ASTM D5056 Standard Test Method for Trace Metals in Petroleum Coke by Atomic Absorption
6. Apparatus
6.1 Furnace, electric, capable of regulation of temperature at 525°C +/- 10°C.
6.2 Magnetic Stirring Hot Plate .
6.3 Platinum Dish, 50 to 58-mL capacity.
6.4 Platinum Dish, 150 to 200-mL capacity.
6.5 Platinum-Tipped Tongs.
6.6 Furnace, electric, capable of regulation of temperature at 950 +/- 10°C or a Meker type forced air burner.
6.7 Atomic Absorption Spectrophotometer (AAS), equipped as follows:
6.7.1 Background Correction, using either a deuterium (D2) arc background corrector or other comparable simultaneous background correction system.
6.7.2 Burner Head, capable of supporting a nitrous oxide-acetylene flame.
6.7.3 Burner Head, single or multiple-slot, capable of supporting an air-acetylene flame.
6.7.4 Hollow Cathode Lamps, one for each of the elements to be analyzed: aluminum, calcium, iron, nickel, silicon, sodium, and vanadium.
NOTE 1 - Multi-elemental lamps can also be used; however, spectral interferences are possible (see 5.1).
7. Reagents
7.1 Purity of Reagents - Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all reagents shall conform to the specifications of the Committee on Analytical Reagents of the American Chem-ical Society where such specifications are available. Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purity to permit its use without lessening the accuracy of the determination.
7.2 Purity of Water - Unless otherwise indicated, references to water shall be understood to mean reagent water as defined by Type II of Specification D 1193.
7.3 Hydrochloric Acid, Solution 1, 20 % by volume (20 mL of concentrated HCl diluted to 100 mL with Type II reagent water).
7.4 Lanthanum Additive, Solution 2, 100 g/L lanthanum (dissolve 175 g LaCl3 in water and dilute to 1 L with water).
7.5 Lanthanum Chloride (LaCl3) powder (high purity).
7.6 Lithium Tetraborate (Li2B4O7), powder (high purity), or Lithium Metaborate (LiBO3), powder (high purity).
7.7 Standard and Sample Dilution Additive, Solution 3 - Weigh 40.0 g, to the nearest 0.1 g, of Li2B4O7 into a 150 to 200 mL platinum dish, fuse with a Meker type burner to form a liquid, and cool. Alternatively, heat in a furnace at 950 +/- 10°C for 10 min or until a liquid forms. Place the cooled platinum dish containing the fused recrystallized Li2B4O7, and a magnetic stirring bar into a 2-L beaker. Add 1000 mL of Solution 1 (20 % HCl). Heat and stir the solution on a magnetic stirring hot plate until the melt completely dissolves. After dissolution, remove the platinum dish with a glass rod. Rinse the platinum dish and glass rod with water into the lithium borate solution. Immediately transfer the warm solution quantitatively to a 2-L flask. To avoid crystallization add about 100 mL of water; stir the solution and cool to room temperature. Add 400 mL of Solution 2 (lanthanum additive) and mix. Dilute to 2000 mL with water, mix thoroughly, and vacuum filter the entire solution through Dow filter paper.
NOTE 2 - Fifty millilitres of Solution 3 contains 1 g Li2B4O7, 25 mL of Solution 1, 20 % HCl, and 10 mL of Solution 2, lanthanum additive.
7.8 Standard Stock Solutions - Prepare standard stock solutions from high purity (99.9 % or better) metals, oxides, or salts. Stock solutions of 1000 ppm (mg/L) for each metal are needed for preparation of dilute standards in the range from <1.0 to 50 ppm (mg/L). Working standards containing aluminum, calcium, iron, nickel, silicon, sodium, and vanadium in concentration ranges below 10 ppm (mg/kg) are to be prepared daily to ensure stability.
7.9 Quality Control (QC) Samples , preferably are portions of one or more petroleum coke samples that are stable and representative of the samples of interest. These QC samples can be used to check the validity of the testing process as described in Section 13.
8. Sample Preparation
8.1 Crush and divide the initial sample to obtain a laboratory analysis sample. Crush to pass a No. 60 (0.250 mm) sieve by the procedure in Practice D346, Section 9.
8.2 Crush approximately a 30 g of representative portion of the minus No. 60 sieve analysis sample to pass a No. 200 (0.075 mm) sieve. Use a tungsten carbide mill to minimize metal contamination. Dry this sample to constant weight at 110 to 115°C (approximately 8 h) and store in a desiccator until cool. (Warning - Preparation of the minus 200 mesh analysis samples, from the minus 60 mesh analysis samples, neither remove metals through loss nor increase metals through contamination. Full dissolution of the ash is required.)
9. Preparation of Apparatus
9.1 Consult the manufacturer's instructions for the operation of the atomic absorption spectrophotometer. The present method assumes that good operating procedures are followed. Design differences between spectrophotometers make it impractical to specify the required manipulations in detail here. (Warning - Proper operating procedures are required for safety as well as for reliability of results. An explosion can result from the flame blow-back unless the correct burner head and operating sequence are used.)
