Solute partitioning in polymer–salt ATPS: The Collander equation

The partition coefficients for several solutes (five nitrophenylated-monosaccharides and four proteins) were experimentally determined, at 23 °C, in three different tie-lines of two polymer–salt aqueous two-phase systems (ATPS): UCON-K₂HPO₄ and UCON-NaH₂PO₄. These partition coefficients together with others obtained from the literature for five dinitrophenylated-amino acids were used to investigate the suitability of the Collander equation to correlate partition coefficients in polymer–salt ATPS. This equation was first proposed to describe the linear correlation between partition coefficients of solutes in different water–organic solvent systems. More recently, it was proved that partition coefficients for several biomolecules in polymer–polymer ATPS can also be correlated with this equation. In this work, several correlations were tested: partition coefficients obtained for different tie-lines within the same system and also partition coefficients obtained from different systems. In both cases, a linear relation was observed, despite a less satisfactory correlation was found when different ATPS were compared. Overall, it was demonstrated that the Collander equation can be used to satisfactorily correlate solute partitioning in the studied polymer–salt ATPS.     

Glass capillary column chromatography of mixed derivatives of primary prostaglandins, 6-keto prostaglandin F1α and thromboxane B2

This work describes the use of glass capillary columns (GCC) in the rapid concurrent analysis of primary prostaglandins (PGs) (e. g. PGE₂, PGE₂, PGF_2α) and other functionally significant metabolites of arachidonic acid (AA) such as TXB₂ and 6-keto PGF_1α. The use of a new multistep mixed derivatization approach that generates the methyl esters of n-butylboronate, pentafluorobenzyloxime, trimethylsilyl ether derivatives of these compounds remarkably simplifies the GC profiling of the three main pathways of AA metabolism (PGs, thromboxane, and prostacyclin). Furthermore, isomeric species giving very similar or identical mass spectral patterns can be easily identified by their relative retention times on high efficiency capillary columns.     

15‐Hydroperoxy‐PGE2: Intermediate in Mammalian and Algal Prostaglandin Biosynthesis

Arachidonic‐acid‐derived prostaglandins (PGs), specifically PGE₂, play a central role in inflammation and numerous immunological reactions. The enzymes of PGE₂ biosynthesis are important pharmacological targets for anti‐inflammatory drugs. Besides mammals, certain edible marine algae possess a comprehensive repertoire of bioactive arachidonic‐acid‐derived oxylipins including PGs that may account for food poisoning. Described here is the analysis of PGE₂ biosynthesis in the red macroalga Gracilaria vermiculophylla that led to the identification of 15‐hydroperoxy‐PGE₂, a novel precursor of PGE₂ and 15‐keto‐PGE₂. Interestingly, this novel precursor is also produced in human macrophages where it represents a key metabolite in an alternative biosynthetic PGE₂ pathway in addition to the well‐established arachidonic acid‐PGG₂‐PGH₂‐PGE₂ route. This alternative pathway of mammalian PGE₂ biosynthesis may open novel opportunities to intervene with inflammation‐related diseases.     

Carrier‐Mediated Transport of Hg(II) through Bulk and Supported Liquid Membranes

The transport of Hg (II) ions from an aqueous solution into an aqueous receiving solution through bulk and supported liquid membranes containing a calix[4]arene derivative 1 as a carrier was examined. The kinetic parameters of bulk liquid membrane studies were analyzed assuming two consecutive, irreversible first‐order reactions. The influence of temperature, stirring rate, carrier concentration and solvent on the kinetic parameters (k₁, k₂, R_m ^max, t_max, J_d ^max, J_a ^max) has also been investigated. The membrane entrance rate, k₁, and the membrane exit rate, k₂, increased with increasing temperature and stirring rate. The activation energy values are calculated as 4.87 and 48.63 kj mol^?1 for extraction and reextraction, respectively. The values of calculated activation energy indicate that the process is diffusionally controlled by species. Also, the transport behavior of Hg²⁺ from aqueous solution through a flat‐sheet supported liquid membrane has been investigated by the use of calix[4]arene derivative 1 as carrier and Celgard 2500 as the solid support. A Danesi mass transfer model was used to calculate the permeability coefficients for each parameter studied. The highest values of permeability were obtained with 2‐nitrophenyloctyl‐ether (NPOE) solvent and the influence was found to be in the order of NPOE>chloroform>xylene.     

