Relative Partition Coefficients Research Articles

Effect of Iodide-Based Organic Salts and Ionic Liquid Additives in Dye-Sensitized Solar Cell Performance.

The use of ionic liquid and organic salts as additives for electrolyte systems in dye-sensitized solar cells have been widely described in recent years. The tunability of their physical-chemical properties according to the cation–anion selection contributes toward their high efficiencies. For this purpose, several iodide-based organic salts including imidazolium, picolinium, guanidinium and alkylammonium cations were tested using acetonitrile/valeronitrile electrolytes and their photovoltaic parameters were compared. A best efficiency of 4.48% (4.15% for the reference) was found for 1-ethyl-2,3-dimethylimidazolium iodide ([C2DMIM]I) containing electrolyte, reaffirming the effectiveness of these additives. 4-tertbutylpyridine was included into the formulation to further improve the performance while determining which iodide salts demonstrate the highest synergy with this additive. [C2DMIM]I once again proved to be the superior additive, achieving an efficiency of 6.48% (6% for the reference). Electrochemical impedance spectroscopy was employed to elucidate the effects of the various additives, demonstrating the relevance of the counter electrode resistance on device performance. Finally, several computational descriptors for the cationic structures were calculated and correlated with the photovoltaic and resistance parameters, showing that properties related to polarity, namely relative positive charge, molecular polarizability and partition coefficient are in good agreement with the counter-electrode resistance.

The Influence of Newly Synthesized Demulsifiers on the Interfacial Rheological Properties of a Naturally Occurring Water/Oil Emulsion.

This research aimed to synthesize new polymeric nonionic demulsifiers (DA, DB, and DC) to break 50% of naturally occurring water/oil emulsions. The prepared demulsifiers were synthesized in only two stages utilizing simple techniques. 1H and 13CNMR, MS, and FTIR spectroscopies were performed to validate the chemical composition of the synthesized demulsifiers. The relative solubility number (RSN) and partition coefficient (Kp) were determined for the three demulsifiers. The interfacial tension (IFT) and dehydration ratios of DA, DB, DC, and their triblock copolymers were investigated. Also, interfacial rheological properties for the three demulsifiers were measured. The findings demonstrate that DB possesses a higher RSN value than DA and DC owing to its hydrophilicity. DC exhibited the lowest IFT value compared to DA, DB, and their corresponding triblock copolymers. DB and DC are more effective in demulsifying than DA and triblock copolymers. DC achieved a 100% dehydration ratio at a low dosage of 75 ppm after 120 min. DC’s remarkable performance can be attributed to its aromatic core, molecular weight, and high interfacial activity. According to the rheological data, a higher dehydrating ratio is attained when the demulsifier has a great capacity to lower the viscoelasticity of the W/O emulsion interface. The maximum decrease in G′ and G″ values was attained by DC. The mechanism of DC’s demulsifying interaction on a naturally occurring W/O emulsion was elucidated.

Novel synthesized polymeric surfactants additives based on phenethylamine as an emulsion breaker for water droplet coalescence in naturally Egyptian crude oil emulsion

This work aims to prepare three non-ionic surfactants (DI, DII, and DIII) based on phenethylamine in different ratios of propylene oxide to ethylene oxide (PO/EO) in just two steps as novel polymeric additives to break down naturally crude oil emulsions. The first step was the propoxylation process followed by the ethoxylation process in the second step. FTIR, NMR, and mass spectroscopic techniques were used to validate their chemical composition, and gel permeation chromatography was used to determine their molecular weights. Their activities at the formation water/crude oil interface were inspected to study their adsorption by measuring the dynamic interfacial tension (IFT). Their relative solubility number (RSN), hydrophilic-hydrophobic balance (HLB), and partition coefficient (PC) were also assessed for the three prepared polymeric surfactants. The rheological properties of the dehydrated crude oil, untreated and treated crude oil emulsion were evaluated. The performance of synthesized polymeric emulsion breakers was reported at different concentrations. The demulsification mechanism was photoed using an optical polarizing microscope. Data of IFT, HLB, RSN, and PC participated in elucidating the demulsification performance of the prepared polymeric surfactants. This study showed that the highest coalescence rate of water droplets at 120 min and 500 ppm was achieved by DIII. Emulsion viscosity was reduced by as much as one order of magnitude and reached the oil viscosity in the presence of the DIII. The demulsifying mechanism was observed to go through three phases: adsorption & flocculation, coalescence & the creation of a channel, and separation.

