Table of Contents
Advertisement
Live switching
The two columns are connected by the live T-piece. The
sample then only comes into contact with a platinum-
iridium capillary, but not with valves. The various oper-
ating states of the live switching are activated using
solenoid valves in the gas supply line.
To make live switching function correctly, you must
first adjust the flows using needle valves. This descrip-
tion includes:
4 pages: How live switching functions
2 pages: Adjustment of live switching
2 pages: Fault diagnosis.
Mounting of columns
on the live T-piece
The side with the long, thick connection is always
the column B side. The figure shows the assign-
ment of the connections.
Insert column into live T-piece as far as possible,
and then pull back by 1 mm
Tighten screwed gland. Do not move the column in
the process. This can be guaranteed if you pre-
viously compress the gasket such that it can just
still be moved on the column.
CAUTION
Do not insert the column next to the
coupling capillary! It will otherwise break off.
For capillaries with a solid stationary phase
(plot columns): first scratch clear the end of
the column using a drill and with the carrier
gas flowing. Contamination may block the
coupling capillary or the clearance!
NV
Cut
Column A
Live T-piece for capillary columns
schaltg.chp, Issue August 17, 1999
Purge outlet
Column B
Cut
outlet
NV
Straight
Selection of live T-piece
Different live T-pieces are required for the different col-
umn diameters. The following table lists all live T-
pieces. Ideal for capillary columns: the internal
diameter of the column should be 20% greater than the
outer diameter of the coupling capillary.
Columns
Internal diameter [mm]
Packed
3
2
Capillary
0.2 ... 0.22
0.25
0.32
0.53
Identification of coupling capillary diameter
The small metal plate of the coupling capillary is bent
on the side of the live T-piece. The exact outer diameter
of the coupling capillary is printed on this.
Column diameter
Column A and B usually have the same diameter. The
following applies if columns A and B have different
diameters: selection of the appropriate coupling capil-
lary depends on the thinnest column.
Golden rule: good functioning is always achieved if the
diameter of column A is smaller than that of column B.
You can expect problems if the reverse is the case!
Live switching
Cut
outlet
Column A
NV
Cut
Live T-piece for packed columns
Live switching
Coupling capillary
Outer diameter [mm]
2.8
1.8
0.17
0.20
0.27
0.43
Purge outlet
Column B
NV
Straight
6 - 3
Advertisement
Chapters
Table of Contents
