Recent Advances in the Theory and Practice of Displacement Chromatography

Purification of dirucotide, a synthetic 17-aminoacid peptide, by ion exchange centrifugal partition chromatography

Dirucotide is a synthetic drug candidate for the treatment of multiple sclerosis. This 17-aminoacid peptide was successfully purified by ion exchange centrifugal partition chromatography. The optimized conditions involved the biphasic methyl tert-butyl ether/acetonitrile/n-butanol/water (2:1:2:5, v/v) solvent system in the descending mode, the di(2-ethylhexyl)phosphoric acid cation-exchanger with an exchanger (di(2-ethylhexyl)phosphoric acid)/dirucotide mole ratio of 100 and Ca²⁺ ions in aqueous solution as displacer. Critical impurities were efficiently eliminated and dirucotide was recovered in high yield and purity (69% and 98%, respectively) and with a productivity of 2.29g per liter of stationary phase per hour.

Influence of polyfunctional interactions between organic zwitter-ion eremomycin and carboxylic cation exchangers on forming concentration front

The nature of the polyfunctional interactions between the organic zwitter-ions of eremomycin and the carboxylic sorbents was studied. A cation exchange and hydrophobic mechanisms of interactions in the studied sorption system were determined as preponderant over other ones. The typical features of the eremomycin diffusion into the pores of the structurally segregated carboxylic sorbents were studied. The physical-chemical properties of the sorption system which influence the formation of the target product concentration zone with sharp boundary were investigated. The effect of column sizes on the eremomycin unified elution peak formation was shown. The height to diameter ratio leading to the eremomycin concentration front division into two zones was determined.

Optimization of parameters of high-performance displacement chromatography for separation of soybean phosphatidylcholine and phosphatidylethanolamine

Hundred milligrams of soybean phospholipids were successfully separated by using high-performance displacement chromatography (HPDC) on a 150mm x 4.6mm analytical silica column (3-5 microm packings) with dichloromethane-methanol (9:1, v/v) as carrier and ethanolamine as displacer. From the viewpoint of preparative separation, the effects of loading amount, concentration and flow-rate of displacer on separation efficiency were investigated using throughput and recovery as indices. The parameters were optimized by orthogonal test design and statistical analysis method. Under the optimum conditions, namely displacer concentration being 167 mM, the flow-rate of displacer at 0.2 ml/min and concentration of sample being 211 mg/ml (factual loading amount 211 mg/ml x 0.7 ml = 148 mg), the purity, throughput and recovery of obtained soybean phosphatidylethanolamine (PE) and phosphatidylcholine (PC) were 80.2%, 65.7 mg/h, 70.9% and 90.5%, 272.6 mg/h, 88.3%, respectively. In addition, selections of regenerant and appropriate regeneration condition were also studied.

Anion-Exchange Displacement Centrifugal Partition Chromatography

Ion-exchange displacement chromatography has been adapted to centrifugal partition chromatography. The use of an ionic liquid, benzalkonium chloride, as a strong anion-exchanger has proven to be efficient for the preparative separation of phenolic acid regioisomers. Multigram quantities of a mixture of three hydroxycinnamic acid isomers were separated using iodide as a displacer. The displacement process was characterized by a trapezoidal profile of analyte concentration in the eluate with narrow transition zones. By taking advantage of the partition rules involved in support-free liquid-liquid chromatography, a numerical separation model is proposed as a tool for preliminary process validation and further optimization.

Separation of phosphatidylcholine and phosphatidylethanolamine by using high-performance displacement chromatography

A binary mixture of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) was successfully separated by high-performance displacement chromatography (HPDC) on an 150 mm x 4.6 mm analytical silica column (3-5 microm packing), using dichloromethane-methanol (9:1, v/v) as carrier and ethanolamine as displacer. The effects of displacer concentration, flow-rate, loading amount and the composition of the sample on separation efficiency were studied. Eighty-four milligrams sample (PE:PC 1:1.16) was separated perfectly by using 83 mM ethanolamine (in carrier) as displacer at the flow-rate of 0.1 ml/min. The yields of the pure PE and PC (100% purity) were 94.8% and 87.9%, respectively and the cycle time for a single separation was about 195 min. It was valuable that the optimum loading amount (the allowed maximum of sample loading) was investigated only by using the sample to be simulated the composition of the separated actual one, because the separation efficiency was significantly affected by the composition of the sample. For the same loading amount of 175 mg, the yields of the pure PE and PC were improved greatly from 31.4 and 16.9 to 56.0 and 77.6%, respectively, when the proportion of PE to PC was adjusted from 1:1.16 to 1:4. Furthermore, the separation of PE and PC in an actual sample (soybean phospholipids) was achieved using the proposed HPDC method.

Displacement chromatography of isomers and therapeutic compounds

Displacement chromatography was successfully used to separate a binary isomer mixture, epirubicin and doxorubicin, on Kromasil KR100-10 C18 250x4.6 mm I.D. (10 microm) column. Displacement parameters such as the types and the concentrations of displacer, the composition and the flow rate of the mobile phase were critically examined in this study. The displacer employed was 30 mg/ml benzethonium chloride. Loading of feed at lower initial organic level of mobile phase coupled with displacement at higher organic level was found to give efficient separation. A 30-mg amount of binary isomer mixture was separated on an analytical column. The purification of epirubicin from the closely related impurities present in raw product solution by displacement chromatography was also investigated. The purity of epirubicin required was greater than 99% with a recovery of 60%. The results have indicated that this process made good use of the high feed load, low solvent costs, and high resolution characteristics of displacement chromatography and offered the chromatographic engineer a powerful tool for the preparative purification of therapeutic compounds.

