Hi butterflies. Do not directly know the answer to your question as I am not sure what antique means in relation to white. Yellowy or grey? I have added tubes of acrylic paint (and matchpots) to white emulsions to get the colour I want. My husband is a painter and we always have lots of white and magnolia in the shed.
There are umpteen whites out there now. Suggest you get colour charts from good paint co's like Farrow and Ball and find the colour you want and try and gauge (in natural light) what may have been added to white. If it is an important project it may be safer to get their product.
As you probably know, doing this is trial and error and patience. Sometimes you get the result you want ( I recently got a great stone colour from magnolia and 2 black tubes). Good luck.