Background Electrolyte Research Articles

Development of a sustainable multianalyte MEKC method for quantitation of the antihyperlipidemic drugs ezetimibe together with three statins. Greenness and whiteness appraisal studies

Implementing powerful and sustainable research that complies with green analytical chemistry (GAC) and white analytical chemistry (WAC) fundamentals can downsize the environmental compliance costs and fruitfully affects practical and economic issues. Within this framework, rapid and white analytical micellar electrokinetic capillary chromatography (MEKC) methodology was developed for the synchronized estimation of the antihyperlipidemic drugs Ezetimibe (EZE), Atorvastatin (ATO), Rosuvastatin (ROS) and Simvastatin (SIM). The technique was established using fused silica capillary (50 cm, 50 µm id) and the background electrolyte was 0.025 M borate buffer pH 9.2 containing 0.025 M sodium dodecyl sulfate (SDS) and 10% v/v acetonitrile as the organic modifier. Diode array detector was adjusted at 243 nm for ATO and ROS and 237 nm for EZE and SIM. Separation was accomplished within 10 min with migration times of 4.12, 5.42, 8.23 and 8.74 min for ROS, ATO, EZE and SIM respectively. The 4 drugs were quantitated in the concentration range of 10–100 μg/mL and the correlation coefficients were not less than 0.9993. The high sensitivity was illustrated by values of the detection and quantitation limits. The limits of detection for ROS, ATO, EZE and SIM were 0.52, 0.75, 0.42 and 0.64 μg/mL, respectively, whereas, the limits of quantitation values were 1.73, 2.50, 1.40 and 2.13 μg/mL for the studied drugs, respectively. In addition to validation, as reported by the ICH guidelines, greenness and whiteness assessment using the novel AGREE calculator and the holistic functionality model RGB12 were performed. The results proved the efficiency and whiteness of the suggested technique to be routinely implemented in quality control laboratories for the assay of the four drugs and the binary mixtures of EZE with either ATO, ROS or SIM in fixed-dose combined tablets.

Design of experiments for micellar electrokinetic chromatography method development for the monitoring of water-soluble vitamins in cell culture medium.

Biopharmaceutical production takes place in complex processes which should be thoroughly understood. Therefore, the iConsensus project focuses on developing a monitoring platform integrating several process analytical technology tools for integrated, automated monitoring of the biopharmaceutical process. Water-soluble vitamin monitoring using (microchip) capillary electrophoresis (CE) is part of this platform. This work comprises the development of conventional CE methods as the first part towards integrated vitamin monitoring. The vitamins were divided based on their physical-chemical properties to develop two robust methods. Previously, a method for the analysis of cationic vitamins (pyridoxine, pyridoxal, pyridoxamine, thiamine and nicotinamide) in cell culture medium was developed. This work focused on the development of a micellar electrokinetic chromatography method for anionic and neutral vitamins (riboflavin, d-calcium pantothenate, biotin, folic acid, cyanocobalamin and ascorbic acid). By employing multivariate design of experiments, the background electrolyte (BGE) could be optimised within one experiment testing only 11 BGEs. The optimised BGE conditions were 200mM borate with 77mM sodium dodecyl sulphate at a pH of 8.6. Using this BGE, all above-mentioned cationic, anionic and neutral vitamins could be separated in clean samples. In cell culture medium, most anionic and neutral vitamins could be separated. Combining the two methods allows for analysis of cationic, anionic and neutral vitamins in cell culture medium samples. The next step towards integrated vitamin monitoring includes transfer to microchip CE. Due to the lack of fast and reliable methods for vitamin monitoring, the developed capillary methods could be valuable as stand-alone at-line process analytical technology solutions as well.

