1.1This test method covers a protocol for capturing, extracting and quantifying the cellular adenosine triphosphate (cATP) content associated with microorganisms normally found in laboratory cultures, waters, wastewaters, and in plankton and periphyton samples from waters.

1.2The ATP is measured using a bioluminescence enzyme assay, whereby light is generated in amounts proportional to the concentration of 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 and computation to pg ATP/mL.

1.3This method does not remove all known chemical interferences, known to either luminesce in the 530 ± 20 nm range, or to quench light emitted in that range. It should not be used to determine ATP concentrations in samples with dissolved organic compounds, heavy metals or >10 000 ppm total dissolved solids. Alternative methods have been developed for determining ATP concentrations in fluids samples likely to contain such interferences (Test Methods D7687 and E2694).

1.4Knowledge of the concentration of ATP can be related to viable biomass or metabolic activity of microorganisms (Appendix X1).

1.5This test method offers a high degree of sensitivity, rapidity, accuracy, and reproducibility.

1.6The analyst should be aware that the precision statement pertains only to determinations in reagent water and not necessarily in the matrix being tested.

1.7This test method is equally suitable for use in the laboratory or field.

1.8The method normally detects cATP concentrations in the range of 0.1 pg cATP/mL (–1.0Log₁₀ [pg cATP/mL]) to 4 000 000 pg cATP/mL (6.6 Log₁₀ [pg cATP/mL]) in 50 mL water samples.

1.9Providing interferences can be overcome, bioluminescence is a reliable and proven method for qualifying and quantifying ATP, although the method does not differentiate between ATP from different sources, for example, from different types of microorganisms, such as bacteria, fungi, algae and protozoa.

1.10The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.11This 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.