The research aimed to provide an optimized method for the determination of phosphorous concentration in different types of solid waste using inductive coupled plasma mass spectrometry (ICP-MS) technique. The analyzed waste matrices are: a) vegetable waste (P1), b) ash from the incineration of medical waste (P2) c) sewage sludge (P3) and d) sludge from the meat processing industry (P4). The results obtained by the ICP-MS method were compared with the UV-VIS spectrophotometric method for the determination of total phosphorus. In the case of using the colorimetric method by UV-VIS technique, lower results were obtained compared to the ICP-MS method due to the interferences given by the reagents used to determine the total phosphorus. The interferences given by other elements (metals) were also investigated and the performance parameters were determined such as detection limit, quantification limit, recovery and expandend incertainty using ICP-MS technique.