Fractionation and transport of compost‐derived dissolved organic matter fractions in saturated red soil and black soil columns

AbstractThe fractionation and transport of compost‐derived dissolved organic matter (DOMC) could affect the transport and fate of nutrients and DOM‐associated pollutants in the soil environment. In this study, the humic acid fraction of DOMC (HAC) and fulvic acid fraction of DOMC (FAC) were selected to investigate the fractionation and transport of DOMC in repacked soil columns of a red soil and a black soil under different KCl concentrations. The effluent DOMC fractions were monitored by ultraviolet (UV)‐visible (Vis) light and fluorescence spectroscopy. The results showed that the molecular weight (MW) of the effluent DOM approached that of the influent DOMC fractions with the injection of DOMC fractions. Three‐dimensional fluorescence excitation emission matrices (3D‐EEMs) coupled with parallel factor analysis resolved three fluorescent components, that is, low MW UV humic‐like substances (C1), high MW UV humic‐like substances (C2), and protein‐like substances (C3). The mobility of HAC and FAC decreased with increasing KCl concentrations (1 mM–50 mM), implying that electrostatic interaction was an important mechanism for the retention of DOMC in soil columns. The fact that the mobility of DOMC fractions in the black soil was greater than that in the red soil could be attributed to the high free Fe oxide content in the red soil. The retained DOMC fractions did not entirely desorb by the background electrolyte solution, suggesting that a part of the DOMC fractions retained in soil columns was strongly bound. These results are helpful in understanding the fractionation and transport of DOMC in soil environments.

Efficient removal of tetracycline, ciprofloxacin, and amoxicillin by novel magnetic chitosan/microalgae biocomposites

Two new highly-efficient and eco-friendly biosorbents comprised of magnetite, chitosan and Chlorella vulgaris (MCC) or Arthrospira platensis (MCA) were prepared in such a way to be easily separated and reused for removing different classes of antibiotics such as tetracycline (TC), ciprofloxacin (CIP) and amoxicillin (AMX) from wastewater. They were characterized using SEM, FTIR and TGA. Biosorption experiments were performed to investigate the impact of pH, biosorbent dosage, initial antibiotic concentration, contact time, and concentration of background electrolytes (NaCl, KCl and CaCl2) on adsorption. Both biocomposites showed outstanding performance in antibiotics removal. Equilibrium data were modelled using Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich adsorption isotherms, among which the first one gave the best fit, with maximum TC, CIP and AMX adsorption capacities of 834.0, 394.9, and 150.8 mg/g for MCA and of 831.1, 374.2, and 140.2 mg/g for MCC, respectively. To follow the adsorption time-evolution, the pseudo-first-order, pseudo-second-order and intraparticle diffusion kinetic models were tested, the second of which proved to be the best-fitting one. Thermodynamic parameters revealed that adsorption was spontaneous and endothermic. Both biosorbents were regenerated through microwave-assisted treatment and reused repeatedly for up to four cycles, losing TC, CIP and AMX adsorption capacities at equilibrium by no >7, 4 and 9 %, respectively. This study suggests that both biocomposites may be effective and sustainable alternatives to commercial adsorbents for removing antibiotics from wastewater.

Determination of ticagrelol in rat plasma and tablets by micellar electrokinetic chromatography coupled with large volume sample stacking: Application to a pharmacokinetic study.

A method using micellar electrokinetic chromatography coupled with large-volume sample stacking for the determination of ticagrelol was developed and validated. The analysis was performed in a fused silica capillary (41.5cm effective length, 50μm diameter) with ultraviolet detection at 195nm. The background electrolytes were 30mM phosphate buffer of pH 3.0 with 120mM sodium dodecylsulfate and 10 % (v/v) acetonitrile (120 s X 50mbar; 20°C; -18kV) and 30mM borate buffer of pH 8.5 with 75mM sodium dodecylsulfate (120 s X 50mbar; 20°C; 25kV); under acidic and alkaline conditions, respectively. The method was found to be reliable with respect to specificity, linearity of the calibration line (R2 >0.99), repeatability (relative standard deviation 2.56%-3.34%), and accuracy (recovery in the range 101.21%-102.67%). The limits of detection and quantitation were 0.032, 0.071, and 0.087, 0.188μg/mL, respectively. The method was successfully applied for the determination of ticagrelol concentrations in rat plasma and tablets with good recoveries and reproducibility. The presented method proved to be suitable for monitoring ticagrelor in rat plasma.

