A novel approach for the simultaneous analysis of glyphosate (PMG), and aminomethylphosphonic (AMPA, GlyP), N-methylaminomethylphosphonic (MAMPA. SarP) and methylphosphonic (MPA) acids is presented. This includes a preliminary 31P NMR analysis of mixtures of PMG, MPA, AMPA and MAMPA, their further derivatization to volatile phosphonates by means of the trifluoroacetic acid-trifluoroacetic anhydride-trimethyl orthoacetate reagent and subsequent MS [chemical ionization (CI) MS, GC-CI-MS, GC-electron impact ionization MS] and/or GC-flame ionization detection (FID) analysis of the products of derivatization. The detection limits of PMG, AMPA, MAMPA and MPA by means of GC-CI-MS and GC-FID were determined. The calibration graphs (GC-FID) for these derivatives were in the range 0.1 to 100 nmol linear and sufficiently reproducible for quantitative determinations. The applicability of the method was demonstrated during the analysis of water samples fortified with PMG, AMPA and MAMPA, characterized by recoveries of >95%.