“…An anticoincidence Nal(Tl) or CsI(Tl) shield around the Si(Li) offers useful reduction of the background (Gloystein et ai, 1981). However, if the gamma back ground is strong (e.g., from blood serum samples), ashing may only give marginal improvements (Lecomte et al, 1982). Ashing of biologic material to reduce the organic matrix and hence the bremsstrahlung background helps to lower MDL to -0.2 ppm in the Z -30 region.…”