ASTM D5762 Standard Test Method for Nitrogen in Petroleum and Petroleum Products by Boat-Inlet Chemiluminescence
11. Procedure
11.1 Obtain a test specimen using the procedure described in Section 7. Prepare a test specimen solution by dilution of the test specimen in xylene. Use a dilution factor of at least 1:5 (see Note 2). The nitrogen concentration in the test specimen solution shall be less than the concentration of the highest standard used in calibration and greater than 3 ng nitrogen/µL. The dilution can be performed either on a weight or volume basis.
11.1.1 For gravimetric dilution, record the mass of the test specimen and the total mass of the test specimen and solvent.
11.1.2 For volumetric dilution, record the mass of the test specimen and the total volume of the test specimen and solvent.
11.2 Measure the chemiluminescence response for the test specimen solution using the procedure described in 9.2 and 9.3.
11.3 If the chemiluminescence response from the test specimen solution is greater than the response from the highest calibration standard used, repeat the test specimen dilution described in 11.1 using a higher dilution factor. Repeat the analysis procedure described in 9.2 through 9.3 on this new test specimen solution.
11.4 Inspect the boat and combustion tube to verify complete combustion of the test specimen solution. Increase the residence time for the boat in the furnace if coke or soot is observed on the boat. Decrease the boat drive introduction rate if coke or soot is observed on the exit end of the combustion tube. Clean any coked or sooted parts. After any cleaning or adjustment, repeat instrument calibration prior to reanalysis of the test specimen.
11.5 Measure each test specimen solution three times and calculate the average chemiluminescence response.
12. Calculation
12.1 For analyzers calibrated using a standard curve, calculate the nitrogen content of the test specimen in micrograms per gram (µg/g) as follows:
or,
where:
D = density of test specimen solution, g/mL,
I = average of integrated detector response for test specimen solution, counts (or found ng nitrogen),
Kg = gravimetric dilution factor, mass of test specimen/mass of test specimen and solvent, g/g,
Kv = volumetric dilution factor, mass of test specimen/volume of test specimen and solvent, g/mL,
M = mass of test specimen solution injected, either measured directly or calculated from measured volume injected and density, V x D, mg,
S = slope of standard curve, counts/ng nitrogen (or found ng nitrogen/ng nitrogen),
V = volume of test specimen solution injected, either measured directly or calculated from measured mass injected and density, M/D, µL, and
Y = y-intercept of standard curve, counts (or found ng nitrogen).
12.2 For analyzers calibrated using an internal calibration routine, calculate the nitrogen content of the test specimen in micrograms/gram (µg/g) as follows:
or,
where:
D = density of test specimen solution, g/mL,
I = average of visual display readings of test specimen solution, ng nitrogen,
Kg = gravimetric dilution factor, mass of test specimen/mass of test specimen and solvent, g/g,
Kv = volumetric dilution factor, mass of test specimen/volume of test specimen and solvent, g/mL,
M = mass of test specimen solution injected, either measured directly or calculated from measured volume injected and density, V x D, mg, and
V = volume of test specimen solution injected, either measured directly or calculated from measured mass injected and density, M/D, µL.