was followed.
A 100 mg pepper was taken in a beaker and dissolved in
concentrated nitric acid (5 mL) with heating. The solution was
cooled, neutralised with NaOH solution, diluted and filtered. The
filtrate was made to 100 mL with water in a calibrated flask and
the recommended procedure was followed.
Also, 20 g of tomato, grape, okra, spinach, mint and coriander
was heated in silica crucible for 3 h on a hot plate and the charred
material was transferred to a furnace and heated at 650 C
overnight. The residue was cooled and treated with 10.0 mL con-centrated nitric acid and 3 mL of 30% (w/w) H2O2 and again kept in
a furnace for 2 h. The final residue was treated with 3 mL concentrated
hydrochloric acid and 2–4 mL of 70% (w/w) perchloric acid
and heated till white fumes was removed. After dissolving and filtering
solid residue, the solution was neutralised with NaOH solution
and diluted to the mark, and the preconcentration procedure
was carried out.