A New Multiscale Computational Model for Low Salinity Waterflooding in Clay Bearing Sandstones

We develop a new multiscale model to compute effective properties such as relative permeability, contact angle and partition coefficients in low salinity enhanced oil recovery processes for two-phase flow in sandstones containing reactive surfaces of kaolinite clay. In this setting, we construct a three-scale approach which entails the local nanoscale description ruled by the electro-chemistry of a confined electrolyte solution containing Na+, $$Ca^{2+}$$ , $$H^+$$ , $$Cl^-$$ and $$OH^-$$ ions residing between bounded crude-oil droplets at residual saturation and clay substrate. Our analysis focuses on the case of surface complexation geochemical reactions between the ionic species of the invading water and the electrically charged kaolinite and oil–water interfaces. In this scenario, we construct a local electric double layer problem for the electric potential based on a non-symmetric Poisson–Boltzmann equation supplemented by nonlinear boundary conditions with the magnitude of the surface charge strongly dictated by the geochemical reactions. By invoking the local mechanical equilibrium of the electrolyte solution and solving numerically the nonlinear problem using the finite element method, we compute the local ionic profiles and reconstruct numerically the disjoining pressure and adsorption isotherms for each ionic species for a wide range of brine compositions and pH of the water phase. Furthermore, combining the disjoining pressure results with the Frumkin/Derjaguin wetting theory allows to compute the dependence of the contact angle on wettability, pH and salinity. Subsequently, the formal homogenization procedure is adopted to upscale the pore-scale flow and ion transport to the macroscale giving rise to a new Darcy scale coupled flow/transport model. The hyperbolic part of the nonlinear homogenized model is solved analytically in an 1D example of enhanced oil recovery.

Synthesis of magnetite/lanthanum hydroxide composite and magnetite/aluminum hydroxide composite for removal of phosphate

Two magnetic adsorbents, magnetite/aluminum hydroxide composite (MAC) and magnetite/lanthanum hydroxide composite (MLC), were successfully synthesized by a simple one-pot method and their phosphate adsorption process was investigated. The properties of synthesized adsorbents were studied using Fourier transform infrared spectroscopy (FTIR), zeta potential, vibrating sample magnetometry (VSM) and X-ray photoelectron spectroscopy (XPS). The adsorption isotherms, adsorption kinetics and the effects of solution pH and dissolved organic carbon (DOC) on the adsorption of phosphate in aqueous solution by MAC, MLC-2, MLC-10 and LMB were investigated to evaluate the difference in phosphate removal efficiency of the magnetic adsorbents and non-magnetic adsorbent. According to the results of this study, MLC-10 had a higher phosphate adsorption capacity (19.34 mg P g−1) than LMB (11.55 mg P g−1), MAC (10.48 mg P g−1) and MLC-2 (8.89 mg P g−1). MLC-10 showed a relative higher partition coefficient (PC) (1.74 mg g−1 μM−1) than other three adsorbents at initial P concentration of 15 mg L−1. Also, MLC-10 was less pH dependent than MAC and had higher phosphate adsorption capacities under different DOC concentrations (0–72 mg L−1) than LMB, MAC and MLC-2. Further, MLC-10 had excellent recyclability due to high magnetism. Electrostatic interaction and the inner-sphere surface complexation were the potential phosphate adsorption mechanisms employed by MLC-10. In summary, MLC-10 is a promising adsorbent for phosphate removal from eutrophication water.

