Good's Buffer Ionic Liquids as Relevant Phase-Forming Components of Self-Buffered Aqueous Biphasic Systems

Facile Determination of Aluminum Content in Industrial Brine by Investigating the Effects of Buffer Systems

The aluminum content of concentrated (27 wt%) sodium chloride solutions could be crucial for large-scale chlor-alkali-based industries applying membrane cell electrolysis. Thus, a facile method which enables a fast and reliable protocol to determine the Al content of these solutions on ppb scale in industrial environments is fundamentally important. It was demonstrated that the increased sensitivity of colorful Al-ECR (eriochrome cyanine R) complex by the use of a cationic surfactant and specific biological buffers could effectively indicate the Al content in an extended pH interval of a concentrated saline medium under industrial conditions. The dependence of the analytical protocol on pH, temperature, time, wavelength, and the salinity of the medium was investigated. It was shown that the absorbance-based measurements of the solution should be performed at least 2-4 h after its preparation. By applying the selected two Good's buffers (HEPES: 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid, MOPS: 3-(N-morpholino)-propanesulfonic acid) and Tris (tris(hydroxymethyl)aminomethane), 32.8-38.1 % increase in the sensitivity was achieved for saturated NaCl solutions. Moreover, the limits of detection and quantification (LOD, LOQ) were also lowered by 19.0-29.8 %, and the salinity dependence of the calibration was also reduced.

Accelerated Oxidative Degradation of Phosphonium-Type Ionic Liquid with l-Prolinate Anion: Degradation Mechanism and CO2 Separation Performance

Amino acid ionic liquids (AAILs) are regarded as green alternatives to existing CO₂-sorptive materials because amino acids are readily available from renewable sources in large quantities. For widespread applications of AAILs, including direct air capture, the relationship between the stability of AAILs, especially toward O₂, and the CO₂ separation performance is of particular importance. In the present study, the accelerated oxidative degradation of tetra-n-butylphosphonium l-prolinate ([P₄₄₄₄][Pro]), a model AAIL that has been widely investigated as a CO₂-chemsorptive IL, is performed using a flow-type reactor system. Upon heating at 120-150 °C and O₂ gas bubbling to [P₄₄₄₄][Pro], both the cationic and anionic parts undergo oxidative degradation. The kinetic evaluation of the oxidative degradation of [P₄₄₄₄][Pro] is performed by tracing the decrease in the [Pro]^- concentration. Supported IL membranes composed of degraded [P₄₄₄₄][Pro] are fabricated, and the membranes retain CO₂ permeability and CO₂/N₂ selectivity values in spite of the partial degradation of [P₄₄₄₄][Pro].

Supported Ionic Liquids Used as Chromatographic Matrices in Bioseparation-An Overview

Liquid chromatography plays a central role in biomanufacturing, and, apart from its use as a preparative purification strategy, either in biopharmaceuticals or in fine chemicals industries, it is also very useful as an analytical tool for monitoring, assessing, and characterizing diverse samples. The present review gives an overview of the progress of the chromatographic supports that have been used in the purification of high-value products (e.g., small molecules, organic compounds, proteins, and nucleic acids). Despite the diversity of currently available chromatographic matrices, the interest in innovative biomolecules emphasizes the need for novel, robust, and more efficient supports and ligands with improved selectivity. Accordingly, ionic liquids (ILs) have been investigated as novel ligands in chromatographic matrices. Given herein is an extensive review regarding the different immobilization strategies of ILs in several types of supports, namely in silica, Sepharose, and polymers. In addition to depicting their synthesis, the main application examples of these supports are also presented. The multiple interactions promoted by ILs are critically discussed concerning the improved selectivity towards target molecules. Overall, the versatility of supported ILs is here considered a critical point to their exploitation as alternatives to the more conventional liquid chromatographic matrices used in bioseparation processes.

