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Ultrasound assisted emulsification microextraction of phenolic preservatives in water
(Elsevier, 2009) Elefteria Psillakis; Juan C. Garcia-Monteagudo; Maria Llomparta; Jorge Regueiro; Carmen Garcia-Jaresa
Simultaneous ultrasound-assisted emulsification–microextraction (USAEME) and derivatization combined with gas chromatography–tandem mass spectrometry (GC–MS/MS) is proposed for the first time for the analysis of parabens, triclosan and related phenols in water samples. In situ acetylation was successfully applied for the derivatization of target compounds with high efficiency using non-expensive reagents. The proposed method exhibits many advantages such as simplicity, efficiency, low cost, and minimum solvent consumption. In addition, the whole analytical process, including sample preparation and determination, is performed in only 20 min. A multifactorial experimental design was employed to study and optimize the main variables potentially affecting the microextraction and derivatization processes (extraction solvent, phase ratio, sodium chloride concentration, extraction time, and acetic anhydride volume). The performance of the method was studied in terms of accuracy, linearity, precision, and enrichment factor. Quantitative recoveries (≥85%)were obtained for all target compounds, and method precisionwas also satisfactory (RSD≤13%) even for complex samples. Enrichment factors ranging from 100 to 200were obtained, allowing achieving limits of detection at the low picogram per millilitre for most of the target compounds.
Transport of pseudomonas putida in a 3-D bench scale experimental aquifer
(2012) Chrysikopoulos Constantinos; Χρυσικοπουλος Κωνσταντινος; Vasileios E. Katzourakis; Ioanna A. Vasiliadou; Vasiliki I. Syngouna
This study is focused on the transport of Pseudomonas (P.) putida bacterial cells in a 3-D model aquifer. The pilot-scale aquifer consisted of a rectangular glass tank with internal dimensions: 120 cm length, 48 cm width, and 50 cm height, carefully packed with well-characterized quartz sand. The P. putida decay was adequately represented by a firstorder model. Transport experiments with a conservative tracer and P. putida were conducted to characterize the aquifer and to investigate the bacterial behavior during transport in water saturated porous media. A 3-D, finite-difference numerical model for bacterial transport in saturated, homogeneous porous media was developed and was used to successfully fit the experimental data. Furthermore, theoretical interaction energy calculations suggested that the extended-DLVO theory seems to predict bacteria attachment onto the aquifer sand better than the classical DLVO theory.
Vacuum-assisted headspace solid phase microextraction of polycyclic aromatic hydrocarbons in solid samples
(Elsevier, 2015) Elefteria Psillakis; Nicolas Kalogerakis; Evangelia Yiantzi
For the first time, Vacuum Assisted Headspace Solid Phase Microextraction (Vac-HSSPME) is used for the recovery of polycyclic aromatic hydrocarbons (PAHs) from solid matrices. The procedure was investigated both theoretically and experimentally. According to the theory, reducing the total pressure increases the vapor flux of chemicals at the soil surface, and hence improves HSSPME extraction kinetics. Vac-HSSPME sampling could be further enhanced by adding water as a modifier and creating a slurry mixture. For these soil-water mixtures, reduced pressure conditions may increase the volatilization rates of compounds with a low KH present in the aqueous phase of the slurry mixture and result in a faster HSSPME extraction process. Nevertheless, analyte desorption from soil to water may become a rate-limiting step when significant depletion of the aqueous analyte concentration takes place during Vac-HSSPME. Sand samples spiked with PAHs were used as simple solid matrices and the effect of different experimental parameters was investigated (extraction temperature, modifiers and extraction time). Vac-HSSPME sampling of dry spiked sand samples provided the first experimental evidence of the positive combined effect of reduced pressure and temperature on HSSPME. Although adding 2 mL of water as a modifier improved Vac-HSSPME, humidity decreased the amount of naphthalene extracted at equilibrium as well as impaired extraction of all analytes at elevated sampling temperatures. Within short HSSPME sampling times and under mild sampling temperatures, Vac-HSSPME yielded linear calibration curves in the range of 1–400 ng g−1 and, with the exception of fluorene, regression coefficients were found higher than 0.99. The limits of detection for spiked sand samples ranged from 0.003 to 0.233 ng g−1 and repeatability from 4.3 to 10 %. Finally, the amount of PAHs extracted from spiked soil samples was smaller compared to spiked sand samples, confirming that soil could bind target analytes more strongly and thus decrease the readily available fraction of target analytes.
