Buyers must focus on molecular stability and bioavailability. Key specs include the concentration (mg/ml), pH balance (typically 6.0-7.5) to prevent nasal irritation, and the use of preservative-free formulations or medical-grade preservatives like Benzalkonium chloride. Compliance-wise, products must adhere to regional health authority regulations (such as FDA, EMA, or NMPA guidelines). Always request a COA (Certificate of Analysis) and MSDS (Material Safety Data Sheet) for every batch to ensure the absence of heavy metals and microbial contaminants.