Handbook of Size Exclusion Chromatography and Related ...

process will determine the turn-around time. The importance of high-speed
analytical techniques gets obvious when it is considered that research companies
synthesizeover500targetsperday,butonlyabout100samplescanbeanalyzed.The
potential of new synthetic methods and in-line production control cannot be fully
utilized until the typical SEC run times of 30 minutes are substantially reduced.
2 APPROACHES FOR FAST SEC SEPARATIONS
Thissectionreviewsverybrieflydifferentmethodsthathavebeenusedtoincrease
the number of SEC analyses per unit time. The key benefits and requirements of
each method are discussed and summarized in Table 1.
2.1 Parallelization
Early answers to such challenges have been parallelization and automation of
analytical processes. More samples can be analyzed by using fully automated
instruments, which work day, night, and over the weekend. The number of
processedsamplescanbeincreasedproportionallybysettingupidenticalsystems
in parallel. The time and analytical requirements for each sample are not changed
butthenumberofsamplesperhourcanbeincreased.Sincenochangeinanalytical
methods isnecessary,implementation ofparallelsystemsisnotverycomplexand
is not straightforward.
This approach, however, is clearly limited by a number of important
prerequisites like space, operator instruments, and computers. All of thiswill cost
a lot of money for initial investment, maintenance, and operation. Practical
experiencewith this concept has shown that this approach will hold if the number
of samples increase much less than one order of magnitude.
2.2 Shorter Columns
Column length reduction is the traditional method to reduce analysis time. This
wasdoneinSECapplicationsinthe1960sand1970swhenmoreefficientcolumn
packings allowed smaller column dimensions. Today, the efficiency of SEC
columns is at a stage where a further column length decrease cannot be
compensated without aloss of resolution. Cutting down on column length is also
verylimited.Thereforesomecolumnmanufacturers(mostnotablyPLandTSK,in
Freiburg,Germany)cutcolumnlengthinhalftoincreasethroughput(3).However,
this reduces run times proportionally and only low time and solvent savings are
possible (Fig. 1).
Please note that shorter columns cannot easily meet the polymer resolution
requirements of ISO 13885 or DIN 55672 SEC standards (9).
The advantages and disadvantages of this approach are summarized in Table 1.
© 2004 by Marcel Dekker, Inc.