Trimethylammonium Acetate Research Articles

Crystallization of isoniazid in choline-based ionic liquids: Physicochemical properties and anti-tuberculosis activity

Isoniazid is a drug commonly employed in the treatment of tuberculosis. One major barrier to its widespread use is that it can undergo hydrolysis when stored inadequately, resulting in the formation of hydrazine, a toxic and carcinogenic compound. Therefore, there is a clear need for further research aimed at improving the stability of isoniazid while still maintaining its therapeutic efficiency and solubility. To this end, five choline ionic liquids (ILs) were used for synthesizing improved forms of isoniazid: (2-hydroxyethyl)-trimethylammonium hydroxide [ChOH], (2-hydroxyethyl)-trimethylammonium hydrogen sulfate [ChBis], (2-hydroxyethyl)-trimethylammonium acetate [ChAc], (2-hydroxyethyl)-trimethylammonium citrate [ChCit], and (2-hydroxyethyl)-trimethylammonium benzoate [ChBenz]. The INH:[ChOH] and INH:[ChCit] forms were obtained in powder form, and presented low solubility and a minimum inhibitory concentration for Mycobacterium tuberculosis of 100 μg/mL and 12.5 μg/mL, respectively. The INH:[ChBenz], INH:[ChBis], and INH:[ChAc] forms showed a minimum inhibitory concentration value lower than 6.2 µg/mL. In the process using [ChBis], 2-(4-pyridiniumcarbonyl)-hydrazine sulfate with a water solubility of 155.9 mg/mL at 25 °C was produced, which showed to be more soluble than isoniazid (137.9 mg/mL). Therefore, the IL used had a direct influence on the solubility, conformational structure, and stability of isoniazid. This research is highly relevant and innovative for the use of new solvents in the crystallization of drugs, especially when aiming at the improvement of their properties.

Combined strategies for suppressing nonspecific cationic adduction to G-quadruplexes in electrospray ionization mass spectrometry

G-quadruplex secondary structures are naturally found in genome sequences and play essential roles in regulating a wide variety of important biological processes. Although stabilizing effects of monovalent cations (e.g., K+ and Na+) has been recognized during the past decades, a general and reliable analytical method for accurate characterization of specific interactions of K+/Na+ with G-quartets is still not well established. In the present study, we demonstrate a practical strategy that combined the use of a nanoscale ion emitter, a low-flow drying gas and a volatile salt (trimethylammonium acetate) to almost totally suppress the nonspecific cationic adduction to G-quadruplexes during the ionization process. Our combined strategy takes full advantage of the ultrasmall initial charged droplets when employing a nanoscale ion emitter, the maximum uneven fission of charged droplets under the gentle desolvation conditions, and the effective shielding of the negatively charged phosphate groups by trimethylammonium ions, to eventually producing ions of G-quadruplexes free of non-specific K+/Na+ adduction. For the first time, the accurate binding states as well as the quantitative binding constants between K+/Na+ and G-quadruplexes can be directly obtained even in the presence of tens of millimolar non-volatile salts, which has long been a notorious challenge in mass spectrometry.

DNA G-quadruplexes for native mass spectrometry in potassium: a database of validated structures in electrospray-compatible conditions.

G-quadruplex DNA structures have become attractive drug targets, and native mass spectrometry can provide detailed characterization of drug binding stoichiometry and affinity, potentially at high throughput. However, the G-quadruplex DNA polymorphism poses problems for interpreting ligand screening assays. In order to establish standardized MS-based screening assays, we studied 28 sequences with documented NMR structures in (usually ∼100 mM) potassium, and report here their circular dichroism (CD), melting temperature (Tm), NMR spectra and electrospray mass spectra in 1 mM KCl/100 mM trimethylammonium acetate. Based on these results, we make a short-list of sequences that adopt the same structure in the MS assay as reported by NMR, and provide recommendations on using them for MS-based assays. We also built an R-based open-source application to build and consult a database, wherein further sequences can be incorporated in the future. The application handles automatically most of the data processing, and allows generating custom figures and reports. The database is included in the g4dbr package (https://github.com/EricLarG4/g4dbr) and can be explored online (https://ericlarg4.github.io/G4_database.html).

