Whenever we carry out measurements for our customers, with any technique, it’s vital to carry out a measurement on some traceable reference material to show that the results from the analysis can be believed and trusted, and that the instrument used is working well.
With thermal conductivity, for example, we have a number of reference materials that can be measured to check that the system is measuring these within certain tolerance limits.
When we measure viscosity for customers there are a number of ISO certified viscosity standards available. Many of these are oil based and these are fantastic and can be easily stored for a long time at room temperature with little degradation – but if measuring the oil afterwards the viscometer needs to be cleaned with heptane and then IPA. So the better alternative when measuring materials such as protein solutions is to measure a water based viscosity standard such as MGVS20. This way the standard cleaning protocols for the protein solutions can be used for the standard.
With all standards they have a tolerance range, so MGVS20 is known as 2cP at 25C, but in fact is 2.003cP +/- 0.07% uncertainty of the standard, plus +/-0.17% uncertainty of water, plus our instrument’s 2% accuracy. So in fact if we measured it and everything was working well then we could expect a result between 1.95 and 2.05cP.
During a recent contract testing project on our Rheosense Initium system we ran our MGVS20 sample 10 times before the measurement to test that the system was working well and as accurate as needed for the customer. The result measured by the system was 2.005cP with a very low std deviation. So spot on the expected value of the standard. And here the great thing is that we only required a sample of 40ul to do all 10 measurements, and in fact recovered about 30ul of this after testing should it be needed for other analysis (and all automatically!) – not essential for the water based standard but excellent for the protein solutions that were measured on the same system.
If you’ve an interest in more detailed applications using the Rheosense Initium please visit this page
And visit the following for more biopharma specific applications