ASTM D5708 Method for Nickel, Vanadium, and Iron in Crude Oils and Residual Fuels
ASTM D5708 Standard Test Methods for Determination of Nickel, Vanadium, and Iron in Crude Oils and Residual Fuels by Inductively Coupled Plasma (ICP) Atomic Emission Spectrometry
3. Summary of Test Method
3.1 Test Method A - Approximately 10 g of the sample are dissolved in an organic solvent (Warning - Combustible. Vapor is harmful.) to give a specimen solution containing 10 % (m/m) of sample. The solution is nebulized into the plasma, and the intensities of the emitted light at wavelengths characteristic of the analytes are measured sequentially or simultaneously. The intensities are related to concentrations by the appropriate use of calibration data.
3.2 Test Method B - One to 20 g of sample are weighed into a beaker and decomposed with concentrated sulfuric acid (Warning - Poison. Causes severe burns. Harmful or fatal if swallowed or inhaled.) by heating to dryness. Great care must be used in this decomposition because the acid fumes are corrosive and the mixture is potentially flammable. The residual carbon is burned off by heating at 525°C in a muffle furnace. The inorganic residue is digested with nitric acid (Warning - Poison. Causes severe burns. Harmful or fatal if swallowed or inhaled.), evaporated to incipient dryness, dissolved in dilute nitric acid, and made up to volume. The solution is nebulized into the plasma of an atomic emission spectrometer. The intensities of light emitted at characteristic wavelengths of the metals are measured sequentially or simultaneously. These intensities are related to concentrations by the appropriate use of calibration data.
4. Significance and Use
4.1 These test methods cover, in single procedures, the determination of Ni, V, and Fe in crude oils and residual oils. These test methods complement Test Method D1548, which covers only the determination of vanadium.
4.2 When fuels are combusted, vanadium present in the fuel can form corrosive compounds. The value of crude oils can be determined, in part, by the concentrations of nickel, vanadium, and iron. Nickel and vanadium, present at trace levels in petroleum fractions, can deactivate catalysts during processing. These test methods provide a means of determining the concentrations of nickel, vanadium, and iron.