[kosho]

Hi!

I am measuring concentration of some metal and my concentration curve goes from 10 - 1000 ug/L.

With ten fold dillution I get 50 ug/L, which is basically 5 ug/L at calibration curve. I would have to measure this metal without dilluting it, but this is not possible, in this case I would get 50 ug/L which is in the range of calibration curve (10-1000 ug/L)

Is it OK to say in this case that there is 50 ug/L of this metal present in the sample despite 10 fold dilution of the sample?

[Arkcon]

Sorry, but I can't follow you.  I'm sure what you've written is clear to you, but I'm suspecting it won't be, but lets try.

You have a calibration curve covering concentrations from 10-1000 ug/L

You diluted a sample 10 fold.

You got answer of 5 which corresponds to 50 considering the dilution.

Is it OK to say in this case that there is 50 ug/L of this metal present in the sample despite 10 fold dilution of the sample?

Not despite, but rather because of, is what I would say.  Why do you think different?  What other answers are possible?  Or did I  misunderstand the steps?

[kosho]

Okay, Cal.curve range is 10-1000 ug/L

I have meausred conc 50 ug/L at 10 fold dilution, which means that this result is not inside cal.curve range (50ug/L divided by 10 (DF) is 5 ug/L, curve range is 10-1000 ug/L)

So the appropriate to do would be to measure the conc. without diluting. If I would measure it directly, I would get 50 ug/L, which is ok, because the result is inside the cal.curve range 10-1000ug/L.

Direct measuring is not possible, beacuse it could harm the machine (because of the nature of the sample). What would be the appropriate thing do to do in this situation?

[Borek]

Measuring outside of the calibration curve is not guaranteed to give a correct result, period.

Best approach would be to prepare and use a calibration curve covering 0-10 ppb range.