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Moment analysis method using partial filling CE was developed for the kinetic study on solute permeation at the interface of spherical molecular aggregates. Moment equations for partial filling CE were developed by classifying CE systems into five categories according to the migration velocities of solute and molecular aggregate. The method was applied to the study on the dissolution of electrically neutral solutes into SDS micelles. Elution peaks were measured by partial filling CE while changing the concentration of SDS and the filling ratio of SDS micellar zone to the capillary (ϕM ). Partition equilibrium constants (Kp ) and rate constants of interfacial solute permeation of SDS micelles (kin and kout ) were determined from the first absolute and second central moments of the elution peaks by using the moment equations. Their values were comparable irrespective of ϕM and were almost the same as those previously measured by complete filling CE. The positive correlation of Kp with the hydrophobicity of the solutes was explained in terms of the change in kin and kout . It was demonstrated that the moment analysis method using partial filling CE is effective for studying solute permeation kinetics at the interface of spherical molecular aggregates.

This report presents a study on the determination of total polyphenols together with metals in several samples of olive oil produced in Spain. The results provided by applying a conventional extraction method were compared against those encountered by means of the so-called Dispersive Liquid-Liquid Aerosol Phase Extraction method. The novel method is based on the dispersion of the extracting solution in the sample. To accomplish this, an aerosol is pneumatically generated and directed against the surface of the oil sample. The aerosol was generated in order to increase as much as possible the surface area of the interface between the two involved non-miscible phases. As a result, the partition equilibrium was quickly achieved. The critical variables dictating the characteristics of the obtained aerosols as well as those influencing the partition equilibrium state were studied. With the aerosol phase extraction method, the values corresponding to the total polyphenols and metals in real samples were not statistically different as compared to those obtained by the conventional liquid – liquid extraction method. The new method provided shorter extraction times and lower mass of consumed reagents than the conventional one, thus giving rise to a more environmentally friendly method. For polyphenols, calculated limits of detection and quantification were 0.48 and 1.5 mg of gallic acid kg−1, respectively. The absorbance linearity, in turn, was kept from 0 to 50 mg kg−1 (R2 = 0.998). In the case of metal and metalloid quantification, the limits of detection found with a sample digestion method ranged from 1.3 (Cu) to 291 (Na) ng mL−1. Meanwhile, because of the lower dilution factor, this parameter was one order of magnitude lower when these elements were extracted according to the new method. The new extraction method was applied to the analysis of 42 extra virgin olive oils both bottled and directly collected from the oil press, containing single cultivars or blends and produced from different areas. Fresh oils were analyzed and a preliminary study on the oil thermal degradation was also done. Dispersing the extracting solution as an aerosol into the sample can be considered a versatile method able to provide extensive oil chemical information in a rapid way what is especially important in the case of polyphenols. The authors wish to thank the Spanish Ministry of Science, Innovation and Universities for the financial support (Project Ref. PGC2018-100711-B-I00).

In this study, we report the new application of single nanodroplet electrochemistry to in situ monitor the interfacial transfer kinetics of electroactive species across liquid/liquid interface. Interfacial kinetic information is crucial in drug delivery and membrane transport. However, interfacial information has been mainly studied thermodynamically, such as partition coefficient, which could not manifest a speed of transfer. Herein, we measure the phase-transfer kinetic constant via the steady-state electrochemistry of an extracted redox species in a single nanodroplet. The redox species were transferred from the continuous oil phase to the water nanodroplet by partition equilibrium. The transferred redox species are selectively electrolyzed within the droplet when the droplet contacts with an ultramicroelectrode, while the electrochemical reaction of the redox species outside the droplet (i.e., organic solvent) is effectively suppressed by adjusting the electrolyte composition. The redox species in the water droplets can quickly attain a steady state during electrolysis owing to an extensive mass transfer by radial diffusion, and the steady-state current can be analyzed to obtain kinetic information with help from the finite-element method. Finally, a quick calculation method is suggested to estimate the kinetic constant of phase transfer without simulation.