Displacement chromatography with on-column isomerization

Displacement chromatography was simulated for the separation of two feed components interconverting by a reversible first order reaction and with Langmuirian adsorption behavior. The study was prompted by recent interest in the isolation of cis and trans forms of peptides containing one or more peptidyl-proline residues when the isomerization reaction interferes with the separation. The parameter values used in the simulations are similar to those found experimentally by reversed-phase chromatography and capillary electrophoresis of phenylalanine-proline dipeptide. From the concentration profiles computed by the finite difference scheme, the dependence of both the yield and production rate on the temperature, column length, flow velocity and displacer concentration was evaluated. The most important operational variable of the system is the temperature as it affects both the kinetic and adsorption parameters. The yield and production rate of the component of interest were evaluated as a function of the column length and displacer concentration under conditions that facilitate its efficient separation and the plots show an optimum. Nonetheless, optimal conditions for yield and production rate were considerably different. In the temperature range from 2 to 42 degrees C, the yield always decreases with increasing temperatures and for all the cases, optimum yield by displacement mandates the use of conditions such as pH, solvent and temperature under which the rate of interconversion is reduced to a level where it does not palpably interfere with the separation. On the other hand, under certain conditions optimal production rate can be obtained at higher temperatures.

Comparison of anion-exchange and hydroxyapatite displacement chromatography for the isolation of whey proteins

In displacement chromatography, several substances may be isolated and concomitantly concentrated, which makes this separation procedure attractive for the processing of diluted product streams containing a number of high value substances. Here, the suitability of anion-exchange and hydroxyapatite displacement chromatography for the processing of technical dairy whey is investigated. The pH and flow-rate of the carrier, the displacer chemistry and, in case of the apatite, the particle diameter of the stationary phase are considered. As a consequence of the pH sensitivity of the beta-lactoglobulin, one major whey component, apatite displacement chromatography is less then successful in whey separation. At a denaturing carrier pH (> 8.5) the beta-lactoglobulin zone is broad and stretches over the entire displacement train. At a lower carrier pH, previously successful polyanionic displacers do not bring about separation, while low-molecular-mass ones do, but they tend to overrun and thus contaminate the protein zones. In the case of anion-exchange displacement chromatography, polyanions, especially polyacrylic acid (PAA, M(r) 6000), constitute suitable displacers. Here too, a carrier pH of 8.0 is most suited to the separation of the whey proteins. The low-molecular mass-displacer iminodiacetic acid (IDA, M(r) 133.4), on the other hand, displaces only alpha-lactalbumin. The beta-lactoglobulin remains on the column. PAA is used as the displacer to process a dairy whey sample.

Chromatography in the downstream processing of biotechnological products

Chromatography techniques are essential for the isolation and purification of most of the high value products of modern biotechnology. The economically sensible and technically satisfactory downstream processing of a therapeutic protein, usually involves a number of chromatographic steps. Its development and optimization require considerable knowledge of the various physico-chemical and engineering aspects of biochemical chromatography. This review addresses the various modes of chromatography and the design of chromatographic separation processes from a biotechnologist's point of view. Strategies for optimizing the structure of the downstream process are outlined and scaling up consideration are discussed. The importance of the different chromatographic methods in research and development is estimated in an analysis of protein purification schemes recently published in the literature. Finally, examples of the application of chromatographic procedures for process scale product purification in the biotechnological industry are given.

High-performance liquid chromatography of amino acids, peptides and proteins. CXXXII. Optimisation of operating parameters for protein purification with chromatographic columns

In large-scale chromatography, process optimisation is one of the key elements for success. This paper presents a method for determining the optimum operating parameters for affinity and ion-exchange chromatographic columns when used for protein purification. Based on a mathematical model developed as part of our association investigations, computer programs have been developed to describe the dynamic relationships acting within the chromatographic system. Two basic operating parameters, the flow-rate and the effluent concentration at which the adsorption stage is terminated, can be optimised to give a maximum production rate. The sample loading volume and the processing time then can be determined. The effect of washing conditions on the production rate and the yield is also discussed. Examples are given for a specific system where the optimisation is based on the yield and the percentage utilisation of the column capacity. Contour plots are generated to aid the determination of the range of controlling parameters, and to guide further system design.

Preparative chromatography in biotechnology

The field of preparative chromatography has experienced several important advances recently in both the structure of chromatographic materials and modes of chromatographic operation. This review presents recent applications of preparative chromatography in biotechnology, as well as novel stationary phase materials and engineering approaches to preparative chromatographic bioseparations.

Purification of complex protein mixtures by ion-exchange displacement chromatography using spacer displacers

The anion-exchange separation of complex protein mixtures by displacement chromatography using spacer displacers driven by high-affinity final displacers is demonstrated. Guinea pig serum was separated on a medium-resolution adsorbent using a single heterogeneous mixture of carboxymethyldextran displacers to space the protein components. Mouse liver cytosol was separated on a low-resolution adsorbent using six carboxymethyldextran spacer displacers of increasing column affinity. The demonstration of the purification of alkaline phosphatase from E. coli periplasm by displacement chromatography on a high-performance liquid chromatography column is reviewed. The benefits of spacer displacers for separating minor components from complex biological protein mixtures is discussed. A simplified method for preparing carboxymethyldextran displacers is presented.