Question

For my organic chem lab, we need to do a serial dilution of a sample so that it can be used in a mass spec. If we start out with .1g of an unknown compound in 10ml of DCM, how can we get it to 1000ppb concentration? I have never worked with ppb and don't know how to do the calculations, please explain step by step.

Answer 1

1mg/L = 1000ppb

0.1g = 100mg (1g = 1000mg)

We have 100mg of unknown compound in 10ml or 0.01L of solution.

100mg10ml

1ml 10mg

Measure 1 ml of this solution and add it to another 9ml of DCM, now new solution formed contains 10mg of unknown in 10 ml of DCM.

Now 1 ml of new solution contains 1mg of unknown compound.

Again measure 1ml of the new solution and add it to another 999ml of DCM. Now this solution contains 1mg of unknown in 1000ml or 1L of DCM

and we know 1mg/L = 1000ppb.