Chapters 3 and 5 on the measurement of binding constants by frontal affinity chromatography emphasize that elution volumes are merely quantitative indices of the equilibrium position of solute partition between soluble and adsorbed (matrix-bound) states. Quantitative affinity chromatography was certainly developed initially as a column procedure (Andrews et al., 1973; Dunn and Chaiken, 1974), but was soon modified to allow direct delineation of the partition equilibrium position by measuring the solute concentration in the liquid phase of a slurry of affinity matrix containing a known total concentration of partitioning solute (Nichol et al., 1974). Indeed, in the sense that the basic quantitative expressions are first specified in terms of solute concentrations, the column technique can be regarded as an adaptation of the partition equilibrium method.

When studying the release of poorly water-soluble drugs from colloidal drug delivery systems designed for intravenous administration, the release media should preferentially contain lipophilic components that represent the physiological acceptors present in vivo. In this study, the effect of different acceptor structures was investigated by comparing the transfer of fenofibrate, retinyl acetate, and orlistat from trimyristin nanoemulsion droplets into lipid-containing hydrogel particles, as well as to bovine serum albumin (BSA). A nanodispersion based on trimyristin and cholesteryl nonanoate was incorporated into the hydrogel particles (mean diameter ~40 µm) in order to mimic the composition of lipoproteins. The course of transfer observed utilizing the lipid-containing hydrogel particles as an acceptor was in relation to the lipophilicity of the drugs: the higher the logP value, the slower the transfer. There was no detectable amount of the drugs transferred to BSA in liquid solution, demonstrating clearly that albumin alone does not contribute substantially as acceptor for the lipophilic drugs under investigation in this study. In contrast, cholesteryl nonanoate contributes to a much greater extent. However, in all cases, the partition equilibrium of the drugs under investigation was in favor of the trimyristin emulsion droplets.

Moment equations were developed on the basis of the Einstein equation for diffusion and the random walk model to analytically determine the rate constant for the interfacial solute permeation from a bulk solvent into molecular aggregates (kin ) and the inverse rate constant from the molecular aggregates to the bulk solvent (kout ). The moment equations were in good agreement with those derived in a different manner. To demonstrate their effectiveness in one concrete example, the moment equations were used to analytically determine the values of kin and kout of three electrically neutral solutes, i.e. resorcinol, phenol, and nitrobenzene, from the first absolute (μ1A ) and second central (μ2C ) moments of their elution peaks, as measured by electrokinetic chromatography (EKC), in which the sodium dodecyl sulfate (SDS) micelles were used as a pseudostationary phase. The values of kin and kout should be determined with no chemical modifications and no physical action with the molecular aggregates because they are dynamic systems formed through weak interactions between the components. The moment analysis of the elution peak profiles measured by EKC is effective to unambiguously determine kin , kout , and the partition equilibrium constant (kin /kout ) under appropriate experimental conditions.

The oil-water partition coefficient of organic compounds is an essential parameter for the determination of their behaviors in environments, food, drug delivery, and biomedical systems, just to name a few. In this work, we establish a highly efficient approach to quantify the partition/distribution coefficient using surface femtoliter droplets. In our approach, droplets of 1-octanol were produced on the surface of a solid substrate in contact with the flow of an aqueous solution of the analyte. The analyte was rapidly enriched in the droplets from the flow and reached the partition equilibrium in a few seconds. The entire procedure was automated by continuous solvent exchange, and the analyte partition in the droplets was quantified from the in situ UV-vis spectrum collected by a microspectrophotometer. Our approach was validated for several substances with the octanol-water partition/distribution coefficient ranging from -1.5 to 4, where our results were in good agreement with the values reported in the literature. This method took ∼3 min to detect one analyte with the volume of the organic solvent at ∼50 μL. Thus, our surface droplet platform can greatly minimize the consumption of both solvent and analytes and can shorten the time for the determination of the partition of new compounds, which overcomes the drawbacks of the traditional shake-flask method and presents excellent reproducibility, high accuracy, cost-effectiveness, and labor-saving operation. The highly efficient micro/nanoextraction, partition, and real-time detection enabled by the surface droplets has the potential for many other high-throughput applications.

