Phosphate Ester Sodium (SAP) is the most suitable VC derivative for acne-prone skin. Let's look at the key points directly: 1% concentration of Sodium Ascorbyl Phosphate has a strong antibacterial effect on Propionibacterium acnes, and the antibacterial effect lasts up to 8 hours!In simple terms: Sodium Ascorbyl Phosphate Eucerin (SAP) "kills" all Propionibacterium acnes within 8 hours, but 8 hours is not the limit time, it can actually be longer.