Rapid determination of octanol-water partition coefficient using vortex-sssisted liquid-liquid microextraction
(Elsevier, 2014) Elefteria Psillakis; Antonio Canals; Konstantina Tyrovola; Anna Mastromichali; Iván P Román
Abstract Vortex-assisted liquid–liquid microextraction (VALLME) coupled with high- performance liquid chromatography (HPLC) is proposed here for the rapid determination of octanol–water partitioning coefficients (K ow). VALLME uses vortex agitation, a mild emulsification procedure, to disperse microvolumes of octanol in the aqueous phase thus increasing the interfacial contact area and ensuring faster partitioning rates. With VALLME, 2 min were enough to achieve equilibrium conditions between the octanolic and aqueous .
Boronic acid dendrimer receptor modified nanofibrillar cellulose membranes
(Royal Society of Chemistry, 2010) Elefteria Psillakis; chael J. Bonn; Matthew Helton; Karen J. Edler
Cellulose nanofibrils from sisal of typically 4–5 nm diameter and ca. 250 100 nm length are reconstituted into thin films of ca. 6 mm thickness (or thicker freestanding films). Pure cellulose and cellulose composite films are obtained in a solvent evaporation process. A boronic acid appended dendrimer is embedded as a receptor in the nanofibrillar cellulose membrane. The number of boronic acid binding sites is controlled by varying the dendrimer content. The electrochemical and spectrophotometric properties of the nanocomposite membrane are investigated using the probe molecule alizarin red S. Pure cellulose membranes inhibit access to the electrode. However, the presence of boronic acid receptor sites allows accumulation of alizarin red S with a Langmuirian binding constant of ca. 6000 1000 M1. The 2-electron 2-proton reduction of immobilized alizarin red S is shown to occur in a ca. 60 nm zone close to the electrode surface. With a boronic acid dendrimer modified nanofibrillar cellulose composition of 96 wt% cellulose and 4 wt% boronic acid dendrimer, the analytical range for alizarin red S in aqueous acetate buffer pH 3 is approximately 10 mM to 1 mM.
Fast screening of perfluorooctane sulfonate in water using vortex-assisted liquid-liquid microextraction coupled to liquid chromatography-mass spectrometry
(Elsevier, 2011) Elefteria Psillakis; Antonio Canals; Konstantina Tyrovola; Iván P. Román; Aikaterini Papadopoulou
Fast screening of trace amounts of the perfluorooctane sulfonate anion (PFOS) in water samples was performed following a simple, fast and efficient sample preparation procedure based on vortex-assisted liquid–liquid microextraction (VALLME) prior to liquid chromatography–mass spectrometry. VALLME initially uses vortex agitation, a mild emulsification procedure to disperse microvolumes of octanol, a low density extractant solvent, in the aqueous sample. Microextraction under equilibrium conditions is thus achieved within few minutes. Subsequently, centrifugation separates the two phases and restores the initial microdrop shape of the octanol acceptor phase, which can be collected and used for liquid chromatography–single quadrupole mass spectrometry analysis. Several experimental parameters were controlled and the optimum conditions found were: 50L of octanol as the extractant phase; 20mL aqueous donor samples (pH = 2); a 2 min vortex extraction time with the vortex agitator set at a 2500rpm rotational speed; no ionic strength adjustment. Centrifugation for 2 min at 3500rpm yielded separation of the two phases throughout this study. Enhanced extraction efficiencies were observed at low pH which was likely due to enhanced electrostatic interaction between the negatively PFOS molecules and the positively charged octanol/water interface. The effect of pH was reduced in the presence of sodium chloride, likely due to electrical double layer compression. The linear response range for PFOS was from 5 to 500 ng L−1 (coefficient of determination, r2, 0.997) and the relative standard deviation for aqueous solutions containing 10 and 500 ng L−1 PFOS were 7.4% and 6.5%, respectively. The limit of detection was 1.6 ng L−1 with an enrichment factor of approximately 250. Analysis of spiked tap, river and well water samples revealed that matrix did not affect extraction
Anion-templated assembly of a supramolecular cage complex
(Wiley‐vch verlag gmbh, 1998) Elefteria Psillakis; Michael D Ward; Jon A McCleverty; John C Jeffery; Charles‐Antoine Carraz; Karen LV Mann; James S Fleming
THe templating effect of the tetrafluoroborate ion leads to assembly of four CoII ions and six bridging ligands around this anion to give a tetrahedral complex with a bridging ligand along each edge and the anion trapped in the central cavity (shown below). Surprisingly under identical conditions but with NiII a simpler dinuclear complex forms.