The Affinity of Sterols for Different Phospholipid Classes and Its Impact on Lateral Segregation

Cholesterol is an essential molecule in the membranes of mammalian cells. It is known to be distributed heterogeneously within the cells, between the bilayer leaflets, as well as between lateral domains within the bilayer. However, we do not know exactly how cholesterol is distributed and what forces drive this sorting process because it extremely difficult to study using currently available methods. To further elucidate this distribution, we measured how cholesterol partitions between different phospholipid (PL) environments using different methods based on cholesterol, TopFluor-cholesterol, and cholesta-5,7,9(11)-triene-3-β-ol. Based on the obtained relative partition coefficients, we made predictions regarding how cholesterol would be distributed between lateral domains and between the inner and outer leaflets of the plasma membrane. In addition, using a trans-parinaric acid fluorescence-based method, we tested how cholesterol could influence lateral segregation through its interaction with unsaturated PLs with different headgroups. The results showed that the lower the affinity of cholesterol was for the different unsaturated PLs, the more cholesterol stimulated lateral segregation in a ternary bilayer of unsaturated PL/N-palmitoyl-D-erythro-sphingomyelin and cholesterol. Overall, the results indicate that both the distribution of cholesterol between different lipid environments and the impact of cholesterol on lateral segregation can be predicted relatively accurately from determined relative partition coefficients.

Quantitative chemical analysis of volatile compounds via headspace-solid phase microextraction (HS-SPME) coupled with inverse gas chromatography (IGC)

The compositions of volatile compounds in headspace (HS) analyzed by a solid phase microextraction (SPME) sampling method usually differ from true compositions mainly because the partition coefficients for these compounds between headspace and a SPME fiber are not equal. In this paper we report an analytical strategy to more accurately quantify relative compositions of selected hydrocarbons present in gasoline residue by employing inverse gas chromatography (IGC) coupled with a HS-SPME sampling method. First, IGC measurements using a column packed with a solid support coated with polydimethylsiloxane (PDMS) were conducted to obtain the thermodynamic and chromatographic data needed for the estimation of the relative partition coefficients of n-heptane, toluene, and 1,2,4-trimethylbenzene (TMB) between headspace and a PDMS SPME fiber at 100 and 130 °C. Then, chemical analysis of headspace containing different compositions of vaporized n-heptane, toluene, and TMB were carried out via a PDMS SPME sampling method at 100 and 130 °C. Finally, the relative compositions of these vaporized compounds in headspace were estimated using compositions from a PDMS SPME sampling method and the relative partition coefficients from IGC. Our results showed that the estimated relative compositions of these compounds in headspace are comparable to true compositions obtained from direct headspace vapor analysis within reasonable relative errors.

The Investigation of Perfluoroalkyl Substances in Seasonal Freeze-Thaw Rivers During Spring Flood Period: A Case Study in Songhua River and Yalu River, China.

The occurrence of 15 perfluoroalkyl substances (PFASs) in water, sediments, and fish from Songhua River and Yalu River in Jilin Province, Northeast China, during their spring flood period were investigated for the first time. The short-chain perfluorobutanoic acid was the dominant PFAS in the water with the mean concentrations of 10ngL-1 in Songhua River and 9.0ngL-1 in Yalu River, and also dominant in sediments with the mean concentrations of 2.0 and 1.8ngg-1 dry weight. Perfluorodecane sulfonate was the predominant compound in fish. The detected frequencies and concentrations of perfluorooctane sulfonate and perfluorooctanoic acid were very low in the water, sediments, and fish. Low detected frequencies and concentrations of long-chain PFASs led to relative low sediment-water partition coefficients and bioaccumulation factors. The concentration levels of PFASs in the two rivers were lower than those in other major rivers in China.

Comparison of RESP and IPolQ-Mod Partial Charges for Solvation Free Energy Calculations of Various Solute/Solvent Pairs.

The calculation of solvation free energies ΔGsolv by molecular simulations is of great interest as they are linked to other physical properties such as relative solubility, partition coefficient, and activity coefficient. However, shortcomings in molecular models can lead to ΔGsolv deviations from experimental data. Various studies have demonstrated the impact of partial charges on free energy results. Consequently, calculation methods for partial charges aimed at more accurate ΔGsolv predictions are the subject of various studies in the literature. Here we compare two methods to derive partial charges for the general AMBER force field (GAFF), i.e. the default RESP as well as the physically motivated IPolQ-Mod method that implicitly accounts for polarization costs. We study 29 solutes which include characteristic functional groups of drug-like molecules, and 12 diverse solvents were examined. In total, we consider 107 solute/solvent pairs including two water models TIP3P and TIP4P/2005. Comparison with experimental results yields better agreement for TIP3P, regardless of the partial charge scheme. The overall performance of GAFF/RESP and GAFF/IPolQ-Mod is similar, though specific shortcomings in the description of ΔGsolv for both RESP and IPolQ-Mod can be identified. However, the high correlation between free energies obtained with GAFF/RESP and GAFF/IPolQ-Mod demonstrates the compatibility between the modified charges and remaining GAFF parameters.

