Method to measure the heavy metal content in plant roots, stems and leaves
Each sample is a mixture of 3 to 5 nearby samples. Plant samples were first washed with tap water to remove dust, then washed with deionized water, dried, and incubated at 105 C for 30 minutes. Then, they were dried at 70 C to constant weight, crushed using non-metallic instruments, and passed through a 0.154 mm nylon sieve for testing.
Acid digestion method: Accurately weigh the processed 1.000 0 g sample into a 50 mL polytetrafluoroethylene crucible, add 20 mL of concentrated nitric acid and soak overnight, place it on an electric hot plate and heat it over low heat. After the particles melt, add 4 mL of perchloric acid and continue heating until thick white smoke is emitted and the solution turns pink or light yellow. Then dissolve the residue with 1% HNO3, filter, transfer to 5O mI volumetric flask, and use deionized water Set the appearance.
Dry ashing method: Accurately weigh 1.000 0 g of the sample into a porcelain crucible, place it in a fume hood, and use an electric hot plate to slowly heat it for carbonization (to ensure uniform heating, add 2 mL before heating) 1 HNO. ) until there is no smoke. Ash in a transposed muffle furnace, slowly raise the temperature to 500 C, and ashe for 8 to 9 hours. After cooling, take it out and add 2 mI 1 HNO. Dissolve the ash, transfer to a 5O mL volumetric flask, and dilute to volume with deionized water.
The treated plant samples were measured with atomic absorption spectrophotometer for Pb, Cd and cu contents
The processing of mercury element is different from other methods, and cold atomic absorption is used for determination. The Cr content is measured using diphenylcarbazide spectrophotometry (never seen it before)
The results of plant roots are not very good, which is closely related to the sampling method. The above method is not suitable for root sampling