8000 Series: Chromatographic Separation Methods
- Difference in purge times for SW-846 Method 5030B when using Method 8260 vs. Method 8015
- What is meant by the relative retention time (RRT) window of 0.06 units for SW-846 Methods 8260 and 8270?
- What column should be used as the confirmation column for SW-846 Method 8310?
- Is there an official EPA definition of a volatile compound and a semivolatile compound for SW-846?
- Where can I find wipe sampling methods in SW-846?
- When using SW-846, are we required to use the internal standards listed in Method 8260 or may we select other internal standards?
- Average response factor (RF) from initial calibration or RF from daily calibration for SW-846 Method 8260 (or Method 8270).
- Can commercially available standards of the methyl esters be used for SW-846 Method 8151A?
- In SW-846 Method 8151A, should we spike field samples and the laboratory control samples (LCS) with the herbicide acids, or can we use the methyl esters?
- When EPA releases new updates to SW-846, and a general method is updated, are all methods in that series impacted by the update?
- Use of Sulfuric Acid Cleanup vs. DDT analog standard for SW-846 Method 8082A.
- There is an SW-846 Method 8015D (Revision 2003) and also an EPA 8015C (Revision 2007). Which of these two methods is the latest/updated version?
- Is the DDT and Endrin breakdown check in SW-846 Method 8081 required if not analyzing for those compounds?
- Instrument tuning for SW-846 Method 8260.
- Instrument performance checks for SW-846 Methods 8260 and 8270.
- Holding time for SW-46 Method 8141B for organophosphorus pesticides.
- What is the recommended holding time for SW-846 Method 8082 for PCBs for aqueous, soil, and oil matrices?
- For SW-846 Method 8330B, are the Appendix A drying, sieving, and crushing steps included in the 14 days holding time, or does the 14 days start after the sample is dry?
- What is the EPA doing with regard to the helium shortage and moving to alternative gases for analysis?
- Are SW-846 Methods 3545 and 3546 acceptable substitutions for sonication as the first step of Method 8151A?
- Can alternative esterification agents (i.e., trimethylsilyldiazomethane (TMSD) or boron trifluoride (BF3)) be used for derivatization in SW-846 Method 8151?
- Can the secondary ion be used as the quantitation ion in order to meet the minimum response factors listed in Table 4 of SW-846 Method 8260C?
- Issues with surrogate and target compounds during the soil extraction for herbicides.
- Is it acceptable to use SW-846 3535A for all aqueous samples that are destined to be run by 8270D?
- Low recovery of styrene and several other compounds in soil organics analysis (VOA) samples
- Holding time and preservation requirements for volatile organics analysis (VOA)
- What are the guidelines for the hydrolysis step in SW-846 Method 8151A for environmental samples?
- How to find unique peaks for Aroclors in SW-846 Method 8082A.
- How should the lower limit of quantitation (LLOQ) for total Xylenes be reported for SW-846 test methods?
Difference in purge times for SW-846 Method 5030B when using Method 8260 vs. Method 8015.
Method 5030B specifies a purge time of 11 minutes when using Method 8260 and 15 minutes for Method 8015. Can we change these purge times, or are they cast in stone?
The purge times in Method 5030B (and other sample preparation methods) are recommendations, based on the work performed in developing the original procedures. Under the flexibility inherent in most SW-846 methods, you are free to modify the conditions to meet the objectives of a given analysis. Therefore, if you can demonstrate that other purge times perform well enough for your application, then you are free to use them, provided that you use the same purge time for the calibration associated with the samples. The Office of Resource Conservation and Recovery (ORCR) plans to clarify this in the next revision of Method 5030, as it has in other recent methods.
What is meant by the relative retention time (RRT) window of 0.06 units for SW-846 Methods 8260 and 8270?
The Gas Chromatography/Mass Spectrometry (GC/MS) methods, 8260 and 8270, refer to relative retention time (RRT) windows of 0.06 units. Please clarify exactly what that means. As I understand it, the RRT is a ratio of RT of target to RT of internal standard. How can that ratio have units?
Your understanding of relative retention time (RRT) is correct. It is the ratio of the retention time of the analyte over the retention time of the internal standard. Since both retention times will have the same units (whatever the lab chooses to use), those units can be viewed as cancelling one another out. Thus, RRT is often expressed as a unitless quantity. See Sec. 11 of Method 8000D.
