I believe that you need a nightime of nothing in your system for the flush to work.
If you think about it, you would have about eight hours of nothing going in and then you pour in the quart of saltwater. That would be ideal for the saltwater to go right on through, which is what you want.

Hopefully you are bottle feeding if you are doing the Master-Cleanse with a new baby. Otherwise all the toxins you release will go through your breast milk to the baby. So do not do the Master-Cleanse if you are nursing!
It is very important that the SWF (Salt-Water-Flush) be done in the a.m. so your stomach is completely empty of everything, even water. The proportion of h2o to salt is essential so it runs through your body without being absorbed. Hopefully you have read the book, if not it is available to read online. Good luck!