The influence of total monomers concentration and polymerization solvent on the “reactivity” of ω-(p-vinylbenzyl ether) macromonomers of poly(2,6-dimethyl-1,4-phenylene oxide)

The influence of the total monomers concentration and of the copolymerization solvent on the reactivity ratio, r₁, of methyl methacrylate (MMA) (M₁) ω-(p-vinylbenzyl ether) macromonomer of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO–VBE) (M₂) monomer pair was investigated. For two different molecular weights of PPO-VBE macromonomers: M _n = 15,200 and M _n = 5,100, the determined reactivity ratio, r₁, decreases with the increase in macromonomer concentration. Therefore the reactivity of the macromonomer, 1/r₁, follows the opposite trend. The influence of monomers concentration on r₁ is higher for higher molecular weight macromonomers. The nature of polymerization solvent also affects the value of reactivity ratio, r₁. Micelle formation was demonstrated by ¹H-NMR spectroscopy performed on the resulting graft copolymers in different solvent mixtures. An attempt to explain the observed concentration and solvent effects based on the partition of comonomer concentrations between the bulk of solvent and around the growing chain is presented. Based on this explanation, the determined r₁ represents a product of the partition coefficient, k, and the true reactivity ratio, r₁⁰.     

Specific and non-specific interactions of hydropseudohalic acids with water and organic solvents

Partition coefficients P of the HNCS, HNCO and HN₃ hydropseudohalic acids between a number of organic solvents and water were determined. It has been found that log P increases with pKa of the acid and with the basicity of the solvent, but the effect of pKa on P is the smaller the more basic is the solvent. The relationships have been explained in terms of hydrogen bond formation between undissociated acid and solvent molecules. H-bonding between the pseudohalic acids and organic solvents has been confirmed by IR spectra on the example of HN₃ in benzene. Association constants for H-bonding between the three acids and water, benzene, dibutyl ether and tri-n-butyl phosphate were determined from partition data. It has been found that H-bonding increases with the strength of the acid, whereas the contribution to partition from non-specific interactions with water and organic solvents depends on the molecular surface area of the acid molecule.     

Correlation of the Solubilizing Abilities of 1-Butyl-1-methylpiperidinium Bis(trifluoromethylsulfonyl)imide and 1-Butyl-1-methylpyrrolidinium Tetracyanoborate

Chromatographic retention data were measured for a wide range of organic solutes on 1-butyl-1-methylpyrrolidinium tetracyanoborate ([BMPyrr]⁺[B(CN)₄]^?) and 1-butyl-1-methyl-piperidinium bis(trifluoromethylsulfonyl)imide ([BMPip]⁺[Tf₂N]^?) stationary phases at 323 K and 353 K. The measured retention factors were combined with published infinite dilution activity coefficient and gas-to-water partition coefficient data to yield gas-to-anhydrous ionic liquid (IL) and water-to-anhydrous IL partition coefficients. Both sets of partition coefficients were analyzed using the Abraham model. The derived Abraham model correlations describe the observed gas-to-IL (log₁₀ K) and water-to-IL (log₁₀ P) partition coefficient data to within average standard deviations of about 0.10 and 0.15 log₁₀ units, respectively.     

Solvatochromic relationship: Prediction of distribution of ionic solutes in aqueous two-phase systems

Partition ratios of several ionic compounds in 20 different polymer/polymer aqueous two-phase systems (ATPS) containing 0.15 M NaCl in 0.01 M phosphate buffer, pH 7.4, were determined. The differences between the electrostatic properties of the phases in all the ATPS were estimated from partitioning of the homologous series of dinitrophenylated-amino acids. Also the solvatochromic solvent parameters characterizing the solvent dipolarity/polarizability (π*), solvent hydrogen-bond donor acidity (α), and solvent hydrogen-bond acceptor basicity (β) of aqueous media were measured in the coexisting phases of the ATPS. The solute-specific coefficients for the compounds examined were determined by the multiple linear regression analysis using the modified linear solvation energy relationship equation. The minimal number of ATPS necessary for determination of the coefficients was established and 10 ATPS were selected as a reference ATPS set. The solute-specific coefficients values obtained with this reference set of ATPS were used to predict the partition ratios for the compounds in 10 ATPS not included in the reference set. The predicted partition ratios values were compared to those determined experimentally and found to be in good agreement. It is concluded that the presented model of solute–solvent interactions as the driving force for solute partitioning in polymer/polymer ATPS describes experimental observations with 90–95% accuracy.     