Native Hydrogen/Deuterium Exchange Mass Spectrometry of Structured DNA Oligonucleotides.

Although solution hydrogen-deuterium exchange mass spectrometry (HDX/MS) is well-established for the analysis of the structure and dynamics of proteins, it is currently not exploited for nucleic acids. Here we used DNA G-quadruplex structures as model systems to demonstrate that DNA oligonucleotides are amenable to in-solution HDX/MS in native conditions. In trimethylammonium acetate solutions and in soft source conditions, the protonated phosphate groups are fully back-exchanged in the source, while the exchanged nucleobases remain labeled without detectable back-exchange. As a result, the exchange rates depend strongly on the secondary structure (hydrogen bonding status) of the oligonucleotides, but neither on their charge state nor on the presence of nonspecific adducts. We show that native mass spectrometry methods can measure these exchange rates on the second to the day time scale with high precision. Such combination of HDX with native MS opens promising avenues for the analysis of the structural and biophysical properties of oligonucleotides and their complexes.

Abstract 5201: PSMA-targeted alpha radioimmunotherapy for prostate cancer with 225Ac-J591

Abstract Background: Prostate cancer (PC) is a radiosensitive disease. In addition to external beam and brachytherapy, systemic bone-seeking radioisotopes have been utilized clinically for many years, with radium-223 leading to overall survival benefits. However, the available beta and alpha emitting particles in the clinic target tumors / stroma in bone only. Biologically targeted radiopharmaceutical treatment has shown promising results in our earlier multiple clinical trials using beta-emitting anti-PSMA therapy with Leutetium-177 radiolabeled anti-PSMA monoclonal antibody (mAb) J591, with accurate targeting and tumor response, but treatment is limited by myelosuppression. Both beta and alpha-small molecule PSMA ligand directed therapy has been utilized anecdotally outside of the US, but has not been systemically studied. Based upon their biodistribution, targeting of salivary glands and potentially proximal renal tubules may pose longer term toxicity issues. mAb-based targeted alpha-particle delivery may be advantageous with less expected myelosuppression than seen with β-emitters. Experimental procedures: To optimize labeling of humanized DOTA-J591 mAb, actinium-225 (225Ac) nitrate was obtained from Oak Ridge National Laboratories and was dissolved in HCl solution and then mixed with trimethyl ammonium acetate and L-ascorbic acid. This preparation was incubated with DOTA-J591. The labeling efficiency (LE) was determined by ITLC-SG. If the LE is >60%, 225Ac-DOTA-J591 mAb was purified by gel filtration and sterilized by membrane filtration. In a pilot pre-clinical study, we studied the toxicity in non-tumor bearing BALB/c mice. Results: The radiochemical purity is >95% and the immunoreactivity was >80%. Twenty-five BALB/c mice received from 2.1 to 6.3 KBq of 225Ac-J591. Treatment was well tolerated, with all mice alive and healthy at Day 26. Conclusions: A stable alpha emitting-antibody complex has been produced with 225Ac-J591. Initial mouse safety experiments have been successful. A RIT dose escalation study of PSMA-targeted alpha emitter in a LNCaP xenograft model is underway. Citation Format: Jaspreet S. Batra, He Liu, Sae Kim, Vicente N. Navarro, Shankar Vallabhajosula, Scott T. Tagawa, Neil H. Bander. PSMA-targeted alpha radioimmunotherapy for prostate cancer with 225Ac-J591 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5201. doi:10.1158/1538-7445.AM2017-5201

Evaluating the transfer free energies of amino acids from water to ammonium-based ionic liquids at 298.15 K

