Fluidic priorities in five diagnostic instrument categories
Identify the analytical architecture that matches your equipment, then open the corresponding guide. The table lists each guide's main questions; shared topics such as metering and washing are explained in the context of each instrument.
| Instrument and guide | Main tasks | Factors affecting configuration | Evaluation metrics |
|---|---|---|---|
| Clinical chemistry analyzer | Addition of samples and reagents such as R1/R2; probe and reaction cuvette washing | Fixed probe or pipette tip; reagent aspiration from individual bottles or supply through dedicated tubing; reusable or disposable reaction cuvettes | Actual delivered volume, sample carryover and reagent interference |
| Immunoassay analyzer | Sample and reagent addition; magnetic bead separation and washing; substrate or trigger reagent addition | Solid-phase and readout locations, bead resuspension, washing method and whether signal reagents use dedicated paths | Bead retention, residual volume, background and signal |
| Hematology analyzer | Whole-blood sampling, dilution and lysis; counting-channel renewal | Metering valve or pump-based metering; channel architecture; use of sheath flow | Sampling representativeness, dilution ratio, counts and blank recovery |
| Coagulation analyzer | Plasma and reagent addition; prewarming, mixing and timing | Assay method, trigger rules, dispensing order and temperature window | Actual delivered volume, arrival timing and complete reaction results |
| Molecular diagnostics | Lysis, binding, washing, elution and amplification mixture preparation | Combination of fixed liquid supply, tip-based pipetting and magnetic-rod handling; separation of pre- and post-amplification operations | Nucleic acid recovery, inhibitor control and negative/positive control performance |
From assay tasks to fluidic configurations
The flow shows the selection and validation sequence. Valve positions, pump wetted boundaries and operating states still need to be checked for each branch.
Mark liquid sources, destinations and waste outlets on the fluidic diagram, then distinguish three task types: single-volume delivery, continuous supply and washing/flushing. For sample channels, also indicate whether the sample enters the pump chamber. With system-liquid drive, the chamber mainly contacts system liquid, while the probe tip and separation interface require separate treatment. With direct liquid contact, include the pump chamber, valves and tubing in residue and cleaning assessments.
Fixed probes integrate readily with piercing, probe washing and dedicated motion mechanisms, but washing consumes cycle time and wash solution. Disposable tips are replaced after use, reducing repeated cleaning of the wetted front end while requiring tip storage, loading, unloading and disposal. Both approaches require aspiration and dispense programs to be adjusted and validated with actual liquids; settings from similar instruments cannot simply be reused.
Dedicated channels suit liquids requiring reduced switching residue or tightly controlled storage conditions. Shared metering channels reduce the number of metering units but add routing, flushing and first-dose recovery steps. Include these steps in the complete cycle when comparing solutions, rather than considering pump running time alone.
| Configuration question | Compare first | Trade-offs |
|---|---|---|
| Wide variation in individual dose volume | Minimum, routine and maximum delivered volumes; whether auxiliary aspiration/dispense steps consume stroke | Larger capacity can reduce refills; smaller capacity can use more of the stroke for small doses. Actual delivery accuracy must still be validated at the receiving position. |
| Sequential addition from multiple liquid sources | Valve port assignment, shared volume and worst-case switching sequence | Shared channels can reduce component count; dedicated channels can reduce flushing and cross-effects, but generally require more installation space and cost. |
| Liquid supply to multiple stations | Number of simultaneous stations, peak flow, pressure fluctuations and refill window | Central supply simplifies management, but metering and on/off control must still be implemented at each station. |
| Recovery after an alarm | Stage at alarm occurrence, commanded volume, state feedback and sample or cuvette ID | The instrument software associates the event with affected samples, cuvettes or wells. Without actual metering feedback, commanded volume must not be recorded as measured delivered volume. |
Further technical reading
Fluidic roles of common products
The table lists tasks that component categories can perform in representative architectures, not their full range of applications. First establish whether the equipment uses fixed liquid supply, tip-based pipetting or fixed probes; then select configurations for the actual liquids, operating volumes and cycle times.
| Component | Clinical chemistry | Immunoassay | Hematology | Coagulation | Molecular diagnostics |
|---|---|---|---|---|---|
| Piston pump | Sample and reagent metering | Sample and reagent metering | Pump-based metering or system-liquid drive | Plasma and reagent metering | Fixed liquid supply, matched to the design |
| Syringe pump | Reagent and diluent aspiration/dispense | Sequential metering of multiple reagents | Diluent metering and transfer; continuous supply requires planned refills | Reagent preparation and metered aspiration/dispense | Reagent dispensing through fixed fluidics |
| Air-displacement pipetting pump | Tip-based sample dispensing and transfer | Tip-based sample dispensing and transfer | Tip-based sample dispensing and transfer | Tip-based sample dispensing and transfer | Transfer of samples, eluates and amplification mixtures |
| Liquid diaphragm pump | Probe and reaction cuvette wash supply | Wash-station and probe-wash supply | Liquid-source replenishment and washing | Probe-wash supply | Reagent predistribution or wash-station supply |
| Gas–liquid diaphragm pump | Aspiration of air-containing waste liquid | Wash-station waste removal | Removal of air-containing wash waste | Waste aspiration and removal, matched to the design | Aspiration through a fixed waste branch |
| Rotary valve / solenoid valve | Liquid-source selection / branch on/off control | Path selection and signal-reagent isolation | Path selection; metering valve configured separately | Reagent and wash-path control | Routing and isolation of fixed reagent branches |
| Sampling probe / wash probe | Sampling, dispensing and reaction cuvette washing | Dispensing, wash-liquid addition and aspiration | Whole-blood sampling and washing | Plasma dispensing and probe washing | Fixed-probe sampling and dispensing |
| Bubble and pressure detection | Aspiration/dispense anomaly signals | Dispensing and washing anomaly signals | Sampling and counting-channel anomaly signals | Dispensing-stage anomaly signals | Transfer and fixed-supply anomaly signals |
| Tubing and fittings | Connection from metering unit to probe tip | Reagent, wash and waste connections | Sampling, dilution and counting connections | Sample and reagent fluidic connections (consider delay, heat loss and assembly consistency) | Transfer and supply connections (consider adsorption and residue) |
- EA, SM and TM piston pumps: compare capacity, installation space, interfaces and all wetted materials at routine dose volumes. Establish system-liquid drive or direct liquid contact before configuring valves and probes.
