Blank Depletion chem.

[Talvisota]

Доброй ночи всем!
Друзья, подскажите, пожалуйста, грамотный перевод на русский язык термина "blank depletion".

Контекст:

Blank Depletion/Drift Problems Solved

"Before the new criteria came into effect, we would measure a blank sample with every batch of CBOD samples. Five days later,when we took our samples off, we measured our blank again.
The maximum recommended depletion allowed was .20 mg/L"

Буду очень благодарен всем за помощь!

[Karabas]

blank sample - холостая/контрольная проба;
depletion - истощение

Комбинируйте, исходя из контекста.