Demulsification performance and the relative solubility number (RSN) of modified poly(maleic anhydride-alt-1-dodecene) on naturally asphaltenic crude oil emulsion

ABSTRACTThe performance of modified poly(maleic anhydride-alt-1-dodecene) with polyethylene glycol (PEG 1000) and polypropylene glycol (PPG 1000) as emulsion breakers was investigated. The de-emulsifiers were characterized by their chemical structures, relative solubility numbers (RSN), EO content, PO content, and partition coefficient (Kp). All the prepared copolymers were characterized by FTIR and 1H NMR spectroscopic techniques and their molecular weights were determined by gel permeation chromatography (GPC). The surface and interfacial properties for the prepared polymeric surfactants were studied. The results obtained showed that the molecular structure of the prepared de-emulsifiers have direct effect on de-emulsification process. De-emulsifiers with more EO−PO content had higher de-emulsification efficiency.

Evolution of the Main Zone at the Marathon Cu-PGE Sulfide Deposit, Midcontinent Rift, Canada: Spatial Relationships in a Magma Conduit Setting

Various ultramafic Ni-Cu-platinum group element (PGE) deposits associated with the North American Midcontinent rift have been attributed to formation in a magma conduit setting, whereby PGE concentration is controlled by various fluid dynamic processes. The Marathon Cu-PGE sulfide deposit located within the Midcontinent rift-related Coldwell Alkaline Complex has been classified as a gabbro-associated contact-type deposit; however, both magmatic and hydrothermal processes have been proposed to account for the significant concentration of PGE. In light of the growing field of evidence for magma conduit-type settings, this study comprised a comprehensive geochemical investigation of the complicated crosscutting gabbroic to ultramafic units in the immediate vicinity of the Marathon deposit; and a thorough three-dimensional investigation of the distribution of Cu and Pd within the Main mineralized zone. The main objectives of this study were to test the applicability of the magma conduit deposit model to the Marathon deposit and to identify key exploration criteria for use elsewhere in the Coldwell Alkaline Complex. Mineralization is hosted by the Two Duck Lake gabbro, a 4-km-long and 250-m-thick unit of the Marathon Series. The Marathon Series is the latest of three magmatic series that make up the 1- to 2-km-thick Eastern Gabbro Suite, which wraps around the eastern and northern margin of the Coldwell Alkaline Complex. The three magmatic series are shown here to have distinct trace element signatures that enable reliable discrimination of potentially sulfide and PGE-bearing units of the Marathon Series from the barren rocks of either the Fine-Grained or Layered Series. At the Marathon deposit, sulfides consist of disseminated chalcopyrite, pyrrhotite, and minor bornite and occur within the Main, Footwall, and Hanging-wall zones and in the PGE-enriched W Horizon. This paper focused on sulfides located within the Main zone, including the keel-shaped feeder channel that continues downdip to over 550-m depth. The spatial distribution of Cu, Pd, and Cu/Pd were examined in relation to a three-dimensional surface model for the footwall contact; in a vertical profile through the Main zone; and in a longitudinal section that cuts the feeder channel. There are three important observations: (1) trends for elevated Cu and Pd are parallel to numerous troughs and ridges in the footwall, (2) Cu, Pd, and Cu/Pd varies up section in a saw-toothed pattern from high to low values, and (3) the proportion of high Cu/Pd sulfides is greatest within the thickest accumulations of sulfides within the feeder channel. Evaluation of interelement relationships between Cu and Pd and between Pd and Ir, Rh, Pt, and Au for mineralization within the Main zone indicate positive associative, but nonlinear behavior for all elements. Briefly, the data show nonlinear correlations between Cu and Pd in which Cu/Pd decreases with increasing Pd; and coherent but nonlinear behavior for Ir, Rh, Pt, and Pd in which Pd/Ir, Pd/Rh, Pd/Pt, and Pd/Au all increase with increasing Pd. The observed variation in Cu/Pd is consistent with a magmatic model calculated by others for deposits in the Duluth Complex, in which sulfides accumulated in a closed system from a melt with mantlelike Cu/Pd and an elevated silicate to sulfide ratio. The observed variations in Pd/Ir, Pd/Rh, and Pd/Pt are consistent with R factor fractionation related to differences in the relative partition coefficients between sulfide and silicate melts, and rule out the possibility that processes such as fractionation of sulfide melt by monosulfide solid solution (mss) or redistribution of metals during hydrothermal alteration played a significant role in the mineralizing event. The Two Duck Lake gabbro and associated sulfides of the Marathon deposit are proposed to have formed by multiple injections of plagioclase crystal mush that carried droplets of sulfide liquid along a conduit system that was controlled by radial and ring fault structures in the Coldwell Alkaline Complex. The accumulation of sulfides was controlled by flow dynamic processes within the magma channels, but Cu/Pd was controlled by local proportions of silicate melt to sulfide liquid. Key characteristics of the deposit that are critical to exploration elsewhere in the Coldwell Alkaline Complex include the following: (1) the recognition that gabbroic to ultramafic intrusions of the Marathon Series are the host for Cu and PGE mineralization, (2) the distribution of Cu/Pd data within sulfide occurrences are useful as vectors toward the feeder channel, (3) topographic lineaments are indicators of potential mineralized feeder zones, and (4) oxide- and apatite-rich, irregularly shaped gabbroic to ultramafic pods are potential indicators of an underlying feeder channel.

