Hello, having
Vitamin C in the formula has an effect on the formula, i.e. lowering the pH of the formula, it is possible that
สารกันเสีย that members choose to use works well in lower pH. Ask the seller that
สารกันเสีย used, suitable for the value pH in what range?
สารกันเสีย work well over a narrow pH range if the formula has a higher or lower pH. It may not work.