Phase Partitioning Process Research Articles

Integrated green one-step strategy for concurrent recovery of phycobiliproteins and polyunsaturated fatty acids from wet Porphyridium biomass

A novel and green one-step simultaneous extraction process of phycobiliproteins and polyunsaturated fatty acids (PUFAs) from wet Porphyridium biomass has been done and optimized by using three phase partitioning (TPP) process. Results showed that the coupling of ammonium sulfate and protein buoyancy-promoting t-butanol afforded the best TPP to extract phycobiliproteins and PUFAs in term of the extraction performance and cost-effectiveness. TPP process gave the best capability to simultaneously extract Porphyridium-derived phycobiliproteins and PUFAs in 20% ammonium sulfate, 0.5% biomass, and 1:0.5 slurry to t-butanol ratio at 100 rpm and 20 °C for 10 min of extraction time. Moreover, the established TPP system achieved excellent reproducibility in the extraction of Porphyridium biomass from different sources (Porphyridium cruentum and P. purpureum); and was successfully implemented in pilot-scale (20-L), indicating its industrial potential as a promising integrated approach to comprehensively exploit Porphyridium as a renewable bioresource for high-value bioproducts.

Determination of eight neonicotinoid insecticides in Chinese cabbage using a modified QuEChERS method combined with ultra performance liquid chromatography-tandem mass spectrometry

A modified QuEChERS method was developed and combined with ultra performance liquid chromatography-tandem mass spectrometry to analyze eight neonicotinoid insecticides in Chinese cabbage. Herein, acetonitrile served as extraction solvent. Anhydrous sodium sulfate replaced the traditional anhydrous magnesium sulfate in the phase partition process to eliminate the influence of salt caking and heat release. Primary secondary amine and graphitized carbon black were selected as dispersive-solid phase extraction sorbents according to the clean-up efficiency evaluated by post-column infusion. The method showed good sensitivity with the limits of quantification below 1.0 μg/kg for eight analytes. The average recoveries ranged from 79.0% to 108.4% for three fortification levels, and the matrix effect could be ignored. For the tested samples, six neonicotinoids were detected, while cycloxaprid and imidaclothiz were not. The developed analytical method provided a powerful tool for monitoring neonicotinoid insecticides residues in Chinese cabbage.

A simple downstream processing protocol for the recovery of lactic acid from the fermentation broth

Lactic acid is one of the essential platform chemicals, and despite the availability of a range of downstream processes, its effective recovery is still elusive. A phase partitioning process using n-butanol and a chaotropic salt ammonium sulphate was developed to recover lactic acid from the fermentation broth of Lactobacillus pentosus SKL-18. During the optimization of various process parameters, the extraction medium's pH was found to be critical, with 2.5 being the best. The optimized process resulted in a lactic acid yield of 86% and found it to be 93% pure. The purity and characteristics of lactic acid were confirmed by FTIR and NMR spectra. This solvent-based extraction procedure is an economical and straightforward downstream process for purifying lactic acid produced from agro- and bakery-residues. The pure lactic acid can further be used for enzymatic synthesis of high value-added product PLA, a biodegradable and biocompatible plastics.

Lipid extraction from wet Nannochloropsis biomass via enzyme-assisted three phase partitioning

A green and efficient enzyme assisted three phase partitioning (EA-TPP) process was firstly developed to extract microalgal lipids using wet Nannochloropsis sp. biomass. In the pretreatment of microalgal biomass by four hydrolytic enzymes, TPP obtained a higher TFAs lipid extraction efficiency by cellulase compared with the resting enzymes. After optimization by EA-TPP of the wet disrupted Nannochloropsis biomass (3 g), the maximum TFAs extraction yield (90.40%) was attained at 20% ammonium sulphate, 6–7 pH, 1:2 slurry/tert-butanol ratio and 70 °C for 2 h incubation time and two extraction cycles. Moreover, results also revealed that the lipidic species compositions of Nannochloropsis sp. biomass were greatly related with the EA-TPP parameters. In the laboratory scale for wet disrupted microalgae biomass, EA-TPP process achieved 88.70% TFAs extraction yield under the optimized conditions. In all, EA-TPP process could be a promising approach to extract microalgae lipids for food application using wet microalgae biomass.

