ASTM D3237 Test Method for Lead In Gasoline By Atomic Absorption Spectroscopy
8. Calibration
8.1 Preparation of Working Standards - Prepare three working standards and a blank using the 0.02, 0.05, and 0.10-g Pb/gal (5.3, 13.2, and 26.4 mg Pb/L) standard lead solutions described in 6.11.
8.1.1 To each of four 50-mL volumetric flasks containing 30 mL of MIBK, add 5.0 mL of low lead standard solution and 5.0 mL of lead-free gasoline. In the case of the blank, add only 5.0 mL of lead-free gasoline.
8.1.2 Add immediately 0.1 mL of iodine/toluene solution by means of the 100-µL Eppendorf pipet. Mix well and allow to react for 1 min.
8.1.3 Add 5 mL of 1 % Aliquat 336 solution. Dilute to volume with MIBK and mix well.
8.2 Preparation of Instrument - Optimize the atomic absorption equipment for lead at 283.3 nm. Using the reagent blank, adjust the gas mixture and the sample aspiration rate to obtain an oxidizing flame which is fuel lean and light blue in color.
8.2.1 Aspirate the 0.1-g Pb/gal (26.4 mg Pb/L) working standard and adjust the burner position to give maximum response. Some instruments require the use of scale expansion to produce an absorbance reading of 0.150 to 0.170 for this standard.
8.2.2 Aspirate the blank to zero the instrument and check the absorbances of the three working standards for linearity.
