AFAIK, the derivatives are less researched, so hard to argue about. Often, the concentration isn’t disclosed, too.
I would just go DIY, since commercial products are either very, very expensive, or ineffective. Once you got your measurements down, mixing it freshly takes no time. And you can afford to use it all over the body, not just the face. This way you know, it’s not oxidized, it’s exactly what’s used in some better studies, it is effective. Even DIYing a stabilized formulation with ferulic acid is possible and still much cheaper.
Personally, I have trust issues with vitamin C chemistry tho :D
Anyone who can afford the equipment to make fresh vitamin c serum could easily afford several years supply of high end commercial products that have been tested to confirm their ingredients and effects.
You need a mg scale and pH strips as equipment (~ 20€, once); tap water, pure vitamin C and sodium bicarbonate as ingredients (~ 6€, lasts for many, many preparations). Aluminium foil to make any glas container light-tight.
The chemicals are food grade from your next supermarket or drug store. The "recipe" is used in some studies.
I would just go DIY, since commercial products are either very, very expensive, or ineffective. Once you got your measurements down, mixing it freshly takes no time. And you can afford to use it all over the body, not just the face. This way you know, it’s not oxidized, it’s exactly what’s used in some better studies, it is effective. Even DIYing a stabilized formulation with ferulic acid is possible and still much cheaper.
Personally, I have trust issues with vitamin C chemistry tho :D