The U.S. EPA monitors a variety of compounds that pose public health risks when they are present in our air, soil or water and they have spent decades publishing methods to help us extract and quantify those compounds. The 8000 Series EPA Methods describe the extraction and analysis of contaminants in groundwater and Method 8270 specifically covers semi-volatile compounds. The EPA has been monitoring semi-volatile compounds in solid waste, soils and groundwater for almost 40 years, and Method 8270 has undergone several revisions during that time. For example, revision C allowed air samples to be included in the list of sample matrices that can be analyzed under this method.
The latest revision was released in June 2018 and brings the current method to 8270e. Unlike some of the previous method updates, the most recent revision change included quite a few changes – 65 changes to be exact! The extensive list of changes are outlined in Appendix A toward the end of the EPA Method 8270e. For the purposes of this blog post, I’ve highlighted 6 updates, along with some detail behind each, and an explanation as to how they benefit your laboratory.
- Expanded Target Analyte List
The EPA added several new compounds to the list of accepted analytes. These include:
Since changes were being made to the compound list, the EPA used the opportunity to review the existing list to make sure it harmonized with the way compounds are listed in the NIST standard reference database. When the compound names don’t align, it can be very hard to identify them in the database, so the following compound names were updated for easier identification:
- 2,4-toluene diisocyanate
Adding new compounds and updating existing ones expands the usefulness of the method. Samples that used to be processed using 2 different methods can now be processed once, per Method 8270e. Processing data for these samples is also faster when the compound names are aligned with those in the identification database.
- Updated Sample Preparation Methods
There are dozens of methods that outline procedures for quantifying semi-volatile organic compounds in wastewaters. Method 3560 is one of those methods and it was referenced in Method 8270, version D. In the latest revision, this method was replaced with 2 alternative methods for extraction – Methods 3511 and 3546. Method 3560 involves supercritical fluid extraction in recovering petroleum hydrocarbons within fly ash, soil, solid phase extraction media, sediments, and any other solid material that conventional solvents will extract. Method 3511 now allows semi-volatile and volatile compounds to be extracted from a water sample within a water matrix via microextraction. Method 3546 is used for extracting compounds from waste solids, soil, sludge, sediment, and clay that are insoluble or slightly soluble in water via microwave extraction. The addition of these acceptable methods of extractions expands the scope over which EPA Method 8270 can be used.
- Analytical Flexibility to Allow GC/MS/MS for Quantitation
The latest version of the method now allows the use of GC/MS/MS for analyzing samples extracted via EPA Method 8270. The previous version allowed only GC/MS, which is a less sensitive technique. The use of GC/MS/MS expands the applicability of the method so that a wider range of sample matrices can be analyzed. In addition to that, GC/MS/MS has other benefits (compared to GC/MS), including:
- Higher tolerance of complicated matrices
- Improved identification of volatile analytes
- High sensitivity and better detection limits – great for low level quantitation
All of these benefits are ideal for processing samples per Method 8270!
- Added GC Inlet Flexibility
Method 8270 indicates that GC/MS or GC/MS/MS is to be used for sample analysis and revision E allows multiple GC inlet types to be used. In section 6.1.1 of the method, it is outlined that the laboratory can use split as an injection technique which reduces the amount of sample that is injected onto your column, improving peak sharpness and shape. If a laboratory wants to continue to use splitless injections, that is acceptable as well. In EPA Method 8270d, split injections were only allowed if the mass spectrometer had sufficient sensitivity.
Another modification that is included in revision E is to allow laboratories to use programmable temperature vaporization split or splitless injection port methods which allow for larger injection volumes.
Lastly, the latest revision of Method 8270 allows for on-column injections which allows you to inject your sample into the GC in liquid form via a thin needle. Once injected the pre-programmed GC method will trigger an increase in the vapor pressure which starts your chromatographic analysis. This injection approach eliminates the need to have evaporation within the heated space, which improves recoveries for compounds which have relatively high-boiling points. On-column injections can also be used for trace level analysis, as long as the sample is relatively clean.
- Added GC Column Flexibility
Method 8270 no longer contains references to specific column vendors within the method. In revision D, section 4.1.2, Method 8270 outlines the use of a “J&W Scientific DB-5 or equivalent column.” Many laboratories feel compelled to use equipment that’s called out within a method – a J&W Scientific DB-5 column in this case. Removing the reference to a specific column allows laboratories to evaluate a range of columns which vary in size and type and select one that is optimal for their instrument and their target analytes. As long as the selected column meets the general requirements that are outlined in section 6.1.2 of the method (30 m x 0.25 mm ID (or 0.32 mm ID) 0.25, 0.5, or 1 μm film thickness silicone-coated fused-silica capillary column (5% phenyl-methylpolysiloxane, 5% phenyl-arylene dimethylpolysiloxane, or equivalent)), a laboratory can make a selection based on the data for their application and supports a performance-based approach to analysis.
- Added Guidance for Storing and Discarding Standards
The EPA added some more helpful tools in determining when standards should be discarded. This guidance allows laboratories to set appropriate expiration dates on their standards and reduces the chance that an analyst will use an expired standard and spend an entire day producing results that fail the QC requirements of the method.
This post only contains 6 of the 65 changes made in this revision! Check out the EPA Method 8270e to read about all the changes that were made!