This article will guide you how to perform labware teaching and explain what different z-values mean and should be.
Correct z-teaching on labware is crucial for precise and accurate pipetting, so please consider the points below while performing the teaching in Freedom EVOware®.
Z-Value Definitions and Settings
Z-Travel
- Definition: Height at which the tip moves between positions within a rack.
- Setting: Should be above the highest point of the well/tube in the rack to avoid collisions when tips move in the X and Y directions at this height.
Z-Start
- Definition: Height at which liquid detection is activated.
- Setting: Should be set according to the liquid volume inside the tube/above the well. It is recommended to position it within 1 mm of the top of the well or just inside the well.
Z-Dispense
- Definition: Height at which liquid is dispensed.
- Setting: Should be high enough to prevent cross-contamination during non-contact (free dispense) pipetting, but low enough to ensure that liquid does not drop into adjacent wells/tubes.
Z-Max
- Definition: Lowest position of the well/tube in the rack, and the lowest possible position the tip is allowed to reach.
- Setting: For routine operation, set Z-Max 5 steps above the bottom of the vessel to ensure the tip is not blocked by the bottom of the well when aspirating or dispensing at this height. All liquid below this point is considered "dead volume" and unavailable for aspiration.
Specific Guidelines
Microplates
- Z-Start Position: Should be positioned 1 mm above the rim of the well. If wells in a microplate are full and the Z-Start is too low, the tip will already be submerged in the liquid when liquid level detection is activated. This will prevent the instrument from detecting any change in signal, causing it to not detect the presence of any liquid at all.
- Z-Start Position: Should be positioned 1 mm inside the rim of the well. When a tip passes the rim of the tube/trough, an electrostatic discharge (ESD) occurs. If the Z-Start is too high, liquid level detection will be activated there, and once the tip enters the rim of the labware, the ESD can cause the instrument to mistakenly identify it as the liquid level, leading to false liquid level detection and air aspiration.
Further Help
For further help, please refer to our Helpdesk.
Link to Tecan Product Page:
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