The present invention provides methods, compositions, kits, and devices for detecting heavy metals in dried blood (e.g., dried blood spots). For example, the present invention provides: 1) dried blood spot paper that is detectably free of heavy metals and methods of preparing such paper using organic acid； 2) dried blood extraction solutions optimized for heavy metal detection (e.g., extraction solutions containing acetic acid and/or gold)； 3) methods for estimating venous blood volume from dried blood mass； and 4) kits and kit components optimized for heavy metal detection in dried blood (e.g., kits with paper detectably free of heavy metals, heavy metal free skin wipes, metal free collection case, etc.).
