Interlaboratory Validation of EPA Method 1103.1 (mTEC) for E. coli in WastewaterEffluent

摘要

The U.S. EPA recently conducted a validation study of Method 1103.1 (mTEC) for E. coli in wastewater effluent torncharacterize method performance across multiple laboratories and disinfected wastewater matrices and to developrnquantitative quality control (QC) acceptance criteria. Ten volunteer participant laboratories, a verificationrnlaboratory, and two research laboratories participated in the study. Each laboratory spiked samples with laboratorypreparedrnand BioBall? E. coli (ATCC 11775) spikes. Method 1103.1 mean laboratory-specific recoveries of E.rnColi from disinfected wastewater samples spiked with laboratory-prepared and BioBall? spikes had an overallrnmean recovery of 75.8% and 57.8%, respectively. Laboratory-specific relative standard deviations (RSDs) fromrndisinfected wastewater samples spiked with laboratory-prepared spikes ranged from 3.7% to 114.6%, with anrnoverall pooled, within-laboratory RSD of 40.8%. Laboratory-specific relative standard deviations (RSDs) fromrndisinfected wastewater samples spiked with BioBalls ranged from 0% to 34.6%, with an overall pooled, withinlaboratoryrnRSD of 15.4%. Method 1103.1 laboratory-specific false positive confirmation rates for unspikedrndisinfected/secondary results combined, ranged from 0% - 50%. Laboratory-specific false negative confirmationrnrates for unspiked disinfected/secondary results combined, ranged from 0% - 66.7%. Results from therninterlaboratory validation studies of Method 1103.1 and Method 1603 were used to compare method performancernbased on recovery, precision, false positive and false negative confirmation rates. Method 1103.1 had significantlyrnhigher false positive and negative confirmation rates in comparison to Method 1603.