Comparison of one-step acidic extraction versus two-step basic and acidic extraction procedures for semivolatile analysis of wastewater

The feasibility of using the U.S. Environmental Protection Agency's (U.S. E PA's) contract laboratory protocol method for analyzing semivolatile compou nds in industrial wastewater pretreatment program samples was investigated because of time and labor savings involved. Various laboratory evaluation s tudies were conducted to determine whether this alternate one-step acidic e xtraction method would give comparable results to U.S. EPA Method 625. Thes e studies consisted of comparisons of method detection limits, spike recove ries in reagent water and actual field samples, and the precision between M ethod 625 and the alternate one-step acidic extraction. More than 60 base-neutral and acid extractables (55 target compounds and 6 surrogates) were used in the comparative study of method detection limits a nd spike recoveries of the two procedures. Using reagent water, one-step ac idic extraction gave consistently better recoveries than two-step basic and acidic extraction. Similar results were obtained with representative field sample matrices. Based on results of this investigation, the Metropolitan Water Reclamation District of Greater Chicago, Illinois, submitted an application to U.S. EPA to have one-step acidic extraction accepted as a site-specific alternate t est procedure for analyzing industrial wastewater samples. After thorough r eview, U.S. EPA Region V approved the use of this alternate one-step acidic extraction method. It is recommended that other municipal analytical labor atories apply to U.S. EPA for similar approval.