Which branches make up clinical chemistry analyzer fluidics?
Arrows indicate task relationships, not that every component is connected in series in one tube. Check valve positions, pump wetted boundaries and operating states for each branch.
Sample and reagent metering deliver liquid to reaction cuvettes; wash supply and waste aspiration restore wetted surfaces. Branches may share a water source or waste system, but metering, washing and waste removal require separate operating points.
Identify the liquid-contact arrangement before selecting metering hardware. With system-liquid drive, the pump mainly contacts system liquid and the probe tip contacts sample; control air gaps, interface mixing and auxiliary stroke. With direct contact, sample enters the pump chamber, so materials, cleaning and residue management must cover the chamber and seals. The two arrangements need different wetted-path assessments.
Common product roles and application guides
Select functions by branch first, then match candidate capacity, materials and drive configurations to actual operating points. The following component roles apply to the architecture discussed here.
| Component | Task performed | Configuration priorities |
|---|---|---|
| Piston pump / syringe pump | Metered aspiration and dispensing of samples, reagents or system liquid | Stroke utilization at actual doses, auxiliary stroke and aspiration/dispense timing |
| Liquid diaphragm pump | Supply for probe washing, cuvette washing or reservoirs | Flow under installed resistance and supply during concurrent demand |
| Gas–liquid diaphragm pump | Aspiration of air-containing waste liquid | Aspiration height, gas–liquid mixture state and peak incoming flow |
| Rotary valve / solenoid valve | Liquid-source selection and wash/waste on/off control | Shared volume, cross-leakage and switching states |
| Sampling probe / wash probe | Sampling from containers, cuvette delivery and cleaning of inner/outer surfaces and cuvette bottoms | Positioning, retained droplets, wash coverage and residual liquid |
| Bubble and pressure detection, tubing and fittings | Provide state signals and connect branches | Installation position, wetted materials, dead volume and assembly consistency |
- View the IVD product–task matrix
- Piston pumps in clinical chemistry analyzers
- Syringe pumps in clinical chemistry analyzers
- Diaphragm pumps in clinical chemistry analyzers
- Multiport rotary valves in clinical chemistry analyzers
- Sampling and wash probes in clinical chemistry analyzers
- Bubble and pressure detection in clinical chemistry analyzers
- Tubing and fittings in clinical chemistry analyzers
Operating conditions to confirm at each stage
Define requirements for specific liquids, containers and actions before using capacity and flow as selection criteria.
| Stage | Project inputs | Selection directly affected |
|---|---|---|
| Sample aspiration | Method-permitted serum, plasma or urine; dose, tube type and low remaining volume | Liquid-contact arrangement, pump capacity, probe positioning and aspiration program |
| Reagent dispensing | Actual dose of each reagent, addition order, aspiration architecture and timing window | Bottle-by-bottle aspiration or dedicated branch; refill and dispensing timing |
| Path switching | Liquid combinations, valve positions, shared segments and allowable residue | Shared or independent channels, flushing and cleaning programs |
| Probe and cuvette washing | Wash-liquid composition, surfaces to clean and peak simultaneous inflow | Supply, station distribution and waste-removal capacity |
| Monitoring and maintenance | Fault-handling rules, measurable signals and allowable recovery time | Detection locations, record fields and post-maintenance checks |
Sample aspiration: dose range, liquid-level detection and wall contact
Screen capacities using minimum, routine and maximum delivered volumes, leaving stroke for required air gaps, suck-back and other actions. Larger capacity reduces refills but lowers the stroke fraction used by the same small dose. Setting resolution describes command granularity only; small-dose performance depends on actual delivery at the probe tip.
At low remaining volume, level detection and probe positioning determine whether sample aspiration can continue. Shallow immersion can draw air, while deep immersion increases external wetted area; wall contact and tip droplets also alter delivery. If aspiration lags, check inlet resistance and sample condition before adjusting speed or dwell time. Longer waits consume test cycle time; microclots require an abnormal-sampling procedure.
System-liquid drive also requires assessment of system-liquid mixing into the sample: a correct total weighed volume can still accompany a change in sample concentration. Observe delivered volume and sample preservation separately.
Further technical reading
Reagent dispensing: R1/R2 delivery and refill coordination
R1/R2 names, volumes and addition order must come from the method sheet for the same assay. Reusable reagent probes can aspirate from individual bottles and dispense into cuvettes, as described in the AU5800 manual. For this arrangement, check internal and external probe washing after each aspiration rather than assuming a permanently reagent-filled supply line.[1]
For dedicated reagent branches using one aspiration for multiple dispenses, subtract the program's priming and reserve volumes from available capacity before scheduling refills. Independent channels reduce switching but add components, space and retained liquid. Shared channels reduce hardware but add flushing consumption and waiting. After bottle changes or refills, restore filling and confirm the first dose before normal dispensing.
Further technical reading
Fluidic switching: valve positions, shared volume and flushing
Define the source, destination, pump action and allowable pressure for each valve position. Shared segments retain the previous liquid after the valve reaches position. Geometric volume can estimate an initial flushing volume; adequate cleaning is established by residue and assay results under the worst-case switching sequence.
