Which of the following actions are recommended when releasing fluid from the pipette tip into a container? 在将液体从移液器尖端释放到容器时，推荐以下哪些操作？

Question

BlackTom AI · Accepted Answer

Holding the pipette completely vertical minimizes surface contact and ensures the dispensed liquid falls straight out of the tip, so option b is the correct and recommended action.

1) Relevant knowledge points and concepts
- Most common pipettes are air-displacement types with two stops on the plunger: the first stop dispenses the set volume; the second stop (blow-out) expels residual liquid from the tip.  
- Tip orientation affects liquid behavior: a vertical tip directs liquid downwards into the container; an angled tip can cause liquid to run along the outside of the tip or to cling to the inside wall, causing loss and inaccuracy.  
- Tip ejection is for removing the tip, not for dispensing sample; ejecting into a container risks contaminating the contents or producing aerosols.

2) Step-by-step reasoning
- When releasing liquid, you want the fluid to transfer fully and reproducibly into the receiving vessel without splashing, running down the tip exterior, or producing aerosols.  
- Holding the pipette vertically aligns gravity with the tip opening so the drop detaches cleanly and falls into the container; this reduces the chance of liquid clinging to the tip or contacting the container wall in an uncontrolled manner.  
- Pressing the plunger to the second stop is specifically to blow out residual liquid; it is a specific technique used when complete removal of liquid from the tip is required (e.g., with viscous liquids or fixed-volume transfers), but it is not universally recommended as the single action when simply releasing fluid into a container.  
- Releasing the tip with the ejector is unrelated to dispensing and can contaminate the receiver or generate aerosols.

3) Intermediate/technical notes
- No numerical calculations apply; reasoning is procedural and based on pipetting physics and contamination control.

4) Why the correct answer is correct
- Holding the pipette completely vertically ensures accurate, reproducible transfer and minimizes errors due to liquid clinging or splashing. It is a basic best-practice for releasing fluid into a container.

5) Why the other options are incorrect
- a (push to second stop): Not always appropriate as a default; second stop is blow-out and may create aerosols or be unnecessary for routine dispensing.  
- c (push to first stop only): While first stop dispenses the set volume, this alone doesn’t address orientation; the question asks which actions are recommended when releasing fluid — orientation is the primary recommendation.  
- d (hold on a slight angle): Angle increases risk of liquid running down tip or uneven delivery, reducing accuracy.  
- e (push the tip release button): Ejecting the tip is for disposal and can contaminate the container or produce aerosols; it is not a dispensing action.

Conclusion: Holding the pipette completely vertically (option b) is the recommended action. This matches the provided correct answer: b.

Which of the following actions are recommended when releasing fluid from the pipette tip into a container? 在将液体从移液器尖端释放到容器时，推荐以下哪些操作？多项选择题

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