For each of the following situations, explain the most likely cause of the error and error should be corrected.
a. After aspirating 300 ul with P1000, a small air space is seen at the end of the tip.
b. While aspirating 1 ml with a P1000, a small air bubble is observed rising t the top of the liquid inside of the tip.
c. A P20 tip-holder is stained with methylene blue.
a. The most likely cause of the small air space at the end of the tip when aspirating with a P1000 is improper technique. This can happen if the pipette tip is not inserted fully into the liquid or if the aspiration speed is too fast. The error can be corrected by ensuring that the tip is fully submerged in the liquid before aspirating and by adjusting the aspiration speed to a slower rate.
b. The most likely cause of the small air bubble rising to the top of the liquid inside the tip when aspirating 1 ml with a P1000 is trapping air during the aspiration process. This can occur if the pipette tip is not inserted fully into the liquid or if the liquid is viscous and causes air to be trapped. The error can be corrected by ensuring that the tip is fully submerged in the liquid before aspirating and by using a slower aspiration speed to avoid trapping air.
c. The most likely cause of a P20 tip-holder being stained with methylene blue is spillage or contact with the staining solution. This can happen if the pipette tip is not securely attached to the tip-holder or if the tip-holder is in contact with the staining solution. The error can be corrected by carefully attaching the pipette tip to the tip-holder to ensure a secure fit and by avoiding contact between the tip-holder and any staining solutions. If the staining is not removable, it may be necessary to replace the tip-holder.
a. The most likely cause of the air space at the end of the tip after aspirating 300 ul with a P1000 is that some liquid may have been left behind in the tip due to improper pipetting technique. To correct this error, gently tap the pipette against a surface to ensure that the remaining liquid inside the tip is expelled. Alternatively, you can also try aspirating a small volume of liquid and then dispensing it back into the source container to compensate for any liquid left in the tip.
b. If a small air bubble is observed rising to the top of the liquid inside the tip while aspirating 1 ml with a P1000, the most likely cause is that the tip was not fully immersed in the liquid at the beginning of pipetting. This can occur if the pipette is not properly inserted into the liquid, causing air to be aspirated instead. To correct this error, ensure that the tip is fully submerged in the liquid before starting to pipette. If an air bubble is observed, dispense the liquid back into the source container and start over.
c. If a P20 tip-holder is stained with methylene blue, the most likely cause is that some of the methylene blue solution came into contact with the tip-holder during pipetting. To correct this error, carefully clean the tip-holder with a suitable solvent or detergent that can effectively remove the stain without damaging the equipment. Follow the recommended cleaning procedures for the specific type of tip-holder being used. If the stain persists, it is recommended to contact the manufacturer or seek assistance from the supplier for further guidance on proper cleaning and maintenance.