ADV01-05_1-298

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www.restekcorp.com

RESTEK Advantage

800-356-1688

By Gary Stidsen, Innovations Team Manager

Minimize Adsorption of Active

Analytes, Using a Drilled

Uniliner

GC Inlet Liner

Now in Two Configurations, to Match

Chromatographic Conditions

✔

Eliminate injector active sites and dead volume—

minimize adsorption and discrimination.

✔

Use one configuration if analytes elute near the solvent peak.

✔

Use alternate configuration if analytes elute later than the solvent.

In sample injections into a hot splitless injection

port liner, a typical 1µL sample expands to a volume

of hundreds of microliters.

The sample solvent

vapor, and the analytes, fill the entire injector sys-

tem. Analyte molecules come in contact with hot,

active surfaces outside the injection port liner, and

occupy the dead volume at the bottom of the injec-

tion port, below the inlet end of the column (Figure

1). In splitless injection mode, there is very little

carrier gas flow in this area to carry the analytes

back up to the column inlet. This situation is most

noticeable with active compounds that degrade

when they come in contact with active surfaces;

recoveries can be significantly reduced. In addition,

late-eluting compounds that do not readily vaporize

are affected by injection port discrimination.

The innovative geometry of a Drilled Uniliner

inlet

liner minimizes active sites in the sample pathway,

and reduces injection port discrimination. The ana-

lytical column connects to the bottom of a Drilled

Uniliner

inlet liner via a Press-Tight

seal (Figure

1), eliminating sample contact with any part of the

injector below the column inlet. Recoveries of active

analytes are significantly improved.

A hole in the

side of the liner allows the injector to be operated in

traditional split/splitless mode.

We now offer Drilled Uniliner

inlet liners in two

configurations (Figure 2). The liner to use depends

on the analysis, and how closely the early-eluting

compounds elute to the solvent peak.

Analytes

contact hot

surface and

dead volume

at base of

splitless

liner

Figure 1

—

Inlet liner geometry affects

analyte recovery.

Drilled

Uniliner

inlet liner

efficiently

conveys

sample onto

column

Rtx

- 5Sil MS 30m, 0.25 ID, 0.25µm (cat.# 12723)

Sample:

methylene chloride, PR grade

Inj.:

0.5µL, splitless (hold 2.5 min.)

4mm single gooseneck inlet liner

(cat.# 20799)

4mm Drilled Uniliner

inlet liner

(cat.# 21055)

4mm Drilled Uniliner

inlet liner

(cat.# 20756)

Inj. temp.:

260°C

Carrier gas:

helium, constant pressure

Linear velocity:

17cm/sec. @ 50°C

Oven temp.:

50°C, isothermal

Det.:

FID @ 330°C

Figure 3

— Solvent peak profiles

from Drilled Uniliner

inlet liners and a

splitless liner.

GC_EV00680

3a) 4mm single gooseneck splitless liner

Use hole near top configuration if analytes elute later than

the solvent peak, or when the sample solvent is water

Figure 2

—

Drilled Uniliner

inlet liners

are available in two configurations. The hole

allows the injector to be operated in

split/splitless mode.

Use hole near bottom configuration if analytes elute near

the solvent peak

In flash on-column injection all of the solvent is

transferred from the injector to the column, produc-

ing a substantial solvent peak tail. Splitless injection

eliminates the solvent tail, because the injector goes

into the split mode after the compounds of interest

are transferred to the column, and all solvent

remaining in the injection port is flushed out

through the purge vent. The solvent peak ends

abruptly, as shown in Figure 3a. Elimination of the

solvent peak tail is an advantage to using the splitless

injection technique when analyzing compounds that

elute close to the solvent.

A Drilled Uniliner

inlet liner produces a distinctly

different solvent peak shape than the single goose-

neck splitless liner, as shown in Figure 3b and

Figure 3c. The most noticeable difference is the

peak width; the peak is considerably narrower than

the peak from the single gooseneck liner. The posi-

tion of the hole in the Drilled Uniliner

also affects

solvent peak shape. A Drilled Uniliner

with the hole

near the bottom produces a sharply ending solvent

peak, similar to that from a single gooseneck liner

(Figure 3b). This liner is a direct replacement for a

splitless liner, and should be used when analytes

elute closely behind the solvent.

No solvent peak tail

3b) 4mm Drilled Uniliner

liner,

hole near bottom

No solvent peak tail,

equivalent to single

gooseneck liner

3c) 4mm Drilled Uniliner

liner,

hole near top

Solvent peak tail, from

solvent remaining in liner

The position of the hole in a Drilled

Uniliner

inlet liner affects solvent

peak shape.

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