ASTM D6258 Determination of Solvent Red 164 Dye Concentration in Diesel Fuels
6. Apparatus
6.1 Spectrophotometer, equipped with automated scanning, background correction and electronic data storage capabilities, and the ability to automatically record absorbance or transmittance of solutions in the spectral region from 400 to 800 nanometers (nm) with a spectral slit width of 1.0 nm or less (Note 2). Wavelength measurements shall be repeatable and known to be accurate to within +/-0.2 nm or less at deuterium peak 656.1 nm. In the absorbance range from 0.01 to 1.0, absorbance measurements shall have a photometric accuracy of +/-0.005 or less and a photometric repeatability of +/-0.002 or less.
NOTE 2 - Instruments having different specifications, for example, minimum slit width 2 to 4 nm, no data storage, diode array spectrophotometers, and so forth, may be used if they provide demonstrably equivalent results. Equivalence can be demonstrated by successful (within reproducibility limits) participation in inter- or intra-laboratory studies using this test method.
6.1.1 For applicable general techniques and methods of testing spectrophotometers to be used in this test method, refer to Practices E 169 and E 275.
6.2 Sample Cells (Cuvettes), one or more fused silica or glass cells having sample path length of 1.0 cm.
6.3 Analytical Balance, 0.1 mg sensitivity, +/-0.05 mg precision.
6.4 Volumetric Pipettes, 1, 2, 3, 4 and 5 mL, Class A, according to Specification E 969.
6.5 Volumetric Flasks, 100 mL and 250 mL, Class A, borosilicate glass, according to Specification E 288.
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 shall 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 Solvent Red 26 (Dye Standard) - Dye, Color Index Solvent Red 26, 1-[[2,5-dimethyl-4- [(2-methylphenyl) azo]phenyl]azo]-2-naphthol, Chemical Abstract Services Registry No. 4477-79-6, dry powder with certified purity, and maximum absorbance at 512 +/- 20 nm.
7.3 Kerosine - 1-K, water-white, conforming to Specification D3699, and having a maximum absorbance against air of 0.08 absorbance units over the wavelength range 450 to 750 nm (1.0 cm cell, 120 nm/min scan rate, slit width 1.0 nm.). (Warning - See Note 3.)
NOTE 3 - Warning: Flammable; harmful if swallowed, inhaled, or brought into contact with skin or eyes.
7.4 Xylene - (Warning - see Note 4).
NOTE 4 - Warning: Extremely flammable; harmful if swallowed, inhaled, or brought into contact with skin or eyes.
