Hi, I need to make a 0.1mg/L solution of phosphorus in 250mL flask with a stock solution that reads the following on the label:
1ml=0.050mg (50ppm) P (as PO4 3-)
1ml=0.153mg (153ppm) PO4 3-
The labelling is confusing me and I don't know what initial volume I should take from this stock solution. If anyone knows the answer could you also explain how you got it? This is for total phosphorus analysis, this is the standard.

thanks!