Where fixed-probe sample addition occurs in the instrument
This task covers sample addition with fixed sampling probes. Piston metering coordinates probe position, valves and receiving cuvettes for aspiration and delivery. Distinguish direct sample contact from system-liquid isolation before checking the sample's actual wetted path.
Set separate sequences for sample aspiration, delivery and internal/external probe washing, covering low remaining volume, first doses and high/low concentration changes. Instruments using disposable tips should refer to the air-displacement topic for tip sealing, changes and well rules.
Product responsibilities in this operation
Piston drive creates controlled displacement, working with valve positions and the receiver to deliver this volume. Check working stroke and actual received volume separately.
For this operation, confirm: Sample identity and assay-permitted condition; direct contact or system-liquid drive; remaining source volume; probe immersion; working dose; receiving cuvette and probe-wash coverage.
Organize the sequence by actual architecture
- For the fixed-probe architecture discussed here, confirm sample identity, specified dose, wetted coverage at the tip and receiving reaction vessel.
- Coordinate probe position and metering drive for aspiration and addition, recording tip droplets, actual delivery and affected reaction cuvettes.
- Clean fixed probes and shared segments to meet between-sample contamination requirements, validating received volume and contamination in the next sample separately.
Define operating conditions for this task
| To define | Details |
|---|---|
| Actual operating conditions | Sample identity and assay-permitted condition; direct contact or system-liquid drive; remaining source volume; probe immersion; working dose; receiving cuvette and probe-wash coverage |
| Acceptance target | Measure the sample received by the identified reaction cuvette, covering routine and limiting working volumes, low source volume and the first aspiration after idle. Keep actual reception separate from piston displacement. |
| Fault localization | Air aspiration, probe-wall contact, obstruction or leakage can leave an incomplete sample dose. Droplets and shared-path residue can contaminate the next sample even when the current cuvette receives the intended volume. |
Further technical reading
Compare product configurations by the roles on this page
| Product | Configuration option | Conditions to verify |
|---|---|---|
| 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 |
| TM ultra-miniature piston pump | Discrete metering in limited space | Check installation space and configuration before measuring actual delivery; an ultra-miniature design does not imply a smaller reliable dose |
Validate operation results at the receiver
Measure the sample received by the identified reaction cuvette, covering routine and limiting working volumes, low source volume and the first aspiration after idle. Keep actual reception separate from piston displacement.
After internal and external probe washing, assess sample-to-sample residue with the method-relevant high/low sequence or blanks. Confirm sample identity, received volume and contamination results separately.
Locate abnormalities and restore the next operation
Air aspiration, probe-wall contact, obstruction or leakage can leave an incomplete sample dose. Droplets and shared-path residue can contaminate the next sample even when the current cuvette receives the intended volume.
Hold the affected sample and cuvette, establish what was aspirated and delivered, and check probe position, the liquid column and wash state. Resample or flag the affected reaction according to the method, then verify the next sample after recovery.
This page covers fixed-probe sample addition. Disposable-tip transfer uses a different consumable sequence, and sample-volume checks do not establish solid-phase washing or complete-assay performance.
References
View references (4)
- [1]FOREACH EA standard piston pump: configurations and specifications
- [2]FOREACH SM miniature piston pump: configurations and specifications
- [3]FOREACH TM ultra-miniature piston pump: configurations and specifications
- [4]Beckman Coulter Access: an assay example of magnetic solid-phase separation, washing and substrate detection