Pharmacokinetics of sevoflurane elimination from respiratory gas and blood after coronary artery bypass grafting surgery.

Sevoflurane, with a relative low blood-gas partition coefficient, is an ideal anesthetic to achieve rapid offset and recovery from general anesthesia. This study will determine the profiles of four concentration-time curves to characterize the pharmacokinetics of sevoflurane elimination. Eight patients (aged 54-76 years) undergoing coronary arterial bypass grafting surgery were enrolled in this study. At the end of surgery, anesthetic gas and blood were sampled 20 min before and after stopping sevoflurane administration, with prior maintenance of a fixed 5% inspired sevoflurane (CIsev) in 6 L/min oxygen flow for 60 min before the cessation of sevoflurane administration for the subsequent 20 min elimination. An infrared analyzer was used to determine both CIsev and end-tidal sevoflurane (CEsev). The sevoflurane concentrations in the internal jugular-bulb (Jsev), arterial (Asev) and pulmonary arterial blood (PAsev) were analyzed by gas chromatography, and cardiac output was measured using an Opti-Q pulmonary artery catheter. A bi-exponential decay function was the best fit for the CEsev,Jsev, Asev, and PAsev time curves. There were two distinct components, the initial 5-min fast or distribution phase and the subsequent 15-min slow or elimination phase. Before cessation of the sevoflurane supplement, the step-down concentration of sevoflurane was listed in the following order: CIsev > CEsev > Asev ≧ Jsev > PAsev. During the elimination phase, the fastest decay occurred in CEsev, followed by Jsev, Asev and PAsev. Therefore, a reverse step-down pattern was observed (PAsev > Asev ≧ Jsev > CEsev) after 20 min. The ratio of Asev to CEsev was 89% at baseline before stopping sevoflurane administration, but the ratio of Asev to CEsev increased to 128% at the twentieth min of the sevoflurane elimination phase. During elimination, the initial washout of sevoflurane from the functional residual capacity of the lungs was reflected in the fast component of the CEsev, Jsev, Asev, and PAsev time curves. In contrast, the slow component was dominated by the tangible effects of the physiological membrane barriers, such as the alveoli-pulmonary capillary and blood-brain barriers.