Contaminant transport in a variable aperture fracture in the presence of monodisperse colloids
(2005) Chrysikopoulos Constantinos; Χρυσικοπουλος Κωνσταντινος; Scott C. James; Tanya K. Bilezikjian
A quasi-three-dimensional particle tracking model is developed to characterize the spatial and temporal effects of advection, molecular diffusion, Taylor dispersion, fracture wall deposition, matrix diffusion, and co-transport processes on two discrete plumes (suspended monodisperse or polydisperse colloids and dissolved contaminants) flowing through a variable aperture fracture situated in a porous medium. Contaminants travel by advection and diffusion and may sorb onto fracture walls and colloid particles, as well as diffuse into and sorb onto the surrounding porous rock matrix. A kinetic isotherm describes contaminant sorption onto colloids and sorbed contaminants assume the unique transport properties of colloids. Sorption of the contaminants that have diffused into the matrix is governed by a first-order kinetic reaction. Colloids travel by advection and diffusion and may attach onto fracture walls; however, they do not penetrate the rock matrix. A probabilistic form of the Boltzmann law describes filtration of both colloids and contaminants on fracture walls. Ensemble-averaged breakthrough curves of many fracture realizations are used to compare arrival times of colloid and contaminant plumes at the fracture outlet. Results show that the presence of colloids enhances contaminant transport (decreased residence times) while matrix diffusion and sorption onto fracture walls retard the transport of contaminants. Model simulations with the polydisperse colloids show increased effects of cotransport processes.
Transport of human adenoviruses in water saturated laboratory columns
(2015) Chrysikopoulos Constantinos; Χρυσικοπουλος Κωνσταντινος; P. Kokkinos; V. I. Syngouna; M. A. Tselepi; M. Bellou; Apostolos Vantarakis
Groundwatermay be contaminated with infective human enteric viruses from various wastewater discharges, sanitary landfills, septic tanks, agricultural practices, and artificial groundwater recharge. Coliphages have been widely used as surrogates of enteric viruses, because they share many fundamental properties and features.Although a large number of studies focusing on various factors (i.e. pore water solution chemistry, fluid velocity, moisture content, temperature, and grain size) that affect biocolloid (bacteria, viruses) transport have been published over the past two decades, little attention has been given toward human adenoviruses (hAdVs). The main objective of this study was to evaluate the effect of pore water velocity on hAdV transport in water saturated laboratory- scale columns packed with glass beads. The effects of pore water velocity on virus transport and retention in porous media was examined at three pore water velocities (0.39, 0.75, and 1.22 cm/min). The results indicated that all estimated averagemass recovery values forhAdVwere lower than those of coliphages, which were previously reported in the literature by others for experiments conducted under similar experimental conditions.
Degradation of PAHs by high frequency ultrasound
(Elsevier, 2011) Chrysikopoulos Constantinos; Χρυσικοπουλος Κωνσταντινος; Hrissi K. Karapanagioti; Ioannis D. Manariotis
Polycyclic aromatic hydrocarbons (PAHs) are persistent organic compounds, which have been reported in the literature to efficiently degrade at low (e.g. 20 kHz) and moderate (e.g. 506 kHz) ultrasound frequencies. The present study focuses on degradation of naphthalene, phenanthrene, and pyrene by ultrasound at three different relatively high frequencies (i.e. 582, 862, and 1142 kHz). The experimental results indicate that for all three frequencies and power inputs 133 W phenanthrene degrades to concentrations lower than our experimental detection limit (<1 mg/L). Phenanthrene degrades significantly faster at 582 kHz than at 862 and 1142 kHz. For all three frequencies, the degradation rates per unit mass are similar for naphthalene and phenanthrene and lower for pyrene. Furthermore, naphthalene degradation requires less energy than phenanthrene, which requires less energy than pyrene under the same conditions. No hexane-extractable metabolites were identified in the solutions.
