ASTM D3348 Rapid Field Test for Trace Lead in Unleaded Gasoline
ASTM D3348 Standard Test Method for Rapid Field Test for Trace Lead in Unleaded Gasoline (Colorimetric Method)
3. Summary of Test Method
3.1 The gasoline is treated with iodine and tetraethyl ammonium chloride in chloroform and subjected to ultraviolet light. The lead alkyls form water-soluble lead alkyl iodides, which are removed from the gasoline by shaking it with an aqueous ammonium nitrate solution. The aqueous extract is filtered into a solution of 4-(2-pyridylazo)-resorcinol disodium salt (PAR) and ammonium hydroxide. The lead is determined by measuring its PAR complex colorimetrically at 490 nm using a previously prepared calibration curve.
4. Significance and Use
4.1 This test is used to determine trace quantities of lead in unleaded gasoline. Unwarranted amounts of lead may cause deposits in automotive pollution control equipment and poisoning of catalytic mufflers.
5. Interferences
5.1 PAR also reacts with many other metals forming highly colored complexes. However, none of these are normally found present in a soluble form in gasoline. The following metals were found to form colors with PAR and if present may interfere to give high results: Fe II, Fe III, Co II, Ni II, Cu II, Zn II, Cd II, Mn II, Sn II, V IV, Pb II, U VI, Ti IV, and the rare earths.
