Intermittent rivers, which do not flow all year round, have biophysical functioning specificities which need to be considered when defining management policies, even more so in the current context of ...global change. However, in Europe intermittent rivers benefit from the same regulations as permanent rivers, which undoubtedly leads to their degradation. This paper aims to identify (1) how perceptions and values of intermittent rivers interact with their management and (2) determine whether the prospect of climate change leads the stakeholders to questioning their perceptions and values of intermittent rivers and the way we should manage them. Semi-structured interviews and mental mapping exercises were conducted with 28 various stakeholders (elected officials, fishers, river managers, and residents), all of whom lived along the French intermittent Albarine River. Qualitative analysis of the discourses and maps confirms strong interactions between the perceptions and values related to intermittent rivers and their management. The results highlight social devaluation of the intermittent section in terms of aesthetics, recreation, and biological values. They also point to the role of power plays between river managers and fishers, in the prioritization of management actions that favor perennial sections to the detriment of intermittent ones. These dynamics of devaluing and discarding intermittent sections or rivers from management plans are all the more alarming as there is little propensity among river stakeholders to think about the future of these intermittent rivers and their value in the context of climate change, where the prevalence of intermittent rivers is likely to increase dramatically.
•Stakeholders devalue intermittent rivers (IR) compared to perennial rivers.•Devaluation is due to aesthetic, recreational and biological reasons.•Devaluation leads to IR or IR sections being excluded from management plans.•Stakeholders do not consider a future with increased intermittency with climate change.
The improvement of separation efficiency for protein analysis in capillary electrophoresis (CE) is a challenging topic in which protein adsorption onto the capillary wall plays a crucial role. In ...this work, a simple method allowing the quantification of the adsorption of proteins onto the coated or untreated inner surface of the fused silica capillary was developed based on the determination of the retention factor by measuring separation efficiency of individual proteins at different separation voltages (i.e., different linear velocities). This approach was applied to the quantification of the residual adsorption of four test proteins on five-layer polyelectrolyte coatings and bare fused silica capillary. It allows to get a fair ranking of the coating performances toward protein adsorption, whatever their apparent electrophoretic mobilities (migration times) are. Due to the existence of (even low) residual adsorption, the electrophoretic operating conditions (electric field, capillary length, and internal diameter) can be optimized to improve the separation performances resulting in experimental separation efficiency up to ∼600 000 plates.m–1 in conditions compatible with MS coupling. This approach represents a crucial step in the course to get antifouling coatings for protein separation in CE. It can be used for the evaluation and ranking of virtually any coating (neutral or charged) in CE.
The inline coupling of capillary electrophoresis (CE) to Taylor dispersion analysis was used for the characterization of polyelectrolyte complexes. The charge stoichiometry and the hydrodynamic radii ...of the two polyelectrolyte constituents were determined in a fully automated single run using standard commercial CE apparatus with a single detection point. The proposed methodology utilizes unusual high ionic strength (1.3 M) background electrolyte to obtain the dissociation and electrophoretic separation of polyelectrolyte constituents. Such highly saline conditions in combination with neutrally coated capillary were found to avoid any polyelectrolyte interactions onto the capillary surface. This innovative methodology should greatly contribute to simplify and accelerate the characterization of polyelectrolyte complexes or polyplexes.
Quantitative analysis in capillary electrophoresis based on time-scale electropherograms generally uses time-corrected peak areas to account for the differences in apparent velocities between ...solutes. However, it could be convenient and much more relevant to change the time-scale electropherograms into mass relative distribution of the effective mobility or any other characteristic parameter (molar mass, chemical composition, charge density, ...). In this study, the theoretical background required to perform the variable change on the electropherogram was developed with an emphasis on the fact that both x and y axes should be changed when the time scale electropherograms are modified to get the distributions. Applications to the characterization of polymers and copolymers by different modes of capillary electrophoresis (CE) are presented, including the molar mass distribution of poly-l-lysine oligomers by capillary gel electrophoresis (CGE), molar mass distribution of end-charged poly-l-alanine by free solution CE, molar mass distribution of evenly charged polyelectrolytes by CGE, and charge density distribution of variously charged polyelectrolytes by free solution CE.
•Non-gel capillary electrophoresis was optimized for inter-generation DGL separation.•SMIL-based capillary coatings with a final PEGylated polycation layer were prepared.•Fine tuning of the EOF ...improved the intergeneration separation of DGL.•Polydispersity indexes and inter-generation purity of DGL were determined.
Dendrigraft poly(L-lysine) (DGL) constitutes a promising dendritic–like drug vehicle with high biocompatibility and straightforward access via ring-opening polymerization of N-carboxyanhydride in water. The characterization of the different generations of DGL is however challenging due to their heterogeneity in molar mass and branching ratio. In this work, free solution capillary electrophoresis was used to perform selective separation of the three first generations of DGL, and optimized conditions were developed to maximize inter-generation resolution. To reduce solute adsorption on the capillary wall, successive multiple ionic polymer layer coatings terminated with a polycation were deposited onto the inner wall surface. PEGylated polycation was also used as the last layer for the control of the electroosmotic flow (EOF), depending on the PEGylation degree and the methyl-polyethylene glycol (mPEG) chain length. 1 kDa mPEG chains and low grafting densities were found to be the best experimental conditions for a fine tuning of the EOF leading to high peak resolution. Molar mass polydispersity and polydispersity in effective electrophoretic mobility were successfully determined for the three first generations of DGL.
