Guaranteeing a sustainable supply with raw materials for industrial needs is essential. Especially, there is high interest in critical metals and metalloids. Without those materials numerous modern technical products such as mobile phones are unimaginable. Research and development of new technologies of recycling processes for these materials grow to an important challenge for modern societies. An aspect of those recycling processes is presented in this work. Via gas phase reactions an enrichment and separation of metals and metalloids even in small amounts are possible. The thermodynamic principles of those reactions and their possibilities and limits are also explained in this work.