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)
6. Apparatus
6.1 Ultraviolet Lamp, long wavelength, 3660 Å, placed in a standard 4-W fluorescent fixture.
NOTE 3 - A 3-min electric timer is connected to the fixture in the prototype kit.
6.2 Measuring Block, aluminum, drilled to hold an 18 by 150-mm test tube, with a mark at a level equal to 5.0 mL of liquid in the test tube.
6.3 Colorimeter, Portable, capable of operating at 490 mm. Any equivalent instrument capable of measurement near 514 nm (the optimum Pb-PAR complex wavelength) may be used.
6.4 Test Tubes, borosilicate, 18 by 150 mm.
6.5 Pipets, glass, dropping, capable of delivering 2.0 mL with a 2-mL bulb. (Warning - Gasoline or any of the reagents must not come in contact with rubber. If this happens, discard the bulb and pipet and start again.)
6.6 Funnel, plastic, 2 in. in inside diameter.
6.7 Filter Paper, ashless, hardened, smooth, very fast, 11.0 cm in diameter.
NOTE 4 - Certain filter papers that would allow the organic layer (gasoline/chloroform) to filter through are not acceptable.
6.8 Graduated Cylinder, plastic, 10-mL.
6.9 Glass Vials, with caps, disposable, 1-oz capacity.
7. Reagents
7.1 Purity of Reagents - Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all reagents conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society, where such specifications are available. Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purity to permit its use without lessening the accuracy of the determination.
7.2 Purity of Water - Unless otherwise indicated, reference to water shall be understood to mean distilled water or water of equal purity.
7.3 Ammonium Hydroxide (sp gr 0.90) - Concentrated ammonium hydroxide (NH4OH).
7.4 Ammonium Nitrate Solution (Reagent B) - Dissolve 15.0 +/- 0.1 g of ammonium nitrate (NH4NO3) in 750 mL of water in a 1-L volumetric flask. Dilute to the mark with water.
7.5 Chloroform (CHCl3) - (Warning - May be fatal if swallowed. Harmful if inhaled. May produce toxic vapors if burned. Chronic or repeated exposure can cause liver or kidney damage. Harmful if inhaled or swallowed. Carcinogen (animal positive). Skin and eye irritant. May produce toxic vapors if burned. See A1.1.)
7.6 Disodium Salt of 4-(2-pyridylazo)-Resorcinol Dihydrate (PAR•2H2O) (Reagent C) - Dissolve 25.0 +/- 0.1 mg of PAR in 750 mL of water in a 1-L volumetric flask. Add 10.0 +/- 0.1 mL of concentrated NH4OH. Dilute to the mark with water. Store this in brown bottles out of direct sunlight or in the dark. (Warning - Low results are obtained if the monosodium or unsalted PAR is used in this test. Field experience has shown that the PAR reagent can deteriorate within two to six months. The PAR reagent should be tested by adding the reagent to a test tube and determining the percent transmittance. If the percent transmittance is less than 80 %, the reagent should be discarded.)
7.7 Gasoline, Lead-Free - Gasoline containing less than 0.05 g Pb/gal (13.0 mg Pb/L). (Warning - Extremely flammable. Harmful if inhaled. Vapors may cause flash fire. See A1.2.)
7.8 Iodine.
7.9 Iodine/TEAC/CHCl3 Solution (Reagent A) - Dissolve 1.000 g +/- 1 mg of iodine in 75 mL of chloroform (CHCl3) in a 100-mL volumetric flask. Add 1.000 g +/- 1 mg of tetraethy-lammonium chloride (TEAC) and mix until dissolved. Dilute to the mark with CHCl3.
NOTE 5 - Solutions described in 7.4, 7.6, and 7.9 have been found to be stable for at least 2 months.
7.10 Lead Standards - This method was developed using lead standards prepared by addition of known amounts of various lead alkyls to blended unleaded gasoline to cover the range of this method.
7.11 Tetraethylammonium Chloride Monohydrate (TEAC).
7.12 Quality Control (QC) Sample(s) - preferably are portions of one or more gasoline materials or product standards of known lead content that were not used in the generation of the instrument calibration curve. These (QC) samples are to be used to check the validity of the testing process as described in Section 10. An ample supply of QC sample material shall be available for the intended period of use, and must be homogeneous and stable under the anticipated storage conditions.
