How do method updates work, e.g., how significant is the difference between SW‐846 Method 8270C versus 8270D?
ORCR employs a specific naming convention (i.e., method number and letter suffix) when publishing methods. The naming convention is intended to minimize confusion within the user community regarding a method’s developmental status. The method number designates the underlying technology (e.g., 8000 series methods designate determinative procedures for organic compounds). A revision to a method where the underlying technology does not change is indicated by continued use of the same method number and letter, but with a new issuance date.
If the revision retains the underlying technology, but does not affect the precision and/or accuracy of the data, the revision is considered to be minor or non-significant and the method number and letter is not changed or sequenced. If, on the other hand, the revision retains the underlying technology, but changes the precision and/or accuracy of the data, the change is considered to be significant and is indicated by a subsequent letter suffix (e.g., changes from 8270C to 8270D) and a new issuance date. For example, if the quality control recommendations are changed in a manner that improves the bias or precision of the method, but does not change the underlying technology (e.g., a tightening of the calibration acceptance criteria), the method number stays the same, but the letter suffix is sequenced to the next letter. The differences between the earlier and later versions of a method are detailed in the method summary section of the revised version regardless of the type of change.
Examples of changes that may be considered minor or non-significant include, but are not limited to: Language added to a method to provide increased clarity or guidance; expansion of lists of acceptable instrumentation, applicability of the method to a matrix not previously referenced, adding new compounds to the list of applicable compounds, or changes to instrument specifications which do not result in an existing acceptable instrument being rendered unacceptable; or formatting and editorial changes that are designed to improve readability or correct spelling or grammatical errors.
ORCR has defined a ‘‘significant change’’ as a change that results in improved analytical results (e.g., changes that result in reducing analytical bias or improving data precision). Examples of significant changes may include, but are not limited to: a change in the operating parameter which reduces analytical flexibility; a change in instrumentation specification which minimizes interference and/or optimizes instrument performance (if the use of such interference reduction technique or performance enhancement is required); a change in calibration guidance which results in more restrictive recommendations; a change that institutes tighter QC recommendations; or a change in the reagents that are required by the method.
ORCR strongly advises that laboratories use the latest version of a SW-846 method whenever possible, especially in new monitoring situations, since updated versions of methods generally are either less subject to misinterpretation, yield improved precision and/or bias or provide for the use of newer and, often, more cost effective technologies, and may be greener (e.g., generate less waste). In situations where it may not be appropriate to use the latest method in SW-846, earlier versions may be used. These may include, but are not limited to, situations where an earlier version of a method is required for existing permits, consent decrees, waste analysis plans or sampling analysis plans. The Agency does not impose restrictions on the use of earlier versions of non-required methods contained in SW-846 or preclude the use of previous guidance. Nonetheless, the adoption of the latest method version is recommended and should be accomplished as soon as possible, as appropriate. When methods are employed, it is the responsibility of the user to ensure that the method yields data of a quality appropriate for that particular application.