8 Introduction
Eluent Blending
The gradient proportioning valve blends up to four eluents or buffers in any combination.
It produces predictable gradient segments regardless of eluent compressibility and system
backpressure.
Eluent selection and proportioning take place on the low-pressure (intake) side of the
600E system.
Flow Path
The pump flow path begins with the eluent reservoirs and ends with the column as
follows:
1. In the eluent reservoirs, sparging with helium degasses the eluents.
2. The eluents flow through Teflon tubing to the gradient proportioning valve, which
blends the eluents.
3. The inlet manifold directs flow to the two inlet check valves.
4. The pump heads move a volume of 100 or 225 µL with each stroke at a flow rate of
0.01 to 20 or 45 mL/min, depending on the size of the installed pump head.
5. From the pump heads, the eluent converges at a reference valve before flowing into
the high pressure noise filter and then to the pressure transducer.
6. Flow continues from the pressure transducer outlet to the injector.
7. Flow continues out of the system to the column and the detector.
Injector
The optional Rheodyne 7725i Manual Injector is designed for variable-volume, full- or
partial-loop filling operation.
The volume of the sample injected is determined by the volume of the sample loop plus
the valve passages.
Vent Valve
The vent valve on each injector allows you to direct eluent flow from the pump to the
column or to divert the eluent flow waste.
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