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Lab Glassware and Glassware Equipment

Lab Glassware and Glassware Equipment

Lab Pro's Buyer’s Guide to Volumetric Pipettes

Pipettes are one type of precision calibrated glassware, also referred to as volumetric glassware. This piece of lab equipment is all about precision measurements. Pipettes calibrate at specific temperatures typically at 68°F [20°C] or 77°F [25°C] and are usually made out of borosilicate glass due to its natural strength against thermal shift, chemicals, and mechanical stress. Volumetric pipettes are accurate at the temperature at which it has been calibrated.

Pipettes with a marking of TD deliver the volume with free drainage, while the last drop must be blown out of pipettes that have the marking of TC. The tolerance of the pipette depends on the ASTM standard. Class A pipettes that hold volumes greater than 5mL have a +/- 0.2% tolerance or better. The tolerance of the smaller Class A pipettes and Class B are less. The tolerance depends on the size of the pipette. They are designed to be highly accurate for a specific volume.

What is the Use of Volumetric Pipettes?

Volumetric pipettes transfer a fixed volume of liquid from one container to another. They can only deliver the volume at which the pipette calibrates. These pipettes are typically used in analytical chemistry to make lab solutions and to prepare solutions for titration. Their use is for high-accuracy research and chemical analysis. The liquid is drawn into the pipette and drains from the pipette in a controlled manner. With its single graduation, it can deliver one specific volume accurately.

How Does a Volumetric Pipette Work?

Volumetric pipettes have a bulb in the middle of a long thin tube with a single calibration mark and a narrow tip. Volumetric pipettes calibrate for single volumes. These pipettes have a single calibration, deliver a specific volume, and have free drainage.

To transfer a liquid with a volumetric pipette, you should do the following:

  • Be sure there is enough liquid in the beaker to fill the pipette.
  • Place the pipette’s tip below the surface of the water in the beaker. Using the bulb, draw the liquid into the pipette. Draw more fluid than is needed without it entering the bulb. Remove the pipette from the liquid and tap it on the side of the container to remove excess liquid.
  • Drain the liquid into another beaker until the meniscus bottom is aligned with the graduation mark.
  • Release the liquid in a beaker or flask until the fluid no longer flows from the pipette.

What is the Difference Between Volumetric Pipettes and Graduated Pipettes?

A Mohr or graduated pipette is calibrated in milliliters and delivers any amount of water in various capacities such as 10 mL, 25 mL, and 50 mL. A transfer or volumetric pipette transfers a specified volume in a single delivery. These pipettes come in various sizes ranging from 0.5-200 mL. Both graduated and volumetric pipettes deliver specific volumes at 20°C or 68°F.

The two pipettes also empty differently. A graduated pipette fills to the top graduated mark, and the water dispenses within that range of graduated marks. The water below the bottom graduated mark does not dispense. Transfer pipettes fill above the capacity marks, and water releases until the meniscus reaches zero graduation.

What is the Difference Between the Serological Pipette vs. the Volumetric Pipette?

Serological pipettes have graduated calibration markings that go to the tip and, with their design, deliver various volumes of liquid. The volume delivered is the difference between the before and after delivery amounts. The last drop is blown out of serological pipettes. Volumetric pipettes have a single calibration mark, deliver a fixed volume, and have free drainage.

Where to Buy Volumetric Pipettes

Lab Pro offers volumetric pipettes that are extremely precise and accurate. These come with built-in tip ejectors to access narrow tube openings and are autoclavable. The Class A pipettes come in 1 mL, 2 mL, 5 mL, 10 mL, 20 mL, 25 mL, and 50 mL. Class B includes 1 mL, 2 mL, 5 mL, 10 mL, 20 mL, 25 mL, and 50 mL.

Lab Pro offers a large variety of lab chillers and volumetric pipettes for all types of applications. For over 40 years, Lab Pro Inc. has been committed to delivering the highest quality chemicals, lab equipment, distance learning kits, lab supplies, and cleanroom PPE apparel to medical device companies and laboratories worldwide. To learn more, visit the biggest Lab Supply showroom in California, or contact us online or at 888-452-2776.