The interactions between ionic liquids (ILs) and amino acids (AAs) can easily be quantified using the apparent transfer free energy (∆G′tr) values that can be used to interpret the stability of the proteins in the same solvent medium. In this study, ∆G′tr values of AAs such as phenylalanine (Phe), histidine (His), threonine (Thr), glutamine (Gln) and serine (Ser) from the water to ILs have been obtained from the solubility measurements, as a function of IL concentration at 298.15K under atmospheric pressure. The investigated ILs contain diethylammonium acetate (DEAA), diethylammonium hydrogen sulfate (DEAS), triethylammonium acetate (TEAA), triethylammonium hydrogen sulfate (TEAS), triethylammonium dihydrogen phosphate (TEAP), and trimethylammonium acetate (TMAA). The results reveal that the IL effect was specific and independent for each AA in the aqueous medium. Apparently, we observed a positive as well as negative ∆G′tr values for Phe, His, Glu, Thr, and Ser AAs in the ammonium-based ILs.

Thermophysical properties of aqueous solution of ammonium-based ionic liquids.

Experimental densities (ρ), ultrasonic sound velocities (u), viscosities (η), and refractive indices (n(D)) of binary mixtures of ammonium-based ionic liquids (ILs) such as diethylammonium acetate (DEAA) [(CH3CH2)2NH][CH3COO], triethylammonium acetate (TEAA) [(CH3CH2)3NH][CH3COO], diethylammonium hydrogen sulfate (DEAS) [(CH3CH2)2NH][HSO4], triethylammonium hydrogen sulfate (TEAS) [(CH3CH2)3NH][HSO4], trimethylammonium acetate (TMAA) [(CH3)3NH][CH3COO], and trimethylammonium hydrogen sulfate (TMAS) [(CH3)3NH][HSO4] with water are reported over the wide composition range at 25 °C under atmospheric pressure. The excess molar volumes (V(E)), deviation in isentropic compressibilities (Δκ(s)), deviation in viscosities (Δη) and deviation in refractive indices (Δn(D)) are calculated from experimental values and are correlated by Redlich-Kister polynomial equations. The V(E) and Δκ(s) values for the aforesaid systems are negative over the entire composition range while the Δη and Δn(D) values are positive under the same experimental conditions. The intermolecular interactions and structural effects were analyzed on the basis of measured and derived properties. A qualitative analysis of the results is discussed in terms of the ion-dipole, ion-pair interactions and hydrogen bonding between ILs and water. Furthermore, the hydrogen bonding features between ILs with water were analyzed by using a molecular modeling program with the help of HyperChem7.

Native electrospray mass spectrometry of DNA G-quadruplexes in potassium solution.

A commonly used electrolyte in electrospray mass spectrometry (ESI-MS) of biomolecules is ammonium acetate (NH4OAc). Although some nucleic acid structures such as duplexes require only proper physiological ionic strength (whatever the monovalent ions) to be properly folded in ESI-MS conditions, the folding of some other nucleic acid structures such as DNA G-quadruplexes also depends on direct binding of specific cations. Here, we developed ESI-MS compatible conditions that allow one to observe DNA G-quaduplexes with K+ ions specifically bound between G-quartets. NH4OAc was replaced with trimethylammonium acetate (TMAA), at concentrations up to 150 mM to provide physiological ionic strength, and the solution was doped with KCl at concentrations up to 1 mM. The trimethylammonium ion is too large to coordinate between G-quartets, where only K+ ions bind. Compared with the equivalent NH4OAc/KCl mixtures, the TMAA/KCl mixtures provide cleaner spectra by suppressing the nonspecific adducts, and favor the formation of similar stacking arrangements as in 100 mM KCl (physiologically relevant cation) for the polymorphic human telomeric DNA G-quadruplexes. This new sample preparation method can be exploited to determine the number of potassium binding sites in new sequences, to screen ligand binding to the structures favored in potassium, and to transfer potassium-bound G-quadruplexes to the mass spectrometer for gas-phase structural probing, as illustrated herein with ion mobility spectrometry experiments. Figureᅟ Electronic supplementary materialThe online version of this article (doi:10.1007/s13361-014-0890-3) contains supplementary material, which is available to authorized users.

