ASTM D5863 Nickel, Vanadium, Iron, and Sodium in Crude Oils and Residual Fuels
ASTM D5863 Standard Test Methods for Determination of Nickel, Vanadium, Iron, and Sodium in Crude Oils and Residual Fuels by Flame Atomic Absorption Spectrometry
TEST METHOD A - FLAME ATOMIC ABSORPTION AFTER ACID DECOMPOSITION OF THE SAMPLE
7. Apparatus
7.1 Atomic Absorption Spectrometer, complete instrument with hollow cathode lamps and burners with gas supplies to support air-acetylene and nitrous oxide-acetylene flames (Warning - Hazardous. Potentially toxic and explosive. Refer to the manufacturer's instrument manual for associated safety hazards.).
7.2 Sample Decomposition Apparatus (optional) - This apparatus is described in Fig. 1. It consists of a borosilicate glass 400-mL beaker for the test solution, an air bath (Fig. 2) that rests on a hot plate and a 250 W infrared lamp supported 2.5 cm above the air bath. A variable transformer controls the voltage applied to the lamp.
7.3 Glassware - Borosilicate glass 400-mL beakers, volumetric flasks of various capacities and pipettes of various capacities. When determining concentrations below 1 mg/kg, all glassware must be thoroughly cleaned (or soaked overnight) with 5 % HNO3 and rinsed five times with water.
7.4 Electric Muffle Furnace, capable of maintaining 525 ± 25°C and sufficiently large to accommodate 400-mL beakers. The capability of an oxygen bleed is advantageous and optional.
7.5 Steam Bath.
7.6 Temperature Controlled Hot Plate, (optional).
7.7 Drying Oven, (optional), explosion-proof, if used to heat crude oils to obtain fluidity.
8. Reagents
8.1 Aqueous Standard Solutions - Individual aqueous standards with 1000 mg/kg concentrations of vanadium, nickel, and iron, purchased or prepared in acid matrix to ensure stability.
8.2 Nitric Acid - Concentrated nitric acid, HNO3 (Warning - Poison, oxidizer. Causes severe burns. Harmful or fatal if swallowed or inhaled.).
8.3 Nitric Acid 50 % (V/V) - Carefully add, with stirring, one volume of concentrated nitric acid to one volume of water.
8.4 Dilute Nitric Acid, 5 % (V/V) - Carefully add, with stirring, one volume of concentrated nitric acid to 19 volumes of water.
8.5 Sulfuric Acid - Concentrated sulfuric acid, H2SO4 (Warning - Poison, oxidizer. Causes severe burns. Harmful or fatal if swallowed or inhaled.).
8.6 Aluminum Nitrate, Al(NO3)3 9HOH.
8.7 Potassium Nitrate, KNO3.
9. Preparation of Standards
9.1 Multi-Element Standard - Using the aqueous standard solutions, prepare a multi-element standard containing 100 mg/kg each of vanadium, nickel, and iron. Standards should be prepared to ensure accuracy and stability and should be stored in clean containers to safeguard against physical degradation.
9.2 Working Standards - Prepare at least two working standards to cover the concentration ranges specified in Table 1. For vanadium, add the specified interference suppressant. Each working standard must contain 5 % (V/V) nitric acid. Standards should be prepared to ensure accuracy and stability and should be stored in clean containers to safeguard against physical degradation.
9.3 Standard Blank, the standard blank contains 5 % (V/V) nitric acid and any interference suppressant specified in Table 1.
9.4 Check Standard - Prepare a calibration check standard in the same way as the working standards and at analyte concentrations that are typical of the specimens being analyzed.
10. Preparation of Test Solutions
10.1 Into a beaker, weigh an amount of sample estimated to contain between 0.0025 and 0.12 mg of each metal to be determined. A typical mass is 10 g. Add 0.5 mL of H2SO4 for each gram of sample.
NOTE 1 - If it is desired to extend the lower concentration limits of the test method, it is recommended that the decomposition be done in 10-g increments up to a maximum of 100 g. It is not necessary to destroy all the organic matter each time before adding additional amounts of the sample and acid. When it is desired to determine higher concentrations, reduce the sample size accordingly.
