Monday morning, representatives from the EPA’s wastewater office reviewed the significant changes for the three major GC wastewater methods: 608.3, 624.1, and 625.1.

The overarching goals were to modernize the methods and bring the language and QC requirements in line with the methods from the drinking water and hazardous waste offices. The methods have been modified to include capillary columns, and the QC requirements have been updated to reflect this. Maximum Calibration RSDs have been dropped to 20% from 35%, and they want to see full list QC spikes.

The most disappointing change is the requirement that the CCV be prepared from a 2nd source. The 500 and 8000 series methods have recently and explicitly moved away from this practice because a 2nd source doesn’t so much verify ICAL stability (precision) as it does accuracy. I’m including the relevant sections for 8270D Rev 5 below:

9.3.2 There must be an Initial Calibration of the GC/MS system as described in Sec. 11.3. In addition, the initial calibration curve should be verified immediately after performing the standard analyses using a second source standard (prepared using standards different from the calibration standards). The suggested acceptance limits for this initial calibration verification analysis are 70-130%. Alternative acceptance limits may be appropriate based on the desired project-specific DQOs. Quantitative sample analyses should not proceed for those analytes that fail the second source standard initial calibration verification. However, analyses may continue for those analytes that fail the criteria with an understanding these results could be used for screening purpose and would be considered estimated values.

11.4.3 The initial calibration (Sec. 11.3) for each compound of interest should be verified once every twelve hours prior to sample analysis, using the introduction technique and conditions used for samples. This is accomplished by analyzing a calibration standard (containing all the compounds for quantitation) at a concentration either near the midpoint concentration for the calibrating range of the GC/MS or near the action level for the project. The results must be compared against the most recent initial calibration curve and should meet the verification acceptance criteria provided in Secs. 11.4.5 through 11.4.7.

You’ll notice that the ICV acceptance criteria when using a 2nd source is 70-130%, while the daily (or 12 hour) CCV acceptance criteria is ± 20%. This is because the 2nd source brings additional uncertainty.

I’m making the revised methods available for anyone to review.

Method 608.3 – Organochlorine Pesticides and PCBs by GC/HSD

Method 624.1 – Purgeables by GC/MS

Method 625.1 – Base/Neutrals and Acids by GC/MS