Separation of Albumin from Bovine Serum Applying Ionic-Liquid-Based Aqueous Biphasic Systems

In this work, the extraction and separation of bovine serum albumin (BSA) from its original matrix, i.e., bovine serum, was performed using a novel ionic-liquid-based aqueous biphasic system (IL-based ABS). To this end, imidazolium-, phosphonium-, and ammonium-based ILs, combined with the anions’ acetate, arginate and derived from Good Buffers, were synthesized, characterized, and applied in the development of ABS with K2HPO4/KH2PO4 buffer aqueous solutions at pH 7. Initial studies with commercial BSA revealed a preferential migration of the protein to the IL-rich phase, with extraction efficiencies of 100% obtained in a single-step. BSA recovery yields ranging between 64.0% and 84.9% were achieved, with the system comprising the IL tetrabutylammonium acetate leading to the maximum recovery yield. With this IL, BSA was directly extracted and separated from bovine serum using the respective ABS. Different serum dilutions were further investigated to improve the separation performance. Under the best identified conditions, BSA can be extracted from bovine serum with a recovery yield of 85.6% and a purity of 61.2%. Moreover, it is shown that the BSA secondary structure is maintained in the extraction process, i.e., after being extracted to the IL-rich phase. Overall, the new ABS herein proposed may be used as an alternative platform for the purification of BSA from serum samples and can be applied to other added-value proteins.

Good's buffer ionic liquid tunes the phase behavior of an anionic surfactant SDBS-stabilized n-octane-water microemulsion and the stability of the solubilized horseradish peroxidase

A Good's buffer ionic liquid (GB-IL) composed of quaternary ammonium cations and Good's buffer anions is first introduced into a microemulsion system as a self-buffering and biocompatible electrolyte. The effects of the constituting ions of a GB-IL and their concentrations on the phase behavior of the anionic surfactant SDBS stabilized n-octane-H₂O microemulsion system were studied for the first time using the ε-β fish-like phase diagram method. The result indicates that the phase behavior of the above microemulsion system is greatly affected by GB-IL cations with a longer alkyl chain on the cation being more favorable for phase inversion. Compared with NaCl, a GB-IL of the same concentration is more efficient for achieving phase inversion, due to the dual role of an electrolyte and a co-alcohol. In addition to the phase behavior, the stability of horseradish peroxidase (HRP) solubilized in an SDBS stabilized bicontinuous microemulsion is also affected by a GB-IL. It is found that the variation of the cationic alkyl chain has a negligible effect on the microemulsion microstructure, but has a significant influence on the stability of the solubilized HRP. At a fixed concentration of the GB-IL, the quaternary ammonium cation with a longer alkyl chain is better for the stabilization of the HRP activity. For a given GB-IL, a higher level of the GB-IL results in a better HRP stability. More importantly, the GB-IL-buffered microemulsion, at the same level of the buffering salt, is more advantageous than the phosphate-buffered one for the stabilization of the HRP activity. This advantage is more pronounced for higher concentrations of the GB-IL. This difference in the HRP stability, caused by the buffering salts, should be ascribed to the microemulsion microstructure effect as well as the Hofmeister effect. The present study provides a guideline for the construction of a bicontinuous microemulsion with a simplified composition and stabilizing effect on the solubilized enzyme.

Towards the differential diagnosis of prostate cancer by the pre-treatment of human urine using ionic liquids

Prostate specific antigen (PSA) is the most widely used clinical biomarker for the diagnosis and monitoring of prostate cancer. Most available techniques for PSA quantification in human fluids require extensive sample processing and expensive immunoassays that are often unavailable in developing countries. The quantification of PSA in serum is the most common practice; however, PSA is also present in human urine, although less used in diagnosis. Herein we demonstrate the use of ionic-liquid-based aqueous biphasic systems (IL-based ABS) as effective pre-treatment strategies of human urine, allowing the PSA detection and quantification by more expedite equipment in a non-invasive matrix. If properly designed, IL-based ABS afford the simultaneous extraction and concentration of PSA (at least up to 250-fold) in the IL-rich phase. The best ABS not only allow to concentrate PSA but also other forms of PSA, which can be additionally quantified, paving the way to their use in differential prostate cancer diagnosis.

Cucurbit[7]uril complexations of Good's buffers

Cucurbit[7]uril forms host–guest complexes with “Good's” and related biological pH buffers of varying stability in aqueous solution.