ASTM D3605 Test Method for Trace Metals in Gas Turbine Fuels
ASTM D3605 Standard Test Method for Trace Metals in Gas Turbine Fuels by Atomic Absorption and Flame Emission Spectroscopy
5. Apparatus
5.1 Atomic Absorption Spectrophotometer, capable of measuring radiation over the wavelength range from 280 to 600 nm. The instrument must be capable of measuring low-level signals (approximately 1 % absorption or 0.004 absorbance unit per mg/L vanadium). The instrument should also be equipped as follows.
5.1.1 Burner, with variable nebulizer and auxiliary oxidant supply to reduce nonatomic absorption from unburned hydrocarbons which cause interferences.
5.1.1.1 Burner Head, capable of supporting a nitrous oxide-acetylene flame.
5.1.1.2 Burner Head, single- or multiple-slot, capable of supporting an air-acetylene flame.
5.1.2 Electronic Detection System, capable of reading to the nearest 0.1 % absorption or 0.0004 absorbance.
5.1.2.1 The text describes the measurement of absorption signals that is, either percent absorption or absorbance. For instruments reading in percent absorption, absorption signals of 0.1 % absorption must be measurable. For instruments reading in absorbance, signals of 0.0004 absorbance must be measurable.
5.1.3 Hollow Cathode Lamp Power Supply, regulated to minimize drift.
5.1.4 Monochromator, capable of resolving the 318.34 - 318.40-nm vanadium doublet from the 318.54-nm vanadium line.
5.1.5 Hollow Cathode Lamps, one each for calcium, sodium, lead, and vanadium.
NOTE 2 - Electrodeless-discharge lamps can be an acceptable alternative, but the precision of this method was determined with hollow cathode lamps.
5.1.6 When the instrument has flame-emission capability, the emission technique can be used for the analyses of sodium, calcium, and vanadium.
5.2 Volumetric Flasks, 25-mL.
5.3 Glass Vials, 40-mL, screw-cap type, polyethylene-lined caps.
5.4 Syringe, 100-µL, Hamilton type or equivalent.
6. Reagents
6.1 Purity of Reagents - Reagent grade chemicals shall be used in tests. Unless otherwise indicated, it is intended that all reagents conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society where such specifications are available. Other grades may be used, provided it is ascertained that the reagent is of sufficiently high purity to permit its use without lessening the accuracy of the determination.
6.2 1,2,3,4-tetrahydronaphthalene, practical grade, analyte-sterile.
NOTE 3 - Analyte-sterile 1,2,3,4-tetrahydronaphthalene can be prepared by extracting a portion of tetralin with an equal amount of hydrochloric acid in a covered screw-cap vial. Heat the vial on a steam bath for 1 h and shake the vial for 1 h. If the acid extracted 1,2,3,4-tetrahydronaphthalene and unextracted 1,2,3,4-tetrahydronaphthalene give indistinguishable absorption signals for each of the analytes under optimal experimental conditions, the unextracted 1,2,3,4-tetrahydronaphthalene can be used throughout this method.
6.3 Organometallic Standards - Oil-soluble salts of sodium, lead, calcium, and vanadium of known concentration.
6.4 Mixed Standard - Prepare a mixed standard containing 250 mg/L each of sodium, lead, calcium, and vanadium by dissolving the appropriate amounts of organometallic standards in 1,2,3,4-tetrahydronaphthalene and making the required dilutions. Prepare fresh daily, as needed.
7. Sampling
7.1 Samples shall be taken in accordance with the instructions in Practice D4057.