Beginning with the earliest EPA GC/MS methods, EPA has provided an acceptance limit for the agreement of the RRT between the sample and the standard. The language has always read very much like what is in Sec. 18.104.22.168 of Methods 8260C and 8270D, namely that:
"The relative retention time (RRT) of the sample component is within +/- 0.06 RRT units of the RRT of the standard component."
All that one is doing here is comparing the RRT of the peak in the sample analysis to the peak in the calibration standard. The RRTs must be within 0.06 of one another. Thus, for example, if the RRT of compound A in the calibration standard is 0.98, then the RRT of the peak in the sample analysis that you want to call compound A must be within the RRT range of 0.92 to 1.04. If the peak in the sample run is not within that window, then you may not call that peak compound A, since the RRT does not agree well enough.
We believe that the intent of the original wording of "0.06 RRT units" was to keep one from thinking that the acceptance limit of 0.06 is a simple 6% window. Otherwise, one might think that the two RRT values have to agree within 6% of the standard, which is a slightly narrower window (i.e., 6% of 0.98 is less than 0.06).
What column should be used as the confirmation column for SW-846 Method 8310?
Method 8310, the high performance liquid chromatographic (HPLC) method for Polynuclear Aromatic Hydrocarbons (PAHs), does not list a confirmation column. What column should I use to confirm my results from the primary column?
The following columns have been demonstrated to be appropriate for the analysis of PAHs by HPLC:
- Standard analytical column - C-18 reversed-phase column, 3-5 µm particle size, 100-250 mm x 4.6 mm ID, (Perkin-Elmer ChromSPHERE-3-PAH, Supelco Supelcosil LC-PAH, or equivalent).
- Narrow-bore analytical column - C-18 reversed-phase column, 3-5 µm particle size, 100-250 mm x 2.1 mm ID, (Supelco Supelcosil LC-PAH, or equivalent).
- Confirmation column - CN reversed-phase column, 3-5 µm particle size, 150-250 mm x 3.0-4.6 mm ID, (Supelco Supelcosil LC-PCN, Waters Nova-Pak CN HP, or equivalent).
- Other HPLC columns also may be available to provide a sufficient change in elution order to be useful for confirmation.
- Finally, you should consult Method 8000D for information on confirmation analyses, including when confirmations are needed and when they may not be needed.
Is there an official EPA definition of a volatile compound and a semivolatile compound for SW-846?
SW-846 does not contain formal definitions for volatiles or semivolatiles and there is no "official" definition of volatile or semivolatile compounds that can be used across all EPA programs.
Some compounds can even be considered either a volatile or a semivolatile depending on the analytical technique used (e.g, naphthalene, nitrobenzene, dichlorobenzene, hexachloroethane). Generally speaking, volatiles have been defined elsewhere as compounds with boiling points below 150°C and vapor pressures of greater than 0.1 mm Hg. However, such definitions are not hard and fast, and should only be considered descriptive of a general trend. In fact, Method 8260C contains a few compounds that are exceptions to this definition.
Where can I find wipe sampling methods in SW-846?
There are two instances where wipe sampling is addressed within SW-846, Method 3572 and Appendix A of Method 8290A. The two methods differ in their approach and applicability, method 8290A has a limited discussion of wipe sampling only in the context of laboratory safety concerns relative to dioxins and furans, the wipe sampling procedure in method 3572 is intended to assess surface contamination both inside and outside of the laboratory. However, EPA does not recommend that the procedures described in either of these methods be extended to other analytes or other situations.
Outside of SW-846, wipe sampling is specified as a means for determining compliance with certain cleanup and decontamination requirements in the TSCA PCB regulations (40 CFR 761). The method for conducting wipe sampling under the TSCA PCB regulations can be found at 40 CFR 761.123 under “standard wipe sample.” When the TSCA PCB regulations require wipe sampling as the method for determining compliance, the unit used is micrograms per 100 cm2.
While wipe sampling has been described in the open literature, one of the biggest problems is that it is very difficult to interpret the results. By its very nature, the analysis of whatever material is used to wipe a surface (often filter paper wet with a solvent) yields the mass of the analyte(s), for example nanograms of dioxin or micrograms of another analyte. However, there is no straightforward way in which to convert that mass into a concentration per unit area, nor any good way in which to compare results from different wipes, except to say that one wipe picked up more material than another. If the surfaces that are wiped have different characteristics, for example a smooth metal surface versus a rough concrete block, there is no way to judge the efficiency of the wiping process itself. Therefore, use caution in interpreting the results of wipe samples.
