Pumps, valves, probes, fittings, tubing and sensing components for precise sample preparation, reagent handling and instrument fluidics.
Valveless Metering Pumps for Automated Titration
Application guide · Titrant metering
A valveless pump can deliver repeated titrant increments, but endpoint control depends on the smallest useful volume that reaches the vessel and on the reaction and electrode response after each addition. Separate coarse addition from the near-endpoint step before choosing one pump for the entire titration.
Engineering example: if an endpoint is expected near 2.00 mL and the volume-contribution budget is 0.2%, the budget is 4 μL. A pump whose practical minimum increment is larger cannot meet that budget by software timing alone; use a finer metering stage or revise the method.[1][2]
01Define the liquid, receiver and complete duty before selecting the component
Translate the analytical task into an engineering duty
Use case
Inputs to define
Decision supported
Coarse titrant addition
Expected range and maximum addition rate
Choose fast displacement without overshooting transition zone
Near-endpoint addition
Smallest useful vessel increment and settle time
May require a different fine-metering channel
Refill/standardization
Titrant concentration, refill path and standard method
Retain traceability and avoid dilution
02Calculate the working point and the margin the instrument really needs
Calculations to complete before prototype selection
Use minimum, routine and maximum conditions rather than one nominal point. Include the first cycle after priming or idle, the lowest source level, the highest expected restriction and the actual receiving geometry. A nominal capacity, free-flow value or theoretical command increment is not an acceptance result.
03Map the task to a FOREACH configuration and the rest of the fluid path
04Program the full liquid cycle, including prime, wash and recovery
Prime and standardize→Add coarse increments→Mix and read→Reduce increment near endpoint→Confirm endpoint→Rinse tip and path
A complete method cycle is more than the active delivery step
The exact physical order and parallel actions depend on the instrument. Retain each state in the control and verification plan.
Record valve states, motion, dwell, sensor windows and rejected recovery cycles. This makes throughput and liquid consumption auditable and prevents a fast component movement from being reported as the complete analyzer cycle.
05Design abnormal-state diagnosis before the fault occurs
Observed result, likely mechanism and useful next action
Observed condition
Likely mechanism
Engineering response
Endpoint overshoot
Increment too large or reading too early
Reduce delivered step or increase settle time
Cumulative volume differs
Tip drip or incomplete delivery
Measure at vessel and inspect outlet
Drift after idle
Titrant change or crystal formation
Prime, standardize and clean
The controller should distinguish a recoverable event from a result-invalidating event. A retry is useful only after the original cause has been removed and the liquid path has returned to a verified state.
06Accept performance where the liquid is actually used
Minimum qualification plan for the integrated channel
Result
Where or how to measure
Acceptance question
Delivered increment
Collect near-endpoint commands at the actual tip
Meets volume budget
Reference titration
Certified or suitable standard material
Endpoint and repeatability meet method
Cumulative log
Sum accepted deliveries and refills
Matches reported titrant consumption
Test the exact liquid and complete wetted path at minimum, routine and maximum conditions.
Separate first-cycle, steady-state and post-idle results; do not average away recovery behavior.
Challenge the relevant fault and confirm the controller prevents an invalid result from being accepted.
Retain the configuration, software sequence, consumables and receiving-position result together as the qualification record.
