The execution of that procedure started as early as 1998 [2]. The use of a Marinelli container in a specially shielded low-background detector (Figure 1), instead of a common plastic container, has improved detection effi-ciency by almost five times (from 0.58% to 2.86%).
Table 1 shows K concentration in several foodstuff samples being obtained by γ rays detection emitted by 40K [3,4].
Validation of analytical method provides the basis for testing reliability of obtained results in a given uncer-tainty range. Potassium activity is related to 40K, a natu-ral radioisotope emitting β− and γ rays. A sample activity emitting typical potassium γ rays energy can be linearly related to its whole potassium quantity. Shown data are aimed to validate potassium quantification method in a