Biomedical subjects

C Vidal-Madjar

Publications and source records attributed to C Vidal-Madjar.

22 records · Page 2Linked to original sources

PubMed1991

Application of the split-peak effect to study the adsorption kinetics of human serum albumin on a reversed-phase support.

The adsorption step of human serum albumin on a reversed-phase support was analyzed by studying the "split-peak" effect in mass-overload conditions. This behavior is characterized by the occurrence of a first non-retained fraction and is described by an analytical expression in the case of a Langmuirian adsorption isotherm. The method was applied to determine the column loading capacity, the number of mass-transfer units and the apparent adsorption rate constant measured at a given flow-rate. The nature of the organic modifier influences the split-peak effect: it increases with the eluotropic strength of the organic solvent added to the buffer. Compared to the results with pure buffer, it is the association of two effects, the decrease of the column loading capacity and that of the apparent adsorption rate constant, which increases the split-peak effects observed when methanol and 2-propanol are added to the eluent. These results allow us to gain a better understanding of the role of the organic solvent in the elution behavior of proteins in reversed-phase high-performance liquid chromatography.

1-Propanol↗

PubMed1987

Microcomputer system for data acquisition and software handling in chromatography.

A complete, powerful yet simple and inexpensive microcomputer system for chromatography is described. It consists of an electronic interface card and an exploiting software, both controlled by an independent microcomputer. The interface includes all necessary circuits for digitizing the chromatographic signal and for controlling the actuators and the sensors connected with the chromatograph. The software, clock-interrupted, allows simultaneous data acquisition, mathematical treatment, connected plotting, and printing, and drives injection valves and gradient elution pumps. This system is both suitable for high-speed capillary gas chromatography and for high-performance liquid chromatography.

Chromatography↗

PubMed1987

Modeling of peak profiles. Application to the preparative liquid chromatography of steroids.

The solution of the mass balance equations in liquid chromatography describes the propagation of signals of finite concentration through the column. The general numerical solution requires the prior determination of the partition isotherm. For low solute concentrations, when the isotherm equation can be replaced with a two-term expansion, an analytical solution for the peak profiles is obtained. The theory is applied to predict, as a function of solute concentrations, the elution profiles of two steroids of similar structure, cis- and trans-androsterone, with organic solvents as the mobile phase and buffered silica gel as the stationary phase. At infinite dilution both steroids are well resolved, the trans isomer being eluted before the cis isomer. At high concentrations their adsorption isotherms intercept each other and, for large amounts injected, their elution order is reversed, with marked differences in the elution peak shapes of both steroids.

Adsorption↗

PubMedDate not supplied

Chromatographic kinetic measurements of human serum albumin adsorption on monoclonal antibodies.

A chromatographic method was employed to study the kinetics of human serum albumin (HSA) adsorbed on immobilized monoclonal antibodies. The antibodies of various specificities were covalently bound to a high-performance liquid chromatography (HPLC) silica support. For very low desorption rates, successive amounts of the reacting protein were injected until column saturation. The analysis of the increase of the non-retained fraction calculated from peak area measurements gives the capacity of the support and the rate of the biospecific adsorption process. The model is based on a second-order Langmuir kinetic law and assumes a global mass transfer for the adsorption process. The use of a silica support of small pore size permits the reduction of the contribution for mass transfer in the stagnant fluid and the decrease in the column capacity: due to its large size, the reacting molecule is adsorbed on the external surface of the particle. The adsorption rate constants of HSA on five monoclonal anti-HSA antibodies of different specificities were determined. For all the immuno-adsorbents studied, the adsorption rate constant is significantly lower than that found on immobilized polyclonal antibodies. Measurements at different flow rates reveal that the mass transfer due to the transport to the adsorbent surface is small and can be estimated.

Adsorption↗