移液器选型正确使用和日常维护.pptVIP

* * Pre-Rinsing and Temperature When pipetting solutions at or close to ambient room temperature, RAININ recommends two pre-rinses every time you change a pipette tip and whenever critical reproducibility is required. However, choosing to pre-rinse tips at ambient solution temperature is a decision you would make if you are concerned about a variation in your results of about 0.2 percent of sample volume – an error generally of significance only to pipette calibrators. If liquid sample temperatures are very cold, such as ice baths, or warm - at incubation temperature - choosing to pre-rinse will actually cause variations in the volume delivery by as much as 5%. Under these conditions it is better to pipette without pre-rinsing, or consider using a positive-displacement pipette to reduce errors. * Aspiration Rate Effects When the pipette plunger button is released too rapidly, the aspirated liquid sample can cause several technique related problems in pipetting. Introduction of aerosols is probably the most common effect, and is caused by rapid plunger release which propels micro-sized liquid droplets onto the pipette shaft or internal components. These aerosol droplets can cause cross contamination when droplets from one sample are transferred to the next sample. Even more dramatic are the effects of liquid splash up. Splash up also occurs when the plunger is released too quickly and liquid is propelled into the the internal mechanism of the pipette. In both cases – introduction or aerosols and liquid splash up – sample may come into direct contact with the air-displacement’s pipette’s piston and can cause piston damage if the sample is corrosive. * Dispensing technique If dispensing directly into the liquid, you might want to consider using the reverse-mode pipetting technique (which we’ll cover later today) to reduce the chance of liquid rising back up into the tip after dispensing. * * Slide # 20 Hand-Warming Effects One additional effe