well icp (inductively coupled plasma) is the gold standard (expensive but highly sensitive and used for heavy metals like lead in stuff).
xrf can spot higher concrntrations, but one can concentrate beforehand and then use xrf. while xrf fixed cost is 30k usd its cost is a dropjn the bucket compared to icp and solid state keeps on going.
It probably isn't important whether the lead content is 10 ppm or 20 ppm in most cases, since neither is acceptable, so the standard of sampling involved here is far less demanding than the standard of sampling needed for analytical chemistry. You just need to avoid contaminating your sample with lead from some other source.
xrf can spot higher concrntrations, but one can concentrate beforehand and then use xrf. while xrf fixed cost is 30k usd its cost is a dropjn the bucket compared to icp and solid state keeps on going.
forgive my typos commenting via phone