Table 1.

Certified mean values (mg kg-1) for Montana I (SRM 2710a) soil reference material and the mean values we found for selected elements from this sample following aqua regia digestion.

Element	As	Cd	Fe	Mn	Pb	Zn
Certified value	1540 ± 100	12.3 ± 0.3	43200 ± 800	2140 ± 60	5520 ± 30	4180 ± 150
Found value	1430 ± 90	11.3 ± 0.7	34500 ± 320	1610 ± 70	5580 ± 240	3760 ± 80
% Recovery	93	90	80	75	101	80
Detection limita	0.1	0.002	3.9	0.1	0.3	1.3

^a Detection limits were calculated as 3 × standard deviation (3 × Std. Dev.) of blank values.