Could residual solvents (TFA) or heavy metals be present?

Potentially — which is exactly why they are tested. Trifluoroacetic acid (TFA) is widely used in peptide synthesis and purification and can remain as a counter-ion or residual solvent; it is quantified by methods such as ¹⁹F-NMR, and pharmaceutical residual-solvent limits are set by USP <467>. Heavy metals (for example lead, cadmium, arsenic) can carry over from low-grade starting materials and are screened by ICP-MS at parts-per-billion levels, with elemental-impurity limits in USP <232>/<233>. A comprehensive COA may include residual-solvent and heavy-metal results alongside purity and identity. As above, these are materials-testing parameters, not a safety assurance for human use.