Oyun kuramında, çözümlemeler için denge konseptleri büyük önem taşımaktadır. Oyun kuramının bir dalı olan koalisyonel oyun kuramı oyuncuların aralarında koalisyonlar kurabildiği varsayımı altında tanımlanan denge konseptlerini kullanır. Stratejik formda bir oyunda, kurulu olan hiçbir koalisyonun stratejilerini ortaklaşa değiştirerek "refahını" artıramadığı strateji profillerine (koalisyonel) denge denir. Daha zayıf veya güçlü denge konseptleri koalisyonların formasyonu üzerine yapılan çeşitli sınırlamalarla tanımlanabilir. Örneğin, bir Nash dengesinde, sadece tek bir oyuncudan oluşan koalisyonların kurulduğu varsayılmaktadır. Diğer zıt duruma karşılık gelen güçlü Nash dengesinde ise her koalisyonun (yani oyuncuların boş olmayan her alt kümesinin) kurulduğu kabul edilmektedir. Ancak, her koalisyonun kurulduğu varsayımı çalışmaya değer çoğu oyun için fazla zorlayıcıdır ve dolayısıyla çoğu oyunda güçlü Nash dengesi yoktur. Öte yandan, bir partisyon dengesinde, koalisyon formasyonu oyuncuların partisyonları ile sınırlanmaktadır. Bunun güçlü Nash dengesine göre çok daha az zorlayıcı olduğuna dikkat ediniz (zira bir partisyon dengesinde kurulu koalisyon sayısı Θ(n) iken güçlü Nash dengesinde 2^n-1'dir). Örneğin, bir partisyon dengesi kaynak seçme oyunlarında her zaman varken, bir güçlü Nash dengesi bu oyunların çok basit durumlarında bile yoktur. Koalisyon formasyonu üzerine daha sofistike sınırlamalar iletişime, kordinasyona ve kurumlaşmaya bağlı kısıtlar ile motive edilebilir. Bu tezde, genelgeçer sosyal yapılaşmalardan ilhamla koalisyon formasyonu üzerine çeşitli sınırlamalar ve bu esasla tanımlanmış çeşitli denge konseptleri tanıtıyoruz. Bu denge konseptlerini kaynak seçme oyunlarında çalışıyoruz ve bu oyunların hem genelinde hem de önemli özel durumlarında varlık garantisinin olup olmadığını her denge konsepti için eksiksiz bir şekilde gösteriyoruz. Ayrıca varlık garantisi olan durumlarda dengeyi bulmak için verimli algoritmalar sunuyoruz., In game theory, the centerpiece of analysis is the notion of equilibrium. A branch of game theory (called coalitional game theory) uses equilibrium notions that are defined under the assumption that agents can form coalitions between themselves. In a strategic form game, a strategy profile is a (coalitional) equilibrium if no viable coalition of agents benefits from jointly changing their strategies. Weaker or stronger equilibrium notions can be defined by considering various restrictions on formation of coalitions. In a Nash equilibrium, for instance, the assumption is that viable coalitions are simply singletons. In a strong Nash equilibrium, which lies at the other extreme, every possible coalition (i.e., every non-empty subset of agents) is viable. However, deeming every coalition viable is too demanding for most games that are worth to study; and hence, a strong Nash equilibrium rarely exists in those games. On the other hand, in a partition equilibrium, viable coaliations are restricted to partitions of agents, which is much less demanding then strong Nash equilibrium (since notice that the number of viable coalitions is Θ(n) in the case of a partition equilibrium, and it is 2^n-1 in the case of a strong Nash equilibrium). For example, a partition equilibrium always exists in resource selection games, whereas a strong Nash equilibrium does not exist even in most simple instances of these games. More sophisticated restrictions on coalition formation can be justified by communicational, coordinational or institutional constraints. In this thesis, inspired by social structures in various real-life scenarios, we introduce certain restrictions on coalition formation, and on their basis, we introduce various equilibrium notions. We study our equilibrium notions also in resource selection games, and we present a complete set of existence and nonexistence results for general reseource selection games and their important special cases. We also provide efficient algorithms to compute an equilibrium for the cases where one exists.