Rational discovery and development of a mitochondria-targeted antioxidant based on cinnamic acid scaffold

A novel mitochondria-targeted antioxidant (TPP-OH) was synthesized by attaching the natural hydrophilic antioxidant caffeic acid to an aliphatic lipophilic carbon chain containing a triphenylphosphonium (TPP) cation. This compound has similar antioxidant activity to caffeic acid as demonstrated by measurement of DPPH/ABTS radical quenching and redox potentials, but is significantly more hydrophobic than its precursor as indicated by the relative partition coefficients. The antioxidant activity of both compounds was intrinsic related to the ortho-catechol system, as the methoxylation of the phenolic functions, namely in TPP-OCH3 and dimethoxycinnamic acid, gave compounds with negligible antioxidant action. The incorporation of the lipophilic TPP cation to form TTP-OH and TPP-OCH3 allowed the cinnamic derivatives to accumulate within mitochondria in a process driven by the membrane potential. However, only TPP-OH was an effective antioxidant: TPP-OH protected cells against H2O2 and linoleic acid hydroperoxide-induced oxidative stress. As mitochondrial oxidative damage is associated with a number of clinical disorders, TPP-OH may be a useful lead that could be added to the family of mitochondria-targeted antioxidants that can decrease mitochondrial oxidative damage.

Relative Partition Coefficient Measurements by HPLC

Relative Partition Coefficient Measurements by HPLC

Limiting Partition Coefficients of Solutes in Biphasic Trihexyltetradecylphosphonium Chloride Ionic Liquid−Supercritical CO2 System: Measurement and LSER-Based Correlation

Limiting partition coefficients of a selection of low-to-medium volatility solutes between both phases in a biphasic trihexyltetradecylphosphonium chloride ([thtdp][Cl]) ionic liquid (IL)-supercritical carbon dioxide (scCO2) system were obtained by capillary column chromatography with [thtdp][Cl] as the stationary liquid and scCO2 as the carrier fluid. It is shown that supercritical fluid chromatography can be used to probe the partitioning behavior of solutes in biphasic IL-scCO2 systems even when the IL has nonzero solubility in scCO2. Relative partition coefficients of solutes at a particular temperature and density of CO2 can be correlated within Abraham's linear solvation energy relationships. Compared with our previous results in a [bmim][BF4]-scCO2 system, the solute partition coefficients in the [thtdp][Cl]-scCO2 system are more sensitive to the solute hydrogen bond acidity descriptor.

An Example of Lipophiloselectivity: The Preferred Oxidation, in Water, of Hydrophobic 2-Alkanols Catalyzed by a Cross-Linked Polyethyleneimine−Polyoxometalate Catalyst Assembly

A cross-linked polyethyleneimine polymer containing the [ZnWZn2(H2O)2(ZnW9O34)2]12- polyoxometalate was prepared from branched polyethyleneimine (Mw = 600), the polyoxometalate, and a n-octylamine-epichlorohydrin cross-linking reagent. This catalytic assembly was active for the selective oxidation of 2-alkanols to 2-alkanones with aqueous H2O2 with reactions presumably occurring at a hydrophobic domain. Most importantly, the catalyst showed distinctive lipophiloselectivity, that is selectivity as a function of the lipophilic nature of a reaction substrate. The lipophiloselectivity was proportional to the relative partition coefficient (1-octanol/water) of the substrates.

REE abundances in ancient seawater inferred from marine limestone and experimental REE partition coefficients between calcite and aqueous solution

In our earlier work, we determined relative REE partition coefficients between calcite and aqueous (CaCl2 + NaCl) solution, but absolute values could not be obtained because of small overgrowths of calcite. In this study, we have made similar experiments in order to determine the absolute REE partition coefficients between calcite and aqueous solution, and have evaluated partition coefficients between calcite and seawater. Calcite-supersaturated solution doped with REEs was constantly pumped into a reactor to form calcite overgrowths on the seeds under CO2 + N2 gas. Absolute values of REE partition coefficients, Kd(REE)=(XREE/XCa)calcite/([REE,tot.]/[Ca])solution, have been obtained. The patterns of Kd(REE) show convex tetrad effects and Y/Ho fractionation, which is consistent with our earlier work. We have calculated REE abundances in Permian seawater using the partition coefficients corrected to seawater compositions and REE analyses of Permian seamount-type limestones. All the estimated REE abundances in Permian seawater indicate concave tetrad effects, large Y/Ho fractionation and negative Ce and Eu anomalies in their chondrite-normalized patterns, which are quite similar to those for present-day seawater. The estimated REE abundances in Permian seawater, however, are lower than those in present-day seawater by approximately one order of magnitude. This suggests that significant parts of marine limestones could not incorporate seawater REEs after the permeability and porosity of the original biogenic carbonate sediments with low-REE contents had been reduced to certain critical levels.

