Composite samples of rice grains as well as the common weed
shoots (three samples each) from each farm were homogenized
by grinding in stainless steel blender and then passed through a
sieve of 2 mm mesh size. Grinded sample of 1 g was digested in
20 ml tri-acid mixture of HNO3:H2SO4:HClO4 (5:1:1, v/v/v) till a
transparent color appeared, then plant digests were filtered and
diluted to 25 ml with double de-ionized wate