Moment equations were developed for quantitatively studying the separation characteristics of micellar electrokinetic chromatography (MEKC). They explain how the first absolute and second central moments of elution peaks are correlated with some fundamental parameters of the partition equilibrium and mass transfer kinetics in MEKC systems. In order to discuss the influence of the mass transfer kinetics on peak broadening, the moment equations were used to analyze the separation behavior in MEKC systems. Separation conditions were chosen on the basis of practical MEKC experiments previously conducted. It was quantitatively clarified that both the solute permeation at the interfacial boundary of surfactant micelles and axial diffusion of solute molecules in a capillary had a predominant contribution to the spreading of the elution peaks in MEKC systems. This is a preliminary study for the analytical determination of rate constants concerning solute permeation at the interface of surfactant micelles from elution peak profiles measured by MEKC. In addition, it was also indicated that the experimental conditions of MEKC systems could be controlled so that the interfacial solute permeation would have a predominant role for the band broadening. For example, the contribution of the interfacial permeation was about 33 times larger than that of the axial diffusion of solute molecules under the MEKC conditions in a previous study. This means that the rate constants could appropriately be determined for the interfacial solute permeation.

Alkaline transesterifications (methanolysis, ethanolysis) of vegetable oils (soybean, sunflower) were conducted under conditions selected by an experimental design, producing biodiesels (fatty methyl esters 97.5 wt%; fatty ethyl esters 96.7 wt%) with high quality characteristics identified by reduced sodium content (0.11 mg kg−1), low levels of glycerol concentration (0.01 wt%), acidity (0.31 mg NaOH g−1) and viscosity (4.81 mm2 s−1). Evidence indicated that in a first stage, the triglyceride slowly dispersed in the alcohol phase, and then promoted the rapid production of esters: the biodiesel yield increased from 52.0 to 97.5% in methanolysis and from 44. 0 to 96.7% in ethanolysis. A mathematical model was formulated, including biphasic effects between the liquid phases, with respect to partition equilibrium, mass transfer and chemical reaction. The kinetics of the biphasic transesterification processes were characterized quantitatively through the order of magnitude of the mass transfer coefficient of the triglycerides (K TG = 5.82 × 10−4 s−1, at 303 K − 5.86 × 10−2 s−1, at 353 K), and of the specific reaction rate (k = 3.48 × 10−3 s−1, at 303 K − 5.78 × 10−3 s−1 at 353 K). Resistances related to these effects indicated that they compete during the evolution of the processes.

Plants growing in the soils at military ranges and surrounding locations are exposed, and potentially able to uptake, munitions compounds (MCs). The extent to which a compound is transferred from the environment into organisms such as plants, referred to as bioconcentration, is conventionally measured through uptake experiments with field/synthetic soils. Multiple components/phases that vary among different soil types and affect the bioavailability of the MC, however, hinder the ability to separate the effects of soil characteristics from the MC chemical properties on the resulting plant bioconcentration. To circumvent the problem, this work presents a protocol to measure steady state bioconcentration factors (BCFs) for MCs in barley (Hordeum vulgare L.) using inert laboratory sand rather than field/synthetic soils. Three MCs: 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (2,4-DNT), and 2,4-dinitroanisole (2,4-DNAN), and two munition–like compounds (MLCs): 4-nitroanisole (4-NAN) and 2-methoxy-5-nitropyridine (2-M-5-NPYNE) were evaluated. Approximately constant plant biomass and exposure concentrations were achieved within a one–month period that produced steady state log BCF values: 0.62 ± 0.02, 0.70 ± 0.03, 1.30 ± 0.06, 0.52 ± 0.03, and 0.40 ± 0.05 L kgplant dwt−1 for TNT, 2,4-DNT, 2,4-DNAN, 4-NAN, and 2-M-5-NPYNE, respectively. Furthermore, results suggest that the upper–bounds of the BCFs can be estimated within an order of magnitude by measuring the partitioning of the compounds between barley biomass and water. This highlights the importance of partition equilibrium as a mechanism for the uptake of MCs and MLCs by barley from interstitial water. The results from this work provide chemically meaningful data for prediction models able to estimate the bioconcentration of these contaminants in plants.