Noble gases solubility models of hydrocarbon charge mechanism in the Sleipner Vest gas field

Noble gases are chemically inert and variably soluble in crustal fluids. They are primarily introduced into hydrocarbon reservoirs through exchange with formation waters, and can be used to assess migration pathways and mechanisms, as well as reservoir storage conditions. Of particular interest is the role groundwater plays in hydrocarbon transport, which is reflected in hydrocarbon–water volume ratios. Here, we present compositional, stable isotope and noble gas isotope and abundance data from the Sleipner Vest field, in the Norwegian North Sea. Sleipner Vest gases are generated from primary cracking of kerogen and the thermal cracking of oil. Gas was emplaced into the Sleipner Vest from the south and subsequently migrated to the east, filling and spilling into the Sleipner Ost fields. Gases principally consist of hydrocarbons (83–93%), CO2 (5.4–15.3%) and N2 (0.6–0.9%), as well as trace concentrations of noble gases. Helium isotopes (3He/4He) are predominantly radiogenic and range from 0.065 to 0.116RA; reported relative to air (RA=1.4×10−6; Clarke et al., 1976; Sano et al., 1988), showing predominantly (>98%) crustal contributions, consistent with Ne (20Ne/22Ne from 9.70 to 9.91; 21Ne/22Ne from 0.0290 to 0.0344) and Ar isotopes (40Ar/36Ar from 315 to 489). Air-derived noble gas isotopes (20Ne, 36Ar, 84Kr, 132Xe) are introduced into the hydrocarbon system by direct exchange with air-saturated water (ASW). The distribution of air-derived noble gas species are controlled by phase partitioning processes; in that they preferentially partition into the gas (i.e., methane) phase, due to their low solubilities in fluids. Therefore, the extent of exchange between hydrocarbon phases and formation waters – that have previously equilibrated with the atmosphere – can be determined by investigating air-derived noble gas species. We utilize both elemental ratios to address process (i.e., open vs. closed system) and concentrations to quantify the extent of hydrocarbon–water exchange (i.e., volumetric gas–water ratios). These data are discussed within the framework of several conceptual models: (i) total gas-stripping model, which assumes all noble gases have been stripped from the water phase, thus defining the minimum volume of water to have interacted with the hydrocarbon phase; (ii) equilibrium model, which assumes equilibration between groundwater and hydrocarbon phase at reservoir P, T and salinity; and (iii) open and closed system gas-stripping models, using concentrations and elemental ratios. By applying these models to Ne–Ar data from Sleipner, we estimate volumetric gas–water ratios VgVw between 0.02 and 0.07, which are lower than standard geologic gas–water estimates of ∼0.24, estimated by combining gas-in-place estimates with groundwater porosity estimates. Sleipner Vest data can be best approximated by an open system model, which predicts more than an order of magnitude more groundwater interaction during migration than geologic estimates, indicating a dynamic aquifer system and/or a hydrous migration pathway. In an open system, the extent of gas loss can be estimated to be between 8 and 10 reservoir volumes, which have passed through the system and been lost (i.e., filled and spilled).

