Frequent Questions

In the original method, prior to Rev. 1.0, I believe I read that two adjustment to the method can be made: the column and the detector. Is this true? Our laboratory would like to use LC-MS for the analysis of method 555 analytes. Can we do it?

Method 555 is an ancient method and a likely candidate for removal in a future method update rule. The QC criteria defined in the method are inappropriate for drinking water analysis because they have been surpassed by more reliable, robust methods (e.g., EPA Method 515.4). But until we can get that method off the books through rulemaking, labs can still technically use it. The method does contain a provision for the use of ‘alternate detectors’. HOWEVER, at the time that Method 555 was published, LC-MS was only being performed in research laboratories. Method 555 employs a photodiode array for UV detection. The intent behind the option to use alternate detectors was to allow the use of simpler, cheaper single- and dual-channel UV detectors. The performance data shown in the method is based on UV detection, not mass spec. Changes to the detection technique would need to be discussed with the Drinking Water Alternate Test Procedure (ATP) Coordinator who would determine the appropriate course of action for properly validating the change as an alternate test method. For drinking water, this would entail a multi-laboratory validation and the lab seeking the ATP would be responsible for coordinating it. There are no single-laboratory or region-specific methods permitted.

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