A1: Liquid Sample vs A4: Modified Soak

When completing LifeCheck ATP Testing it is important to understand when best to muscle up to get that 1 mL sample out and when to tap out and use the modified soak procedure (LifeCheck ATP Handbook A4: Modified Soak). Why?

The regular procedure outlined in our LifeCheck ATP Handbook for liquid samples (A1) captures ATP from within living cells. ATP that exists in your sample but outside of living cells passes through the filter and isn’t counted within your results (also known as extracellular ATP). The modified soak procedure omits the filtering step. As a result this ATP that exists outside of living cells is not removed, and is counted within your results. This is important to understand when it comes to comparing data using different methods. The other key step to the A1 procedure is the rinse step that washes away interfering components of the fluids like hydrocarbon residuals. The soak method doesn’t incorporate this step so interfering agents may remain.

Whenever possible, ATP testing using the filter method (A1) is always preferable to the modified soak. It is only when you absolutely cannot filter through 1 mL of the sample that the modified soak procedure can be used. If the modified method is used, ideally you should then use it in all steps of the process so that you can qualitatively compare the data. The rule of thumb is consistency is key when it comes to trending results. KPI’s established using the A1 method should not be applied to samples analyzed using the modified soak method.

Contact the OSP Technical Service team for more information.

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