# Does using same calibration curve for chemical analysis introduce correlation in sample error/uncertainty values?

I am using a hypothetical case to explain my question

Let us consider a chemical analysis method A (using a certain instrument), which is used to quantify the value of a particular species b. According the instrument manufacturer's notes, the instrument used needs to be calibrated once a month. I am analyzing several samples of b in the duration of a month, and using the same calibration curve to obtain the quantity of b along with the uncertainty bound for the value.

I want to understand the following,

1. If number of samples (over the period of a month) of b are using the same calibration curve to quantify it value, are their errors/uncertainties correlated (by any means, the calibration curve introduces it, however small it may be) ?
2. Additionally, method A has the ability to quantify several species (b, c, d,$$\dots$$), does errors/uncertainty of species from the same sample (containing different species like b, c,$$\dots$$) correlated in any way?
3. If there exists even a very small correlation, does it make sense to consider it for any further analysis?

I am new to the realm of chemistry (analytical chemistry to be precise), I request your help.

Thank you.

PS: Apologies if the tags are inaccurate

• 1.) Of course, 2.) very likely, but you need to be a lot more specific about A, 3.) how would you do that? You need to have a superior analytical method to only find that correlation. – Karl Dec 4 '20 at 6:17
• You should distinguish between errors and uncertainties. If your calibration is somehow systematically wrong (an error has been introduced while determining the relation between observable and expected values) then all values subsequently derived from that calibration will suffer from the same systematic error. This does not mean that the uncertainties due to noise are otherwise correlated. – Buck Thorn Dec 4 '20 at 7:07