ASTM D7980-15

4.1 This guide is intended to help analysts in the semiconductor industry. Examples of the usefulness of anion monitoring include: (1) determining when ion-exchange resin beds (in water-purification systems) need to be regenerated, and (4.2 To ensure that the anions are indeed at low-ppt levels, it is recommended to check the conductivity of a subsample before proceeding with Section 5 of this guide. This check does not need to be exact; its purpose is simply to let the analyst know if the conductivity is higher than that of the highest-level standard solution being tested. Any high reading signifies that the sample, if analyzed, might contaminate the instrument.

1.1 This guide applies to ultrapure water that is thought to contain low ppt (parts-per-trillion, weight/weight) levels of anionic contaminants (for example, bromide, chloride, fluoride, nitrate, nitrite, phosphate, and sulfate). To minimize carry-over problems between analyses, it is best to limit the concentration of any one contaminant to approximately 200 ppt (although this limit is only an approximation and may vary, depending on the user’s application).

1.2 This guide is intended to help analysts avoid contamination of ultrapure-water samples, since contamination control is the primary challenge when quantifying ppt-level anions in grab samples.

1.3 This guide does not include recommendations for collecting samples from the water source.

1.4 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.