Other Category: Sampling
When using SW-846, are we required to use the internal standards listed in Method 8260 or may we select other internal standards?
When using SW-846, are we required to use the internal standards listed in Method 8260 or may we select other internal standards? We are using Method 8260 to analyze some samples for only the BTEX compounds and some of the internal standards are not relevant to our analytes of interest.
SW-846 does not require the use of the internal standards listed in the 8000 series methods for analyses. SW-846 only recommends the use of the internal standards listed in the methods. Normally, the internal standards listed in a particular method are those used to validate the procedure. However, all of the internal standards mentioned in the current version of Method 8260 may not be pertinent for a project where the analytes of interest are a subset of the analytes listed in the method. When the list of target analytes is short, the analyst may not need to use multiple internal standards if one or two will suffice to cover the range of retention times of the target analytes. As noted in the current version of Method 8000, the target analytes should have relative retention times in the range of 0.80 to 1.20 compared to the internal standard. In the case of BTEX analyses, the analyst need only use those internal standards that are relevant to the BTEX compounds, e.g., having similar chemical and chromatographic behaviors and retention times.
The same considerations also apply to Method 8270, or any other method that employs internal standards.
Average response factor (RF) from initial calibration or RF from daily calibration for SW-846 Method 8260 (or Method 8270).
Should quantitation for Method 8260 (or Method 8270) be done using the average response factor (RF) from the initial calibration or using an updated RF from the daily calibration check sample?
For SW-846 methods involving quantitative analyses, the average RF from the initial calibration should be used for quantitation. The daily calibration check standard is used for calibration verification, and it is fundamentally different from the approach called "continuing calibration" in the CLP organic Statement of Work (SOW) and some other programs. Use of the "continuing calibration" approach amounts to a daily single-point calibration and is not appropriate nor permitted in SW-846 chromatographic procedures for trace environmental analyses. Section 11.7 of Method 8000D contains the language that clarifies the Office of Resource Conservation and Recovery's (ORCR) intent on this issue. There are a few screening procedures for organics in SW-846 that do utilize a single-point calibration for quantitation. However, these are clearly identified as screening procedures rather than truly quantitative methods.
Can commercially available standards of the methyl esters be used for SW-846 Method 8151A?
Section 5.12 of Method 8151A states that standards may be purchased as certified solutions from commercial vendors. Does this mean that we can use commercially available standards of the methyl esters?
No, except in very specific circumstances. Method 8151A involves the derivatization of the target herbicides in the sample extracts. As a result, the calibration standards undergo the same derivatization process as the samples (although it is not necessary to derivatize them in the same batch as the samples). Therefore, if the samples are to be derivatized, then the standards must be prepared from the target herbicides and derivatized to their esters as well, using the same procedures.
In SW-846 Method 8151A, should we spike field samples and the laboratory control samples (LCS) with the herbicide acids, or can we use the methyl esters?
In Method 8151A, should we spike field samples (matrix spikes) and the laboratory control samples (LCS) with the herbicide acids, or can we use the methyl esters?
You must use the form of the analyte that matches the form that is present in the samples, in other words, the parent acids, not the methyl esters. This is because the procedures in Method 8151A include both the derivatization and the determinative analysis. Therefore, spiking the QC aliquots with the methyl esters will not provide any information on the efficiency of the derivatization itself. If you are having problems with the recoveries of the acids, then spiking with the methyl esters and analyzing the samples again may be a useful diagnostic tool to see if the problem lies in the derivatization or only in the determinative steps. However, this would only be done infrequently, when the results for the parent acids suggested a problem.
When EPA releases new updates to SW-846, and a general method is updated, are all methods in that series impacted by the update?
When the EPA releases new updates to SW-846, and a general method, for example Method 8000, is updated, in this case to 8000D, are all 8000 series methods impacted by the update? For example, is Method 8260C affected by changes presented in 8000D? Can Method 8260C be used in conjunction with 8000D?
