28.02.2013 Views

Handbook of Size Exclusion Chromatography and Related ...

Handbook of Size Exclusion Chromatography and Related ...

Handbook of Size Exclusion Chromatography and Related ...

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

processing <strong>of</strong> 2D-HPLC data. Knowledge <strong>of</strong> the exact elution start is especially<br />

important for the molar mass calculation based on SEC retention volumes.<br />

The least complicated way for sample transfer is collection <strong>of</strong> effluent from<br />

column #1 by means <strong>of</strong> afraction collector <strong>and</strong> their successive reinjection into<br />

column #2. Fractions from column #1 can easily be further manipulated, for<br />

example,concentrated,orcombined (eitheradjacentfractions fromonesinglerun<br />

orcorrespondingfractionsfromseveralindependentruns<strong>of</strong>column#1).Fractions<br />

from column #1 can also be reinjected into column #2 only partially (“heart cut<br />

approach”). Usually the effluent part with maximum concentration is further<br />

analyzed. The entire <strong>of</strong>f-line procedure is, however, too sample, time, <strong>and</strong> work<br />

intensive to compete with modern on-line approaches as far as the latter can be<br />

automated by using electrically or pneumatically operated valves that are<br />

controlled by appropriate s<strong>of</strong>tware.<br />

Some experimental setups for on-line reintroduction <strong>of</strong> eluent from the first<br />

dimension separation column into the second dimension separation column are<br />

showninFigs17–20.ThesimplearrangementinFig.17utilizesonesix-porttwoway<br />

valve provided with asample loop. The procedure necessitates astop-<strong>and</strong>-go<br />

operation<strong>of</strong>thefirstdimensioncolumn,iftheentireeffluentfromcolumn#1isto<br />

betransportedintocolumn#2.Theloopsizemustbeappropriatelyadjusted<strong>and</strong>a<br />

partial loop filling procedure can also be applied.<br />

Two further setups (Figs 18 <strong>and</strong> 19) allow continuous operation <strong>of</strong> the first<br />

dimension separation column C#1. However, the flow rate in C#1 must be adjusted<br />

so that filling time <strong>of</strong> the injection loops is matched with the duration <strong>of</strong> elution in<br />

the second dimension separation column. The highest detected retention volume<br />

<strong>of</strong> column #2 limits throughput <strong>of</strong> the whole 2D analysis. For SEC column #2, the<br />

late eluting peaks are system peaks or peaks <strong>of</strong> eluent from the first dimension<br />

separation column, which was introduced into the second dimension separation<br />

column together with the sample fraction. Large volumes <strong>of</strong> eluent from column #1<br />

Figure 17 Schematic representation <strong>of</strong> the 2D-HPLC sample transfer system with one<br />

six-port two-way valve. C#1 <strong>and</strong> C#2 are column systems, P#2 is the second pump, W is<br />

waste. Column #1 works in the stop-<strong>and</strong>-go mode. L is the loop. For further explanation see<br />

the text.<br />

© 2004 by Marcel Dekker, Inc.

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!