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Using Guard Columns and Retention Gaps in GC (Part 1)
J
P
de
ZIlIIUW,
Inl:ematlol1lll GCCOll5umabllls Speclllll5t,
RllIItIlk
COrponlllon
Guard columns and n1t8n\i)n gllps
111'8
used widely In
!IllS
chromato!lnllphy
(Ge).
Manv users
h
ve
d
~
understanding the dll'l'erence between these two
products, even though th811l
Is
II
slllnmcant dlll'8l1lnat In lJppllcatlon. Retention
gaps mal
tv
are used for foo.lsrng the IlIrTllle colTllonent9 when Introdudng
II
large Olqulcf)
SillTllle
dnctly onto the Cl)klrm. Gulrd colurms
lInI
used to proted:
the analytk.a column from Cl)ntarrlnlltlon. When using
II
retention gap system, the
retention gap w. also
Itt 15 ,
gu,rd Cl)tJrm. but Its primary function
Is
to aeate a toQJslng eft'ed:.
Guard columns and reten\i)n g,pi both
muit
be coupled to the lInalytlall a1lumn, and this a1nncalon
Introduces
1I
potentllll potlt ofr1sk.
A
new Ipprolch Is
tD
Integfllte the retention gap directly Into the
lInalytbll aIlurm.
By
lIpplyt1g I 'segrTll!!nt:' COltlng technology the stationary phase ean
be
deposited In a
certllin pert of tile
00
rm do
lng, deac:tMlted sectfon It the beginning. Ccllumna1upllng
Is
not required
end ITlIIlntenance
II;
greatly 51"1'
/fed .
In Part
1
of
this IIrtfde
WI!
will explore retention gaps and bUild a
foundation for a cc"1',rtson
to gu.,.d ootJrms.
In Pllrt
2.
we will review guard oolumns and dlsQJSS the
new segment
ccat~g
technology.
U_
of
I"IIIadI
p~
In today's laboratory.
GC
mettloos mJst be
s~le.
fast:.
nd low detection limits required. Besld s
that, suffi:ient precision m.Jst
11150
be obblined . It.n stllrts by introducing the Ample In the slTlllllest
possIble
~Jeetlon
band and maldng th band
rrigr1l~
thmugh the a1plllary with mlnlmal105s of the tarvet
components. With on-cckllTI'I injedion
II
liquid saf1'C)1
is
directly introduced Into the capillary C11lumn s a
liquid whill!lthe a1pilary
CII~mn.
kept at
a mITt' ratu
10-15°C
low th bollng pelnt of the lolwlnt.
During this process tile salTt'le Cl)ft1)onents are spread In an unreproducible way oW!r the first 2G-l00cm
orc:apllary whle tha solVent Is evapo1'8t1ng . Pa1'8lT'1lt
rs
I
InJ ctlon ap ad, a1mergaal'low, tempenatuN
of solvent and colul'l'l'l, type of solven t:, and
p
"urean
will
am
ct th Injection band width. Additionally,
when nonbonded stationary phas s are us d,
ttl
dl
tt
contact with liquids will NSUIt In
8
distortion or
the stationary phase
fb
and vary short Cl)lurrn
IlI'IItl lTll!l. Th
1I'IIIjor1ty
oftode.,_ stationary phalles, like the
Rtx~
and
Rx~
phasall,
lrnmobllz d by
D"OSS-
Bnd sur1'llcabond ing techniques.
~n1
1
Retention gaps
re
used
to
1'00.1
co""onent:9 In
a
tight band at the
begInnIng or
ttl
an
Iytbl
column.
.) Simple Inttod ucdon: lloulcl
nlm
or
JOIve
t
I nd
lIImple
are
depoI~cf
In
the
rIlIt
Iengtll
of c.pllliry•
• ) Oven temperetIJre II
Inmued
(temp.
pl'\l9111m
run,-:
,o~nt
ud bllllet Q:lmpoundi
Ire VIIJxHueit
lind trIlvel unret.lnad tlil'\lugtl
retentIOn
all).
10}
Whln b'1l.t<llmpaund. <11m.
In
mnbd
NItl
u..
mtla""ry
ph
tIl,y'l1I ..r.......
d
on
tn••
n.!YtI1:II
I
mlumn ulllng In a
n.....
wlnlll.l
band NdUl.
For proper appkatlon of tI'Ie on-cclurm InJee:tlon technique, the use of retention gaps
Is
essentlal.l, 2 The
Ntentlon gap consists of a 1-3m length of deactivated capillary that Is positioned In fl'ont of
the
analytical
mlumn.
AI
tI'Ie processes desai)eo wil still
take
plate, but now the mmponents are distributed over the
2012
1