Species-specific acid-base and partition equilibrium constants were experimentally determined for the therapeutically important semisynthetic opioid receptor agonist hydromorphone, dihydromorphine, and mixed agonist-antagonist nalorphine and nalbuphine. The acid-base microequilibria were characterized by combining pH-potentiometry and deductive methods using synthesized auxiliary compounds. Independent of the pH, there are approximately 4.8 times as many zwitterionic microspecies than non-charged ones in nalbuphine solutions, while for nalorphine it is the non-charged form that predominates by the same ratio. The non-charged microspecies is the dominant one also in the case of hydromorphone, although its concentration exceeds only 1.3 times that of its zwitterionic protonation isomer. The pH-independent partition coefficients of the individual microspecies were determined by a combination of experimentally measured, pH-dependent, conditional distribution constants and a custom-tailored evaluation method, using highly similar auxiliary compounds. The pH-independent contribution of the zwitterionic microspecies to the distribution constant is 1380, 1070, 3160 and 72,440 times smaller than that of the inherently more lipophilic non-charged one for hydromorphone, dihydromorphine, nalbuphine and nalorphine, respectively.

This chapter provides an updated overview of recent advances in ­emulsion-based delivery systems for food flavors. Volatile flavors are perceived when they are in contact with receptors in the nose either orthonasally by directly sniffing foods or retronasally via the delivery of volatiles during mastication and/or swallowing. Flavor release is mainly controlled by two factors, the volatility of flavor compounds and the resistance to mass transfer from the emulsion to the air phase. Static headspace analysis is widely applied to evaluate flavor release, and it is based on the theory of partition equilibrium. The eating processes usually finish in a short time, and flavor release hardly reaches equilibrium. Therefore, the perception of volatile flavor mainly depends on the initial dynamic release. Food in the mouth undergoes mastication, salivation, bolus formation, and finally swallowing. Flavors in different oils generally have different release behaviors, due to their affinity for different oils.

H2O2 permeation through a cell membrane significantly affects living organisms, and permeation is controlled by the physico-chemical nature of lipids and other membrane components. We investigated the molecular relationship between H2O2 permeation and lipid membrane structure using three oxidized lipids. POVPC and PazePC act as intra- and inter-molecular permeation promoters, respectively; however, their underlying mechanisms were different. The former changed the partition equilibrium, while the latter changed the permeation pathway. PoxnoPC inhibited permeation under our experimental conditions via an intra-molecular configuration change. Thus, both intra- and inter-molecular processes were found to control the role of oxidized lipids as inhibitors and promoters towards H2O2 permeation with different mechanisms depending on structure and composition. Here, we identified two independent H2O2 permeation routes: (i) permeation through lipid membrane with increased partition coefficient by intra-molecular configurational change and (ii) diffusion through pores (water channels) formed by inter-molecular configurational change of oxidized lipids. We provide new insight into how biological cells control permeation of molecules through intra- and inter-molecular configurational changes in the lipid membrane. Thus, by employing a rational design for both oxidized lipids and other components, the permeation behaviour of H2O2 and other ions and molecules through a lipid membrane could be controlled.

