Locate the source, drive and receiving position for this task
The diagram shows the sampling and delivery sequence. With system-liquid isolation, sample does not enter the pump chamber; with direct contact, verify every sample-contacting surface separately.
Required inputs are actual sample volume, remaining source volume, probe-tip height, aspiration/dispensing speed and system liquid. Confirm liquid contact, pressure and destination along each position in the diagram before assigning drive and connection responsibilities.
Roche GLUC3 illustrates why specimen suitability is method-specific: its instructions identify accepted specimen types and preparation conditions for that assay. Use the current method instructions for the intended analyzer; acceptance by one assay does not establish suitability for all clinical chemistry tests.[1]
Ouyang and colleagues studied fixed-tip, liquid-filled handling and found that system liquid could dilute the delivered sample when operating parameters were unsuitable. This supports checking sample composition as well as received volume; their tested settings are not a universal sampling program.[3]
Select capacity from working sample volume and path displacement
Capacity must cover working sample volume and displacement actually required by the sequence; priming volume is not all test sample. Routine small volumes need sufficient working stroke, while maximum volumes must meet cycle timing. Compare supplied configurations against both conditions.
| Condition to compare | Information required | Selection affected |
|---|---|---|
| Available sample | Minimum remaining volume, probe-tip height and retained volume | Define the available sampling window |
| Metering stroke | Effective sample volume and auxiliary path displacement | Compare capacity and reverse movements |
| Contamination paths | Contact inside and outside the probe and in shared segments | Plan cleaning and sample changes separately |
Further technical reading
Compare product options against task requirements
The following candidate options match this page's responsibilities. Compare them against the operating conditions described, then check capacity, materials and interfaces on the product pages. Card images show representative configurations; suitability must still be confirmed at actual operating points and by application results.
| Product category | Corresponding role | Confirm before selection |
|---|---|---|
| EA standard piston pump | Finite-stroke metering | Compare configurations by routine dose, total cycle displacement and wetted materials |
| SM miniature piston pump | Discrete metering in compact installations | Check installation space first, then validate working doses and actual accuracy |
| Custom sampling probe | Sampling interface between source container and fluidic path | Compare custom geometry by minimum liquid level, probe-tip clearance and actual sample |
Check liquid level, probe tip and delivery status
Check liquid level, probe position and valve state before aspiration, maintain the specified dwell, then dispense at the target position. Low remaining volume, wall contact, hanging droplets or compressible air segments may alter probe-tip delivery. After interruption, first establish whether liquid has entered the reaction cuvette before deciding to resample.
Associate the source specimen, receiving cuvette, probe position and completed aspiration or delivery with the actual received result. Mark uncertain or partial delivery explicitly; a completed drive command must not cause automatic resampling into a cuvette that may already contain sample.
Validate volume error and carryover separately
Measure actual sample reception in the target cuvette using the assay-permitted specimen or a justified test medium. Evaluate low remaining volume, the first transfer after idle, high/low concentration sequences and blanks. Investigate under-delivery, unintended dilution and previous-sample residue as separate failure modes.
| Validation scenario | Measurement or observation | Interpretation and action |
|---|---|---|
| Delivery at low remaining volume | Compare normal level with minimum usable remaining volume | If delivery falls, first check air aspiration, wall contact and the probe tip |
| Recovery between samples | Follow a concentrated sample with a low sample or blank | Locate volume and residue issues separately rather than relying on a single calibration |
Quantify the transferred volume for the actual programmed task and record the measurement method and uncertainty. Albert and Bradshaw demonstrate how volume verification reveals delivery changes during liquid-handler parameter optimization; their study supports the verification approach, not a performance claim for this pump or analyzer.[7]
After an abnormality or maintenance, first identify which segment needs recovery
Air aspiration, clots or particles, probe-wall contact and leakage can interrupt sample acquisition. Stop the affected action and identify the specimen, probe state and cuvette before deciding how the assay permits resampling or flagging.
Establish whether the cuvette received no sample, a partial dose or a complete dose. Correct the path or aspiration fault, restore the specified cleaning state and verify the first recovered transfer before restarting; handle an uncertain reaction according to the assay rather than replaying the previous command.
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References
View references (7)
- [1]Roche — Glucose HK Gen.3, cobas c 303 / c 503 / c 703, V7.0 (2024)
- [2]FOREACH — EA Piston Pump Datasheet, basic capacities and test conditions
- [3]Ouyang et al. — Strategies to Maintain Sample Integrity Using a Liquid-Filled Automated Liquid-Handling System with Fixed Pipetting Tips (2008)
- [4]Hortin et al. — Problematic Proteins: A Patient with a High Paraprotein Concentration (2024)
- [5]FOREACH — EAS Easy-to-Degas Piston Pump Datasheet
- [6]Tecan — Liquid handling pump selection: a guide for lab automation engineers
- [7]Albert and Bradshaw — Importance of Integrating a Volume Verification Method for Liquid Handlers: Applications in Learning Performance Behavior (2007)