Pumps, valves, probes, fittings, tubing and sensing components for precise sample preparation, reagent handling and instrument fluidics.
Syringe Pumps for Sequential Injection and Flow Analysis
Application guide · Sequential injection
Sequential injection and low-pressure flow analysis create an ordered train of sample, reagent, carrier and wash segments in a holding path. The syringe pump controls segment volumes and direction; the method succeeds only when valve timing, dispersion and detector arrival are repeatable.
Engineering example: a sequence of 50 μL sample, 25 μL reagent and 100 μL carrier occupies at least 175 μL before air gaps, holding-coil reserve and wash. The syringe must also reverse and propel the train without exceeding the useful holding volume.[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
Segmented reaction
Segment order, volume, contact and reaction time
Keep interfaces reproducible before detector entry
Flow-cell loading
Cell volume, line volume and valid read window
Align detector acquisition to actual arrival
Multiple reagents
Port order and incompatible combinations
Prevent direct contact in shared valve passages when necessary
02Calculate the working point and the margin the instrument really needs
Calculations to complete before prototype selection
Quantity
How to define it
Why it matters
Total aspirated train
Sum of liquid segments and air gaps
Must fit syringe and holding path
Residence time
Path volume ÷ transport flow plus programmed stops
Set reaction time and detector window
Wash turnover
Shared volume × required exchanges
Determines liquid use and cycle time
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 carrier path→Aspirate ordered segments→Reverse into holding path→React during flow or stop→Pass detector in valid window→Wash to baseline
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
Peak arrives late
Changed volume, flow or restriction
Measure actual transit volume and pressure
Peak broadens
Excess dispersion or fitting dead volume
Review tubing ID, connections and segment speed
Baseline does not recover
Incomplete wash or trapped reagent
Locate unswept volume before extending the entire cycle
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
Segment volume
Tracer or gravimetric check for each aspiration
Programmed order and volume are preserved
Detector response
Arrival time, peak shape and repeatability
Valid window is stable across cycles
Recovery
Blank after worst reagent sequence
Baseline and carryover meet the method target
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.
