Optimization of Polymer Separation by Gradient Polymer Elution Chromatography

High Performance Liquid Chromatography (HPLC) has been a versatile separation method for polymers for many years. Analysis of different polymers by HPLC is typically done by utilizing the differential solubility of the polymers by mixing a good solvent and an anti-solvent in various compositions. This method is called Gradient Polymer Elution Chromatography (GPEC). While GPEC has been used extensively, it commonly uses a linear gradient to separate components. Linear solvent gradients consume a lot of solvent and take a relatively long time (\u3e 30 minutes) to complete. The goal of this study is to develop a step gradient from a linear gradient in order to allow quick separation while retaining high resolution of the individual polymers. In this study, 6 different polymers are dissolved separately in a strong solvent. The polymers are then analyzed using a linear gradient. Using the results from the linear gradient, a step gradient is constructed and a known mixture of the pure polymers is analyzed to determine the effectiveness of the step gradient. Two strong solvents and four anti-solvents were used to test the generality of the results. It was found that the step gradient could achieve the same resolution of polymers as the linear gradient, but with as little as half the solvent in some cases. This analytical method of changing a linear gradient into a step gradient can reduce both analysis time and solvent requirement to achieve the desired separation of polymers

A Generalized Design for Affinity Chromatography Columns

In affinity chromatography, an adsorbent with a high selectivity for a target solute is used to isolate the target molecule from other impurities. With sufficient selectivity, the target molecule can be isolated in a highly purified and concentrated state. Common applications of affinity chromatography include Protein A chromatography for antibody purification and Immobilized Metal Affinity Chromatography (IMAC) for protein purification. The well-known design method based on constant-pattern mass transfer zone analysis does not apply to small feed batches, which are insufficient to form constant-pattern frontal waves. Other literature design methods rely on simulation or experimental trials that can be time-consuming and costly. In addition, it can be difficult to optimize the process to achieve the desired purity, yield, and throughput. In this study, a convenient graphical design method based on intrinsic adsorption parameters (void fractions, adsorption isotherm, and solute diffusivity), mass transfer parameters, and dimensionless groups is developed for affinity chromatography systems with Langmuir isotherms. Only a small number of experiments are needed to obtain these parameters. The method is tested with literature data for Protein A chromatography for antibody purification, and close agreement is obtained. Graphs can be used to examine the effects of material properties, capture yield, and throughput on column utilization. In addition, it can easily adjust to meet various design requirements and can take into account variations in the intrinsic parameters. Various sorbents can be evaluated for cost effectiveness based on the intrinsic parameters, making this method applicable to a broad range of affinity chromatography systems

Separation of Rare Earth Elements from Aluminum Using Ion-Exchange Chromatography

Demand of rare earth elements (REEs) has increased tremendously due to their key roles in electronics and emerging technology. Recently, new technology was developed at Purdue to extract REEs from coal fly ash. This study is focused on the separation of aluminum ions (Al), a major impurity in the extract, from REEs. The goal is to test the feasibility of an ion-exchange process for separating REEs from a highly-concentrated Al solution. First, we reduced the resin particle size to decrease dispersion and diffusion effects, to increase resin productivity, and to reduce the amounts of REEs and the ion-exchange resin required for column testing. Different methods of grinding the resin were tested. Grinding the resin in a container with constant stirring was found to be the best method to produce uniformly distributed small particles. The column packed with ground particles showed that porosity and column capacity was unchanged after grinding. Second, optimum loading pH was determined by measuring the effective capacities for an REE, Neodymium (Nd), and Al respectively at different pH values. Loading tests using mixtures of Al and Nd were done to verify if at the optimum pH, the largest REE capture efficiency and the least Al contamination was achieved. This process has potential for recovering REEs and high-purity Al from the extract of coal fly ash

Rare Earth Elements Purification using Ligand-Assisted Displacement Chromatography

Rare Earth Elements (REEs) including the lanthanide series, Yttrium, and Scandium play a critical and essential role in various industries such as electronics, power, and defense. Traditional methods have difficulties in separating REEs due to their high similarities in chemical and physical properties. With increasing demand of REEs, current industrial techniques of REE extractions, two phase liquid-liquid extraction, are not efficient enough to meet the market’s need without causing serious environmental problems. Specifically, two phase liquid-liquid extraction uses a large number of mixer-settler units in series and parallel for purification of REEs. This method consumes excessive solvents and chemicals that are environmentally hazardous. Spedding and Powell studied ligand-assisted displacement chromatography of REE recovery in 1950’s, which showed high yields and high purity but low productivity. Their process was designed based on trials and errors and was not optimized. The first goal of this study is to develop and test a systematic design and optimization method to increase sorbent productivity and reduce separation cost. The second goal is to understand the dynamic separation mechanism using rate model simulations. We tested the design method experimentally using three REEs, Nd, Sm and Pr. Ammonium citrate was used as a ligand displacer. Frontal tests were used to estimate the various parameters corresponding to adsorption, reaction and mass transfer. Rate model simulations were conducted to verify experimental data. The experimental design aimed to achieve an average yield of each product of 97% with a purity of 99%, and sorbent productivity an order of magnitude higher than that of Spedding and Powell

Estimation of partition, free and specific diffusion coefficients of paclitaxel and taxanes in a fixed bed by moment analysis: experimental, modeling and simulation studies - doi: 10.4025/actascitechnol.v34i1.8060

Paclitaxel, as known Taxol®, is an important agent in cancer treatment, founded in mixture with many structural analogs, or taxanes, present in natural source or plant tissue culture broth. The adsorption techniques are used in the purification of placlitaxel from that complex mixture, but despite of the strategy it is important to know the basic parameters associated with any process, such as isotherms and mass transfer parameters. In this paper is presented a simple model to estimate these parameters by moment analysis. After to consider linear isotherm for adsorption, the partition coefficient, free and effective diffusion coefficients of paclitaxel and four major components, in a plant tissue culture broth, were estimated from the first and second moments of peaks in pulse-elution chromatograms. The experimental chromatograms at two flow rates are compared with those ones from model, also proposed in this work. The experimental results of free diffusion coefficient are compared with that ones from the Literature