[jkrueger0408]

I used a test kit to determine the concentration of CaCO3 in a water sample, and it reported the findings in mg/L

It was a 1.5L water sample in which I tested 5 0.3L elutions, and totaled the reported mg/L results of each 0.3L sample

Is it legal to use this method to determine the total Ca content of the 1.5L sample?

(Totaled X mg/L CaCO3 from each 300ml sample)/(100 FW CaCO3) = mmol/L CaCO3

1 mmol CaCO3 =  1 mmol Ca

Total mmol Ca = (X mg/L CaCO3)/(100 FW CaCO3)??

Or do I have to consider the 0.3L volumes or the 1.5L volume??

[voidSetup]

The mg/L is a concentration so you can't just add them up, I'm guessing also that they should be about the same value since they're from the same sample. You could average them, then multiply by 1.5L to get the total mg of CaCO₃ in the sample. Then convert this into mol or mmol from the formula weight (have to multiply by 1000 for mmol).

[jkrueger0408]

I left information out, essentially I was using concentrated NaCl rinses to displace calcium that was loaded onto a weak acid cation exchange resin, so the concentration of calcium varied for each elution.

I realise now however that I must determine the concentration of each sample independently, convert the concentration to total mg contained in the sample by multiplying by the volume used in the elution (0.3L), and then these values can be summed for the total value of calcium contained on the resin.

Thanks for the response!