Phosphate concentration

I have chemical analyses of groundwater samples (I got the analyses from a previous study) and I want to work with it in my master thesis.


In these analyses, phosphate concentration is mentioned in micrograms/liter and it seems phosphate was analysed by means of IC-ICP-MS.


My question is: When measuring phosphate concentration (orthophosphate) either using IC-ICP-MS or any other method as HACH Method 8114, do we measure the three species $\ce{PO4^{-3},HPO4^{-2}}$, and $\ce{H2PO4^{-1}}$ together and report the result as phosphate or we measure just $\ce{PO4^{-3}}$? 


