Volumetric Glassware
Volumetric Glassware from DWK Life Sciences
DWK Life Sciences manufactures several brands containing volumetric glassware products. The majority are manufactured from borosilicate glass, however some are manufactured from soda-lime glass. Soda-lime glass is generally used for products where long-term exposure to chemicals is unlikely, e.g. one mark and graduated pipettes.
Borosilicate glass for volumetric glassware has superior thermal and chemical resistance and is better suited to glassware for storage of solutions, e.g. volumetric flasks. The use of borosilicate glass for volumetric glassware means accuracy is retained over a longer working life than their soda-lime glass equivalents.
With everyday use, volumetric glassware requires recalibration. Soda-lime glass items will generally necessitate twice as many recalibrations as items constructed from borosilicate glass. ASTM 542 and ISO 4787 international standards for calibration of laboratory volumetric glassware recommend that volumetric flasks are recalibrated at the following intervals (or sooner if chemical corrosion is observed): Borosilicate – 10 years; Soda-lime – 5 years.
View the full range of volumetric glassware offered by DWK Life Sciences.
ISO/IEC 17025 Accreditation
DWK Life Sciences manufactured volumetric products are tested and calibrated in an ISO/IEC 17025 accredited calibration laboratory located at DWK Life Sciences’s glass manufacturing facility in Stoke-on-Trent. To receive ISO/IEC 17025 accreditation, a calibration laboratory must demonstrate the highest levels of competency in a number of areas of its calibration procedures, including:
- The technical competence of its staff.
- The validity and appropriateness of test methods.
- The traceability of measurements and calibrations to national standards.
- The suitability, calibration and maintenance of test equipment and the quality assurance of test and calibration data.
- The calibration and testing environment, and sampling, handling and transportation of test items.
The attainment of ISO/IEC 17025 accreditation by DWK Life Sciences is in recognition of the continuous application of strict quality assurance procedures in the testing and calibration of our extensive range of branded volumetric laboratory glassware, and offers our customers an additional assurance of the accuracy and precision of our volumetric glassware.
Volumetric Accuracy
All volumetric glassware is manufactured and calibrated in accordance with international ISO standards to permit very accurate determination and measurement of specific volumes. They are available in two accuracy classes: Class A/AS and Class B. The two classes differ in the accuracy of measurement with a Class A/AS being the highest accuracy, and Class B accuracy tolerances being twice those of Class A/AS. Class AS products are calibrated to the same high tolerances as ClassA, but are designed to permit more rapid outflow of the liquid in burettes and pipettes.
All of our volumetric glassware is marked with a set of inscriptions in accordance with the relevant ISO associated with that product e.g. ISO 1042 for volumetric flasks. These inscriptions include:
Tolerance - Class A/AS or Class B.
The standard to which the product conforms.
Graduations (in millilitres).
Whether the item is calibrated IN (to contain) or EX (to deliver).
Temperature in degrees Celsius at which the item was calibrated. All Pyrex® and MBL® volumetric glassware is calibrated at 20°C.
If the product is calibrated to Class A/AS accuracy tolerances, it is usually marked with a batch or individual serial number for identification and traceability.
Certification of Volumetric Products
Many of our volumetric products are available with certification for conformity or traceability purposes. Below is an overview of the certification that is offered by DWK Life Sciences:
UKAS Certified Products
A range of volumetric flasks and measuring cylinders are available with individual UKAS (United Kingdom Accreditation Service) calibration certificates. As well as detailing the measured volume (at 20℃) and uncertainty of measurement, UKAS calibration certificates also include information on the calibration laboratory environmental conditions (in which the product calibrated) and calibration equipment and procedures used. For example, PYREX® measuring cylinders are calibrated at five points on the graduated scale. i.e. a 250ml cylinder will be graduated at 50, 100, 150, 200 and 250ml.
Works Certified Products
Class A/AS Works Certified volumetric products are inscribed with an individual serial number and are supplied with an individual calibration certificate. Each certificate includes details of the actual volume, uncertainty estimation for the calibration and the required tolerance for compliance.
Batch Certified Products
Batch certificates for Class A/AS volumetric items (Class A volumetric flasks and measuring and mixing cylinders and MBL® Class AS pipettes) are available to download from the DWK Life Sciences certificates website https://cert.dwk.com/. The batch certificate contains detailed information pertaining to the specific production batch including average volume and standard deviation for the batch.
Individual or batch certification is not available for Class B accuracy volumetric products.
Recalibration of Volumetric Glassware
Normally, volumetric glassware only needs recalibrating after extensive or demanding usage, which may have affected the original accuracy.
Recalibration is usually not necessary if:
- The glassware is new but been in storage for some time. Age does not affect accuracy.
- The glassware is only subjected to moderate temperatures such as cleaning in a washing machine or sterilising in an autoclave at 121°C.
- The glassware has been used for less than 5 years with no repeated use of corrosive chemicals or strong acids/ alkalis.
However, recalibration should definitely be considered under the following circumstances:
- The glassware is made from soda-lime glass and has been in use for 5 years.
- The glassware is made from borosilicate and has been in use for 10 years.
- The glassware has been subjected to temperatures in excess of 150°C.
- The glassware is frequently used with strong acids or bases.
- There are any signs of chemical corrosion e.g. frosting of internal glass surfaces.
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Frequently Asked Questions
We’ve listened to customers and designed our pipettes with a colored ring marking at its upper end to make selection quick and easy. This color-coding is carried out according to DIN 12621.
All of our pipettes are used for precise volume measurement and are similar in shape to tubes. The difference between graduated pipettes and bulb pipettes lies in the shape and type of graduation. With bulb pipettes, only the total volume can be read off (there is no partial graduation). Graduated pipettes, however, are characterized by partial scaling, where partial volumes can be measured in addition to the total volume.
According to DIN, EN, and ISO, volumetric instruments are divided into two accuracy classes with a fixed error limit.
Here’s a quick guideline: Accuracy Class A always designates the highest accuracy with the
lowest error limit. For accuracy Class B, the double error limits of A/AS generally apply. For volumetric instruments of Class AS, calibrated to "EX", the suffix S indicates rapid execution. This accuracy variant is used for pipettes and Burets.
We’re happy to offer guidance here as cleaning and care are critical. Volumetricinstruments should be cleaned immediately after use either manually in an immersion bath or mechanically in a laboratory dishwasher. Make sure that the cleaning temperature is low, the residence time is short, and the alkalinity of the cleaning medium is also low. Volumetric instruments can then be dried (at max. 250°C) and autoclaved, disinfected, or sterilized.
The use of abrasive cleaning methods is not recommended at any time as this can damage the surface. Cleaning in an ultrasonic bath is possible, however, contact with the sound membranes should be avoided.
Dispensers are piston lifting attachments that can be used to measure defined quantities of liquid easily, quickly, and precisely, for example, from a laboratory bottle. When our dispensers are screwed onto laboratory bottles, the previously set quantity of liquid is sucked into the cylinder by an upward movement of the piston — accurate every time. The subsequent downward movement ejects the quantity of liquid via a cannula. With this principle, there is no need to adjust the meniscus.
For all Class A and AS volumetric instruments there is a retrace code which can be used to
easily download a batch certificate on our website.
No specific certificates are issued for Class B volumetric instruments.