A Micellar Chromatographic method to determine rivaroxaban in plasma and urine has been developed. The samples were dissolved in the mobile phase (SDS 0.05 M – 1-propanol 12.5%, phosphate buffered at pH 7) and 20 μL directly injected, avoiding the extraction and purification steps. Using a C18 column and running under isocratic mode at 1 mL/min, analyte was eluted without interference from the matrix in

We investigated a combination of approaches to extend the attainment of partition equilibria between silicone passive samplers (samplers) and surface or treated waste water towards more hydrophobic organic compounds (HOC). The aim was to identify the HOC hydrophobicity range for which silicone sampler equilibration in water is feasible within a reasonable sampler deployment period. Equilibrium partitioning of HOC between sampler and water is desirable for a simpler application as a “chemometer”, aiming to compare chemical activity gradients across environmental media (e.g. water, sediment, biota). The tested approaches included a) long sampler exposure periods and high water flow to maximize mass transfer from water to sampler; b) the use of samplers with reduced sheet thicknesses; and c) pre-equilibration of samplers with local bottom sediment, followed by their exposure in surface water at the same sampling site. These approaches were tested at three sites including a fish pond with a low level of pollution, a river impacted by an urban agglomeration and an effluent of municipal wastewater treatment plant. Tested compounds included polychlorinated biphenyls (PCB), polycyclic aromatic hydrocarbons (PAH), DDT, its metabolites and their isomers, hexachlorobenzene (HCB) and polybrominated diphenyl ethers (PBDE). The study shows that samplers with a surface area of 400–800 cm2 consisting of thin (100–500 μm) silicone sheets exposed at sampling rates of 10–40 L d−1 for a time period of up to four months reach partition equilibrium with water for compounds with log Kow ≤ 5.5. Nevertheless, for compounds beyond this limit it is challenging, within a reasonable time period, to reach equilibrium between sampler and water in an open system where water boundary layer resistance controls the mass transfer. For more hydrophobic HOC (log Kow > 6), the kinetic method using performance reference compounds is recommended instead.

The paper presents new experimental data on the chemical equilibrium in the system n-propanol + acetic acid + n-propyl acetate + water at 293.15 and 353.15 K, and the data on liquid–liquid equilibrium at 353.15 K. Based on the experimental and literature data, the possibilities that chemical equilibrium exists in a homogeneous or heterogeneous region of compositions has been analyzed. The temperature shift of chemical and phase equilibria and the values of the thermodynamic constants of chemical equilibrium are discussed.

This study investigated the effect of pretreatment of ultrasonic irradiation on emulsion polymerization of styrene to propose a process intensification method which gives high conversion, high reaction rate, and high energy efficiency. The solution containing styrene monomer was irradiated by a horn mounted on the ultrasonic transducer with the diameter of 5 mm diameter and the frequency of 28 kHz before starting polymerization. The pretreatment of ultrasound irradiation as short as 1 min drastically improved monomer dispersion and increased reaction rate even under the agitation condition with low rotational speed of impeller. Furthermore, the ultrasonic pretreatment resulted in higher monomer concentration in polymer particles and produced larger polymer particles than conventional polymerization without ultrasonic pretreatment.

A generalized approach for the calculation of complex chemical and phase equilibria is presented that is based on the simulation of the dynamic evolution of a mixture from non-equilibrium initial composition towards the final equilibrium composition. The proposed method is able to solve pure chemical or phase equilibria as well as simultaneous chemical/phase equilibria. The advantage of our approach compared to conventional equilibrium calculations is the fact that the approach is physically motivated and can handle chemical and phase equilibria as well as simultaneous chemical and phase equilibria.

The UNIFAC model and its various modified models on behalf of the group contribution methods offer reliable knowledge of phase equilibrium data, which are making great contributions for separation processes. The application of the UNIFAC-ZM model for the silicone polymer system is not only restricted by the poor accuracy under a large temperature range, but also limited by the lack of SiO group related group interaction parameters. In this work, first, modification of the model was made with consideration of the temperature effect on group interactions. Then inverse gas chromatography (IGC), a simple method to determine the infinite dilution activity coefficient, was applied to determine the interaction parameters between the common groups CH3, OH, H2O, CH3CO and SiO contained in polydimethylsiloxane (PDMS) based on the equilibrium chromatography theory. The achieved model was further proved to agree with the experimental results well. The new model was also applied in the calculation of the partition equilibrium between acetone/butanol/ethanol water solutions of different concentrations and PDMS of different polymerization degrees and side chain length. All these results would not only help the improvement of UNIFAC model, but also instruct the separation processes of silicone polymer compounds.

