EUROPEAN PHARMACOPOEIA 7.02.4.27. Heavy metals in herbal drugs and fatty oils— a split-liner consisting of a column about 1 cm long packed with diatomaceous earth for gas chromatography R impregnated with 10 per cent m/m of poly(dimethyl)siloxane R, maintaining the temperature of the column at 150 °C for 5 min, then raising the temperature at a rate of 20 °C per min to 275 °C and maintaining it at 275 °C for 3 min and maintaining the temperature of the detector at 300 °C and that of the injection port at 220 °C. The retention times are: N,N-dimethylaniline about 3.6 min, N,N-diethylaniline about 5.0 min. Inject1 μLofthe test solution and1 μLof the reference solution.METHOD B Examinedbygaschromatography(2.2.28), usingnaphthaleneR as the internal standard. Internal standard solution. Dissolve 50 mg of naphthalene R in cyclohexane R and dilute to 50 mL with the same solvent. Dilute 5 mL of this solution to 100 mL with cyclohexane R. Test solution. To 1.00 g of the substance to be examined in a ground-glass-stoppered tube add 5 mL of 1 M sodium hydroxide and 1.0 mL of the internal standard solution. Stopper the tube and shake vigorously for 1 min. Centrifuge if necessary and use the upper layer. Reference solution. To 50.0 mg of N,N-dimethylaniline R add 2 mL of hydrochloric acid R and 20 mL of water R, shake to dissolve and dilute to 50.0 mL with water R. Dilute 5.0 mL of this solution to 250.0 mL with water R. To 1.0 mL of the latter solution in a ground-glass-stoppered tube add 5 mL of 1 M sodium hydroxide and 1.0 mL of the internal standard solution. Stopper the tube and shake vigorously for 1 min. Centrifuge if necessary and use the upper layer. The chromatographic procedure may be carried out using: — a glass column 2 m long and 2 mm in internal diameter packed with silanised diatomaceous earth for gas chromatography R impregnated with 3 per cent m/m of polymethylphenylsiloxane R, — nitrogen for chromatography R as the carrier gas at a flow rate of 30 mL/min, — a flame-ionisation detector, maintaining the temperature of the column at 120 °C and that of the injection port and of the detector at 150 °C. Inject1 μLofthe test solution and1 μLof the reference solution.01/2008:204272.4.27. HEAVY METALS IN HERBAL DRUGS AND FATTY OILSExamine by atomic absorption spectrometry (2.2.23). CAUTION: when using closed high-pressure digestion vessels and microwave laboratory equipment, be familiar with the safety and operating instructions given by the manufacturer.APPARATUS The apparatus typically consists of the following: — as digestion flasks, polytetrafluoroethylene flasks with a volume of about 120 mL, fitted with an airtight closure, a valve to adjust the pressure inside the container and a polytetrafluoroethylene tube to allow release of gas, — a system to make flasks airtight, using the same torsional force for each of them, — a microwave oven, with a magnetron frequency of 2450 MHz, with a selectable output from 0 to 630 ± 70 W in 1 per cent increments, a programmable digital computer, a polytetrafluoroethylene-coated microwave cavity with a variable speed exhaust fan, a rotating turntable drive system and exhaust tubing to vent fumes,— an atomic absorption spectrometer, equipped with hollow-cathode lamps as source of radiation and a deuterium lamp as background corrector; the system is fitted with: (a) a graphite furnace as atomisation device for cadmium, copper, iron, lead, nickel and zinc. (b) an automated continuous-flow hydride vapour generation system for arsenic and mercury.METHOD In case alternative apparatus is used, an adjustment of the instrument parameters may be necessary. Clean all the glassware and laboratory equipment with a 10 g/L solution of nitric acid R before use. Test solution. In a digestion flask place the prescribed quantity of the substance to be examined (about 0.50 g of powdered drug (1400) (2.9.12) or 0.50 g of fatty oil). Add 6 mL of heavy metal-free nitric acid R and 4 mL of heavy metal-free hydrochloric acid R. Make the flask airtight. Place the digestion flasks in the microwave oven. Carry out the digestion in 3 steps according to the following programme, used for 7 flasks each containing the test solution: 80 per cent power for 15 min, 100 per cent power for 5 min, 80 per cent power for 20 min. At the end of the cycle allow the flasks to cool in air and to each add 4 mL of heavy metal-free sulfuric acid R. Repeat the digestion programme. After cooling in air, open each digestion flask and introduce the clear, colourless solution obtained into a 50 mL volumetric flask. Rinse each digestion flask with 2 quantities, each of 15 mL, of water R and collect the rinsings in the volumetric flask. Add 1.0 mL of a 10 g/L solution of magnesium nitrate R and 1.0 mL of a 100 g/L solution of ammonium dihydrogen phosphate R and dilute to 50.0 mL with water R. Blank solution. Mix 6 mL of heavy metal-free nitric acid R and 4 mL of heavy metal-free hydrochloric acid R in a digestion flask. Carry 。