Maltodextrin is not a standardized product.
Maltodextrin is a chain of glucose molecules, and that chain can be anywhere from 3 to 17 glucose molecules long. Only 1 end of the chain is a reducing molecule so the safe thing is to assume worst case of a 17 glucose chain.
To calculate the required maltodextrin, the steps are:
Calculate the weight of silver in the solution.
Calculate the silver in moles by dividing the weight by the atomic weight of silver
Multiply the moles of silver by the molecular weight of glucose.
Multiply that number by 17
In simplified form, the worst case weight of mailtordextrin is: ppm * ml * .028 0.14
Ex for 20 ppm, 500 ml: 20 * 500 * .014 = 140 mg of maltodextrin.
Ex for 80 ppm, 250 ml: 80 * 250 * .014 = 280 mg
Ex for 100 ppm, 1000ml: : 100 * 1000 * .014 = 1400 mg
For gold, the process is almost the same, except the multiplier is different since gold's atomic weight is a lot more, and it takes 3 times as much because gold is missing 3 electrons instead of 1.
For gold, the constant works out to 0.051 0.025
Ex: 50 ppm 500ml : 50 * 500 * .025 = 625 mg
Ex: 40 ppm 1000ml: 40 * 10000 * 0.025 = 1000 mg
More does not hurt.