A series of amphiphilic polymer mPEG-PUSS-mPEG were developed by a combination of ring opening polymerization (ROP) and polyaddition reaction and its self-assembled micelles were developed for hydrophobic anticancer drugs delivery. Polymeric critical micellar concentration (CMC) values in aqueous solution were about 2.8–5.5 mg/L. And the partition equilibrium constant (Kv) of pyrene in micellar solutions ranged from 1.52 × 105 to 2.20 × 105. The average sizes of the self-assembled blank and DOX-loaded micelles were 160–180 nm determined by dynamic light scattering (DLS). The morphology of the DOX-loaded micelles was spherical by transmission electron microscopy (TEM) and scanning electron microscopy (SEM).The in vitro drug release behaviors of DOX and PTX from mPEG-PUSS-mPEG micelles were investigated at different simulated conditions. We found that the PTX release was significantly accelerated by redox stimuli compared with DOX-loaded reduction-sensitive PU micelles. The change of the size of this system under different conditions was further evaluated by DLS. DOX-loaded mPEG-PUSS-mPEG micelles in 50% fetal bovine serum (FBS) were evaluated the hemocompatibility. In addition, the self-assembly process of polymers mPEG-PUSS-mPEG in aqueous solution for micellar formation was also investigated by means of dissipative particle dynamics (DPD) simulations.AndCCK-8 assays revealed that the mPEG-PUSS-mPEG materials had low toxicity, but the DOX-loaded micelles showed a high cytotoxicity against HepG2 tumor cells. All results demonstrate that mPEG-PUSS-mPEG self-assembled micelles are a very promising for hydrophobic anticancer drugs delivery.

By means of replica Ornstein-Zernike theory (supplemented in a few cases by Monte Carlo simulations) we examined the distribution of an annealed primitive model +1:-1 electrolyte in a mixture with uncharged hard spheres, or another model +1:-1 or +2:-1 electrolyte inside and outside the quenched vesicles, decorated by a model membrane, and across the membrane phase. We explored the influence of the size and charge of the annealed fluid on the partition equilibrium, as well as the effect of the vesicle size and membrane interaction parameters (repulsive barrier height, attractive depth, and membrane width). A hydrophobic cation, present in the mixture with NaCl, slightly enhanced the concentration of sodium ions inside the model vesicle, compared to pure NaCl solution. The replica theory was in good agreement with computer simulations and as such adequate for studying partitioning of small and hydrophobic ions or hydrophobic solutes across model membranes.

Nuclear magnetic resonance (NMR) spectroscopy in combination with chemometrics can be applied in the analysis of complex biological samples in many ways. For example, we can analyze lipids, elucidate their structures, determine their nutritional values, and determine their distribution in blood serum. As lipids are not soluble in water, they are transported in blood as lipid-rich self-assembled particles, divided into different density assemblies from high- to very-low-density lipoproteins (HDL to VLDL), or by combining with serum proteins, such as albumins (human serum albumins (HSA)). Therefore, serum lipids can be analyzed as they are using only a 1:1 (v/v) dilution with a buffer or deuterated water prior to analysis by applying 1H NMR or 1H NMR edited-by-diffusion techniques. Alternatively, lipids can be extracted from the serum using liquid partition equilibrium and then analyzed using liquid-state NMR techniques. Our chapter describes protocols that are used for extraction of blood serum lipids and their quantitative 1H NMR (1H qNMR) analysis in lipid extracts as well as 1H NMR edited by diffusion for direct blood serum lipid analysis.