The Solubility and Stability of Amino Acids in Biocompatible Ionic Liquids

In recent years, ionic liquids (ILs) represent a new class of biocompatible co-solvents for biomolecules. In this work, we report the apparent transfer free energies (ΔG'tr) for six amino acids (AA) from water to aqueous solutions of six ammonium based ILs (diethylammonium acetate (DEAA), diethylammonium sulfate (DEAS), triethyl ammonium acetate (TEAA), triethylammonium sulfate (TEAS), triethylammonium dihydrogen phosphate (TEAP), and trimethylammonium acetate (TMAA)) through solubility measurements, as a function of IL concentration at 298.15 K under atmospheric pressure. Salting-out effect was found for AA in aqueous IL solutions with increasing IL concentrations. In addition, we observed positive values of ΔG'tr for AA from water to ILs, indicating that the interactions between ILs and AA are unfavorable. From the obtained results, we found that the selected ammonium based ILs act as stabilizers for the structure of AA.

Acetate based Supported Ionic Liquid Membranes (SILMs) for CO2 separation: Influence of the temperature

Supported Ionic Liquid Membranes (SILMs) were prepared with the acetate based Room Temperature Ionic Liquids (RTILs) 1-ethyl-3-methylimidazolium acetate ([Emim][Ac]), 1-butyl-3-methylimidazolium acetate ([Bmim][Ac]) and the monomer vinylbenzyl trimethylammonium acetate ([Vbtma][Ac]) in order to perform the selective separation of carbon dioxide (CO2) from nitrogen (N2). The RTILs were supported in a polyvinylidene fluoride porous membrane and permeation experiments were performed in the temperature range 298–333K. Gas permeability increases with temperature while an increase in temperature leads to a decrease in the CO2/N2 selectivity for all the studied RTILs. CO2 solubility was evaluated in the range 298–333K and atmospheric pressure using thermogravimetric techniques. Diffusion coefficients were calculated based on the solution–diffusion theory using gas permeability and solubility data. The temperature influence on the gas permeability, solubility and diffusivity are well described in terms of the Arrhenius–van't Hoff exponential relationships.

Exploring the thermal stability of α-chymotrypsin in protic ionic liquids

Ammonium based ionic liquids (ILs) are biocompatible co-solvents that stabilize the native state of proteins. Experimentally, we have explored the stability of α-chymotrypsin (CT) in the presence of nine ILs, i.e., diethylammonium acetate (DEAA), diethylammonium hydrogen sulfate (DEAS), diethylammonium dihydrogen phosphate (DEAP), triethylammonium acetate (TEAA), triethylammonium hydrogen sulfate (TEAS), triethylammonium dihydrogen phosphate (TEAP), trimethylammonium acetate (TMAA), trimethylammonium hydrogen sulfate (TMAS), trimethylammonium dihydrogen phosphate (TMAP). Thermodynamic folding properties such as transition temperature (Tm), Gibbs free energy change of unfolding (ΔGU), enthalpy change (ΔH) and heat capacity change (ΔCp) of CT in ILs are obtained by fluorescence spectra analysis. Fluorescence and circular dichroism (CD) spectroscopy experiments were performed to probe CT stabilization and structural changes in the presence of ILs. Our experimental results suggest that the ILs act as stabilizers for the CT structure and the stability of CT depends on the structural arrangement of the ions of ILs. Our experimental results reveal that ILs (DEAA, DEAS and DEAP) having more hydrophobic ammonium cations [DEA+] are weak stabilizers for CT, while trimethyl ammonium cations [TMA+] ILs having small alkyl chain length such as TMAA, TMAS and TMAP are strong stabilizers and therefore more biocompatible for the native structure of CT.

