In the context of the corrosion of steel in reinforced concrete, one possible solution of protection is the use of corrosion inhibitors. The aim of this paper is to present two methods to analyse quantitatively the inorganic inhibitor sodium monofluorophosphate (MFP, no. CAS[10163-15-2]) in concrete. The first method using ion chromatography leads to very accurate results and permits the determination of the ionic compounds of MFP (F− or PO3F2−). The second method proposes the analysis of fluoride using an ion specific electrode. This low cost method allows the detection of the presence of MFP and quantification of fluoride ions brought by MFP. The choice of method depends on the type of result needed. For both methods, various ways of extraction have been tested. Finally, it is concluded that extraction using a cation exchanger is the most efficient method to extract the MFP ions from concrete.