In this study, the molecule formation mechanisms of strontium mono fluoride used for the determination of fluorine in a high-resolution continuum source atomic absorption spectrophotometer was investigated. To distinguish between the gas-phase and the condensed-phase mechanisms, the analyte (F) and the molecule forming element (Sr) were injected on the solid sampling platform manually, as mixed or separately, and the absorbances/peak shapes were compared. There was no significant difference between the absorbances. In addition, the peak shapes and the appearance times were almost the same for the two cases. It was proposed that the main pathway for SrF formation is a gas-phase combination reaction between Sr and F. When Sr and F were mixed on the platform, it was expected that at first SrF2 would be formed in the condensed phase, and then at elevated temperatures it was partly decomposed while either losing one F atom to form SrF, or completely decomposed to its atoms in the gas phase.