Influence of anion on thermophysical properties of ionic liquids with polar solvent

In this work, we have reported a series of ionic liquids (ILs) involving a common cation trimethyl ammonium, ([(CH3)3NH]+), with generally used anions (acetate, [CH3COO]−, sulfate, [HSO4]−, phosphate, [H2PO4]−). To address the molecular interactions between the relatively new class of solvents such as trimethylammonium acetate [(CH3)3NH+] [CH3COO–] (TMAA), trimethylammonium hydrogen sulfate [(CH3)3NH+][HSO4−] (TMAS), and trimethylammonium dihydrogen phosphate [(CH3)3NH+][H2PO4–] (TMAP), with the polar solvent, dimethylsulfoxide (DMSO), the density (ρ), speed of sound (u) and viscosity (η) values have been measured over complete concentration range and wide temperature range from 298.15K to 313.15K in steps of 5K under ambient pressure. By using these experimental results, excess volumes (VE), isentropic compressibility deviations (Δκs) and viscosity deviations (Δη) were obtained for all these binary systems at all experimental temperatures. The results are correlated by the Redlich−Kister type function to derive the coefficients and estimate the standard error. Further, the results for observed anion dependent phenomena and temperature influence on measured and derived properties are also discussed.

Structural Basis for the Enhanced Stability of Protein Model Compounds and Peptide Backbone Unit in Ammonium Ionic Liquids

Protein folding/unfolding is a fascinating study in the presence of cosolvents, which protect/disrupt the native structure of protein, respectively. The structure and stability of proteins and their functional groups may be modulated by the addition of cosolvents. Ionic liquids (ILs) are finding a vast array of applications as novel cosolvents for a wide variety of biochemical processes that include protein folding. Here, the systematic and quantitative apparent transfer free energies (ΔG'(tr)) of protein model compounds from water to ILs through solubility measurements as a function of IL concentration at 25 °C have been exploited to quantify and interpret biomolecular interactions between model compounds of glycine peptides (GPs) with ammonium based ILs. The investigated aqueous systems consist of zwitterionic glycine peptides: glycine (Gly), diglycine (Gly(2)), triglycine (Gly(3)), tetraglycine (Gly(4)), and cyclic glycylglycine (c(GG)) in the presence of six ILs such as diethylammonium acetate (DEAA), diethylammonium hydrogen sulfate (DEAS), triethylammonium acetate (TEAA), triethylammonium hydrogen sulfate (TEAS), triethylammonium dihydrogen phosphate (TEAP), and trimethylammonium acetate (TMAA). We have observed positive values of ΔG'(tr) for GPs from water to ILs, indicating that interactions between ILs and GPs are unfavorable, which leads to stabilization of the structure of model protein compounds. Moreover, our experimental data ΔG'(tr) is used to obtain transfer free energies (Δg'(tr)) of the peptide backbone unit (or glycyl unit) (-CH(2)C═ONH-), which is the most numerous group in globular proteins, from water to IL solutions. To obtain the mechanism events of the ILs' role in enhancing the stability of the model compounds, we have further obtained m-values for GPs from solubility limits. These results explicitly elucidate that all alkyl ammonium ILs act as stabilizers for model compounds through the exclusion of ILs from model compounds of proteins and also reflect the effect of alkyl chain on the stability of protein model compounds.

Influence of biocompatible ammonium ionic liquids on the solubility of l-alanine and l-valine in water

Understanding the folding process of proteins or polypeptides in co-solvents is a fascinating and critical issue in biophysical chemistry. In recent years, ionic liquids (ILs) represent a versatility of the new class of co-solvents. To quantify the bimolecular interactions of amino acids (AA), such as l-alanine (Ala) and l-valine (Val) with biocompatible ILs, we report the apparent transfer free energies (ΔG′tr) for AA from water to aqueous solutions of six ammonium based ILs (diethylammonium acetate (DEAA), diethylammonium sulfate (DEAS), triethyl ammonium acetate (TEAA), triethylammonium sulfate (TEAS), triethylammonium dihydrogen phosphate (TEAP), and trimethylammonium acetate (TMAA)) through solubility measurements, as a function of IL concentration at 298.15K under atmospheric pressure. Salting-out effect was found for AA in aqueous IL solutions with increasing IL concentrations. In addition, we observed positive values of ΔG′tr for Ala and Val from water to ILs, indicating that the interactions between ILs and AA are unfavorable. From the solubility results, we envisage that the selected ammonium based-ILs provide stability to the structure of AA. Further, the stability of AA has been studied by means of the UV–vis spectroscopy.

