ASTM D1840 Test Method for Naphthalene Hydrocarbons in Aviation Turbine Fuels
ASTM D1840 Standard Test Method for Naphthalene Hydrocarbons in Aviation Turbine Fuels by Ultraviolet Spectrophotometry
1. Scope
1.1 This test method covers the determination, by ultraviolet spectrophotometry, of the total concentration of naphthalene, acenaphthene, and alkylated derivatives of these hydrocarbons in straight-run jet fuels. This test method is designed to analyze fuels containing not more than 5 % of such components and having end points below 315°C (600°F); however, the range of concentrations used in the interlaboratory test programs which established the precision statements for this test method were 0.03 to 4.25 volume % for Procedure A, and 0.08 to 5.6 volume % for Procedure B. This test method determines the maximum amount of naphthalenes that could be present.

1.2 The values stated in SI units are to be regarded as the standard. The values stated in inch-pound units are for information only.

1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For specific precautionary statements, see 8.1 and 8.2.

2. Referenced Documents
2.1 ASTM Standards:
E 131 Terminology Relating to Molecular Spectroscopy
E 169 Practices for General Techniques of Ultraviolet-Visible Quantitative Analysis
E 275 Practice for Describing and Measuring Performance of Ultraviolet, Visible, and Near-Infrared Spectrophotometers

3. Terminology
3.1 Definitions:
3.1.1 Definitions of terms and symbols relating to absorption spectroscopy in this test method shall conform to Terminology E 131. Terms of particular significance are the following:
3.1.1.1 radiant energy, n - energy transmitted as electromagnetic waves.

3.1.1.2 radiant power, P, n - the rate at which energy is transported in a beam of radiant energy.

3.2 Definitions of Terms Specific to This Standard:
3.2.1 absorbance, A, n - the molecular property of a substance that determines its ability to take up radiant power, expressed by
A = log10(1/T) = log10T
where:
T = transmittance as defined in 3.2.5.

3.2.1.1 Discussion - It may be necessary to correct the observed transmittance (indicated by the spectrophotometer) by compensating for reflectance losses, solvent absorption losses, or refraction effects.

3.2.2 absorptivity, a, n - the specific property of a substance to absorb radiant power per unit sample concentration and pathlength, expressed by
a = A/bc
where:
A = absorbance defined in 3.2.1,
b = sample cell path length, and
c = quantity of absorbing substance contained in a unit volume of solvent.

3.2.2.1 Discussion - Quantitative ultraviolet analyses are based upon the absorption law, known as Beer's law. The law states that the absorbance of a homogeneous sample containing an absorbing substance is directly proportional to the concentration of the absorbing substance at a single wavelength, expressed by
A = abc
where:
A = absorbance as defined in 3.2.1,
a = absorptivity as defined in 3.2.2,
b = sample cell pathlength, and
c = quantity of absorbing substance contained in a unit volume of solvent.

3.2.3 concentration, c, n - the quantity of naphthalene hydrocarbons in grams per litre of isooctane.

3.2.4 sample cell pathlength, b, n - the distance, in centimetres, measured in the direction of propagation of the beam of radiant energy, between the surfaces of the specimen on which the radiant energy is incident and the surface of the specimen from which it is emergent.
3.2.4.1 Discussion - This distance does not include the thickness of the cell in which the specimen is contained.

3.2.5 transmittance, T, n - the molecular property of a substance that determines its transportability of radiant power expressed by
T = P/Po
where:
P = radiant power passing through the sample, and
Po = radiant power incident upon the sample.