Method 8000D (the current version in Update V) is a general guidance method. Other general methods in SW-846 are 3500, 3600, 5000, and 7000. These methods represent the most up-to-date guidance on general techniques such as chromatography and sample preparation in SW-846. The determinative methods (such as Method 8260C) are much more specific in their requirements and the determinative method's criteria supersede any general guidance found in 8000D or Chapter 1, if specific conflicts exist.
The older, published methods (such as 8260B and 8000C) are still valid choices and may still be followed by those with a need to do so. We recommend using the newest version of any SW-846 method, unless your regulator or customer require you to use an earlier version.
Other category: General
Use of Sulfuric Acid Cleanup vs. DDT analog standard for SW-846 Method 8082A.
Our lab does analysis of Polychlorinated Biphenyls (PCBs) as Aroclors by 8082A and uses Sulfuric Acid Cleanup 3665 for all extracts. We were recently audited and got a finding for not running the DDT analog standard. We use pattern recognition for confirmation.
Will the sulfuric acid cleanup remove the DDT?
Is there still a need to run the DDT analog standard?
Method 8082A is meant for guidance only and can be modified according to the Method Innovation Rule (MIR) adopted by SW‐846 in 2005. However, if any modifications are made, the laboratory has to demonstrate equivalency to the satisfaction of the client/auditor/regulator.
Section 11.5 of Method 8082A states: "When conducting either Aroclor or congener analysis, it is important to determine that common single-component pesticides such as DDT, DDD, and DDE do not elute at the same retention times as the target congeners."
It is likely that your auditor considers the use of a stronger word "important" over "recommended" (for example) to be analogous to the use of "must" over "should". "Important" implies the determination stated in Section 11.5 is a requirement. Running the DDT analog standard needs only to be done in conjunction with retention time window studies and may provide some valuable information in the event that you analyze a sample that contains the pesticides.
There is no guarantee the sulfuric acid clean‐up will remove all of the DDT, DDE, DDD, etc. However, the laboratory could perform studies to determine the effectiveness of the cleanup on specific samples. Extending the results of that study to any and all possibilities may be difficult and will most likely require a level of effort well in excess of that required to run the standard as described in the method.
There is an SW-846 Method 8015D (Revision 2003) and also an EPA 8015C (Revision 2007). Which of these two methods is the latest/updated version?
Method 8015C is an official, approved method that was formally included in the SW‐846 via a Federal Register Notice whereas Method 8015D is posted on the RCRA Methods website, considered as “New” for public use and comment to be later finalized. The process for publishing validated methods for inclusion in SW‐846 takes time, and the two methods (i.e., Methods 8015C and 8015D) took slightly different paths before they were published online. The differences between the methods are minimal. Therefore, they should yield similar results.
Other Category: General
Is the DDT and Endrin breakdown check in SW-846 Method 8081 required if not analyzing for those compounds?
Is the DDT and Endrin breakdown check in Method 8081 required if not analyzing for those compounds? For example, is this needed if just analyzing for Toxaphene or Chlordane?
Yes, the DDT and Endrin breakdown check for Method 8081B is still required. The degradation check demonstrates that the instrument injection port is inert (not contaminated with high boiling point residues). This contamination can have negative effects beyond just the breakdown of DDT and Endrin.
Instrument tuning for SW-846 Method 8260.
For Method 8260, if the instrument is tuned not by direct injection but instead by purging a BFB standard, is it acceptable to use the split ratio to determine the amount of BFB that is actually reaching the mass spectrometer?
Method 8260C specifies a "50 ng or less injection" and gives no room for interpretation. Because the method uses the word "must" and not "may" or "should", use a 50-ng or less injection for BFB tune is required.
Additionally, it is not appropriate to consider the split ratio when injecting, because not all the compounds split evenly (i.e., the split may cause loss of low molecular weight gases (CO2, N2, O2, etc.)/water and solvents such as MeOH). The target compounds are much higher boiling point, and, as such, should be retained at much higher ratios.
Instrument performance checks for SW-846 Methods 8260 and 8270.
Is a traditional DFTPP or BFB tune in full scan mode required for SIM analysis?
We know the 8270 GC performance and inlet inertness checks are not required but would they even provide value at all during a SIM analysis as a recommendation?
Instrument performance checks (including tune verification) are still important quality assurance elements in the new revisions of 8260D and 8270E, even for method applications not based on full mass range acquisition like selected ion monitoring (single quadrupole mass spectrometry) or multiple reaction monitoring (ion trap or triple quadrupole mass spectrometry).