Study of Effect of Incubation Time and Temperature on the Linear Polyacrylamide-Coating Performance for the Separation of Proteins by Capillary Zone Electrophoresis

The preparation of linear polyacrylamide (LPA)-coated capillary is a multistep, laborious process. In this study, five different LPA-coating procedures were compared regarding the capillary pretreatment (incubation time and temperature), the formation of the intermediate silyl layer and the attachment of the polymer top layer. LPA coatings were examined by the analysis of a standard mixture solution of insulin, rituximab and hemoglobin using a background electrolyte (BGE) of 50 mM HCOOH (pH 2.6). The results were contrasted with those that were obtained using the bare fused-silica capillary. The reproducibility of the simplest LPA-coating preparation was tested. The long-term stability of the capillary coating was evaluated through inter-day precision data using a large number of injections of the three-protein test mixture solution. The implementation of a short-term procedure at elevated temperature, guided by a comprehensive review of various conditions documented in the literature, yielded an efficiently functional LPA coating.

From capillaries to microchips, green electrophoretic features for enantiomeric separations: A decade review (2013-2022).

Enantioseparation by the electromigration-based method is well-established and widely discussed in the literature. Electrophoretic strategies have been used to baseline resolve complex enantiomeric mixtures, typically using a selector substance into the background electrolyte (BGE) from capillaries to microchips. Along with developing new materials/substances for enantioseparations, it is the concern about the green analytical chemistry (GAC) principles for method development and application. This review article brings a last decade's update on the publications involving enantioseparation by electrophoresis for capillary and microchip systems. It also brings a critical discussion on GAC principles and new green metrics in the context of developing an enantioseparation method. Chemical and green features of native and modified cyclodextrins are discussed. Still, given the employment of greener substances, ionic liquids and deep-eutectic solvents are highlighted, and some new selectors are proposed. For all the mentioned selectors, green features about their production, application, and disposal are considered. Sample preparation and BGE composition in GAC perspective, as well as greener derivatization possibilities, were also addressed. Therefore, one of the goals of this review is to aid the electrophoretic researchers to look where they have not.

Development of a new method for the determination of 4-hydroxyproline as a measurement of collagen content in meat products and dietary supplements by cyclodextrin-assisted electrokinetic chromatography

The rise in consumption of ultra-processed meat and dietary collagen supplements challenges food quality control. 4-hydroxyproline stands out as collagen signature amino acid, and its determination is a well-known way to estimate collagen content, although for this measurement, the majority of the methods require a mandatory derivatization step. Therefore, this study aimed to develop an innovative method using cyclodextrin-assisted electrokinetic chromatography with indirect UV detection to determine 4-hydroxyproline for collagen monitoring in dietary supplements and meat products. Separations were performed in fused silica capillaries, at 12.5 °C, detection at 220 nm, 30 kV voltage, and hydrodynamic injection. Background electrolyte consisted of histidine 25 mmol L-1, butylamine 180 mmol L-1, and β-cyclodextrin 10 mmol L-1 at pH 11.4. Samples were hydrolyzed with sulfuric acid, and their removal was accomplished by simultaneous neutralization/precipitation reactions using strontium carbonate. Validation assured method detectability, accuracy (recoveries 88% - 102%), and precision (CV < 7%). Dietary supplements and meat products were successfully evaluated, indicating that this method is a feasible quality control alternative.

Validated green high performance liquid chromatographic and capillary electrophoretic methods for estimation of dinitolmide in presence of its acid-degradation product

