Though not nearly as famous as the beakers, conical flasks and petri dishes commonly associated with laboratories and scientific research, there are few lab tools as important as the pipette. Also known as pipets or chemical droppers, these small tubes transfer liquids from one container to another in exact and measurable amounts. Though they may seem like mundane tools, pipettes are actually incredibly important to scientific research: Before they appeared in their current form about 50 years ago, scientists would do the same work with their own mouths.
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Pipettes, also called pipets or chemical droppers, are small tubes of glass or plastic used to transfer a measurable amount of liquid from one container to another. They come in two forms: volumetric pipettes, used to transfer a single specific volume of liquid, and measuring pipettes, used to transfer varying, measured volumes. Pipettes in their current form appeared in the 1970s, to replace the old and dangerous practice of mouth pipetting, where scientists would transfer liquids in the lab using straws and suction from their own mouths, regardless of potential hazards.
History of Pipettes
Though modern pipettes have only been around since the late 1950s, pipettes as scientific tools have existed in some form since the late 1800s. First created by French biologist Louis Pasteur, who invented the pasteurization process, pasteur pipettes (or transfer pipettes) could be used to suck up and dispense liquids without fear of contamination. Unfortunately, Pasteur's tools did not catch on quickly because any scientist who wanted to use pipettes would have to create their own personal set from glass.
Many continued to use the tried and true – and incredibly dangerous – method of mouth pipetting, where scientists would transfer liquids using straws and their own mouths, even if that liquid was toxic or radioactive. It wasn't until the late 1950s when former German soldier Henrich Schnitger, who hated the practice of mouth pipetting, that the modern, mass-manufactured pipette would be developed. These, thankfully, would catch on quickly.
Pipettes come in two varieties: volumetric and measuring. Volumetric pipettes are designed to transfer a specific, predetermined volume of liquid. They resemble simple glass tubes and cannot be used to accurately measure liquid amounts less than their specified capacity. Measuring pipettes, on the other hand, are calibrated with small divisions and are often adjustable, allowing users to accurately draw up however much liquid they desire. Measuring pipettes tend to be larger than volumetric pipettes, making them better for general use but less useful when transferring incredibly small volumes of liquid.
Regardless of the type of pipette being used, using them takes care and attention. To prevent damage when drawing in a liquid, place the pipette 1/4th of an inch from the bottom of your container. Then place your finger over the end or gently squeeze the bulb at the end, depending on the type of pipette. When the required volume has been drawn up, gently tap the side of the pipette to remove excess droplets. Then, hold the pipette at a 10 to 20 degree angle when dispensing. Do not blow through a pipette to remove excess liquid.
Pipettes require cleaning after every use, to ensure that they stay accurate and to prevent contamination from any previous contents. To clean one, draw distilled water into the pipette and tilt it, so that the water makes contact with the inside surface of the pipette. Repeat this process twice, then rinse the entire pipette with distilled water to finish cleaning it.
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