Tune checks include verification of mass assignments and mass resolution, which are important considerations for quantitative analysis under all of these conditions. 8260 and 8270 require a tune check to be performed prior to analysis (note the use of the word "must" in Section 7.3.1 in 8260B, 8260C and 8270C and Sections 11.3.1 and 11.4.1 in 8270D). However, 8260D and 8270E method revisions incorporate some additional flexibility with respect to demonstrating appropriate optimization of MS settings by allowing the operator to meet the MS instrument manufacturer’s performance criteria or alternative documented ion ratio criteria for DFTPP or BFB.
Degradation checks and tailing factor checks in Method 8270 are used to minimize problems with measurement of sensitive target analytes as the system becomes contaminated with non-volatile material and as the deactivated coating is stripped off of the chromatographic system. However, these performance checks are not recommended for all method applications in 8270E; exceptions are noted for analyte classes not known to be affected by the same types of inlet reactivity or chromatography issues, like polycyclic aromatic hydrocarbons and polychlorinated biphenyls. Nevertheless, when testing for analytes that are known to be sensitive to inlet reactivity and/or column inertness, these additional quality controls may provide important indications of changes in sensitivity or reactivity specific to certain analytes that may help the laboratory identify quality assurance issues with respect to sensitivity and/or analyte identification that may not otherwise be apparent. Since the methods are published as guidance, it is the responsibility of the laboratory in conjunction with the data user and other stakeholders to determine whether omitting this type of quality control check is acceptable for a specific data application.
Holding time for SW-46 Method 8141B for organophosphorus pesticides.
The SW-46 method 8141B for Organophosphorus pesticides looks to have added a requirement for 7 day holding times for solids. This appears to be a change in practice over what’s been accepted previously as a 14 day holding time.
Method 8141B (Rev 2, February 2007), posted online, states in Section 8.4 "Begin extraction of either aqueous or solid samples within 7 days of collection."
This is much more specific than the language in 8141A, which only referenced Chapter 4 and gave a 48-hour requirement for the derivatization of extracts. From the lack of specificity in earlier versions, we can see where laboratories might have assumed 14 days was the hold time as it was not spelled out clearly one way or the other in 8141A or Chapter 4 regarding organophosphorus pesticides.
Table 4-1 in Chapter 4 (Rev 5, October 2012) addresses the holding times for organochlorine pesticides and semivolatiles, but not for organophosphorus pesticides. The reason Method 8141B calls for lowering the hold time for this specific group of target compounds was based on a study (by D. J. Munch, and C. P. Frebis, on "Analyte Stability Studies Conducted during the National Pesticide Survey," ES & T, 1992, Vol 26, 921-925), cited as Reference 12 in the method. This study showed that the organophosphorus pesticides were not stable, with many compounds degrading before the 14-day hold time would have taken place.
Section 9.1 of 8141B states: "When inconsistencies exist between QC guidelines, method-specific QC criteria take precedence over both technique-specific criteria and those criteria given in Chapter One, and technique-specific QC criteria take precedence over the criteria in Chapter One." Therefore, the determinative method's criteria would supersede the general guidance in Chapter 4. If reporting 8141B results, all samples (both soils and waters) have to be extracted within 7 days to be considered acceptable.
Other category: Holding Time & Preservation
What is the recommended holding time for SW-846 Method 8082 for PCBs for aqueous, soil, and oil matrices?
40 CFR 136 specifies a one-year holding time for PCBs. SW-846 Chapter 4 states “none”.
What is the recommended holding time for Method 8082 for the aqueous, soil, and oil matrices?
SW-846 gives "Recommended Holding Times" in Chapter Four of the SW-846 Compendium: Organic Analytes, Table 4-1.
Footnote "a" of Table 4.1 states: "The information presented in this table does not represent EPA requirements, but rather it is intended solely as guidance. Selection of containers, preservation techniques and applicable holding times should be based on the stated project-specific data quality objectives." Therefore, if the samples were not collected for Clean Water Act (CWA) compliance (40 CFR 136), the hold time for PCBs is usually specified in a site-specific QAPP. Many QA/QC programs, QAPPs, and laboratories usually default to the recommended holding times for SVOCs (7 days water, 14 days soil from sample collection to extraction, and 40 days from extraction to analysis).
