The Types of Droppers and Graduated Pipettes
Photo by Withsight
Graduated Pipettes have many uses. Not only can they be found in the laboratory—nowadays, they can be used domestically for many types of liquids, including eye drops, incense, essential oils, CBD tinctures, and more.
What is a graduated pipette vs a dropper? These two go hand-in-hand, for they are both interchangeable terms, with droppers allowing for controlled dispensing. With that said, a pipette, also called a pipet, pipettor, or chemical dropper is a laboratory instrument used to transport a measured volume of liquid. It comes in several designs for various purposes with differing levels of accuracy and precision.
Glass and Plastic Droppers
The original pipette was made of glass. It is more commonly used in chemistry with aqueous solutions. There are two types of these—the volumetric pipette, which typically has a large bulb and is calibrated for a single volume, and Mohr pipettes, typically straight-walled and graduated for different volumes.
However, today, graduated pipettes come in plastic as well. They are more commonly used in both biology and chemistry. These graduated pipettes are also designed for aqueous solutions but not recommended for use with organic solvents which may dissolve the plastic.
Both glass and plastic graduated pipettes are sterilized and plugged with a polypropylene bulb at the open end, blocking contamination from the rest of the tube. They also both have been widely adapted to be used not only for science and medicinal purposes but also for domestic purposes too, as aforementioned.
Graduated pipettes have become the best scientific tool in both the medical field and in the household. With medical professionals administering medicine using the precise amount, and household parents utilizing graduated pipettes to measure products such as essential oils, pet and child medicine.
The Five Grades of Pipettes
Besides the known materials for pipettes, there are five grades of pipettes—disposable/transfer, graduated/serological, single-channel, multichannel, and repeat pipette. Knowing these and how to use them will ensure that whoever uses the pipette and whatever liquid the pipette is used for will provide the most precise results with the smallest margin of error.
The disposable/transfer grade is the most basic type of pipette, being used for rough measurements only. This type of dropper is only good for single use. It is important to follow the standard pipetting technique when using a disposable pipette, which consists of grabbing a new one, aspirating the liquid at a 90-degree angle, dispensing at a 45-degree angle, and then transferring the liquid to make sure it is fully dispensed.
The graduated/serological grade is typically used when the final volume of a liquid is calculated by the difference of the liquid level before and after it is dispensed. Think of a burette, a long, graduated tube. This type of pipette’s standard technique is more technical and consists of holding the pipette in the solution (do not touch the bottom), squeezing the bulb, holding one’s forefinger on the top of the pipette to control volume aspiration, subtracting the amount needed into a separate beaker, measuring the solution from the bottom of the meniscus, and subtracting the needed volume from the initial volume in order to obtain the desired amount of liquid.
The single-channel grade pipette usually has an air-displacement design that produces accurate measurements. It is a non-disposable instrument with a disposable tip. This type of pipette uses two common techniques—forward and reverse. The forward technique is the most common, pressing the bulb to first stop and slightly submerge the tip of the pipette into the liquid, aspirating the measured volume by releasing the bulb slowly, placing the tip against the side of the receptacle, then gently and carefully pressing the bulb in order to dispense the liquid.
As for the reverse technique, this is good for viscous solutions, which will minimize the interference of air bubbles. To use this technique, press the bulb all the way down, submerge the pipette into the liquid, slowly release the bulb, aspirate the liquid into the tip, place the tip against the wall of the receptacle, press the bulb to the first stop, and remove the tip from the receptacle. This will allow the user to have a sample of liquid that remains in the tip of the pipette that isn’t a part of the measurement.
The multi-channel grade is similar to that of a single-channel pipette. However, it takes more than one tip of liquid at a time. The technique is similar to the single-grade, however, the outcome is much more different. The liquid is able to be aspirated at the same time into multiple channels, ensuring that all liquid levels are equal.
The repeat pipette dispenser is able to allocate a specific volume into multiple receptacles without having to be divided into multiple dispenses, saving time and effort. The main difference between this type of pipette and the others is that it has a filling and dispensing lever instead of a bulb. To use this type of pipette, slide the filling lever down to the furthest point, raise the locking clamp, insert the tip into the barrel and close the lever, immerse the tip into the liquid at a 90-degree angle, carefully slide the filling lever upward to fill the tip completely, prep the tip by disposing the liquid from the first dispense, and then the repeat pipette is ready to go.
Where to Find These Types of Pipettes
Graduated Pipettes are very useful for controlling the amount of substances and liquids that are being dispensed. Not only do they help in accuracy and precision, but they also save time and are efficient to use. They also are essential in ensuring that liquid handling is sterile and safe.
With the single-channel, multi-channel, and repeat dispenser-grade graduated pipettes, these are the ones most typically used for scientific and medicinal purposes. These can be used to store and transfer chemicals, lab samples, medicines, and solvents. They can be found at industrial, clinical, and educational laboratory supply stores.
As for the basic disposable/transfer and graduated/serological grade pipettes, these can be found right here at FH Packaging. These are the ones used more for domestic purposes and everyday use, such as storing or transferring essential oils, tinctures, and dyes. Check out our new medical-grade graduated glass droppers, making them child resistant with a seal that makes it challenging for children to open, high quality with medical-grade printing and the ability to hold up to the most corrosive solutions, and friendly for everyday use.
You can also view an in-depth blog on Labmates’ website explaining more Graduated Pipettes Types.