Glassware Technical Information

Volumetric Glassware

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SciLabware manufactures two brands containing volumetric glassware products, Pyrex® and MBL®. As the name indicates Pyrex® volumetrics are manufactured exclusively from Pyrex® borosilicate glass. MBL® volumetric products are manufactured either from borosilicate and 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.

Pyrex® 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 Pyrex® 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.

ISO/IEC 17025 Accreditation

SciLabware manufactured volumetric products are tested and calibrated in an ISO/IEC 17025 accredited calibration laboratory located at SciLabware’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 SciLabware is in recognition of the continuous application of strict quality assurance procedures in the testing and calibration of our extensive range of Pyrex® and MBL® branded volumetric laboratoryglassware,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)

Temperaturein degrees Celsius at which the item was calibrated. All Pyrex® and MBL® volumetric glasswareiscalibrated 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. Pyrex® and MBL® volumetric flasks are also marked with the date of manufacture.


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 SciLabware:

UKAS Certified Products

A range of Pyrex® volumetric flasks and measuring cylinders is available with individual UKAS (United Kingdom Accreditation Service) calibration certificates. As well as detailing the measured volume (at 20oC) 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. 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 (Pyrex® volumetric flasks, measuring and mixing cylinders, burettes and MBL® pipettes) are inscribed with an individual serial number and are supplied with an individual calibration certificate. Pyrex ® volumetric flasks are also marked with the date of manufacture. 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 (Pyrex® Class A volumetric flasks and measuring and mixing cylinders and MBL® Class AS pipettes) are available to download from the SciLabware website as a .pdf document. The batch certificate contains detailed information pertaining to the specific production batch including average volume and standard deviation for the batch.

Azlon® Class A volumetric flasks are also available with batch certification that can be downloaded from our website.

Individual or batch certification is not available for Class B accuracy volumetric products.


Re-calibration of Volumetric Glassware

Normally, volumetric glassware only needs re-calibrating after extensive or demanding usage, which may have affected the original accuracy.

Re-calibration 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.

Find out more information on our range of volumetric products.

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