This study describes two new, green, fast, specific and highly sensitive stability-indicating techniques for determination of Dinitolmide (DM) in presence of its acid induced degradation product without prior separation; Acid degradation was carried out by hydrolysis with 0.1 N HCl; and the acidic degradation pathway was established by IR, and MS techniques. The first is a HPLC-Diode Array detector was performed by isocratic mode on BDS Hypersil C18 column (150 mm × 4.6 mm × 5 μm particle size) at ambient temperature with a mobile phase consisting of 5 mM sodium acetate buffer (pH 5.5): acetonitrile (40:60, v/v), flow rate of 1 mL/min and detection at 210 nm. DM and its acid degradant were eluted at 4.3 and 2.8 min, respectively offering quick analysis. Linearity of the calibration curves confirm good correlation in range of 1–15 μg/mL with recovery % of 100.02 ± 0.460. The LOD and LOQ were 0.243 and 0.737, respectively. The second method is CE -Diode Array detector was carried out at 25 °C using borate buffer (30 mM, pH 9) as background electrolyte solution and detection at 225 nm. The migration times were 2.26 and 2.97 min for DM and its acid degradant, respectively. The linearity range was 5–50 μg/mL with recovery % of 99.55 ± 0.910, LOD and LOQ were 1.010 and 3.050, respectively. The small LOD and LOQ values for both methods confirm high sensitivity of the methods The developed methods were validated according to the ICH guidelines demonstrating good accuracy and precision. The results were statistically compared with those obtained by a reported method in terms of accuracy, precision, and no significant difference was found. Both methods were successfully applied for estimating DM and its acid degradant in pure and pharmaceutical dosage forms. In addition, the methods were assessed for their greenness profile and CE was greener owing to using safer solvents and less energy consumption.

Investigation of Reduced Graphene Oxide Modified Zinc Anodes Using Various Electrochemical Techniques

Zinc ion batteries are promising battery energy storage systems due to their high capacity, abundancy and low cost, but are held back by competing reactions, passivation, and dendrite formation which all greatly reduce performance. We modify zinc anode by introducing a self-reducing graphene oxide coating. This protects against dendrite formation and reduces side reactions, increasing the performance of the cell. Half-cell experiments are performed to determine whether sodium sulphate, sodium acetate, or a combination of the provides any advantage over the other, as well as to determine the effect the pattern of the reduced graphene oxide coating on performance. Additionally, symmetric zinc coin cells are assembled, and studied by galvanostatic charge/discharge cycles, and chronopotentiometry. The effect of the reduced graphene oxide coating, electrolyte composition, choice of separator (paper/glass) on the cycling stability and over potential of zinc deposition is studied. The partially covered (island) zinc anode greatly reduces the nucleation overpotential to 8.75 mV when assembled in a symmetric coin cell. Excellent cycling stability is observed at a current density of 5 mA cm-2 charged to 5 mAh cm-2 when using a combination background electrolyte of sodium sulphate and sodium acetate using a glass fibre separator.

Carboxymethylated maltodextrin as a chiral selector for the separation of some basic drug enantiomers using capillary electrophoresis

In this work, carboxymethylated maltodextrin (Cm-MD) was successfully synthesized as an efficient anionic chiral selector and applied for the enantiomer separation of some basic drugs including tramadol, venlafaxine, verapamil, hydroxyzine, citalopram, fluoxetine, and amlodipine by capillary electrophoresis (CE). The synthesized chiral selector was characterized by the nuclear magnetic resonance and Fourier transform infrared spectrophotometry. Under the optimized Cm-MD modified CE conditions (background electrolyte: phosphate buffer (pH 5.0, 50 mM) containing 5% (w/v) Cm-MD; applied voltage: 20 kV; and capillary column temperature: 25 °C), successful enantiomer separation of all studied chiral drugs were observed. By comparison of Cm-MD and MD for enantiomer separation of the model drugs, it was revealed that Cm-MD exhibits a higher resolution in comparison to the MD modified CE. This enhanced resolution could be attributed to the electrostatic interactions between the cationic drugs and anionic Cm-MD and opposite direction mobility of the host-guest complex relative to the chiral analyte. The optimized Cm-MD modified CE method was successfully used for the assay of the enantiomers of citalopram and venlafaxine in commercial tablets. The proposed method showed the linear range of 5.0–150.0 mg/L and 10.0–150.0 mg/L for both enantiomers of citalopram and venlafaxine, respectively. The limits of quantification were 5.0 and 10.0 mg/L for the enantiomers of citalopram and venlafaxine, respectively. The limit of detection for all enantiomers was found to be < 3.0 mg/L. Intra- and inter-day RSDs (n = 4) were less than 9.7%. The relative errors were less than 9.4% for all enantiomers. The obtained results in this research show that Cm-MD as a new, efficient and inexpensive chiral selector can be used for enantiomer separation of basic drugs using the CE technique.