Experimental investigation of acoustically enhanced colloid transport in water-saturated packed columns
(2007) Chrysikopoulos Constantinos; Χρυσικοπουλος Κωνσταντινος; J. Matthew Thomas
The effects of acoustic wave propagation on the transport of colloids in saturated porous media were investigated by injecting Uranine (conservative tracer) as well as blue and red polystyrene microspheres (colloids of different diameters; 0.10 and 0.028 μm, respectively) into a column packed with glass beads. Experiments were conducted by maintaining the acoustic pressure at the influent at 23.0 kPa with acoustic frequencies ranging from 30 to 150 Hz. The experimental results suggested that colloid size did not affect the forward and reverse attachment rate coefficients. The acoustic pressure caused an increase in the effective interstitial velocity at all frequencies for the conservative tracer and colloids of both sizes, with maximum increase at 30 Hz. Furthermore, acoustics enhanced the dispersion process at all frequencies, with a maximum at 30 Hz. © 2007 Elsevier Inc. All rights reserved.
Effect of gravity on colloid transport through water-saturated columns packed with glass beads: modeling and experiments
(2014) Chrysikopoulos Constantinos; Χρυσικοπουλος Κωνσταντινος; Vasiliki I. Syngouna
The role of gravitational force on colloid transport in water-saturated columns packed with glass beads was investigated. Transport experiments were performed with colloids (clays: kaolinite KGa-1b, montmorillonite STx-1b). The packed columns were placed in various orientations (horizontal, vertical, and diagonal) and a steady flow rate of Q = 1.5 mL/min was applied in both up-flow and down-flow modes. All experiments were conducted under electrostatically unfavorable conditions. The experimental data were fitted with a newly developed, analytical, one-dimensional, colloid transport model. The effect of gravity is incorporated in the mathematical model by combining the interstitial velocity (advection) with the settling velocity (gravity effect). The results revealed that flow direction influences colloid transport in porous media. The rate of particle deposition was shown to be greater for up-flow than for down-flow direction, suggesting that gravity was a significant driving force for colloid deposition
Modeling of contaminant transport resulting from dissolution of nonaqueous phase liquid pools in saturated porous media
(1994) Evangelos A. Voudrias; Marios M. Fyrillas
A mathematical model for transient contaminant transport resulting from the dissolution of a single component nonaqueous phase liquid (NAPL) pool in two-dimensional, saturated, homogeneous porous media was developed. An analytical solution was derived for a semi-infinite medium under local equilibrium conditions accounting for solvent decay. The solution was obtained by taking Laplace transforms to the equations with respect to time and Fourier transforms with respect to the longitudinal spatial coordinate. The analytical solution is given in terms of a single integral which is easily determined by numerical integration techniques. The model is applicable to both denser and lighter than water NAPL pools. The model successfully simulated responses of a 1,1,2- trichloroethane (TCA) pool at the bottom of a two-dimensional porous medium under controlled laboratory conditions.
Modeling the transport of contaminants originating from the dissolution of DNAPL pools in aquifers in the presence of dissolved humic substances
(1999) Chrysikopoulos Constantinos; Χρυσικοπουλος Κωνσταντινος; Michael E. Tatalovich; Kenneth Y. Lee
A two-dimensional finite difference numerical model was developed to describe the transport of dissolved organics originating from nonaqueous phase liquid (NAPL) pool dissolution in saturated porous media in the presence of dissolved humic substances. A rectangular NAPL pool was considered in a homogeneous porous medium with unidirectional interstitial groundwater velocity. It was assumed that dissolved humic substances and aqueous phase contaminants may sorb onto the solid matrix under local equilibrium conditions. The contaminant in the aqueous phase may undergo first-order decay. Also, the dissolved contaminant may sorb onto humic substances. The transport properties of dissolved humic substances are assumed to be unaffected by sorbing contaminants, because dissolved humic macromolecules are much larger than dissolved contaminants and sorp- tion of nonpolar contaminants onto humic substances do not affect the overall surface charge of humic substances. The sorption characteristics of dissolved humic substances onto clean sand were determined from column experiments. An effective local mass transfer rate coefficient accounting for the presence of dissolved humic substances was developed. Model simulations indicate that dissolved humic substances substantially increase NAPL pool dissolution, and consequently reduce the required pump-and-treat aquifer remediation time.