Phase partitioning of trace metals in a contaminated estuary influenced by industrial effluent discharge

Severe trace metal pollution due to industrial effluents releases was found in Jiulong River Estuary, Southern China. In this study, water samples were collected during effluent release events to study the dynamic changes of environmental conditions and metal partitioning among dissolved, particulate and colloidal phases controlled by estuarine mixing. Intermittent effluent discharges during low tide caused decreasing pH and dissolved oxygen, and induced numerous suspended particulate materials and dissolved organic carbon to the estuary. Different behaviors of Cu, Zn, Ni, Cr and Pb in the dissolved fraction against the conservative index salinity indicated different sources, e.g., dissolved Ni from the intermittent effluent. Although total metal concentrations increased markedly following effluent discharges, Cu, Zn, Cr, Pb were predominated by the particulate fraction. Enhanced adsorption onto particulates in the mixing process resulted in elevated partitioning coefficient (Kd) values for Cu and Zn, and the particle concentration effect was not obvious under such anthropogenic impacts. Colloidal proportion of these metals (especially Cu and Zn) showed positive correlations with dissolved or colloidal organic carbon, suggesting the metal-organic complexation. However, the calculated colloidal partitioning coefficients were relatively constant, indicating the excess binding capacity. Overall, the intermittent effluent discharge altered the particulate/dissolved and colloidal/soluble phase partitioning process and may further influence the bioavailability and potential toxicity to aquatic organisms.

Phase Partition and Phase-Based Process Monitoring Methods for Multiphase Batch Processes with Uneven Durations

Integrated phase partition, online phase identification, and phase-based monitoring methods are proposed for multiphase batch processes with uneven durations. A new phase partition method is developed based on the warped K-means (WKM) clustering algorithm, which divides the entire batch into several operation phases by clustering the trajectory data of phase-sensitive process variables. This WKM-based phase partition method can efficiently cope with the sequentiality of batch data and, thus, ensures a reasonable phase partition result. Besides, because only phase-sensitive variables are used for phase partition, the phase partition accuracy is improved. An online phase identification method is proposed to identify the corresponding operation phase of a new sample according to a phase identification combination index (PICI). PICI quantifies the correlation of a new sample with each operation phase by calculating distance and time difference between the sample and the phase center. The PARAFAC2 and unfolded...

Rapid extraction of andrographolide from Andrographis paniculata Nees by three phase partitioning and determination of its antioxidant activity

Abstract Three phase partitioning (TPP) process was developed for recovery of andrographolide (AP) from the leaves of Andrographis paniculata. AP is a potent anti-inflammatory agent and possesses antioxidant, anticarcinogenic and antidiabetic activity. Optimization of TPP process parameters such as pH, ammonium sulfate saturation, slurry to t-butanol ratio, time and solid to solvent ratio on the extraction efficiency was performed for enhanced yield of AP. Under optimum conditions of extraction (40% w/w ammonium sulfate, 120 min time, pH 7, 1:40 solute to solvent, 1:1 slurry to t-butanol ratio, 40 °C) the maximum AP yield of 26.55 mg/g was obtained. Considering soxhlet extraction as the reference for comparison, TPP showed 62.5% yield in 120 min whereas batch extraction produced 59.89% yield in 140 min. To investigate the antioxidant potential of A. paniculata extract, an in vitro assay (2,2-diphenyl-1-picrylhydrazyl assay) of t-butanol and aqueous layer was performed. Also total phenolic content of both the layers were determined using Folin Ciocalteu reagent. Total phenolic content and antioxidant activity of t-butanol layer was higher as compared to aqueous fraction. A positive correlation of R2=0.988 between total phenolic content and % scavenging of t-butanol layer was observed. The result showed that t-butanol extract of A. paniculata exhibited high antioxidant activity and has the potential to be used as a source of natural antioxidant.