A new surface structural approach for modeling the charging behavior of kaolinite

The concentration of ions in equilibrium with soils and sediments is a function of various interconnected chemical reactions. The charging behavior of minerals provides a set of fundamental information required to model these interactions. Accordingly, in this study, the charging behavior of kaolinite was measured at three concentrations (0.004, 0.04 and 0.40 M) of three electrolytes (LiNO3, NaNO3 and KNO3) using potentiometric titration. The experimental data were described using the CD-MUSIC-G&T model in which ≡AlOH0.5−, ≡SiO− and ≡X− were defined as reactive functional groups on aluminol edge, silanol edge and basal planes, respectively. The charging behavior was a function of the type and concentration of the background electrolytes, but changes in the concentration more than changes in the type of electrolytes affected the surface charge. The thermodynamic equilibrium constants (logK) of the reactions of H+, Li+, Na+, K+ and NO3− with aluminol group were obtained as 9.50, 1.62, 1.37, 1.29 and 10.28 and with silanol group as 4.94, 1.58, 1.79, 2.03 and < −10, respectively. The logK of 4.94 shows that the interaction of H+ ion with the kaolinite ≡SiO− is much stronger than its interaction with the same group on the quartz. The capacitance of both inner and outer Stern layers was measured to be 1.94 F/m2, showing the strong interaction of electrolyte ions with the edge surface. In addition, the equilibrium constants of the reactions of Li+, Na+ and K+ with ≡X− group were obtained as −0.40, −0.02 and 0.32, respectively, which have the same order as reacted with the silanol group. At pH below pHPZC (i.e., <6.3 ± 0.2), increasing ionic strength reduced the surface charge of kaolinite; because increasing electrolyte concentration increased the negative charge on the silanol edge more than increasing the positive charge on the aluminol edge. In addition, it seems that the negative potential due to the isomorphic substitution in the polyhedrons near the edge of kaolinite poses an inward attractive force on the central cations of the edge polyhedrons, which in turn reduces the bonding capacity of ≡Al−OH0.5− and/or ≡Si−O−. Thereby, the adsorption energy of proton and cations on the edge surface may increase due to isomorphic substitution in adjacent polyhedrons.

The Influence of Organic Matter on Phosphorus Fixation in Soils from the Eastern Flank of Mount Cameroon

The maximum phosphate fixation (KF) and phosphorus sorption capacity (PSC) of soil samples collected from the surface and sub-surface horizons of five volcanic soil profiles from the eastern flank of Mount Cameroon were investigated before and after organic matter removal. The aim of this research was to investigate the influence of soil organic matter (OM) on phosphorus (P) fixation. The removal of soil OM from the soil samples was accomplished by the use of sodium hypochlorite. Phosphorus fixation studies were performed on the treated and untreated soil samples using calcium chlorite as the background electrolyte. Fixation data were interpreted with Freundlich adsorption isotherm. The results indicated that the removal of OM had an influence on both KF and PSC. Removal of soil OM decreased PSC and increased KF for all soils. The inhibition of aluminium oxide and the reduction of soil surface area after the removal of OM were the justifications for the increase in P fixation.

Influence of Lanthanum on Stern Layer Conductance in the Nanochannel.

In this report, high-frequency electric impedance spectroscopy was performed to investigate ionic transport through nanochannels. Special attention was focused on (i) conductance behaviors depending on the role of cation valence in three background electrolytes (XCln): monovalent 1-1 (K+ and Cl-), divalent 2-1 (Mg2+ and 2Cl-), and trivalent 3-1 (La3+ and 3Cl-), (ii) the effects of proton and bicarbonate ions on bulk and surface conductance, and (iii) the connected microchannel dimension (surface/height ratio aspect) within the nanochannel apparent conductance. The results highlight a net quantitative increase in surface silanol density and a strong decrease in surface ionization degree when lanthanum cations are employed. The results also demonstrate that La3+ strongly interacts with the silica surface, leading to negative values of standard free energy for ion-site interactions and chemical potential for ion-ion correlations in the Stern layer of -0.8 and -10.2 kT, respectively. We ascribed the evolution of surface charge density to the balance between the mole ratios of water molecules and adsorbed cations at equilibrium. We found that La3+ behaves as an acidic cation (Lewis conceptualization) that neutralizes the negative silica surface accompanying water molecule expulsion due to steric hindrance. This study constitutes a new contribution to ion-site interactions and to ion-ion correlation phenomena on the planar silica surface to explain charge inversion observation in micro-nanofluidic devices.

