-labeled 15-(4-methylphenyl)pentadecanoic acid (MePPA) is an attractive alternative to the radioiodinated 15-(4-iodophenyl)pentadecanoic acid (IPPA) which has widely been used for imaging of fatty acid metabolism. The important physiological aspect is that the iodine atom and the methyl substituent have similar steric and lipophilic properties. For preparation of [¹¹C]MePPA, Stille cross-coupling reaction was applied since the same tin precursor as for the radiosynthesis of IPPA and readily available [¹¹C]CH₃I can be used. Unsaturated tris(dibenzylideneacetone)dipalladium(0)/tri(o-tolyl)phosphine [Pd₂(dba)₃/P(o-tolyl)₃] was taken as the catalytic system. The reaction conditions were optimized with respect to temperature, time, solvent and amount of precursor. The best radiochemical yields of 73 ± 2.8% (decay corr.) were obtained using 0.525 mg tin precursor in DMF at 80 °C already after a reaction time of 10 min. The labeled methyl ester was hydrolyzed by 1 M NaOH/EtOH at 80 °C within 3 min to give [¹¹C]IPPA in a RCY of 62 ± 3.0%. The radiochemical purity of the product assured by HPLC was >99% and the overall preparation time including HPLC purification and formulation was 40 min.