It is important to note that PCBs are quite stable compounds in environmental and waste samples, and a holding time prior to extraction of the sample may not be warranted. However, once extracted, it is advisable to analyze the sample within 40 days because, while the PCBs will likely not degrade, the solvent could evaporate over time, biasing the result high.
Other category: Holding Time & Preservation
For SW-846 Method 8330B, are the Appendix A drying, sieving, and crushing steps included in the 14 days holding time, or does the 14 days start after the sample is dry?
Method 8330B says that the holding time is the same as semivolatiles, which SW-846 Chapter 4 lists as 14 days from sample collection. Are the 8330B Appendix A drying, sieving, and crushing steps included in the 14 days or does the 14 days start after the sample is dry?
If you have to follow the method prescriptively, the drying, crushing, and sieving parts of the sample preparation would need to be completed within 14 days; prior to the extraction phase of the preparation. When the extraction begins, the 14-day hold time clock stops. We realize that this presents a problem for 8330B, as the potentially explosive samples must be dried at room temperature.
Reference 17 from 8330B may be useful as it discusses the drying, crushing and sieving parts, and it includes information on a holding time study. The data in that reference, at least for the compounds chosen, indicates that the 14-day hold time is not an issue. We advise to seek guidance for your holding time question from your regulator or data user (e.g., DoD).
Using the performance-based approach and Methods Innovation Rule (MIR) with Method 8330B, if you can demonstrate a longer hold time is supported for your compounds of interest on representative samples for your study, then your regulatory agency may allow a longer period of time to complete sample preparation before extraction.
Other category: Holding Time & Preservation
What is the EPA doing with regard to the helium shortage and moving to alternative gases for analysis?
Given the worldwide shortage of helium, which is adversely impacting many industries (not the least of which are environmental laboratories, where helium is widely used as a GC carrier gas), what is the EPA doing with regard to the helium shortage and moving to alternative gases for analysis? Are we allowed to use whatever gas can be shown to work? Does the EPA have revised criteria for the BFB and DFTPP ions ratios when hydrogen is employed as a carrier for 8260/8270?
The EPA Office of Resource Conservation and Recovery (ORCR) Methods Team has communicated to other EPA program offices and regions about the helium supply shortage issue and its impact to the analytical community. EPA Regional Labs and the industry (including instrument manufacturers) across the country were looking into alternatives.
In the short term, numerous helium conservation techniques have been developed that can significantly reduce helium consumption without costly modifications or adversely impacting performance. Examples of effective conservation techniques are:
- Converting to nitrogen as a purge gas for purge and trap systems.
- Converting all electron capture detector instruments for pesticides and PCBs to hydrogen.
- Reducing the helium flow to a minimal flow when in standby.
- Switching to nitrogen when the instrument is idle and back to helium when the instrument is operating.
- Using a standby method that puts the inlet in split mode with the split set very low.
The instrument manufacturers may have additional recommendations for helium conservation.
ORCR is revisiting two commonly used organic methods for the analyses of volatile and semivolatile compounds using gas chromatography and mass spectrometry (GC/MS). The revised methods (8260D and 8270E) will include many enhancements and address the helium supply shortage issue. These two revised methods will be a part of the next update to SW-846 (Update VI), anticipated to occur in 2016. These two methods will include BFB/DFTPP ion ratio criteria and an appendix providing guidance for the use of hydrogen carrier gas.
Under the Methods Innovation Rule (MIR), methods may be modified provided it can be demonstrated that precision and accuracy criteria are met for the intended use and that the quantitation limit is the same or lower than the existing method. However, it is incumbent upon the laboratory modifying the method to demonstrate the validity of the modifications and get the approval for these modifications from the regulating agency and/or client. Most of the gas chromatographic methods using helium as a carrier gas are not method‐defined parameters and can be modified for use with an alternate carrier gas.
Are SW-846 Methods 3545 and 3546 acceptable substitutions for sonication as the first step of Method 8151A?
Are methods 3545 and 3546 acceptable substitutions for sonication as the first step of Method 8151A, assuming of course that proper initial and ongoing QC are acceptable?
Method 8151A was last updated in 1996. Methods 3545A and 3546 were last updated in 2007. Therefore, the herbicide analysis method (8151A) was published 10 years earlier than either extraction method.
