By

This is maybe a silly question, but I and a colleague thougt about it and don't know which is the best option.

We have to report, on the one hand, the concentration of 1 component in a mixture, and on the other hand the total concentration (the sum of 4 concentrations). We have 4 individual cal curves and a linear cal curve for the sum of 4 (the software allows to do this).

So we can quantify total concentration in 2 different ways:

1-by manually doing the sum of the 4 individual reported results, or

2-from "total curve"

Depending on the way, we obtain 2 different results (which is logical, I know)- slightly different, but in some cases this could lead to exceed LMR (regulation) or not.

Our question is: which way of quantification gives a more accurate result for calculating total concentration and why?

Thank you in advance

By

Carmen,

Does your 'total cal curve' mean plotting A+B+C+D standard conc. through zero?

since you need to report conc. of 1 component, you would no matter what, need 4 cal curves. Then save the time of plotting the 'total curve'.

From my point of view, since the maths is addictive, shouldn't the 2 sets of readng agree if there is no rounding of figures?

Mike

By

Mike,

Yes, "total cal curve" means plotting A+B+C+D standard conc. through zero. We have to report 2 kinds of results:

-the one for single component "A" and

-the one for the sum of 4 concentrations (so = A+B+C+D)

So we only need single results B-C-D in order to obtain (A+B+C+D) by addition.

We also thougt that the 2 ways of reporting the total concentration (as described before),would lead to equal results, but they don't (!!!???)

They are not strongly differents, but in some cases 2 or 3 ppb more can make a result to depass legal regulations

...