A fluorescent pyrene probe method was applied to measure the critical micelle concentration (CMC) of oligocarbonate-fluorene end-functionalized poly(ethylene glycol) (F(m)E(445)F(m)) triblock copolymers in water. The CMC decreases with lower temperature and higher values of the hydrophobic block length, m. When analyzed by a closed-assembly micelle model, the estimated energetic parameters find a negative ΔH°(mic) and small positive ΔS°(mic) suggestive of enthalpy-driven micellization, which differs from entropy-driven oxyethylene/oxybutylene triblock copolymers and octaethylene glycol-n-alkyl ethers. The enthalpy-driven micellization of F(m)E(445)F(m) may result from the limited hydration of individual hydrophobic F blocks that leads to few hydrogen-bonded waters released during F block association. The π-π stacking oligocarbonate-fluorene system also observed enthalpy-entropy compensation when compared to a series of published data on diblock and triblock copolymer systems. An anomalously low partition equilibrium constant for m = 15.3 implies a tightly-packed core that excludes pyrene intercalation into the fluorene core. This is discussed along with the possible limited applicability to estimate the CMC and potential model drug molecule insertions into the intercalated micelle core.

The octanol/water partition and acid–base dissociation equilibria for a set of six fluoroquinolones have been studied by the shake-flask method at 25 °C and at 0.15 M NaCl ionic strength, determining the partition coefficient (logD) in the pH range 3 to 9. The substances studied are ciprofloxacin (CIP), danofloxacin (DAN), difloxacin (DIF), enrofloxacin (ENR), marbofloxacin (MAR), and sarafloxacin (SAR). After the partition equilibrium, the remaining fluoroquinolone concentration is determined in aqueous phase by liquid chromatography with fluorescence detection. The pKa values obtained are in accordance with the previously published data, ranging between 5.59 and 6.50 for pKa1 and between 7.99 and 8.96 for pKa2. The lipophilicity of the substances is low, with logKOW ranging between −1.09 to 0.68. Additionally, we have determined the octanol/water partition coefficient for the cationic species in all cases.

Two sediment passive samplers, polyethylene (PE) and polyoxymethylene (POM), were compared and mutually validated for measuring freely dissolved concentrations (Cfree) of polychlorinated biphenyls (PCBs) in sediment porewater. PE and POM strips in commonly used dimensions (30 and 76 μm in thickness, respectively) were exposed to sediment slurries for 28 d. The Cfree values calculated using literature polymer-water partition coefficients were consistently higher for PE than for POM by a factor of 2 on average. Time series experiments over 96 d show that 28 d are sufficient for attaining partition equilibrium of PCBs for PE, whereas even 96 d may not be enough for POM. To gain additional insight, POM and PE strips were co-exposed to bovine serum albumin suspension spiked with PCBs. The POM/PE concentration ratios increased over 56 d, and the ratios at 28 d were in agreement with the POM-to-PE ratios of PCB concentrations from the 28-d sediment slurry experiments. This agreement suggests that the use of apparent POM-water partition coefficients (i.e., non-equilibrium concentration ratios) suitable for a 28-d exposure to sediment slurries may correct the non-attainment of equilibrium and could provide more accurate Cfree values.

Lipid nanoparticles are an interesting parenteral delivery system for poorly water-soluble drugs. In order to approach physiological conditions when conducting release studies from such systems the release media should preferentially contain lipophilic acceptor compartments such as lipoproteins or other colloidal lipophilic components. In practice, drug release studies under such close to physiological conditions may be complicated by the small size of lipid nanoparticles, which is in the same range as that of the potential acceptor particles. This study describes a novel differential scanning calorimetry (DSC) method for drug release measurements which works without separation of donor and acceptor particles. The technique is based on measuring the crystallization temperature of trimyristin nanoparticles by DSC. The crystallization temperature of the nanoparticles decreases proportionally with the amount of active ingredient incorporated and thus increases as a result of drug release. Liquid trimyristin nanoparticles loaded with fenofibrate, orlistat, tocopherol acetate and ubidecarenone were studied in three different release media with increasing complexity and comparability to physiological conditions: a rapeseed oil nanoemulsion, porcine serum and porcine blood. Using the new method, a correlation between release behavior and drug lipophilicity was observed: the higher the logP value of the drug, the slower the release. The extent of drug release was influenced by partition equilibrium as indicated by increased drug release in the rapeseed oil nanoemulsion compared to porcine serum and blood.