It is recommended to use our Citric Acid solution between 0.1% - 1% of the final eLiquid formula in sweet citrus flavours where the overtones do not interfere with the flavour palate, while with competing flavours a maximum concentration of 0.1% - 0.5% is recommended. Vapour Depot Citric Acid Contains: 90% PG 10% Citric Acid Comes in a 10ml PET bottle. Vapour Depot Citric Acid 10% eLiquid additive. One of the more common ingredients used to give eLiquids the tart flavour.