Improved measurement for volatile particles: Vapor-particle separator design and laboratory tests

Sampling and measurement of volatile particles is a challenging task. It has been hampered by lack of a reliable technique capable of accurately capturing the phase-partition process of the pollutants without generating bias and artifacts in the data. The objective of this research is to design a new vapor-particle separation technique for performing the phase separation on-line (the sampling aspect), which, simultaneously, enables characterization of the vapors and particles. The new vapor-particle separator (VPS) consists of a thin metallic microporous membrane for (1) extraction of vapor molecules that are thermally desorbed from the condensed particulate phases and (2) collection of the vapors for subsequent chemical analysis. We evaluated this new separator using synthetic particles made of nonvolatile and or semi-volatile chemicals, and reported the laboratory test results in this paper. The laboratory particle test results showed reasonably high particle transmission efficiency across all particle sizes. The thermal dynamics of nanoparticles was succinctly observed on-line. The results successfully demonstrated the ability of VPS to separate particles and vapors thus enabling a faithful observation of the thermal behavior. We believe the new technology will make a great contribution to the measurement of volatile particles.

Modeling the depuration rates of polychlorinated biphenyls in two mussel species with theoretical molecular descriptors

Using theoretical molecular descriptors as well as partial least squares (PLS) regression, two quantitative structure-activity relationship (QSAR) models were developed for depuration rate constants (kd) of polychlorinated biphenyls (PCBs) in two species of mussels, Perna viridis and Dreissena polymorpha. The cross-validated Qcum2 (an indicator of fitting of goodness) values for the two models are 0.501 and 0.756, and the standard deviation (SD) is 0.084 and 0.076, respectively. The achievement of satisfactory Qcum2 and low SD values indicates good predictive ability and precision of the two models. The significant descriptors governing lgkd include polarizability (α), molecular volume (MV), molecular weight (Mw), molecular surface area (S), and total energy (TE). The key descriptors in the models reflect that van der Waals interactions play a dominant role in the depuration of PCBs. The depuration of PCBs in the two mussel species may be mainly attributed to the biota-water phase partitioning processes.

Quantitative structure-activity relationship for the depuration rate constants of polychlorinated biphenyls in the freshwater mussel, Elliptio complanata

Partial least squares (PLS) regression together with 16 theoretical molecular structural descriptors was successfully used to develop a quantitative structure-activity relationship (QSAR) model on the depuration rate constants (k d) of polychlorinated biphenyls (PCBs) in freshwater mussel Elliptio complanata. The cross validated Q 2 cum and the correlation coefficient R for the model is 0.871 and 0.941, respectively. The achievement of satisfactory Q 2 cum and R values indicate significant high robustness and good predictive ability of the model. The model was tested as acceptable for prediction of logk d (the log of the depuration rate constants) by validation set. The significant descriptors governing logk d include polarizability (α), core core repulsion energy (CCR), molecular weight (M w), total energy (TE), and electronic energy (EE). The key descriptors in the model reflect that van der Waals interactions play a dominant role in the depuration of PCBs. The depuration of PCBs in Elliptio complanata may be mainly attributed to the biota-water phase partitioning processes.

Synthesis of Fe-ZrO2 nanocomposite powders by reduction in H2 of a nanocrystalline (Zr, Fe)O2 solid solution

The formation of Fe-ZrO 2 nanocomposite powders by reduction in hydrogen of a nanocrystalline totally stabilized Zr 0.9 Fe 0.1 O 1.95 solid solution was investigated by X-ray diffraction (XRD), field-emission-gun scanning electron microscopy (FEG-SEM) and Mössbauer spectroscopy. The reduction of the stabilized Zr 0.9 Fe 0.1 O 1.95 solid solution and the formation of metallic particles precedes the transformation of zirconia into the monoclinic phase, which becomes the major zirconia phase upon reduction at 950 °C. α-Fe particles with a size distribution slightly increasing from 10–50 to 20–70 nm upon the increase in reduction temperature are observed and a second population of smaller (<5 nm) γ-Fe nanoparticles is also noticed when the reduction is performed at 1000 °C. Another metallic phase with a hyperfine field of ∼200 kOe at RT (∼250 kOe at 80 K) is detected, which could account for an Fe/Zr phase. It could be formed by the reduction on an Fe 2+ -rich transient phase incorporating a small fraction of the Zr 4+ ions, formed by a phase partitioning process superimposed to the reduciton processes.

