ASTM D 7687 : 2011

1.1 This test method covers a protocol for capturing, extracting and quantifying the cellular adenosine triphosphate (cellular-ATP) content associated with microorganisms found in fuels, fuel/water mixtures and fuel-associated water.

1.2 The ATP is measured using a bioluminescence enzyme assay, whereby light is generated in amounts proportional to the concentration of cellular-ATP in the samples. The light is produced and measured quantitatively as relative light units (RLU) which are converted by comparison with an ATP standard, computation to pg ATP/mL and optional further transformation to Log₁₀[pg ATP/mL].

1.3 This test method is equally suitable for use as a laboratory or portable method.

1.4 This test method is limited to fuels with a nominal viscosity ≤ 75cSt at test temperature.

1.5 This test method detects ATP concentrations in the range of 5.0 pg ATP/mL (0.699 log₁₀[pg ATP/mL]) to 100 000 pg ATP/mL (5.000 log₁₀[pg ATP/mL]) for 20 mL samples of fuel or fuel/water mixtures, and 20 pg ATP/mL (1.301 log₁₀[pg ATP/mL]) to 400 000 pg ATP/mL (5.602 log₁₀[pg ATP/mL]) for 5 mL samples of fuel-associated water.

Note 1—These ranges were calculated with the formula for calculating sample ATP in pg/mL provided in 12.1 based on the minimum recommended RLU for a 1 ng ATP/mL standard when using the reagents specified in Section 7 and the luminometer specified in 6.4 and corrected with a reagent-method blank as determined in Appendix X5.

1.6 Providing interferences can be overcome, bioluminescence is a reliable and proven method for qualifying and quantifying ATP. This test method does not differentiate between ATP from different sources, for example: from different types of microorganisms, such as bacteria and fungi.

1.7 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.8 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.