Purity and Concentration A good Vitamin C serum should have a concentration of 10–20% L-Ascorbic Acid or its stable derivatives like Sodium Ascorbyl Phosphate. This ensures both potency and safety for the skin. Packaging and Stability Vitamin C oxidizes quickly when exposed to light and air. The best serums come in dark or amber-colored bottles with air-tight pumps to maintain ef... https://skinsciences.com.pk/products/vitamin-c-serum