Influence of temperature on thermophysical properties of ammonium ionic liquids with N-methyl-2-pyrrolidone

To address the molecular interactions between ionic liquids (ILs) such as trimethylammonium acetate [(CH3)3NH][CH3COO] (TMAA), trimethylammonium hydrogen sulphate [(CH3)3NH][HSO4] (TMAS), trimethylammonium dihydrogen phosphate [(CH3)3NH][H2PO4] (TMAP) and triethylammonium dihydrogen phosphate [(CH3CH2)3NH][H2PO4] (TEAP) with N-methyl-2-pyrrolidone (NMP), density (ρ), ultrasonic sound velocity (u) and viscosity (η) measurements have been performed across the entire concentration range and the wide temperature range from 298.15 to 313.15K in steps of 5K under ambient pressure. Further, on the basis of the measured properties, excess volumes (VE), isentropic compressibility deviations (Δκs) and viscosity deviations (Δη) were obtained for all these systems under the same experimental conditions. The results are correlated by the Redlich–Kister type equation. The results are also analysed on anion dependent phenomena and temperature influence on measured and derived properties of ILs with NMP mixtures. A qualitative analysis of molecular interactions between ILs and NMP is discussed in terms of the ion-dipole, ion-pair interactions, and hydrogen bonding.

Influence of protic ionic liquids on the structure and stability of succinylated Con A

We report the synthesis of a series of ionic liquids (ILs) from various ions having different kosmotropicity including dihydrogen phosphate (H2PO4−), hydrogen sulfate (HSO4−) and acetate (CH3COO−) as anions and chaotropic cation such as trialkylammonium cation. To characterize the biomolecular interactions of ILs with protein, we have explored the stability of succinylated Con A (S Con A) in the presence of these aqueous ILs, which are varied combinations of kosmotropic anion with chaotropic cation such as triethylammonium dihydrogen phosphate [(CH3CH2)3NH][H2PO4] (TEAP), trimethylammonium acetate [(CH3)3NH][CH3COO] (TMAA), trimethylammonium dihydrogen phosphate [(CH3)3NH][H2PO4] (TMAP) and trimethylammonium hydrogen sulfate [(CH3)3NH][HSO4] (TMAS). Circular dichroism (CD) and fluorescence experiments have been used to characterize the stability of S Con A by ILs. Our data distinctly demonstrate that the long alkyl chain IL TEAP is a strong stabilizer for S Con A. Further, our experimental results reveal that TEAP is an effective refolding enhancer for S Con A from a thermally denatured protein structure.

Thermodynamic contributions of peptide backbone unit from water to biocompatible ionic liquids at T = 298.15 K

To quantify the biomolecular interactions of protein functional groups with biocompatible ionic liquids (ILs), transfer free energies ( Δ G tr ′ ) of model compounds from water to aqueous ILs solutions have been determined from the solubility measurements, as a function of ILs concentration at T = 298.15 K under atmospheric pressure. The aqueous systems investigated contain amino acids of zwitterionic glycine peptides: glycine (Gly), diglycine (Gly 2), and cyclic glycylglycine (c(GG)) with ILs of diethylammonium acetate ([Et 2NH][CH 3COO], DEAA), triethylammonium acetate ([Et 3NH][CH 3COO], TEAA), and trimethylammonium acetate ([Me 3NH][CH 3COO], TMAA). It was found that the solubility of model compounds in aqueous IL solutions decreases with increasing IL concentration (salting-out effect). We observed positive values of Δ G tr ′ for Gly, Gly 2, and c(GG) from water to ILs, indicating that the interactions between ILs and protein surface are unfavourable, which leads to stabilization of the native structure of amino acids. Moreover, our experimental data is used to determine transfer free energies ( Δ g tr ′ ) of the peptide backbone unit (–CH 2C ONH–) from water to IL solutions. These results explicitly elucidate that all alkyl ammonium ILs acted as stabilizers for tested model compounds through the exclusion of ILs from surface of model compounds and also reflect the effect of alkyl chain on the stability of protein model compounds. To obtain the mechanism events of the ILs role in enhancing the stability of the model compounds structure, we further studied the UV–vis spectrum analysis.

