'Ask Lab Tech Guy' is a regular feature in the e-newsletter from Mourne Training Services and is posted on the MTS blog. Find out more on the MTS website at http://www.mournetrainingservices.co.uk/Blog.html

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2. ©2010 Mourne Training Services Dear Lab Tech Guy, I have often wondered if the high temperatures used when cleaning and drying volumetric glassware have any effect on the delivered volume. Can you shed any light on this? Yours, Martin (Stockport, England)

3. Dear Martin, Most modern laboratory glassware is made from Pyrex, a material which is resistant to irreversible volume changes. A study by D.R.Burfield* showed that exposing volumetric flasks and pipettes to 320⁰C, either continuously or thermally cycled, does not significantly affect the calibration, the conclusion being that "oven temperatures in the range of 110-150⁰C should provide efficient drying of glassware with no risk of discernible volume changes, even after prolonged use, providing that Pyrex glass is the material of construction". If you read the manufacturer’s instructions for your glassware then it is likely to warn against exposing to direct heat but will advise that use of automatic dishwashers and autoclaves at 121⁰C is acceptable. * ’Oven Drying of Volumetric Glassware’ D.R.Burfield and G.HefterJ.Chem.Ed. v.64 p.1054 (1987) ©2010 Mourne Training Services Phew! Does it have to be so hot?

4. In fact, you don’t usually need to dry volumetric glassware since it can be rinsed with the appropriate solution or diluent at the time of use but you DO need to be very sure it is clean. Not only to prevent contamination but also to ensure that the correct volume is measured. Dirt, and especially grease, can distort the shape of the meniscus and also cause droplets of liquid to adhere to the vessel walls. Both seriously impair accuracy. My advice is to get your hands on a copy of the manufacturer’s recommendations for cleaning your volumetric glassware and follow the instructions provided. Also, make sure to clean glassware thoroughly for good measure. Yours volumetrically, ©2010 Mourne Training Services What’s he so happy about? He’s been like that ever since the Prozac® analysis

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