An efficient particle tracking equation with specified spatial step for the solution of the diffusion equation
(2001) Chrysikopoulos Constantinos; Χρυσικοπουλος Κωνσταντινος; ScottC.James
The traditional di(usive particle tracking equation provides an updated particle location as a function of its previous location and molecular di(usion coe cient while maintaining a constant time step. A smaller time step yields an increasingly accurate, yet more computationally demanding solution. Selection of this time step becomes an important consideration and, depending on the complexity of the problem, a single optimum value may not exist. The characteristics of the system under consideration may be such that a constant time step may yield solutions with insu cient accuracy in some portions of the domain and excess computation time for others. In this work, new particle tracking equations speci%cally designed for the solution of problems associated with di(usion processes in one, two, and three dimensions are presented. Instead of a constant time step, the proposed equations employ a constant spatial step. Using a traditional particle tracking algorithm, the travel time necessary for a particle with a di(usion coe cient inversely proportional to its diameter to achieve a pre-speci%ed distance was determined. Because the size of a particle a(ects how it di(uses in a quiescent 8uid, it is expected that two di(erently sized particles would require di(erent travel times to move a given distance. The probability densities of travel times for plumes of monodisperse particles were consistently found to be log-normal in shape. The parameters describing this log-normal distribution, i.e., mean and standard deviation, are functions of the distance speci%ed for travel and the di(usion coe cient of the particles. Thus, a random number selected from this distribution approximates the time required for a given particle to travel a speci%ed distance. The new equations are straightforward and may be easily incorporated into appropriate particle tracking algorithms. In addition, the new particle tracking equations are as accurate and often more computationally e cient than the traditional particle tracking equation
One-dimensional virus transport in homogeneous porous media with time-dependent distribution coefficient
(1996) Chrysikopoulos Constantinos; Χρυσικοπουλος Κωνσταντινος; Youn Sim
A stochastic model for one-dimensional virus transport in homogeneous, saturated, semi-infinite porous media is developed. The model accounts for first-order inactivation of liquid-phase and adsorbed viruses with different inactivation rate constants, and time-dependent distribution coefficient. It is hypothesized that the virus adsorption process is described by a local equilibrium expression with a stochastic time-dependent distribution coefficient. A closed form analytical solution is obtained by the method of small perturbation or first-order approximation for a semi-infinite porous medium with a flux-type inlet boundary condition. The results from several simulations indicate that a time-dependent distribution coefficient results in an enhanced spreading of the liquid-phase virus concentration.
Analytical solutions for one-dimensional colloid transport in saturated fractures
(1994) Chrysikopoulos Constantinos; Χρυσικοπουλος Κωνσταντινος; Assem Abdel-Salam
Closed-form analytical solutions for colloid transport in single rock fractures with and without colloid penetration into the rock matrix are derived for constant concentration as well as constant flux boundary conditions. A single fracture is idealized as two semi-infinite parallel plates. It is assumed that colloidal particles undergo irreversible deposition onto fracture surfaces and may penetrate into the rock matrix, and deposit irreversibly onto rock matrix solid surfaces. The solutions are obtained by taking Laplace transforms to the governing transport equations and boundary conditions with respect to time and space. For the case of no colloid penetration into the rock matrix, the solutions are expressed in terms of exponentials and complimentary error functions; whereas, for the case of colloid penetration into the rock matrix, the solutions are expressed in terms of convolution integrals and modified Bessel functions. The impact of the model parameters on colloid transport is examined. The results from several simulations indicate that liquid-phase as well as deposited colloid concentrations in the fracture are sensitive to the fracture surface deposition coefficient, the fracture aperture, and the Brownian diffusion coefficient for colloidal particles penetrating the rock matrix. Furthermore, it is shown that the differences between the two boundary conditions investigated are minimized at dominant advective transport conditions. The constant concentration condition overestimates liquid-phase colloid concentrations, whereas the constant flux condition leads to conservation of mass.
