ARCHIVED REPORTS_XR0002239 - Laserfiche WebLink

Home Browse Search

f � J i achieving a total chromium reporting limit of 1 gg/L or better. The advantages of a total chromium screening approach are that (1)total chromium determinations are less costly, and (2)total chromium determinations are not subject to the short holding time constraints of the Cr(VI) method. Of the atomic spectrometry techniques generally used for total chromium determinations, i.e., Flame-AAS, GFAAS, ICP-AES, and ICP-MS, only GFAAS and ICP-MS appear to i have the potential to achieve the required RL. This is based on the results of the recent multi-analyte and multi-laboratory study performed by the Reporting Level Work Group N (RLWG). Utilities and their laboratories may use ICP-MS or GFAAS for initial screening for total chroi��ium in lieu'of performing the more time-consuming hexavalent chromium method (EPA 218.6). Iii order to use these screening tools, laboratories must demonstrate that they can analyze water samples at the 1 gg/L level with a precision(RSD) of 20% and an accuracy, as measured by percent recovery, in the range 80-120%. A method detection limit(MDL) must be established following EPA protocol (40CFR136 Appendix B). The reporting limit should be no less than three times the MDL. EPA approved methods for + the analytical technology selected must be followed and all of the QC criteria specified in those methods must be met. Laboratories should maintain their QC criteria for review . should any questions arise regarding the results and their adequacy for screening. When samples yield screening results above 1 µg/L, the respective sources should be re- sampled as soon as practically possible and analyzed by EPA method 218.6 for Cr(VI). NOTE: Labs using ICP-MS should digest the samples to avoid any positive interference by carbon that can occur in the analysis of Total Chromium. UCMR Guidance,January 30,2001 Page 4