The aim of this study was to develop an analytical method for fluorinated silanes. Furthermore, as a secondary aim, to explore if there would be possible to detect 1H,1H,2H,2H-perfluorooctyl triethoxysilane (6:2 PTrEtSi) and 1H,1H,2H,2H-perfluorodecyl triethoxysilane (8:2 PTrEtSi) in two different matrices, sludge and cosmetic extract. The method development included experiments using LC-MS, LC-MS/MS, UPC2, GC-MS and APGC-MS/MS and was carried out using standards containing 6:2 PTrEtSi and 8:2 PTrEtSi. The analytical method that worked best for the compounds was GC-MS/MS and an analytical method using APGC-MS/MS was developed for fluorinated silanes. The IDL for 6:2 PTrEtSi was 0.0012 μg/mL and 1.32 μg/mL for 8:2 PTrEtSi. This makes the developed method suitable for high contaminated samples, such as extracts from cosmetic products. It was concluded that a method using LC as the analytical instrument would not work for the two target compounds since they were too reactive with the mobile phase. However, LC could be a good choice for siloxanes, compounds that are formed from hydrolysis and condensation of fluorinated silanes. The samples analyzed in this study were three sludge extracts and one extract from a cosmetic product. 6:2 PTrEtSi was expected to be detected in the cosmetic sample since the compound was stated on the table of contents of the cosmetic product. No detection of 6:2 TrEtSi or 8:2 TrEtSi could be made in either of the samples. The reason for this was suspected to be transformation or degradation of the compounds into other compounds. Therefore, a full scan of the cosmetic sample using LC-MS/MS was included in the experiment as an addition to verify the suspicions that compounds such as siloxanes could have been formed. An interesting peak was discovered with m/z 947 which could be a disiloxane of 6:2 PTrEtSi.