Longitudinal diffusion and resistance to mass transfer as causes of nonideality in chromatography

✍ Scribed by J.J. van Deemter; F.J. Zuiderweg; A. Klinkenberg

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 1022 KB
• Volume: 50
• Category: Article
• ISSN: 0009-2509
• DOI: 10.1016/0009-2509(96)81813-6

✦ Synopsis

Al~tract--The mechanisms of band broadening in linear, nonideal chromatography are examined. A development is presented of a rate theory for this process, wherein nonideality is caused by axial molecular diffusion; axial eddy diffusion; finiteness of transfer coefficient. The correspondence with the plate theory is given, so that the results can also be expressed in heights equivalent to a theoretical plate.

The plate theory has been extended to the case of a finite volume of feed; the requirement for this feed volume to be negligible has been examined and a method is presented for evaluating concentration profiles obtained with a larger volume of feed.

An analysis is given of experimental results, whereby the relative contributions to band broadening for various cooperating mechanisms could be ascertained.

R~nm~-Une 6tude a 6t6 faite des m6canismes de l'61argissement des bandes dans la chromatographie lin6aire non-id/~ale. On a d6velopp6 une th6orie sur la vitesse de ce processus, selon laquelle la non-id6alit6 est caus6e par: la diffusion mol6culaire axiale; la diffusion turbulente axiale; le fait que le coefficient de transfert aune valeur finie. La correspondance &ablie entre cette thgorie et celle des plateaux permet d'exprimer les r6sultats obtenus aussi en termes de la hauteur de colonne 6quivalente ~ un 6tage th~orique.

La th6orie des plateaux a 6t6 rendue applicable sur le ces d'un 6chantillon de volume fini; les conditions dans lesquelles le volume de cet 6chantillon est n6giigeable ont 6t6 6tudi6es et on pr6sente une m6thode pour interpreter les profiles de concentration obtenus avec des 6chantillons plus grands.

Une analyse des r6sultats exp&imentaux a permis de d6terminer les contributions relatives des diff6rents m6canismes en question ~. l'61argissement des bandes.