Temperature Dependence Measurements and Structural Characterization of Trimethyl Ammonium Ionic Liquids with a Highly Polar Solvent

We report the synthesis and characterization of a series of an ammonium ionic liquids (ILs) containing acetate, dihydrogen phosphate, and hydrogen sulfate anions with a common cation. To characterize the thermophysical properties of these newly synthesized ILs with the highly polar solvent N,N-dimethylformamide (DMF), precise measurements such as densities (ρ) and ultrasonic sound velocities (u) over the whole composition range have been performed at atmospheric pressure and over wide temperature ranges (25-50 °C). The excess molar volume (V(E)) and the deviation in isentropic compressibilities (Δκ(s)) were predicted using these temperature dependence properties as a function of the concentration of ILs. The Redlich-Kister polynomial was used to correlate the results. The ILs investigated in the present study included trimethylammonium acetate [(CH(3))(3)NH][CH(3)COO] (TMAA), trimethylammonium dihydrogen phosphate [(CH(3))(3)NH][H(2)PO(4)] (TMAP), and trimethylammonium hydrogen sulfate [(CH(3))(3)NH][HSO(4)] (TMAS). The intermolecular interactions and structural effects were analyzed on the basis of the measured and the derived properties. In addition, the hydrogen bonding between ILs and DMF has been demonstrated using semiempirical calculations with help of Hyperchem 7. A qualitative analysis of the results is discussed in terms of the ion-dipole, ion-pair interactions, and hydrogen bonding between ILs and DMF molecules and their structural factors. The influence of the anion of the protic IL, namely, acetate (CH(3)COO), dihydrogen phosphate (H(2)PO(4)), and hydrogen sulfate (HSO(4)), on the thermophysical properties is also provided.

Comparison of detection performance of UV and electrochemical detection in NACE for a range of different capillary inner diameters

A systematic comparison of UV and electrochemical detection (ED) in conjunction with NACE has been performed for capillaries with different ids ranging from 75 down to 2 microm. Ferrocene, (ferrocenylmethyl)trimethylammonium acetate, atropine and scopolamine served as model analytes. All studies were done using an ACN-based nonaqueous electrophoresis buffer. For the comparison of detection performance, particular attention was paid to the absolute and relative LODs for decreasing capillary dimensions. In case of UV detection, a significant increase in relative LODs was typically observed for capillaries smaller than 25 microm in diameter, while the absolute LODs remained nearly constant over a wide range of capillary dimensions. In contrast, ED showed some increase in relative LODs for capillaries smaller than 10 microm in diameter, but the absolute LODs decreased over the complete range of capillary diameters studied. It could be demonstrated that the straightforward end-column ED with microdisk electrodes can be applied in conjunction with small id (2 microm) capillaries. Studies with (ferrocenylmethyl)trimethylammonium acetate using such small capillaries resulted in relative and absolute LODs of 7.5 x 10(-7) and 8 x 10(-18) mol/L, respectively.

Preparation and Utilization of Cationized Sawdust

ABSTRACT Glycidyl trimethyl ammonium acetate (GTMAA) was prepared. Factors affecting the cationization of sawdust with GTMAA in presence of sodium hydroxide were investigated. These factors include sodium hydroxide/GTMAA molar ratio, liquor ratio, reaction duration, and temperature. The extent of cationization was traced by estimating the nitrogen content of the cationized sawdust, and its structural features were confirmed by IR analysis. The ability of cationized sawdust to adsorb anionic dyes, viz., Acid Fast Red 1, Acid Green 16, and Direct Blue 75, was investigated at 30°C. The adsorption data follow both Langmuir and Freundlish isotherms. The adsorption capacity, Qmax, were 82, 86.2, and 81.3 mg/g, for Acid Red 1, Direct Blue 75, and Acid Green 16, respectively. Cationized sawdust exhibited a much better adsorption capacity towards anionic dyes than native sawdust.