The laboratory propipette is an instrument that allows the measurement of liquids in routine procedures within the laboratory. It is an essential element for many researchers, from pharmacists, nurses, microbiologists and chemists, to anyone else who requires the measurement of a desired volume.
The simplest ones by themselves cannot quantify the amount of volume; For these cases, as is the case with the well-known rubber pears, the analyst must use the glass material known as a pipette, which is a graduated sterilized glass tube through which the “pipetted” liquid rises.
On the other hand, there are propipettes that can measure graduated amounts of liquid. An example is micropropipets, like the one that can be seen in the image above. The number 400 that appears on the display indicates the volume that has been measured, allowing the analyst a precise manipulation of the liquid intake.
Although the market offers a wide variety of propipettes, for any measurement and type of liquid, they all hide within their device the same mechanism: they generate vacuum and cause the liquid to rise from the container or beaker, to the pipette level. or the instrument needle.
All propipettes must have a mechanism capable of generating a vacuum inside them. Then, through the movement of the thumb, the liquid is allowed to enter, which compensates for the pressure difference within your breast and the propipette.
As a consequence, the liquid rises according to its affinity for glass or its viscosity. Also, depending on the amount of vacuum it can generate, some propipettes are more suitable for measuring viscous fluids, such as wax, heavy oils, syrups, etc.
They are plastic or polymeric material
All kinds of unexpected accidents can happen in the laboratory. One of the most frequent is the fall of the propipette to the floor from the edge of the counter.
For this reason they are made of soft and resistant materials, which must also resist contact with any corrosive liquid, such as acids and alkalis.
The propipettes should also be easy to wash, in case they get dirty in any of the measurements.
A good pipette should have a design that makes it comfortable to handle and hold with one hand.
Propipettes with different designs and materials have emerged. Although precision and performance are important, if its ergonomics are not to the analyst’s liking then it takes a back seat when it comes to volume measurement.
Simple and moderately sensitive
The propipette should be simple, so that the time spent reading its manual is as short as possible.
This is due to the fact that during laboratory work it is essential that volumetric measurements be performed quickly, without wasting time in understanding how the propipette is maneuvered. Similarly, they are required to be moderately sensitive to finger contact.
Some measurements require them to be exact, so the liquid level should be right on the graduated line that indicates the desired volume. If the propipette is very sensitive, it will be difficult to dislodge and suck the liquid up to this volume.
For example, if you wanted to measure an exact 10 mL of a dye solution, and the propipette is very sensitive to the touch of the thumb, then the surface of the liquid would fluctuate wildly between 9 and 11 mL. In routine operations, the ideal is to minimize this type of difficulty.
In the image above, a series of propipettes is shown in a row, from the simplest (on the far left) to the most complex (on the opposite right). All these propipettes are of the mechanical type, because they work just like pumps do.
As can be seen, they consist of a reddish rubber bulb that expels the air after pressing it with the fingers; As you slowly release your fingers, the liquid moves up the glassware.
This mechanism is the same as that of the droppers found in the box of some medicines, or also that of the famous Pasteur pipette.
There are many accessible designs of mechanical propipettes, some rudimentary and others modern, allowing a range of precision according to the demands of the work or laboratory study.
Because propipettes go hand in hand with the pipette, the smaller the second, the more refined and special the first should be. For this reason, propipettes have been designed exclusively for micropipettes; These accommodate very small volumes and are expressed in units of microliters (µL).
Micropipettes are widely used in the areas of pharmacy, biochemistry, bioanalysis, among others.
Electronic pipettes allow much more accurate measurements than mechanical or manual pipettes.
They are made to perform several measurements at the same time, especially in microbiological analysis. They also consist of a digital display in which they show the quantity of liquid pipetted.
The propipette facilitates precise and accurate measurements of small volumes. One of the great benefits of its use is to have discarded the old practice of pipetting with the mouth (as if it were a straw).
Thanks to this, dangerous liquids can be measured in the laboratory without the need to put the analyst at greater risk.
How to use?
To use a propipette correctly it is necessary to know how to pipet liquid from a container. This is done by inserting the pipette in a vertical position with respect to the surface of the liquid, its lower end descending to the bottom of the container, which, in most cases, is a test tube or a beaker.
Then, depending on the type of propipette, the thread is moved with the thumb or a certain button is pressed; after this the liquid begins to rise through the propipette.
If you work with a graduated or volumetric pipette, you simply have to wait for the liquid to reach the mark marked on the glass. On the other hand, if a digital or display propipette is used, the number will indicate the volume of liquid that has been pipetted.
- Lab Depot Inc. (2018). Pipettes. Taken from: labdepotinc.com
- Flournoy, Blake. (2018, May 15). What Is the Purpose of a Pipette? Sciencing. Taken from: sciencing.com
- Electron Microscopy Sciences. (2018). Specimen Preparation and Embedding Supplies. Taken from: emsdiasum.com
- Wikipedia. (2017). Propipet. Taken from: es.wikipedia.org
- Pipette Filler Instructions CE-PIPFILL. [PDF]. Taken from: homesciencetools.com
- Nitika182. (2015, November 13). Rubber Bulb. [Figure]. Taken from: commons.wikimedia.org