A conceptual model of organo-mineral interactions in soils: self-assembly of organic molecular fragments into zonal structures on mineral surfaces

In this paper, we propose a structure for organo-mineral associations in soils based on recent insights concerning the molecular structure of soil organic matter (SOM), and on extensive published evidence from empirical studies of organo-mineral interfaces. Our conceptual model assumes that SOM consists of a heterogeneous mixture of compounds that display a range of amphiphilic or surfactant-like properties, and are capable of self-organization in aqueous solution. An extension of this self-organizational behavior in solution, we suggest that SOM sorbs to mineral surfaces in a discrete zonal sequence. In the contact zone, the formation of particularly strong organo-mineral associations appears to be favored by situations where either (i) polar organic functional groups of amphiphiles interact via ligand exchange with singly coordinated mineral hydroxyls, forming stable inner-sphere complexes, or (ii) proteinaceous materials unfold upon adsorption, thus increasing adhesive strength by adding hydrophobic interactions to electrostatic binding. Entropic considerations dictate that exposed hydrophobic portions of amphiphilic molecules adsorbed directly to mineral surfaces be shielded from the polar aqueous phase through association with hydrophobic moieties of other amphiphilic molecules. This process can create a membrane-like bilayer containing a hydrophobic zone, whose components may exchange more easily with the surrounding soil solution than those in the contact zone, but which are still retained with considerable force. Sorbed to the hydrophilic exterior of hemimicellar coatings, or to adsorbed proteins, are organic molecules forming an outer region, or kinetic zone, that is loosely retained by cation bridging, hydrogen bonding, and other interactions. Organic material in the kinetic zone may experience high exchange rates with the surrounding soil solution, leading to short residence times for individual molecular fragments. The thickness of this outer region would depend more on input than on the availability of binding sites, and would largely be controlled by exchange kinetics. Movement of organics into and out of this outer region can thus be viewed as similar to a phase-partitioning process. The zonal concept of organo-mineral interactions presented here offers a new basis for understanding and predicting the retention of organic compounds, including contaminants, in soils and sediments.

Distribution of dissolved species and suspended particulate copper in an intertidal ecosystem affected by copper mine tailings in Northern Chile

The coastline near Chañaral in Northern Chile is one of the most highly Cu-contaminated zones in the world due to discharges from mining activities for more than 60 years. The speciation of Cu has been studied to determine the importance of organic complexation in highly contaminated areas, and to assess the likely physiological impacts of Cu on marine organisms. Dissolved Cu concentrations of up to 500 nM were measured, completely saturating organic ligands and leading to free Cu 2+ concentrations in excess of 10 − 8 M. These values are higher than those reported in any other marine environment, and because they occur over an extensive area, provide a unique opportunity to study the effects of Cu on marine ecosystems and to see how Cu behaves when its speciation is predominantly inorganic. We found strong gradients in free Cu 2+ between Chañaral and adjacent areas with lower Cu, where speciation is dominated by organic complexation. There is also a significant increase in the partitioning of Cu onto suspended particles in the contaminated areas, consistent with previous studies that showed that organic ligands stabilize Cu in the dissolved phase, whilst “excess” Cu is rapidly scavenged. Those high dissolved Cu concentrations persist in spite of solid phase partitioning and advective processes along this open-ocean coastline, suggesting that Cu inputs into the system are still very large. Measurements were made using anodic stripping voltammetry with a thin mercury film coated with Nafion, which previous workers have shown can mitigate ambiguity in the data arising from inadvertent reduction of organic complexes. Our findings suggest that this is a useful methodology for contaminated systems.