10.2 At the same time prepare reagent blanks using the same amount of sulfuric acid as used for sample decomposition. Reagent blanks should be carried through the same procedure as the samples. Warning - Reagent blanks are critical when determining concentrations below 1 mg/kg. To simplify the analysis, use the same volume of acid and the same dilutions as used for the samples. For example, if 20 g of sample is being decomposed, use 10 mL of sulfuric acid for the reagent blank.
10.3 The use of the air bath apparatus (Fig. 2) is optional. Place the beaker in the air bath, which is located in the hood. The hot plate is off at this time. Heat gently from the top with the infrared lamp (Fig. 1) while stirring the test solution with a glass rod. As decomposition proceeds (indicated by a frothing and foaming), control the heat of the infrared lamp to maintain steady evolution of fumes. Give constant attention to each sample mixture until all risk of spattering and foaming is past. Then, gradually increase the temperature of both the hot plate and lamp until the sample is reduced to a carbonaceous ash.
10.4 If the air bath apparatus is not used, heat the sample and acid on a temperature controlled hot plate. As described in 10.3, monitor the decomposition reaction and adjust the temperature of the hot plate accordingly. Warning - Hot fuming concentrated sulfuric acid is very corrosive and a strong oxidizing acid. The analyst should work in a well-ventilated hood and wear rubber gloves and a suitable face shield to protect against spattering acid.
10.5 Place the sample in the muffle furnace maintained at 525 ± 25°C. Optionally, introduce a gentle stream of oxygen into the furnace to expedite oxidation. Continue to heat until the carbon is completely removed.
10.6 Dissolve the inorganic residue by washing down the wall of the beaker with about 10 mL of the 1 + 1 HNO3. Digest on a steam bath for 15 to 30 min. Transfer to a hot plate and gently evaporate to incipient dryness.
10.7 Wash down the wall of the beaker with about 10 mL of dilute nitric acid (5 % V/V). Digest on the steam bath until all salts are dissolved. Allow to cool. Transfer quantitatively to a volumetric flask of suitable volume and make up to volume with dilute nitric acid. This is the test solution.
10.8 Pipette aliquots of the test solution into two separate volumetric flasks. Retain one flask for the determination of nickel and iron. To the other flask add aluminum interference suppressant for vanadium determination (refer to Table 1) and dilute up to mark with dilute nitric acid (5 % V/V). Similarly, prepare a reagent blank solution for vanadium analysis.
11. Preparation of Apparatus
11.1 Consult the manufacturer's instructions for the operation of the atomic absorption spectrometer. This test method assumes that good operating procedures are followed. Design differences between spectrometers make it impractical to exactly specify required instrument settings.
11.2 Set up the instrument to determine each analyte sequentially.
12. Calibration and Analysis
12.1 For each analyte in turn, perform the following operation.
12.2 Nebulize the appropriate blank standard and zero the instrument.
12.3 Nebulize the working standards, determine the absorbance and construct a calibration curve of absorbance versus analyte concentration utilizing the instrument's concentration mode if available, otherwise plot these values.
12.4 Use the check standard to determine if the calibration for each analyte is accurate. If the results obtained on the check standard are not within ±5 % of the expected concentration for each analyte, take corrective action and repeat the calibration.
12.5 Nebulize the test solutions and measure and record the absorbance. If appropriate, blank correct this absorbance by subtracting the reagent blank absorbance.
12.6 After measuring absorbances for a test solution, check the blank standard. If this does not read zero, check the system and then repeat steps 12.2-12.5.
12.7 Test solutions that give absorbances greater than that obtained with the most concentrated working standard must be diluted. The dilution must contain interference suppressant at the specified concentrations.
13. Quality Assurance/Quality Control (QA/QC)
13.1 Confirm the performance of the instrument and the test procedure by analyzing a control QC sample.
13.1.1 When QA/QC protocols are already established in the testing facility, these may be used to confirm the reliability of the test result.
13.1.2 When there is no QA/QC protocol established in the testing facility, Appendix X1 can be used as the QA/QC protocol.
13.2 Users of this test method are advised that in contractual agreements, one or more of the contracting parties can and may make Appendix X1 a mandatory practice.
