Reader

The following microplate reader type is supported and always mounted on the instrument worktable:

• Tecan® Sunrise™

The microplate is loaded and unloaded by means of a RoMa arm. For more information about the microplate reader, refer to the reader’s documentation.

5.4.1 Capacitive Liquid Level Detection

Work? The integrated capacitive liquid level detection (cLLD) measures the capacitance between the tip and the instrument worktable; i.e. the corresponding carrier. As soon as the tip touches the liquid surface, the change in capacitance serves to trigger a detection signal.

The conductivity of the liquid and the labware type have influence on the detectability.

Liquid level detection

1) The tip moves downwards to detect liquid.

2) The tip is at detection level.

3) The tip has contact to the liquid sur-face after detection.

The liquid level detection evaluates both the liquid detection signal (when the tip moves into the sample liquid) and the exit signal (when the tip retracts).

Each channel has an individual liquid detection.

Influencing

Variables The application software offers the following adjustments of influencing variables:

• The sensitivity of the liquid level detection can be adjusted.

• In order to improve the detection, “Double Detection” is used; i.e. the detection is performed once, then the tip retracts by a short distance and a second detection is performed. The results are only considered valid if the measured detection levels are within a specified limit. This is useful, e.g. if there are bubbles on the liquid surface.

o The first detection run detects the surface of the bubble.

o The bubble bursts at the latest when the tip retracts.

o A second detection run will measure a different detection level.

o The first value is rejected and the detection is repeated Advantages Advantages due to the liquid detection feature:

• Minimum submerge depth of the tip

• Reduced tip contamination and accordingly less washing effort for tip

A Tip B Liquid level C Sample D Tube

• Appropriate message if no liquid or not enough liquid available for sampling

• Software controlled, constant submerge depth during aspiration and dispensing

• Enabling clot detection

5.4.2 Clot Detection

Work? The clot detection is based on the liquid level detection. The application software moni-tors the exit signal while the tip is retracted after aspiration of a liquid and compares the level at which the exit signal appears with the liquid level detection value.

In the following the function of the clot detection and its limits are scrutinized.

Sample aspiration

1) The tip detects the liquid level.

2) The tip moves down into the liquid to the specified submerge depth (S).

3) The tip aspirates a sample while con-tinuously maintaining the submerge depth (called “tracking”).

The application software calculates the theoretical level of the liquid surface after aspiration.

If There Are No Clots

No clot detected

After aspiration:

1) The tip retracts from the sample.

Normally, i.e. if there is no clot, the exit sig-nal is detected shortly after passing the level of the calculated liquid surface.

This delay is caused by adhesion forces that make the liquid stick to the tip.

2) The clot detection checks if the exit signal is within a predefined limit (L).

3) The tip is still within the limit after detection of the exit signal.

No error message will be generated.

A Tip B Liquid level

C Sample

D Tube

E Original liquid level F Liquid level after aspiration S Submerge depth

If There Is a

Clot Detected The clot detection generates an error message during retraction of the tip in two situa-tions. In both situations, a clot sticking to the tip or clogging the tip is the most possible cause for the non-appearance of the exit signal within the limit.

Clot Sticking to

the Tip Situation 1:

A clot sticking to the tip may be the cause for the delayed exit signal.

Clot Detected

1) The tip is beyond the limit (L) and there is still no exit signal.

2) When the exit signal appears, the tip is out of the limit.

An error message will be generated.

Expected Volume not Aspirated

Situation 2:

Alternatively, a clogged tip or other problems may be the cause for the fact that no or too little liquid is aspirated.

No liquid aspirated

1) There is an attempt to aspirate liquid, but the liquid level remains the same (e.g. because the tip is clogged).

The liquid surface is expected to be at level (A) after aspiration.

2) The tip retracts and there is no exit sig-nal within the limit (L).

An error message will be generated.

This error situation is only given when larger volumes in relation to the geometry of the vessel are to be aspirated. At very low volumes the expected difference of the liquid sur-face level before and after aspiration is not sufficient for the detection.

A Theoretical liquid level after aspiration

Limits of the

Clot Detection The following critical situation may occur if the sample has not been centrifuged properly.

Sample not completely aspirated

A – Theoretical liquid level after aspiration.

1) There are floating particles in the sam-ple. The tip aspirates liquid.

2) During aspiration (in the worst case shortly before the end of the aspira-tion process), a particle clogs the tip (see arrow).

The liquid surface is expected to be at level (A) after aspiration.

3) The tip retracts and the exit signal ap-pears within the limit (L).

No error message will be generated though the tip is clogged.

Though a certain amount of liquid has been aspirated, the expected difference of the liq-uid surface level before and after aspiration is too small for proper functioning of the clot detection.

IMPORTANT

For that reason it is very important that the samples are properly centrifuged and handled carefully to avoid floating particles.

5.4.3 Lower DiTi Eject Option

The lower DiTi eject option enables disposable tip ejection at a lower position.

With the optional cover DiTi waste and the DiTi waste slide, it reduces risk of projection from elevated positions and thus minimizes contamination risks.

The rocker spreads over the corresponding number of tips.

5.4.4 Carriers and Racks

Carriers and Racks?

Carriers are supports that hold racks - which contain tubes or other containers and are placed at precisely definable positions on the worktable.

Example of typical carrier/rack/container assembly A Carrier (can slide on worktable)

B Rack (here: Tube rack)

C Container (here: Tube)

Carrier

Positioning PyroTec™ PRO utilizes a fixed deck layout. The carriers should be used in the same position where they are left during installation.

Barcode

Identification Barcodes on the carriers and on most of the individual containers can be identified.