Some vitamins can be lost in food preservation, depending on technique. Minerals should stay the same unless there is some liquid lost in processing, other than that evaporated.

FWIW, if you are specifically looking to replace potassium, consider potatoes. A medium white potato has about double the potassium of a medium banana. Surprised me when I looked them up in a nutrition database. Mashed potatoes seem to be very popular with many backpackers. I thought it was just because they are cheap and readily available. Maybe they appeal to an unrecognized craving for potassium. Loaded with cheese, the potatoes also provide fat, sodium, and protein. Toss in some dried parsley, also readily available, and you have a high-potency green added.

CM