Toxicokinetic parameters of toluene in the rat and guinea pig: a comparative study

Toluene is the most widely used industrial solvent. It has been shown to cause cochlear disruptions in rats but markedly less ototoxic effects in guinea pigs. Susceptibility to the ototoxic properties of toluene is, therefore, species specific. In recent publications, an important difference in the solvent concentration in blood has been identified when rats and guinea pigs were exposed in strictly identical experimental conditions. Solvent concentrations in blood were greater in rats than in guinea pigs. The present studies were designed to compare blood affinity and toxicokinetic parameters of toluene in an attempt to understand the susceptibility differences in both species. The in vitro experiment, in which the headspace concentration of toluene was measured within a sealed vial containing blood, highlighted the greater toluene partition coefficient in rat than in guinea pig blood. The in vivo experiment showed that 10 min after a single intravenous administration of 28 μL of toluene, the solvent concentration is approximately two-fold lower in guinea pig than in rat blood. Based on the toxicokinetic parameters of toluene and on the relative partition coefficient of toluene in blood, it seems plausible that guinea pigs are not susceptible to organic solvents because the solvent concentration in blood does not reach the concentration required to induce permanent damage. Attempts to explain differences of vulnerability between the rat and guinea pig are addressed in the present paper.

Assessment of genotoxicity of benzidine and its structural analogues to human lymphocytes using comet assay.

Benzidine (BZ) and its six structural analogues (2-aminobiphenyl [2-ABP], 4-aminobiphenyl [4-ABP], 3,3'-diaminobenzidine [DABZ], 3,3'-dichlorobenzidine [DCBZ] 3,3'-dimethoxybenzidine [DEBZ], and 3,3'-dimthylbenzidine [DMBZ]) were examined for DNA damage in human lymphocytes using the alkaline comet assay. All the tested compounds showed a distinct disparity in their respective DNA-damaging capacities with an order of DABZ > BZ > DCBZ > 2-ABP > DEBZ > 4-ABP > DMBZ when lymphocytes were exposed to these chemicals for 2 h. Results show that the DNA-damaging effects of these compounds had no bearing on some physicochemical parameters including oxidation potentials, the energy differences between the lowest unoccupied molecular orbital and the highest occupied molecular orbital, ionization potentials, dipole moment, and relative partition coefficient. On the other hand, the free radical scavengers, including catalase, SOD, BHT, EDTA, and histidine exerted varying degrees of inhibitory effects on the DNA damage caused by benzidine. This suggests that genotoxicity in lymphocytes caused by benzidine proceeded via a reactive oxygen species (ROS)-mediated mechanism.

Optical sensor for amine vapors based on dimer-monomer equilibrium of indium(III) octaethylporphyrin in a polymeric film.

A novel transduction chemistry for the development of a polymer film-based optical sensor that responds reversibly to gas-phase amine species at sub-ppm levels is described. The sensor is based on the equilibrium of a indium(III) octaethylporphyrin hydroxide ion-bridged dimer species with corresponding monomeric porphyrins within a thin poly(vinyl chloride) film as a function of the level of volatile amine in the surrounding gas phase. The presence of amines causes the dimeric species to be converted to monomer via the ligation of the amine with the In(III) center of the porphyrin structure. This yields a significant change in the visible absorption spectrum of the film, with a decrease in the intensity of the Soret band corresponding to the dimer (lambdamax = 390 nm) and a concomitant increase in the Soret band for the monomer lambdamax = 406-408 nm). Response to different amines is based on their relative partition coefficient into the polymer film and their strength of axial ligation reactions, with a selectivity pattern of 1-butylamine > 1-propylamine > pyridine > triethylamine > ethylamine > methylamine > diethylamine > tert-butylamine > ammonia. It is further shown that a significant concentration of dimeric species within the polymer film can only be achieved if appropriate amounts of lipophilic anionic sites are also incorporated into the polymer in the form of a tetraphenylborate derivative and the resulting film is equilibrated briefly with water prior to gas-phase measurements. With optimized film compositions, 1-butylamine can be detected in the gas phase to levels approaching 0.1 ppm, while less lipophilic ammonia can be monitored down to 10 ppm, with fully reversible responses to each species. A simple mathematical model for the response of the amine sensor is presented and shown to predict the optical behavior observed.