Taylor dispersion analysis (TDA) is a simple and absolute method to determine the hydrodynamic radius of solutes that respond to UV or fluorescence detections. To broaden the application range of ...TDA, it is necessary to develop new detection modes. This study aims to study capacitively coupled contactless conductivity detector (C4D) for the analysis of charged macromolecules. The detection sensitivities and hydrodynamic radii were compared for a C4D detector and a UV detector on positively or negatively charged polymers responding both to UV and C4D (poly-L-lysine and poly(acrylamide-co-2-acrylamido-1-methyl-propanesulfonate). The influence of the composition of the background electrolyte on the detection sensitivity has been studied and optimized for C4D detection. The influence of the molar mass and of the polymer chemical charge density on the C4D and UV sensitivities of detection have been investigated based on well-characterized copolymers samples of different molar masses and charge densities. The advantages and disadvantages compared to UV detection, as well as the range of applicability of C4D detection in TDA were identified. C4D detection can be an alternative method for sizing charged polymers of reasonable molar mass (typically below 105 g mol−1) that do not absorb in UV. A decline in the sensitivity of detection in C4D was observed for higher molar masses.
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•C4D detector can be used for TDA of charged polymers of low to moderate molar mass.•C4D response increases with higher polymer charge up to counterion condensation.•C4D response drops above a certain molar mass (about 105 g mol−1).•Small ions present in the sample can be a limitation for C4D detection in TDA.•Application of TDA-C4D to the sizing of PAA 37000 g mol−1 is demonstrated.
Taylor dispersion analysis is an absolute and straightforward characterization method that allows determining the diffusion coefficient, or equivalently the hydrodynamic radius, from angstroms to ...submicron size range. In this work, we investigated the use of the Constrained Regularized Linear Inversion approach as a new data processing method to extract the probability density functions of the diffusion coefficient (or hydrodynamic radius) from experimental taylorgrams. This new approach can be applied to arbitrary polydisperse samples and gives access to the whole diffusion coefficient distributions, thereby significantly enhancing the potentiality of Taylor dispersion analysis. The method was successfully applied to both simulated and real experimental data for solutions of moderately polydisperse polymers and their binary and ternary mixtures. Distributions of diffusion coefficients obtained by this method were favorably compared with those derived from size exclusion chromatography. The influence of the noise of the simulated taylorgrams on the data processing is discussed. Finally, we discuss the ability of the method to correctly resolve bimodal distributions as a function of the relative separation between the two constituent species.
Taylor dispersion analysis (TDA) is an absolute method (no calibration needed) for the determination of the molecular diffusion coefficient (D) based on the band broadening of a solute in a laminar ...flow. TDA is virtually applicable to any solute with size ranging from angstrom to sub-micrometer. The higher sizing limit is restricted by the occurrence of possibly two regimes: convective and hydrodynamic chromatography (HDC) regimes, which have different physical origins that should not be confused. This work aims at clearly defining the experimental conditions for which these two regimes can play a role, alone or concomitantly. It also calculates the relative error on D due to the HDC regime according to the solute to capillary size ratio. It is demonstrated in this work that HDC does not significantly affect the TDA measurement as long as the hydrodynamic radius of the solute is lower than 0.0051 times the capillary radius. Experimental illustrations of the occurrence of the two regimes are given taking polystyrene nanoparticles as model solutes. Finally, application of TDA to the sizing of large real-life solutes is proposed, taking cubosomes as new drug nanocarriers of potential interest for drug delivery purposes.
The interaction between two hydrophilic polyelectrolytes of opposite charges was investigated using poly(l-lysine) (PLL) as the polycation and a library of copolymers of acrylamide and ...2-acrylamido-2-methyl-1-propanesulfonate (P(AM-co-AMPS)) with various chemical charge densities as polyanions. The formation of polyelectrolyte complexes (PECs) was comparatively studied by varying different parameters, such as the mixing order, the P(AM-co-AMPS) chemical charge density and the initial polycation to polyanion molar ratio. PECs were then characterized in terms of charge stoichiometry and of stability toward ionic strength. The results showed a strong dependency of precipitated PEC stoichiometry on the P(AM-co-AMPS) chemical charge density and the initial polycation to polyanion molar ratio. In contrast, PEC stoichiometry was not affected by the mixing order of the two polyelectrolyte partners. A general rule capable of predicting the PEC stoichiometry is proposed.
We introduce a new estimator of particle size polydispersity for dynamic light scattering data, which quantifies the relative width of the intensity-weighted distribution of diffusion coefficients. ...Simulated dynamic light scattering data are analyzed to (i) compare the accuracy and precision of the new polydispersity indicator to polydispersity measurements from standard cumulant and moment analysis (MA) fits and (ii) establish for each method the optimum data range for fitting. Although MA is preferable at low polydispersity, the new estimator is the most accurate and precise at intermediate and large polydispersities. Finally, we successfully apply the method proposed here to real data from colloidal particles, microgels, and polymer solutions.
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