Recovery of organic acids from waste salt solutions derived from the manufacture of cyclohexanone by electrodialysis

The possibility of recovery of organic acids from waste salt solution, derived from the manufacture of cyclohexanone, by means of single anion-exchange membrane electrodialysis was studied in this paper. Some key parameters, such as voltage, current density, pH value, current efficiency and specific energy consumption are studied and analyzed in details on theoretical basis. Results indicate that single anion-exchange membrane electrodialysis is found to be a feasible method for recovery of organic acids. Several valuable acids, such as butyric and adipic acids are effectively separated from waste salt solution by only one-step electrodialysis. And it consumes less energy compared to the conventional processes.     

Hydrophobic solid phase extraction using n-alkanoic acid-immobilized anion-exchange membranes as adsorbents

In this study, n-alkanoic acids (C7-COOH, C11-COOH, and C17-COOH) were immobilized onto strong basic anion-exchange membranes to form a stationary phase for hydrophobic solid phase extraction (SPE) application. The effects of feed surfactant amount, membrane counter ions, and surfactant chain length were investigated. Immobilized surfactant capacity increased with increasing feed surfactant amount, decreasing chain length, and the existence of OH⁻ counter ions. Moreover, according to TGA analysis, a surfactant bi-layer was formed on the membrane surface. Following successful surfactant immobilization, batch adsorption experiments for doxepin (feed concentration of 0.2 mg/mL) were conducted. The adsorbed doxepin amount increased with the use of longer-chain surfactants, indicating that doxepin adsorption was dominated by hydrophobic interaction with the immobilized surfactant. An optimal desorption performance was achieved using 1 M NaCl in 50% ethanol for both C7-COOH and C11-COOH-immobilized membranes. In the SPE process with one C11-COOH-immobilized membrane, a concentration factor of 2 and complete doxepin recovery was achieved from 10 mL of a 0.1 ppm load.     

Evaluation of an anion-exchange hollow-fiber membrane adsorber containing γ-ray grafted glycidyl methacrylate chains

It is widely recognized that membrane adsorbers are powerful tools for the purification of biopharmaceutical protein products and for this reason a novel hollow-fiber AEX type membrane adsorber has been developed. The membrane is characterized by grafted chains including DEA ligands affixed to the pore surfaces of the membrane. In order to estimate the membrane performance, (1) dynamic binding capacities for pure BSA and DNA over a range of solution conductivity and pH, (2) virus reduction by flow-through process, and (3) HCP and DNA removal from cell culture, are evaluated and compared with several other anion-exchange membranes. The novel hollow-fiber membrane is tolerant of high salt concentration when adsorbing BSA and DNA. When challenged with a solution containing IgG the membrane has high impurity removal further indicating this hollow-fiber based membrane adsorber is an effective tool for purification of biopharmaceutical protein products including IgG.     

Separation of oxidized variants of a monoclonal antibody by anion-exchange

Monoclonal antibodies are subject to a variety of degradation mechanisms, therefore orthogonal techniques are required to demonstrate product quality. In this study, the three individual antibodies comprising a multi-antibody drug product, XOMA 3AB were evaluated by both cation-exchange (CEX) and anion-exchange chromatography (AEX). In contrast to CEX analysis which showed only a single, broad peak for the force-oxidized antibodies, AEX analysis of Ab-A (pI=7.6) revealed two more basic peaks. Ab-B (pI=6.7) bound but exhibited only a single major peak while Ab-C (pI=8.6) flowed through. Peptide mapping LC/MS analysis of the isolated Ab-A fractions demonstrated that the basic peaks resulted from oxidation in a complementary determining region (CDR). Differential scanning calorimetry (DSC) analysis of the oxidized Ab-A species showed a decrease in the Fab melting point for the oxidized species consistent with unfolding of the molecule. Greater/lesser surface exposure of ionic residues resulting from a conformational change provides a likely explanation for the dramatic shift in retention behavior for the Ab-A oxidized variants. Peptide mapping analysis of the Ab-B antibody showed, in contrast to Ab-A, no detectable CDR oxidation. Hence, the lack of separation of oxidized variants in Ab-B can be explained by the absence of CDR oxidation and the associated changes in secondary/tertiary structure which were observed for oxidized Ab-A. In summary, anion-exchange HPLC shows potential as an orthogonal analytical technique for assessing product quality of monoclonal antibody therapeutics. In the case of the XOMA 3AB drug product, two of the antibodies bound and one, Ab-A, exhibited separation of CDR oxidized variants.     

Separation of U and Pu in spent nuclear fuel sample using anion-exchange-group-introduced porous polymer sheet for ICP-MS determination

Anion-exchange porous sheets were prepared by radiation-induced graft polymerization and subsequent chemical modifications. A diethylamino (DEA) group as an anion-exchange group was introduced into the polymer chain grafted onto a porous sheet. The DEA group-introduced porous sheet was cut into disks 13 mm in diameter and 3 mm in thickness to fit an empty cylindrical cartridge (DEA cartridge). The DEA sheet had a DEA group of 3.4 mol/kg of the DEA-group-containing porous sheet and a linear velocity of 46 m/h at a permeation pressure of 0.1 MPa at 298 K. The adsorption capacity of the DEA cartridge for FeCl₄⁻ as a model ion in equilibrium with 1 g-Fe(III)/L in 10 M HCl was 0.17 mmol-Fe(III)/DEA cartridge. No Pu leakage during the permeation of 5 mL of 10 M HCl-0.1 M HNO₃ containing Pu ionic species through the DEA cartridge was observed irrespective of the permeation rate ranging from 0.3 to 80 mL/min. A solution containing known amounts of ²³³U, ²⁴⁰Pu, and ²⁴¹Am in 10 M HCl-0.1 M HNO₃ was loaded onto the DEA cartridge. U and Pu were retained on the DEA cartridge, while Am was allowed to pass through the DEA cartridge. Subsequently, 7 M HNO₃ and 1 M HCl as eluents were permeated to elute U and Pu from the DEA cartridge, respectively. The decontamination factor of U in a Pu fraction, defined by dividing the activity of U in the feed solution by that of U in the Pu fraction, was 2.7 × 10⁵, which is desirable for the highly accurate ICP-MS determination of Pu for samples containing both U and Pu. The method using the DEA cartridge was validated by measuring isotopic compositions and quantities of U and Pu in a spent nuclear fuel sample by double-focusing magnetic sector ICP-MS.     

Disposable microcolumns with welded metal frits

This study reports the preparation of disposable microcolumns with welded metal frits for the first time. First, the bottom of glass‐lined stainless‐steel tubing of 30 cm length, 1.6 mm od, and 0.5 mm id was welded with a stainless‐steel screen frit of 1.6 mm diameter. A micro‐welding machine was used for this. Next, the column was connected to a slurry packer and packed with porous silica particles. Then, the inlet of the column was carefully welded with another frit. The column was tested for separation of a test mix composed of phenol, 2‐nitrophenol, acetophenone, aceanilide, and benzamide. Another column of the same physical dimension was also prepared with frits that were not welded to the column. The chromatographic performances of the two groups of columns (welded frits versus non‐welded frits) were examined. The columns of welded frits showed ca. 18% better separation efficiency (number of theoretical plates) than those of non‐welded frits.