Comparison of pah levels and sources in pine needles from Portugal, Spain, and Greece
(Taylor & Francis Group, 2012) Elefteria Psillaki; Arminda Alves; Damià Barceló; Nuno Ratola; José Manuel Amigo; Sílvia Lacorte
The main objective of this work was to assess and compare the levels, patterns, and sources of contamination of 16 polycyclic aromatic hydrocarbons (PAHs) between Portugal, Spain, and Greece (in the island of Crete). A total of 9 sampling sites were chosen (4 in urban and 5 in non-urban areas) in each country and pine needles from the Pinus pinea L. species were collected. Although the mean total PAH levels was similar in the three countries (279 ± 236 ng g−1 for Portugal, 294 ± 258 ng g−1 for Spain, 301 ± 253 ng g−1 for Greece, all dry weight) and, in general, 3-ring and 4-ring PAHs were predominant (being phenanthrene consistently the most abundant), there were some visible differences in the aromatic ring patterns and possible sources between the three regions. Source apportionment was done using PAH ratios (Phen/Ant and Flt/Pyr crossplots) and reflected mixed petrogenic and pyrogenic sources. Furthermore, Principal Component Analysis (PCA) clearly separated the urban and the non-urban sites and all three countries, which reinforces that the sources of contaminations vary in each case and the suitability of pine needles for trans-boundary biomonitoring of PAHs.
Degradation of sodium dodecylbenzene sulfonate in water by ultrasonic irradiation
(Elsevier, 2004) Manousaki Eleni; Μανουσακη Ελενη; Psyllaki Eleftheria; Ψυλλακη Ελευθερια; Kalogerakis Nikos; Καλογερακης Νικος; Mantzavinos Dionysis; Μαντζαβινος Διονυσης
The potential of using ultrasonic irradiation for the removal of sodium dodecylbenzene sulfonate (SDBS) from aqueous solutions has been investigated. Experiments were performed at initial concentrations of 15, 30 and 100 mgl1, ultrasonic frequencies of 20 and 80 kHz, applied power values of 45, 75 and 150W and liquid bulk temperatures of 20, 40 and 60 1C. At the conditions in question, SDBS conversion was found to decrease with increasing temperature and initialsol ute concentration and decreasing power and frequency. Investigations using the radicalscavengers 1-butanol and KBr revealed that SDBS degradation proceeds through radical reactions occurring predominately at the bubble–liquid interface and, to a lesser extent, in the liquid bulk. Addition of NaCl or H2O2 had little or even an adverse effect on SDBS conversion. Conversely, addition of Fe2+ either alone or in conjunction with H2O2 (Fenton reagent) had a positive effect on degradation. Finally, shake flask tests with activated sludge were performed to assess the aerobic biodegradability before and after sonochemical treatment. At the conditions under consideration, the use of ultrasound enhanced the aerobic degradability of the substrate in question
Lanthanide complexes of the hexadentate n-donor podand tris[3-(2-pyridyl)pyrazolyl]hydroborate: Solid-State and solution properties
(1997) Elefteria Psillakis; Peter L Jones; Angelo J Amoroso; Jon A McCleverty; John C Jeffery; Michael D Ward; Leigh H Rees
The hexadentate N6-donor podand tris[3-(2-pyridyl)pyrazolyl]hydroborate (TpPy) contains 2-pyridyl fragments attached to the pyrazolyl C3-positions such that each arm is a bidentate chelate. Three series of lanthanide(III) complexes were prepared: [M(TpPy)(MeOH)2F][PF6] (series A), [M(TpPy)(NO3)2] (series B), and [M(TpPy)2][BPh4] (series C). Crystallographic studies showed that series A and B have a 1:1 metal:TpPy ratio, with the metal ion lying within the podand cavity and the remaining coordination sites occupied by solvent molecules and/or counterions to give 9-coordination (A, with one fluoride and two methanol ligands) or 10-coordination (B, with two bidentate nitrate ligands). The C complexes were prepared in the absence of any coordinating anions and have a 1:2 metal:TpPy ratio with an unusual icosahedral geometry arising from coordination of the 12 nitrogen donors from two interleaved podands. Conductivity studies on the B complexes show that in water the nitrates dissociate to give [M(TpPy)(H2O)q](NO3)2; the relaxivity of [Gd(TpPy)(NO3)2] in water is 4.4 s-1 mM-1, a value comparable to those of clinically useful MRI contrast enhancement agents. Comparison of emission lifetimes of [M(TpPy)(NO3)2] (M = Eu, Tb) in H2O/D2O and CH3OH/CD3OD give values for q, the number of coordinated solvent molecules, of 3.6 (water) and 2.6 (methanol). The C complex [Tb(TpPy)2][BPh4] also has q = 2.6 in methanol, suggesting that partial ligand dissociation allows access of solvent molecules to the metal coordination sphere.

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