Anti-Alzheimer Drug Delivery via Pickering Emulsions Stabilized by Plate-like Cellulose Nanocrystals.

In this work, we studied for the first time the formation of olive oil emulsions in water stabilized by plate-like nanocrystals with the supramolecular structure of cellulose II (pCNC). Effects of storage, pCNC concentration, and NaCl on the stability and properties of Pickering emulsions, including the creaming index, droplet size, zeta potential, acid-base surface properties, and rheology, were studied. A significant influence of the shape of nanoparticles (compared to the classical rod-like shape) on the stability parameters and rheological characteristics of emulsions is shown. Plate-like cellulose nanocrystals at a concentration of 16 g/L are able to form delamination-resistant emulsions without added electrolytes. The viscosity of pCNC-stabilized emulsions tends to decrease with increasing electrolyte concentration in the system, which is not characteristic of rod-like CNC-stabilized emulsions. This effect in pCNC-stabilized emulsions assumedly can be associated both with weak mechanical engagement between drops due to the shape of stabilizer particles and with an insignificant participation of background electrolyte cations in the formation of interdroplet interactions. Therefore, the resulting aggregates are unstable and easily destroyed, even under weak mechanical stress. As a consequence, the acid-base properties of the pCNC surface are practically independent of the emulsion preparation method (with or without electrolyte) as well as the concentration of the background electrolyte. The reduced viscosity of pCNC-stabilized emulsions in the presence of an electrolyte, coupled with the absence of acute toxicity, allows us to recommend them as a convenient oral delivery system for fat-soluble, biologically active substances. Our emulsions carrying donepezil (an anti-Alzheimer drug) showed better performance than a solution of donepezil hydrochloride in preventing memory impairment tested on laboratory mice.

Comparative study on the deamidation of three recombinant human insulins using capillary electrophoresis

The applicability of capillary zone electrophoresis (CZE) for the separation of different recombinant human insulins and their deamidated isoforms was studied. The high resolving power of CZE is demonstrated by its ability to separate insulin isoforms differing only by 0.984 Da (different-fold deamidated forms) and even components having the exacts same mass but slightly different shapes (same-fold deamidated forms). From among the several insulins available, humulin, glargine and glulisine were selected for our study because their sequences and chemical parameters are quite similar, however, the small differences present in their amino acid sequences influence the deamidation processes. Using a background electrolyte with basic pH was favourable not only for the separation of the different types of insulin but also for the separation of deamidated protein forms even in a bare fused silica capillary. The LOD values ranged between 0.6 - 0.93 mg/L and 2.17 - 4.37 mg/L for UV and ESI-MS detection, respectively. At -20 - -80 °C, the deamidation is minimal, but at temperatures above +5 °C deamidation is accelerated. At +5 °C only 1-fold deamidation forms could be observed for each insulin. Acidified samples incubated for 1-month at room temperature showed varying levels of deamidation: 1-fold, 1–2-fold and 1–2–3-fold forms for glargine, glulisine and humulin, respectively.

Cathodic stripping of elemental Te in dichloromethane

The cathodic stripping of Te in CH2Cl2 with 0.1 M [NnBu4]Cl has been studied. In background electrolyte the cathodic stripping of Te behaves in the expected way. In contrast, when the stripping occurs in the [NnBu4]2[TeCl6] plating solution, unusual voltammetry is observed. Microelectrode and EQCM studies show that cathodic stripping of Te in the plating solution occurs with the passage of very little charge and leads to the formation of Te(0) in solution due to a rapid reaction between the reduced Te(-II) species and the Te(IV) salt. As a result, the limiting current for reduction of the Te(IV) is unchanged with 4 electron reduction leading to the formation of Te(0) on the electrode at potentials positive of the Te cathodic stripping potential and Te(0) in solution at potentials negative of the Te cathodic stripping potential. The same behaviour is found when a Te(II) precursor is used in place of the Te(IV) salt.

