Locate the pump in the LC fluid path
Needle-wash supply, wash-station drainage and post-column reagent addition are branches, not additional pumps in series along this main path.
An autosampler metering device may be isolated from the high-pressure side or exposed to it, depending on the injection architecture. Check aspiration, switching, injection and washing states before selecting an auxiliary pump. A post-column reagent branch is needed only when the analytical method requires it.[1][2]
Different positions have different pump names and duties
| Position | Common name | Duty and boundary |
|---|---|---|
| Mobile-phase delivery | LC pump; solvent-delivery pump; binary or quaternary pump | Deliver the analytical flow against column backpressure and support the system's gradient arrangement. This is the instrument's core high-pressure pumping function. |
| Autosampler metering | Metering device; sample syringe; metering pump | Create controlled displacement for aspiration and sample transfer, coordinated with the needle, loop and injection valve. |
| Needle-wash supply | Needle-wash pump; rinse pump; wash-solvent pump | Deliver cleaning liquid to the wash port. Solvent choice, coverage and contact time determine how effectively residue is removed. |
| Wash-station drainage | Waste pump; drain pump; waste-aspiration pump | Remove spent wash liquid. Include gas-liquid capability if the inlet intermittently draws air or foam. |
| Post-column reagent addition | Derivatization-reagent pump; post-column dosing pump | Feed a separate reagent branch before detection. Verify flow, mixing, backpressure and detector response with the actual method. |
Choose the product family from the task
| Task | FOREACH candidates | Selection gate |
|---|---|---|
| Autosampler metering | EA or SM; TM only where a constrained installation warrants it | Actual dose, useful stroke, pressure exposure, materials and valve sequence. Nominal capacity does not establish minimum reliable injection volume. |
| Needle-wash delivery | DPL30; DPL30H for a demonstrated higher-resistance requirement | Installed liquid flow, controllable operating range, wash chemistry and outlet load. Higher pressure is not automatically better. |
| Wash-station waste | DPL30 for a suitable liquid path; DPGL800 for a suitable gas-liquid path | Inlet media, suction and peak drainage demand. Gas free-flow is not liquid drainage capacity; DPGL800 is not for 100% liquid transfer. |
| Post-column reagent supply | RPL single-head valveless metering configurations | An engineering candidate only: confirm speed, displacement, backpressure, pulsation and complete-method performance. |
For the metering branch, use the piston-pump selection guide to prepare dose, materials and control requirements. Confirm pressure isolation before treating a dispensing configuration as an autosampler candidate.
Continue to the pump and task guide
Start with the result your instrument must achieve
| Customer requirement | First checks | Relevant task |
|---|---|---|
| Consistent volume for every injection | Working injection volumes, injection architecture and pressure at the metering device | Sample aspiration and metering |
| Less sample consumption | Loop size, needle and tubing volume, loading mode and usable vial volume | Sample-loop loading |
| Faster blank recovery after concentrated samples | Residue location, solvent formulation, effective contact time and drainage | Needle-wash supply |
| No liquid accumulation at the wash station | Peak incoming liquid, allowable hold-up, lift, air content and waste-vessel ventilation | Waste aspiration |
| Stable post-column response | Reagent flow, actual backpressure, permitted fluctuations, reaction tubing and detection method | Continuous reagent dosing |
For a liquid-only wash branch, the DPL30 selection guide explains the product's operating limits. Apply these checks to the installed wash path rather than assuming the free-flow rating is the wash-port delivery rate.
If the analytical method requires post-column reagent addition, review the RPL selection guide for displacement, drive and material choices. Suitability still depends on the reagent branch and complete-method validation.
Questions before choosing a model
Can one pump series cover the whole LC system?
Do not select by instrument name alone. Discrete volume metering, wash delivery, mixed air-liquid drainage and continuous reagent addition impose different stroke, flow, pressure and wetted-path requirements. First define the duty; then compare the suitable configurations.
Can a FOREACH pump directly replace the original instrument pump?
Provide the original model, interface drawing, control method, fluid-path diagram, media, pressures and acceptance criteria. Mechanical fit is only the first check: valve timing, firmware behaviour and complete-instrument results also need validation. These guides do not promise plug-and-play replacement of a particular instrument.
What should I send if I have not selected a model?
Start with a fluid-path sketch, liquid composition, dose or flow, available time, inlet and outlet conditions, and installation space. Add the injection mode for sample metering, gas-liquid state for drainage, or baseline requirements for post-column dosing.