Total synthesis of anhydro levug̀landin D2

Total synthesis of anhydro levuglandin D₂ [9-acetyl-8-formyl-5(Z),9(E),11(E)-hepta-decatrienoic acid] confirms the structure assigned to this 9,10-seco prostanoic acid product from solvent induced rearrangement of the prostaglandin endoperoxide PGH₂ in aqueous solution.     

Linear free energy relationship correlations for the solubilising characterisation of room temperature ionic liquids containing 1-hexyloxymethyl-3-methylimidazolium and 1,3-dihexyloxymethylimidazolium cations

Gas-to-room temperature ionic liquid (RTIL) partition coefficients have been compiled from the published literature for solutes dissolved in 1-hexyloxymethyl-3-methylimidazolium bis(trifluoromethylsulphonyl)imide, {[HxomMIm]⁺[(Tf)₂N]^?}, and in 1,3-dihexyloxymethylimidazolium bis(trifluoromethylsulphonyl)imide, {[(Hxom)₂Im]⁺[(Tf)₂N]^?}. These partition coefficients are converted into water-to-RTIL partition coefficients using the corresponding gas-to-water partition coefficients. Both sets of partition coefficients are analysed using the Abraham model with cation-specific and anion-specific equation coefficients. The equation coefficients are reported for the 1-hexyloxymethyl-3-methylimidazolium and 1,3-dihexyloxymethylimidazolium cations. The calculated cation coefficients can be combined with our previously determined nine sets of anion-specific equation coefficients to yield expressions capable of predicting the partition coefficients of solutes in 18 different RTILs.     

An unprecedented transformation mode in aluminium oxazoline-amido-phenolate complexes

This paper describes the effect of solvent-induced synthetic routes of aluminium pendant oxazoline-amido-phenolate complexes. Treatment of ligand precursor L with AlMe₃ in a 1:1 ratio in diethyl ether yielded the four-coordinated complex (LAlMe)₂. Reaction of ligand precursor L with AlMe₃ in a 1:2 ratio in hexane generated the four-coordinated complex L(AlMe₂)₂. A novel transformation mode occurred from L(AlMe₂)₂ to (LAlMe)₂ when using diethyl ether or tetrahydrofuran as solvent. A density functional theory computational study also supports a plausible mechanism. All results were supported by spectroscopic data and in agreement with single-crystal X-ray diffraction structural analysis.     

Abraham Model Correlations for Transfer of Neutral Molecules to Tetrahydrofuran and to 1,4-Dioxane,and for Transfer of Ions to Tetrahydrofuran

Data have been compiled from the published literature for the partition coefficients of solutes and vapors into anhydrous tetrahydrofuran and 1,4-dioxane. The logarithms of the water-to-ether partition coefficients, log₁₀ P, and gas-to-ether partition coefficients, log₁₀ K, were correlated with the Abraham solvation parameter model. The derived correlations described the observed log₁₀ P and log₁₀ K values for both ether solvents to within average standard deviations of 0.16 log₁₀ units or less. The log₁₀ P correlation for tetrahydrofuran was extended to include the partition of ions by inclusion of a cation-solvent and an anion-solvent term.     