Sources:[1]
- HMD / HLD syringe pumps: HMD uses solenoid valves for routing, with single- and multiple-metering-channel configurations in the series. HLD3/HLD6 use one metering unit with a multiport rotary valve for sequential aspiration and dispensing. Valve port count indicates selectable paths and must be distinguished from the number of independent metering channels.
- SMTP2 / SMTP4 air-displacement pipetting pumps: prioritize evaluation of SMTP2 when integrated drive and process detection are required; evaluate SMTP4 when the instrument supplies drive and detection. Both require confirmation against actual liquid volumes, tips, motion mechanisms and cycle times.
Sources:[3]
- Liquid / gas–liquid diaphragm pumps: in the washing branches described here, liquid diaphragm pumps supply wash liquid and gas–liquid diaphragm pumps aspirate and remove air-containing waste. Select each task separately for installed resistance, peak load, medium and duty cycle. Per-cuvette volume is determined by the selected metering and station-control arrangement and validated at the receiving position.
Sources:[4]
Further technical reading
Two validation layers: fluid delivery and assay results
Layer one validates fluid delivery: use the intended liquid with the actual probes, tubing, valve positions and action sequence. Measure delivered volume and repeatability at the receiving position, and check switching residue, wash coverage and waste removal. For small volumes, select gravimetric or tracer methods as appropriate and control errors from evaporation, density conversion and the measuring apparatus.
Layer two validates assay results: clinical chemistry evaluates carryover and reagent interference; immunoassay evaluates background and signal; hematology evaluates dilution, counts and blanks; coagulation evaluates the complete reaction; molecular diagnostics evaluates nucleic acid recovery, reaction inhibition and contamination control. Passing volume tests does not remove the need for this layer.
Cover minimum, routine and maximum operating volumes, plus low source levels, bottle changes, restart after standby and the first cycle after maintenance—conditions that can alter filling or residue. Record liquid, temperature, probe/tubing configuration, program version and measurement method to help locate the cause of anomalies.
| Operating state | What to record | Decision supported |
|---|---|---|
| Routine cycle | Actual delivered volume, cycle time, pressure or bubble signals, assay results | Establish a normal baseline and acceptable variation range |
| First dose and liquid change | Priming and flushing steps; first-dose and subsequent-dose performance | Define the recovery procedure, required time and reagent consumption |
| Simultaneous operation of multiple stations | Supply pressure, peak flow entering the waste system and waste-removal status | Confirm that central supply and waste removal meet concurrent operating demands |
| Recovery after faults or maintenance | Stage, valve position and affected samples, cuvettes or wells; not delivered, partially delivered, fully delivered or unknown state | Decide whether to continue, repeat or stop; retain traceable records |
Related application areas
This page starts from assay requirements for samples, reagents and results. For microplate operations, pipetting robots and workstation scheduling, see laboratory automation. For extraction, purification or sample processing in research workflows, see life science.
- Life science
Nucleic acid, cell and protein processing: evaluate target recovery, cell condition, surface adsorption and contamination in addition to delivered volume.
- Laboratory automation
Pipetting, microplates, dispensing and sample preparation: focus on dose and cycle time, resource scheduling and fault recovery.
- Analytical instruments
Chromatography, elemental analysis, water analysis and sample preparation: distinguish discrete metering, auxiliary continuous supply, washing and waste removal.
- Environmental monitoring
Field water samples, wastewater and gas pretreatment: focus on sample representativeness, washing, waste removal and long-term maintenance.
- Synthetic biology
Microbioreactors, screening, feeding and online sampling: manage cumulative material quantities, volume disturbances, contamination control and recovery during long-term operation.
Information needed to start a configuration discussion
Provide a fluidic diagram showing sources, valves, pumps, probes and waste destinations, together with as much of the information below as possible. We can then narrow the choices for capacity, materials, channels and control interfaces. Items not yet known may be marked “to be determined.”
| Information category | Information required |
|---|---|
| Instrument and method | Instrument type, assay method and sample type; fixed probe or disposable tip; direct sample contact or system-liquid drive |
| Actual operating point | Minimum / routine / maximum dose or flow; liquid composition; inlet conditions and outlet load; liquid-contact temperature |
| Timing and space | Complete action cycle, parallel stations, refill window, motion and installation space, communication and feedback requirements |
| Washing and waste removal | Wash-liquid types, surfaces to cover, flushing consumption, peak waste flow and its duration, waste isolation and maintenance method |
| Acceptance and faults | Accuracy / repeatability targets at actual operating points, assay-result requirements and rules for handling affected samples after alarms |