ASTM D1318 Test Method for Sodium in Residual Fuel Oil (Flame Photometric Method)
8. Calibration
8.1 Dilute the sodium solution (1000 mg Na/L) so as to obtain solutions containing 2, 4, 6, 8, 10, 12, 15, 18, and 20 mg/L (approximately equivalent to mg/kg). Store all dilute sodium solutions in polyethylene bottles.
8.2 Prepare the flame photometer for use as described in the manufacturer's instruction manual. Carefully adjust the pressure of the gases (Warning - Danger) used for flame combustion in the order described by the manufacturer until optimum control is achieved. Select a standard approximately in the middle of the optimum range of the instrument being used. While atomizing this medium-range standard, adjust the wavelength selector to the greatest response for the sodium doublet at about 589 nm and adjust all controls of the instrument to optimum performance. Finally, adjust the sensitivity control to give a proper scale reading.
8.3 Atomize each of the standard solutions and record the scale response for each. Run repeat checks on the medium-range standard selected in 6.2 after each of these standards to determine whether the flame photometer is functioning properly. Make the indicated adjustments, if required, and rerun the standards.
8.4 Prepare a working curve by plotting the milligrams of sodium per litre against the scale readings.
