Metrohm 2.850.2230, Manual, Page: 48 / 150

3.11 Low pressure gradient
￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭
38
￭￭￭￭￭￭￭￭
850 Professional IC–Anion – MSM-HC – MCS – LP Gradient
3 Tubing flare
With tubing nipple.
4 Clamping screw
5 Eluent aspiration tubing 6.1834.080
For aspirating the eluent. The clamping
screw
(17-
4
) is firmly mounted.
6 Connection capillary 6.1834.090
Connection from the eluent degasser to the
high pressure pump
(see Chapter 3.12, page
42) . The clamping screw (17-
4
) is firmly
mounted.
1
CAUTION
The clamping screws (17- 4 ) must be tightened carefully. Use the
6.2621.050 wrench for this.
￭
Insert the eluent aspiration tubing (17- 5 ) in the eluent degasser
input (17- 1 ) .
￭
Carefully tighten clamping screw (17- 4 ) .
2
￭
Insert connection capillary (17-
6
) (the end with the longer clamp-
ing screw (17-
4
) ) into the eluent degasser output (17-
2
) .
￭
Carefully tighten clamping screw (17-
4
) .
￭
Connect the other end of the connection capillary (17-
6
) (with
the shorter clamping screw ) to the high pressure pump .
3.11 Low pressure gradient
Up to three different eluents can be mixed with the low pressure gradient.
The three "normally closed" valves are usually closed. With each pumping
cycle, the valves are kept open until the desired percentage of eluent has
flowed, after which they are closed again. This results in a situation where
the valves also open and close audibly when 100% of a solution is con-
veyed.
The eluent gradient generated in the mixing valve is aspirated by the high
pressure pump and conveyed into the IC system. Because of the physical
restrictions of the mixing valve, the flow must not exceed 3 mL/min. when
using a low-pressure gradient.
In general, the use of the low pressure gradient is recommended for elu-
ent percentages ranging from 10…90%. However, depending on the
installed pump head and the set flow, the smallest possible eluent per-
centage can vary
(see Table 1, page 39) .