Page 327 - Multidimensional Chromatography

Industrial and Polymer Applications 317

Table 12.1 Compositions of the compound rubber stocks

Content a
Component Chemigum N-615 Plioflex 1502
Polymer 100 100
HAF carbon black 50 50
Aromatic processing oil – 5
Dibutyl phthalate 5 –
Stearic acid 1 1
Wingstay 100 b – 1
Wingstay 300 c 1 –
Zinc oxide 5 5
MBTS d 1 1
TMTD e 0.3 0.3
Sulfur 1.5 1.5
Total 164.8 164.8
a Expressed as parts per hundred of ‘pure’ polymer.
b Mixed diarylphenylenediamine.
c Alkylarylphenylenediamine
d 1
2,2 -thiobis (benzothiazole).
e
Tetramethyltrhiuradisulfide.
with other components in the SEC trace (see Figure 12.12(a)). Hence, analysis in
the second dimension by RPLC of the transferred fractions allowed the identification
of these components.

12.7 GC–GC APPLICATIONS

When columns of the same polarity are used, the elution order of components in GC
are not changed and there is no need for trapping. However, when columns of differ-
ent polarities are used trapping or heart-cutting must be employed. Trapping can be
used in trace analysis for enrichment of samples by repetitive preseparation before
the main separation is initiated and the total amount or part of a mixture can then be
effectively and quantitatively transferred to a second column. The main considera-
tions for a trap are that it should attain either very high or very low temperatures over
a short period of time and be chemically inactive. The enrichment is usually carried
out with a cold trap, plus an open vent after this, where the trace components are held
within the trap and the excess carrier gas is vented. Then, in the re-injection mode
the vent behind the trap is closed, the trap is heated and the trapped compounds can
be rapidly flushed from the trap and introduced into the second column. Peak broad-
ening and peak distortion, which could occur in the preseparation, are suppressed or
eliminated by this re-injection procedure (18).
Heart-cutting, with trapping and re-injection, using isothermal dual capillary
column chromatography for separation of the UV photolysis products of methyl