Question

5) Low iron concentration (as low as 0.02 nM) in the open ocean limits phytoplankton growth. Preconcentration is required to determine such low concentrations. Trace Fe3 from a large volume of seawater is concentrated onto a 1.2 mL chelating resin column, the column is then rinsed with 30 mL of high purity water and eluted with 10 mL of 1.5 M high purity HNO3. a.) For each sample, seawater is passed through the column of 17 h at 10 mL./min. How much is the concentration of Fe3 in the 10 mL of HNO3 eluate increased by this preconcentration procedure

Answer 1

Check the explanation

Step-by-step explanation:

Sample volume V= 10 mL/min x 17 h x 60 min/h / 1000 mL/L = 10.2 L

The concentration is increased

10200 mL (sample volum) / 10 mL (eluted sample) = 1020 times.

57x10-9 M / 1020 = 5.6x10-12 M

1.5 M HNO3 will contain ≤ 2ppm x (1.5M/15.7M ) ≤ 0.190 ppm ≤ 190 ppb

Ignoring this is reagent impurity and calculating for sea water

≤ 190 ppb /1020 = 0.186 ppb = 0.186 x 10-9g/mL = 0.186 x 10-6g/L =

0.186 x 10-6g/L / 56 g/mol = 0.003 x10-6 M = 3 nM