Modification of Crystal Habit of Ibuprofen Using the Phase Partition Technique: Effect of Aerosil and Tween 80 in Binding Solvent

A ternary diagram, representing the solubility of binding solvent (chloroform) in a mixture of ethanol and water, was constructed. For this study, the solvent mixture that gave the best ibuprofen pellets (IPs) was composed of chloroform:ethanol:water at a ratio of 1.5%:8%:90.5%. The suitable agitator speed, temperature, and mixing time were found to be 1500 rpm, 25°C ± 2°C, and 20 min, respectively. In addition, suitable stirring time when the phase partition process of IPs began was 15 min. IPs obtained from these conditions were small and round, approximately 1 mm; surface determination by scanning electron microscopy (SEM) indicated that the IPs were composed of drug microcrystals rearranged on the surface. For the dissolution, IPs showed lower drug release when compared with pure ibuprofen crystal (IC) (f2 analysis). An attempt to modify the dissolution property of IP by incorporating various concentrations of Aerosil and Tween 80 in the binding solvent was made. Microscopic appearance showed that both Aerosil and Tween 80 gave less spherical pellets when compared with the use of binding solvent alone. For both the Aerosil and Tween 80 employed, the results indicated a change in rearrangement of drug microcrystals and a change in crystal habit. However, Tween 80 gave more change of the crystallographic direction of drug microcrystals than Aerosil. In term of dissolution, the results showed that employing Tween 80 at 1.2% gave the highest drug release compared to the use of Aerosil and IC alone (f2 analysis). These pellets had a good flow property, as indicated by Carr's compressibility, flow rate, and angle of repose, and they can be compressed into a tablet, encapsulated by suitable polymer, or pulverized to obtain micronized crystals. In the case of compression into tablets, the dissolution profiles of these tablets compared with those of commercial product meet the USP 24 requirement (Q ≥ 80% at 60 min).

Influence of the presence of PAHs and coal tar on naphthalene sorption in soils

The mobility of the most water-soluble polynuclear aromatic hydrocarbons (PAHs) such as naphthalene in contaminated soils from manufactured gas plant (MGP) sites or other similar sites is influenced not only by the naturally occurring soil organic matter (SOM) but also, and in many cases mostly, by the nature and concentration of coal tar xenobiotic organic matter (XOM) and other PAH molecules present in the medium under various physical states. The objective of the present study was to quantify the effects of these factors using batch experiments, in order to simulate naphthalene transport in soil–tar–water systems using column experiments. Naphthalene sorption was studied in the presence of (i) solid coal tar particles, (ii) phenanthrene supplied as pure crystals, in the aqueous solution or already sorbed onto the soil, (iii) fluoranthene as pure crystals, and (iv) an aqueous solution of organic molecules extracted from a liquid tar. All experiments were conducted under abiotic conditions using short naphthalene/sorbent contact times of 24–60 h. Although these tests do not reflect true equilibrium conditions which usually take more time to establish, they were used to segregate relatively rapid sorption phenomena (“pseudo equilibrium”) from slow sorption and other aging phenomena. For longer contact times, published data have shown that experimental biases due to progressive changes in the characteristics of the soil and the solution may drastically modify the affinity of the solutes for the soil. Slow diffusion in the microporosity and in dense organic phases may also become significant over the long term, along with some irreversible aging phenomena which have not been addressed in this work. Results showed that PAHs had no effect on naphthalene sorption when present in the aqueous solution or as pure crystals, due to their low solubility in water. Adsorbed phenanthrene was found to reduce naphthalene adsorption only when present at relatively high concentrations (about 120 mg/kg) in the soil. In contrast, experiments carried out with coal tar particles revealed a significant effect. Naphthalene sorption appeared to be proportional to the amount of coal tar added to the sand or soil, and a much higher affinity of naphthalene for XOM ( K oc above 2000 cm 3/g) than SOM ( K oc around 300 cm 3/g) was observed. Naphthalene transport in the columns of sand or soil spiked with coal tar particles was simulated very satisfactorily with a dual double-domain model. Around 90% of naphthalene retention by coal tar was found to occur within the organic phase, suggesting a phase partition process which may be explained by the amorphous nature of the XOM and its extreme affinity for naphthalene. For SOM, however, which is present as porous microaggregates of clay and humic substances, with less affinity for naphthalene, only 1/3 of naphthalene retention was found to occur within the organic phase, underlining the significant role of surface adsorption in the short term behavior of naphthalene in soil. For longer contact times, the model simulations proposed in the present study should be coupled to slow sorption, aging and biodegradation models to describe long-term behavior of naphthalene in soil–tar–water systems.