When returning from cleaner to system liquid, flush to waste before resuming metering. If certain reagent combinations require long flushing, independent channels may be preferable to additional rinsing. Compare cross-effects, per-test liquid consumption and cycle time together.
Further technical reading
Probe and cuvette washing: treat inner surfaces, outer surfaces and cuvette bottoms separately
Probe interiors require adequate flushing and effective wash solution; exteriors require the wash well to cover the wetted area; cuvette bottoms depend on aspiration position and waste capacity. For insufficient supply, examine installed resistance and concurrent demand. For poor coverage or misplaced aspiration, correct positioning and coverage before assessing whether increased supply helps.
Use separate sequences for sample carryover and reagent cross-effects. Follow high samples with low samples to examine sample residue; choose potentially interacting assay sequences for reagents. The AU5800 manual describes internal/external reagent-probe washing separately from contamination-avoidance parameters, showing that assay-combination controls complement routine washing.[1]
Further technical reading
Tubing and fittings: why recheck shared volume after servicing?
Changes in tube length, bore or fitting cavities alter retained volume, resistance and arrival delay together. Shorter paths reduce residue, but retain bend radius and stress margins needed for assembly and maintenance. Material selection must cover every wetted surface of tubing, seals, valves and probes, checked against actual reagents, cleaners and contact durations.
Record assembly dimensions and component versions during maintenance. After replacement, check leaks, prime and purge air, then compare routine doses and first-cuvette results. Leak-tight interfaces alone do not address effects from changed shared volume.
Level, bubble and pressure detection: linking alarms to specific tests
Level signals help establish aspiration position; pressure and bubble signals describe local fluidic conditions. Pressure changes during aspiration and dispense mean different things. Interpret anomalies using action stage, valve position and intended air segments rather than one diagnostic threshold.
The instrument controller associates signals with samples, assays and cuvettes, recording commanded volumes, available estimates and measured values separately. Without measurement, do not label the command as delivered volume. After partial dispensing, handle the cuvette and decide on retesting according to the method, avoiding repeated addition onto an unknown remaining volume.
Explore configurations through product application guides
Use the following routes to narrow candidates when discussing configurations with FOREACH, then provide actual doses, wetted media, allowable deviations and cycle times. Model-specific performance must be based on the corresponding specifications and operating-point data.
For reagent dispensing with multiple metering units, start with HMD multichannel configurations combining glass syringes and solenoid valves. When multiple sources share one metering unit sequentially, compare HLD configurations combining a glass syringe and multiport rotary valve. Port count denotes selectable paths; verify it separately from independent metering-channel count.[2][3]
- Small-dose metering: compare usable stroke, wetted arrangements and actual delivery for both piston and syringe pumps. Pump category alone does not establish priority.
- Batch dispensing: plan refills from usable capacity and individual dose, comparing how larger capacity and repeated refills affect small-dose performance and cycle time.
- Washing and waste: select supply and air-containing aspiration configurations separately and validate simultaneous multi-station operation.
- Shared paths: reduce residue by considering rotary valves, probes, tubing and fittings together, and compare extra flushing costs with independent channels.
- State detection: choose configurations according to target faults, sensor positions and control programs. Confirm level functions and pressure detection separately.
- Organize configurations using the IVD product–task matrix
- Piston pumps in clinical chemistry analyzers
- Syringe pumps in clinical chemistry analyzers
- Diaphragm pumps in clinical chemistry analyzers
- Multiport rotary valves in clinical chemistry analyzers
- Sampling and wash probes in clinical chemistry analyzers
- Bubble and pressure detection in clinical chemistry analyzers
- Tubing and fittings in clinical chemistry analyzers
Validate the complete cycle through application results
Confirm delivery at the cuvette first, then use assay results to evaluate contamination and recovery. Allowable deviations and carryover targets come from the specific project and must remain consistent with the test sequence and calculation method.
| Stage | What to measure | Priority checks when abnormal |
|---|---|---|
| Sample | Actual received volume at boundary doses, sample preservation and high/low switching results | Air aspiration, wall contact, interface mixing and inner/outer probe residue |
| Reagent | Individual aspirations or first/middle/last batch doses; first dose after bottle change and R1/R2 timing | Incomplete filling, bubbles, retained droplets and partial dispensing |
| Switching and washing | Shared-segment residue, cuvette-bottom liquid and cross-effects between assays | Flushing sequence, station coverage and accumulated waste |
| Maintenance and monitoring | First cuvette after maintenance, alarm detection/false alarms and affected-cuvette tracing | Assembly changes, baseline and stage association |
Common selection and recovery questions
Can one calibration correct both low sample volume and high carryover?
Diagnose them separately. For low cuvette delivery, first check filling, seals, probe tip and actual stroke. For abnormal high/low sequences, check inner/outer probe surfaces, shared segments and cuvette washing. Displacement calibration can change volume but cannot automatically remove residue.
Where should you check first if the first cuvette is abnormal after a bottle change or refill?
Identify bottle-by-bottle aspiration versus dedicated-branch refill, then check low level, valve position, priming and probe-tip condition. Compare actual first-dose and subsequent-dose delivery and retain the cuvette's action record. If delivered volume is unknown, follow the method's handling rules rather than directly resending the same dispense command.