Keep the reagent pump on a separate branch
Column effluent does not pass through the RPL reagent pump in this arrangement. Post-column derivatization adds and reacts reagent with separated components before detection; the method determines whether this additional branch is needed.[1]
Shortlist by displacement, speed and method demand
| Series | Published displacement range | When to evaluate |
|---|---|---|
| RPL-P4 | 12–80 µL/rev | An initial candidate when a smaller displacement is useful for the required reagent flow |
| RPL-P6.35 | 50–300 µL/rev | A candidate where mechanical displacement adjustment and speed can provide the required operating range |
| RPL-P15 | 300–1,200 µL/rev | Only where the method requires substantially more reagent; not a default low-flow LC selection |
The range is neither a minimum reliable dose nor a guaranteed continuous-flow range. Confirm the permitted speed, displacement setting, duty and installed load. A larger RPL model is not included simply because it belongs to the same family.
The RPL selection guide covers displacement and configuration choices for the separate reagent branch. Use it to prepare an engineering shortlist, not as evidence that a model is validated for every derivatization method.
Validate the method, not just the pump's average output
- Match reagent flow to column effluent, reaction chemistry and permitted dilution.
- Check mixing uniformity while controlling added volume and peak broadening.
- Evaluate whether output variation, speed changes or backpressure changes create unacceptable baseline noise.
- Use reagent composition, precipitation risk and cleaning procedure to assess every wetted material.
These checks establish an application candidate, not a prequalified reagent-pump replacement for every LC method. Obtain performance data at the intended working point before fixing the configuration.
Add a reagent branch only when the detection method needs it
A method that detects the separated compounds without a post-column reaction does not need this pump branch. When derivatization is required, define reagent concentration and flow, mixing geometry, reaction conditions and detector acceptance first.
Understand what valveless construction changes
RPL metering combines rotating and reciprocating ceramic-piston motion to organize inlet and outlet transfer without conventional dynamic check valves inside the pump. Displacement per revolution and rotational speed provide the basis for a metering configuration.[3]
Valveless does not mean instantaneous pulse-free delivery, nor does it remove the system's need for shutoff, source selection or anti-siphon measures. Check the detector baseline and standards as well as liquid collected over time.
Review the valveless metering-pump principle to understand the pumping mechanism and its boundaries. Valveless operation does not remove the need to measure flow variation, compatibility or detector response.
Questions before selecting an RPL configuration
Can an RPL candidate replace the high-pressure LC main pump?
That is not the use described here. The candidate serves a post-column reagent branch. Main mobile-phase delivery requires its own validated high-pressure, continuous-flow and gradient capabilities.
Is a displacement range sufficient to select the model?
No. You also need speed range, continuous-duty capability, actual backpressure, wetted materials, control and allowable flow fluctuation. A value in µL/rev cannot be compared directly with a target in mL/min.
What remains unconfirmed without method data?
The final pump configuration, reagent compatibility, low-flow stability, baseline contribution and maintenance interval. Treat the shortlist as an engineering evaluation until these are established.