A simple method to optimize the HSCCC two-phase solvent system by predicting the partition coefficient for target compound

A simple method was developed to optimize the solvent ratio of the two-phase solvent system used in the high-speed counter-current chromatography (HSCCC) separation. Some mathematic equations, such as the exponential and the power equations, were established to describe the relationship between the solvent ratio and the partition coefficient. Using this new method, the two-phase solvent system was easily optimized to obtain a proper partition coefficient for the CCC separation of the target compound. Furthermore, this method was satisfactorily applied in determining the two-phase solvent system for the HSCCC preparation of pseudolaric acid B from the Chinese herb Pseudolarix kaempferi Gordon (Pinaceae). The two-phase solvent system of n-hexane/EtOAc/MeOH/H(2)O (5:5:5:5 by volume) was used with a good partition coefficient K = 1.08. As a result, 232.05 mg of pseudolaric acid B was yielded from 0.5 g of the crude extract with a purity of 97.26% by HPLC analysis.     

Spectroscopic analysis of naphtholazobenzimidazole in organised solution

Micelle–water partition coefficient (K_x ) of naphtholazobenzimidazole dye (NAB) in aqueous solutions of cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulphate (SDS) has been determined spectrophotometerically. Changes in absorption patterns of dye caused by surfactants and solvents were quantified in terms of dye–surfactant ratio (n _D/n _S) and solvent water partition coefficients (P), respectively. Multiple residence sites have been suggested for dye molecules within micelles, based on shifts in azo-hydrazone tautomeric equilibrium. Micelle–water partition coefficients were used to evaluate the influence of dye on critical micelle concentration of CTAB and SDS. At same micelle concentration, M, the relative solubility of NAB was greater in cationic surfactant CTAB than in anionic surfactant SDS.     

Separation of Delphinidin-3-O-sambubioside, Cyanidin-3-O-sambubioside and p-Coumaric Acid from Cranberry by CCC Followed by prep-HPLC Using Robotic CCC Solvent System Selection

High-performance counter-current chromatography has been used for the separation of delphinidin-3-O-sambubioside, cyanidin-3-O-sambubioside and p-coumaric acid from crude extract of cranberry. The separation was performed with a two-phase solvent system composed of butanol/0.05% aqueous trifluoroacetic acid/methanol at a volume ratio of 4:5:1. The two-phase solvent system was selected following the determination of partition coefficients (K) in a range of solvent systems using a robotic solvent system selection method. Analytical scale CCC confirmed that this phase system separated the components from a crude cranberry extract (40 mg scale) with acceptable purities. Preparative CCC of 400 mg of crude yielded 4.2 mg of p-coumaric acid at a purity of over 98%, 3.6 mg of delphinidin-3-O-sambubioside at a purity of over 97% and 4.5 mg of cyanidin-3-O-sambubioside at a purity of 73%, which was further purified by preparative high-performance liquid chromatography to yield 3 mg cyanidin-3-O-sambubioside at 95% purity. The identification of delphinidin-3-O-sambubioside, cyanidin-3-O-sambubioside and p-coumaric acid was performed by ESI-MS, 1H-NMR and 13C-NMR spectra.     

Phase equilibrium and macrolide antibiotics partitioning in real water samples using a two-phase system composed of the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate and an aqueous solution of an inorganic salt

An ionic liquid-salt aqueous two-phase system (ILATPS) based on the hydrophilic ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF₄) and inorganic salt was developed for direct separation and analysis of macrolide antibiotics coupled with molecular fluorescence spectrophotometry. Liquid–liquid equilibria of [Bmim]BF₄-salt aqueous two-phase systems were studied for different salts and temperatures. It was found that the salting-out ability of different salts may be related to the Gibbs energy of hydration of the ions, and the two-phase area was expanded with a decrease in temperature. The partition coefficients as well as extraction efficiencies of azithromycin and mydecamycin in [Bmim]BF₄-salt aqueous two-phase system were influenced by the types of salts, concentration of salt, and the extracting temperature. Under the optimum conditions, the average partition coefficient of azithromycin in [Bmim]BF₄-Na₂CO₃ ILATPS was 162, and that of mydecamycin in [Bmim]BF₄- NaH₂PO₄ ILATPS was 90.9. This method has been satisfactorily applied to the determination of azithromycin and mydecamycin in real water samples with detection limits of 0.059 µg mL^?1 and 0.019 µg mL^?1. This extraction method is a simple, non-toxic and effective sample pretreatment technique with promise also for the separation of other small biomolecules.