Size separation of sodium dodecyl sulfate-proteins by capillary electrophoresis in dilute and ultra-dilute dextran solutions.

SDS capillary gel electrophoresis is a widely used in the biopharma and the biomedical fields for rapid size separation of proteins. However, very limited information is available on the use of dilute and ultra-dilute sieving matrices for SDS-protein analysis. Here, background electrolytes (BGEs) containing 1%-0% dextran were used in borate-based BGE to separate a protein sizing ladder (PSL)≤225kDa and the intact and subunit forms of a therapeutic monoclonal antibody (mAb). The separation performance for the PSL and mAb components differed significantly with decreasing dextran concentration. Ferguson and reptation plots were used to elucidate the separation mechanism. Highly diluted dextran solutions resulted in linear Ferguson plots for both solute types (cf. Ogston theory) in spite of this model assumes a rigid pore structure, thus cannot describe the separation mechanism in ultra-dilute polymer solutions with no reticulations. The saddle differences between the resolution of the PSL and the intact/subunit mAb forms in ultra-dilute dextran-borate matrices suggested the importance of shape selectivity, manifested by the adequate separation of the SDS covered intact as well as light and heavy chain subunits of the therapeutic mAb even at zero dextran concentration.

A review of the zone broadening contributions in free-flow electrophoresis.

The broadening of analyte streams, as they migrate through a free-flow electrophoresis (FFE) channel, often limits the resolving power of FFE separations. Under laminar flow conditions, such zonal spreading occurs due to analyte diffusion perpendicular to the direction of streamflow and variations in the lateral distance electrokinetically migrated by the analyte molecules. Although some of the factors that give rise to these contributions are inherent to the FFE method, others originate from non-idealities in the system, such as Joule heating, pressure-driven crossflows, and a difference between the electrical conductivities of the sample stream and background electrolyte. The injection process can further increase the stream width in FFE separations but normally influencing all analyte zones to an equal extent. Recently, several experimental and theoretical works have been reported that thoroughly investigate the various contributions to stream variance in an FFE device for better understanding, and potentially minimizing their magnitudes. In this review article, we carefully examine the findings from these studies and discuss areas in which more work is needed to advance our comprehension of the zone broadening contributions in FFE assays.

Implicatons of Metal Complexes in Biology and Medicine the System Cadmium (II)/ Iron (II)/ Zinc (II)-Hydroxyproline

The importance of metal ions to essential functions of living systems and for the well being of living organisms is known. Metal ions are fundamental elements for the maintenance of the life spans of the human, animals and plants. The stability constants of Cd2+, Fe2+ and Zn2+ complexes with hydroxyproline were determined by Paper Electrophoretic Technique (PET). This method is based on the movement of a spot of metal ion in an electric field at various pH of background electrolyte. A graph of pH against mobility gives information about the formation of binary complexes and permit to calculate their stability constants. The stability constant of the ML and ML2 complexes of Cd (II) – hydroxyproline, Fe (II) – hydroxyproline and Zn (II) – hydroxyproline, have been found to be (4.41 ± 0.01; 2.95 ± 0.06) (4.11 ± 0.01; 2.81 ± 0.11 and (4.83 ± 0.02; 3.28 ± 0.07) ( logarithm stability constant values), respectively at ionic strength 0.1 mole L-1 (per chloric acid as background electrolyte) and a temperature of 35 0C, The first and second stability constants of metal complexes follow the order Zn (II) &gt; Cd (II) &gt; Fe (II). Metal complexes can offer their action such as anti-inflammatory, antibiotic, anti-thyroid and anticancer compounds. Metal based drugs bioactivity can be increased by metal chelation, which in turn increase their absorbance and stability. Recent advances in inorganic chemistry have made possible formation of a number of metal complexes with organic ligands of interest which can be use as therapeutic agents.