Environmental Standards Edges Closer to a Regulatory-approved Method for Dissolved Light Gases in Groundwater
Environmental Standards has moved closer to gaining regulatory approval of a light-gas analytical method highlighted in prior newsletters. In October 2019 Environmental Standards initiated the final phase of our study to advance the light-gas analytical method on behalf of the Marcellus Shale Coalition (MSC). The MSC commissioned Environmental Standards to perform the final interlaboratory study (ILS) with participation from 12 laboratories, which were provided with replicate synthetically prepared dissolved methane standards at four concentrations, along with two Certified Reference Material (CRM) standards containing light gases. Prior phases entailed challenging a total of 23 participating laboratories with blind samples for dissolved methane analysis as well as providing a known concentration for self-diagnosis of precision and accuracy problems. The information collected from the prior phases resulted in the preparation of a light-gas method prepared by Environmental Standards. A draft version of the method was issued to 12 laboratories, 10 of which had participated in at least one of the prior phases. The laboratories reviewed the draft method and provided logistical and technical comments in preparation for a collaborative method-validation study. The result was a final method used as the basis of this Phase 5 ILS.
The objective of a collaborative ILS was to evaluate a sampling of laboratories that have expertise in a procedure in order to provide sufficient evidence that precision and accuracy are confirmed, which would tentatively result in the adoption of the method by regulatory agencies. The precision and accuracy goals from the ILS were identified at < 20% relative standard deviation and 70-130% recovery, respectively. In preparation for the ILS, the full complement of laboratories that participated in prior phases were invited to participate in this Phase 5 ILS. Ten laboratories that demonstrated expertise in prior phases agreed to participate, and two additional laboratories were recruited. Each laboratory was instructed to select one of the three calibration options described in the method, and to perform the light-gas analysis exactly as written in the method.
The 12 laboratories were each provided single-blind, replicate prepared dissolved methane standards at four concentrations, along with two CRM standards, which are now commercially available.
The Phase 5 ILS study was a success and has statistically demonstrated the validity of the proposed method. Environmental Standards is in contact with the ILS Group of ASTM and the United States Environmental Protection Agency Office of Resource Conservation and Recovery for publishing the Method in either SW-846 and/or as an ASTM standard.
