Some source water samples may produce a pellet with non-neutral pH characteristics. Low recoveries could result if acidity or alkalinity of the pellet is not adequately buffered during the IMS process.
Some laboratories have determined the addition of HCl or NaOH to the sample, after buffers have been added, can neutralize the pH to improve recoveries. The pH of the sample can also be checked before buffers are added, and after the 1-hour rotation to ensure the pH is stable.
See the IMS Supplement for the protocol and required quality control.
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