Chromatography Forum

hi everyone
i have a gas CRM with these description:

component name: hydrogen
concentration (moles) :4.9 %
accuracy(+/- %):2

now i want to calibrate my GC with this CRM, i calculate the uncertainty in this way:

u=d/√3 u=2/1.73= 1.154

so when i inject the CRM to GC, my results could be in 4.9 ± 1.154 range

is it right?

Hi,

The range calculated by your formula is too high (>20%) so I don't think the formula is correct. In fact if you have the access to GPA2261 the uncertainty is listed inside and has been widely accepted as the square root of (CRM uncertainty ^ 2 + instrument reproducibility ^ 2). This formula works much better as it takes into account the instrument drift which definitely affects the CRM reading when running on your GC. Reproducibility often can be found in a standard method if you are following any, otherwise you could easily google how to estimate it.

Hope this helps.

Peter.

thanks for your answer
i found this method in this study:

A Practical Guide to the Calculation of Uncertainty of Measurement
Mario Zilli*
ARPA F.V.G., Settore Laboratorio Unico, Laboratorio di Gorizia, Italy


https://imgur.com/ZX8DRnR

Hi,

The range calculated by your formula is too high (>20%) so I don't think the formula is correct. In fact if you have the access to GPA2261 the uncertainty is listed inside and has been widely accepted as the square root of (CRM uncertainty ^ 2 + instrument reproducibility ^ 2). This formula works much better as it takes into account the instrument drift which definitely affects the CRM reading when running on your GC. Reproducibility often can be found in a standard method if you are following any, otherwise you could easily google how to estimate it.

Hope this helps.

Peter.

thanks for your answer
i found this method in this study:

A Practical Guide to the Calculation of Uncertainty of Measurement
Mario Zilli*
ARPA F.V.G., Settore Laboratorio Unico, Laboratorio di Gorizia, Italy


https://imgur.com/ZX8DRnR