Bulb pipette 20ml, one mark, class B, soda-lime glass. Pack of 5

Which volumetric glassware is going to deliver the required level of accuracy? Let DWK Life Sciences help...

Different levels of volumetric glassware accuracy are required across a broad scope of applications. The ability to precisely measure the volume of a solution can be critical to the outcome of many experiments and analytical testing procedures. It is therefore essential to ensure that the glassware selected to make these important measurements has the requisite accuracy and precision.

Here are a few tips to ensure you choose the right volumetric products for your application:

Graduated products are accurate, right?

• Volumetric glassware is a class of glass vessels that are calibrated to contain or deliver specific volumes of substances. Although many glassware items are graduated i.e. beakers, flasks, bottles, etc. these graduations are approximate and only calibrated products should be used where accurate volumetric measurement is required.

Borosilicate vs Soda-lime

• Volumetric glassware can be made from both 3.3 borosilicate glass (such as Pyrex^®) and soda-lime glass. Borosilicate glass is much more chemically resistant than soda-lime glass. As a result, borosilicate should be used where the longer term exposure to chemicals is more likely, such as the storage of solutions in volumetric flasks. Soda-lime glass can be used with less aggressive chemicals, or where long term exposure to chemicals is unlikely, such as pipettes. 3.3 borosilicate volumetric glassware will retain its accuracy over a longer working lifetime than a soda-lime glass equivalent

Glass with Class

• Most volumetric glassware is available in two accuracy classes – Class A/AS and Class B. 
• Class A/AS is the highest volumetric accuracy and is suitable for analytical applications where precision volumetric measurement is essential. 
• Class B products are calibrated to accuracy tolerances twice those of Class A/AS tolerances and are suitable for general volumetric applications.
• Class AS burettes and pipettes are calibrated to the same accuracy tolerances as Class A, but are designed to permit a more rapid outflow time than the standard Class A equivalents.

Volumetrics Stand and Deliver

• All volumetric products are calibrated either ‘to contain’ or ‘to deliver’ at a specific temperature, usually 20^oC. For example, a 50ml volumetric flask that is calibrated ‘to contain’ is calibrated at 20^oC to precisely contain 50ml when filled to the graduation mark. Volumetric products usually calibrated ‘to contain’ are measuring cylinders and volumetric flasks. 
• With a product calibrated ‘to deliver’, the delivered volume of liquid corresponds to the graduation mark on the vessel. The drainage holdback error (i.e. the amount of liquid remaining within the vessel to wet the inner surface or the liquid remaining in the jet of a pipette or burette) has already been taken into account during calibration. All volumetric glassware is marked either ‘to contain’ (ISO designation ‘IN’) or ‘to deliver’ (ISO designation ‘EX’) to indicate which type of calibration applies to that product.

Why UKAS?

• All DWK Life Sciences manufactured Pyrex^® and MBL^® volumetric products are tested and calibrated in an ISO/IEC 17025 UKAS (United Kingdom Accreditation Service) accredited calibration laboratory located at DWK Life Sciences’s glass manufacturing facility in Stoke-on-Trent.

To receive ISO/IEC 17025 accreditation, DWK Life Sciences had to demonstrate the highest levels of competency in a number of areas of its calibration procedures. The achievement of this accreditation provides customers with an additional assurance of the accuracy and precision of DWK Life Sciences’s volumetric glassware.

Certification to Suit Your Needs

• Pyrex^® and MBL^® Class A/AS volumetric glassware is available with different types of certification depending on what level of product traceability is required. 
• All Pyrex^® and certain MBL^® volumetric products can be supplied either batch certification or individual calibration certificates. Pyrex^® Class A volumetric flasks and measuring cylinders can also be supplied with individual UKAS calibration certificates, where certification proving compliance to the highest levels of accuracy is required.   

Visit our dedicated page for further technical information about DWK Life Sciences’s Volumetric Glassware.

We hope you found this interesting! Please stay tuned for the next instalment on volumetric glassware which will be available on our website later this month.

Please note that the advice given is for general laboratory applications and may not necessarily apply to all tests and procedures.