# Dosing leaves with Zinc Nitrate for pollution experiment - Need specific concentration

I am trying to assess the pollution tolerance of an insect using Zn as a proxy. I have a supply of Zinc Nitrate Hexahydrate that I want to use to contaminate dried leaves (the insect's food). The LD50 for my insect is around 2000 micrograms g^-1.

I was thinking I could achieve this by using 0.1 g squares of dried leaf that I would contaminate by topically applying 1 ml of Zn solution. To get my desired concentration, I am thinking that I would dissolve 200 micrograms of Zn into 1 ml of distilled water, so that when I apply 1 ml of this solution to a 0.1 g square of leaf I would have a final concentration of 2000 micrograms/gram of food. But if I wanted to apply only 0.5 ml of Zn solution to 0.1 g of leaf but still have the same final concentration of 2000 microg/g food, I would create a solution of 400 micrograms/ml. And if I wanted to use 1.0 gram of leaf and have a concentration of 2000 micrograms/g, I would make a solution of 2000 micrograms/ml. Is all of this correct?

I am also open to suggestions of how to better contaminate the food in a more consistent way. I thought about soaking leaves in a defined concentration, but then I am worried that some leaves will absorb more or less liquid than others, making the final Zn/g food concentrations unequal across different leaves.

Thank you for any solutions (pun intended) anyone might provide.

• Could you please incorporate the comments within and following the posted answer to update your question. It seems the quesiton of what the wt/wt measure of LD50 refers to is not clear. – Buck Thorn Jun 13 '19 at 8:17