The Effect of Temperature on the Bioventing of Soil Contaminated with Toluene and Decane

The effect of temperature on evaporation and biodegradation rates during soil bioventing (SBV) was studied for a mixture of toluene and decane in bench-scale soil columns at a continuous air flow and consecutively at two different flow rates. The effect of temperature on SBV was monitored by GC headspace analysis of contaminant, CO2 and O2 concentrations in the soil gas over time. Separation of evaporation and biodegradation processes into three different phases based on their rates was used together with Q10 and E10 (values that give the factor by which biodegradation and evaporation rates increase when the temperature is raised by 10 degrees) to compare quantitatively the removal kinetics at 10 and 20°C. Adsorption of toluene and decane onto soil (a phase partitioning process) at 20 and 10°C was described with linear Freundlich isotherms. A temperature decrease from 20 to 10°C resulted in an increase of soil-air partitioning coefficients by a factor of 1.8 and of 2.1 for toluene and decane, respectively. The mean Q10 value for the biodegradation of toluene was found to be 2.2 for a temperature rise from 10 to 20°C. A toluene content in the soil gas above 75% of the saturation concentration inhibited biodegradation at both temperatures. The SBV efficiency was dependent on temperature with respect to remediation time. SBV at 20°C resulted in a 99.8% and a 98.7% reduction of toluene and decane initial concentrations, respectively. To reach similar results at 10°C, about 1.6 times as much time and 1.4 times as much air were required; however, at both temperatures the total amounts of biodegraded hydrocarbons were approximately the same. The evaporation-to-biodegradation ratios at 20°C were 82.5:17.5 for toluene and 16:84 for decane, whereas at 10 °C they were 71:29 and 2:98, respectively. A comparison of Q10 values showed that, except during the initial phase of SBV, only a modest decrease in biodegradation rates should be expected after a decrease in temperature from 20 to 10°C. Flow rate reduction had a significant impact on the toluene evaporation rate at a higher temperature, whereas for decane this rate was only slightly affected by temperature. In contrast to decane, the ratio between toluene vapor pressures at 20 and 10°C may be used to predict the removal of toluene by evaporation during the above-mentioned phases of SBV, when evaporation is important.

Cell surface energy, contact angles and phase partition. I. Lymphocytic cell lines in biphasic aqueous mixtures

The surface energy of cells is the quantity which dominates certain physical interactions of cells such as adhesion to hydrophobic surfaces and phagocytosis. A linear relationship is derived relating the equilibrium constant obtained from phase partition in liquid-liquid systems with the surface energy difference obtained from contact-angle measurements. Using biphasic mixtures of Dextran and poly(ethylene glycol) in a medium of constant salt composition the expression is confirmed for transformed lymphocytic cell lines. The results demonstrate the importance of van der Waals' interactions in the phase-partition process, that phase partition can be used as a direct measure of cell surface hydrophobicity, and that the equilibrium constant of phase partition is directly related to the difference in the surface energy of the partitioned particle between the two phases.

Cell surface energy, contact angles and phase partition. II. Bacterial cells in biphasic aqueous mixtures

Partition coefficients in biphasic mixtures of poly(ethylene glycol) and Dextran are compared to cell surface energies obtained from contact angles of each liquid phase on cell layers. Linear relationships are observed between these two independent measurements for a variety of bacterial cells. The results demonstrate the importance of interfacial phenomena and contact angles in the phase-partition process.