I wonder to what extent the cooking time impacts the nutritional content when boiling unpeeled potatoes with unsalted water.
Boiling potatoes whole in their skins minimizes the amount of vitamin C that is lost. According to the Food and Agriculture Organization of the United Nations, boiling unpeeled potatoes results in losses of up to 30 percent of vitamin C, but boiling peeled potatoes can cause losses of up to 40 percent. About 2 percent of the vitamin B-6 is lost due to boiling potatoes, as well as about 23 percent of the thiamine. A 3.5-ounce serving of potato boiled in the skin provides 22 percent of the daily value for vitamin C, but boiled peeled potatoes provide only 12 percent. Peeling potatoes before boiling can also increase vitamin B-6 losses, with unpeeled boiled potatoes containing 15 percent of the DV per 3.5-ounce serving and peeled boiled potatoes containing only 13 percent of the DV. There is no difference in thiamine content between peeled and unpeeled boiled potatoes.
The higher the temperature and the longer the cooking time, the more of the vitamins will be lost
However, it does not mention how the loss curve looks like.