ISO 23956:2022 pdf download – Traditional Chinese medicine — Determination of benzopyrene in processed natural products. b) Add 100 ml of hexane with 1 ml of internal standard (50 μg/kg or 50 μg/l: purity ≥ 96 % for analysis grade) to a mixture by homogenization for 5 min, and extract the samples mixtures in an ultrasonic bath for 30 min. c) Transfer all mixtures into a separating funnel and collect the supernatants. d) Extract the residue twice with 50 ml of hexane as detailed in step b). e) Add water (50 ml; ≥ 18,2 MΩ) to the combined hexane fraction...