Absorption of Gases from the Atmosphere

Gases from the atmosphere can be absorbed by the sample during handling, for example, when liquids are being poured into containers. Gases such as O₂,CO₂, and volatile organics may dissolve in the samples.

  Oxygen may oxidize species, such as sulfite or sulfide to sulfate. Absorption of CO₂ may change conductance or pH. This is why pH measurements are always made at the site. CO₂ can also bring about precipitation of some metals. Dissolution of organics may lead to false positives for compounds that were actually absent. Blanks are used to check for contamination during sampling, transport, and laboratory handling.