Method 3545A expressly allows the extraction of chlorinated herbicides in Section 7.7.5 which states, “Chlorinated herbicides may be extracted with an acetone/methylene chloride/phosphoric acid solution or an acetone/methylene chloride/trifluoroacetic acid solution".
Research for Method 3546 has demonstrated the effectiveness of microwave extractions for chlorinated herbicides. As with any technique, a demonstration of effectiveness at your laboratory, with your specific equipment would be needed though before the procedures are used on samples.
Can alternative esterification agents (i.e., trimethylsilyldiazomethane (TMSD) or boron trifluoride (BF3)) be used for derivatization in SW-846 Method 8151?
Can alternative esterification agents (i.e., trimethylsilyldiazomethane (TMSD) or boron trifluoride (BF3)) be used for derivatization in method 8151?
Alternatives to diazomethane or pentafluorobenzyl bromide would be acceptable to use for Method 8151 under the PBMS approach.
There is support for TMSD in the EPA literature for pesticide and herbicide analyses. Please visit About the Office of Research and Development (ORD) for references.
The use of TMSD as a safer alternative to diazomethane seems to be well-documented with regard to reactivity and carcinogenic properties. However, high toxicity warnings are plentiful with all methylating agents. There are also concerns that TMSD (for example) will cause more artifacts as a more efficient methylating agent.
Likewise, BF3 has a good track record with many accredited laboratories using it for derivatization instead of diazomethane or PFBBr.
Can the secondary ion be used as the quantitation ion in order to meet the minimum response factors listed in Table 4 of SW-846 Method 8260C?
Can the secondary ion be used as the quantitation ion in order to meet the minimum response factors listed in Table 4 of 8260C?
The laboratory currently cannot meet the minimum response factor for acetone using ion 58 (however, this can be achieved by using ion 43). The same situation also applies to 2-Butanone and 2-Hexanone.
The secondary ion can be used for quantitation. In the case of the compounds in question, the ions listed in Table 5 of 8260C are 43 and 58 for Acetone, 43 and 72 for 2-butanone and 43, 57, 58 and 100 for 2-hexanone. The primary ion is generally used as it is the most abundant or most characteristic, but secondary ions can be used if a compound co-elutes or there is a good reason to do so. The ketone compounds in question are known to be poor responders.
Table 4, which lists the recommended minimum response factor criteria, has this to say in the footnote: "The project-specific response factors obtained may be affected by the quantitation ion selected and when using possible alternate ions the actual response factors may be lower than those listed. In addition, lower than the recommended minimum response factors may be acceptable for those compounds that are not considered critical target analytes and the associated data may be used for screening purposes."
The method acknowledges that every laboratory may not be able to achieve the recommended minimum response factor in Table 4 and allows for the reporting of data that does not meet this criteria to be reported with qualifiers. The minimum response factors published in 8260C were provided as guidance and were not intended to be used as prescriptive quality control criteria for the laboratory. The response factors were derived from a Gas Chromatography/Mass Spectrometry (GC/MS) system at the time the method was revised in 2006. In the newer version, Method 8260D (soon to be posted on the RCRA Methods website), Table 4 is revised to list relative response factors criteria from the EPA Contract Laboratory Program. A statement is added under Table 4 noting these response factors are provided as guidance only and are not intended to be a requirement.
There are no prohibitions in the method to use a secondary ion to quantitate, but if the only motivation for doing so is to meet the minimum response factors in Table 4, that would not be needed to consider the data reportable if all other QC checks were in control.
Issues with surrogate and target compounds during the soil extraction for herbicides.
We have had continuous issues with surrogate and target compounds during the soil extraction for herbicides. Could you give us any insight into where in the process we are most likely to incur these losses?
- Method 8151A, Section 22.214.171.124 details the solvent exchange from acetone/ether to ether. Ensure that the target pHs are met or exceeded (i.e., more basic or more acidic as applicable), and be prepared to leave a little (<5%) of the aqueous phase behind in order to avoid acetone crossover to the hydrolysis phase.
- Residual acetone may cause low recovery of some compounds during hydrolysis due to aldol condensation. Aldol condensation is a reversible reaction between two constituents (or sometimes two of the same constituent) that contain aldehyde, ketone, and even acidic alcohol functional groups. It may occur in acidic or alkaline media, although it proceeds by two different reaction mechanisms.
- The drying step is very critical to ensuring complete esterification. Any moisture remaining in the ether will result in low herbicide recoveries.
- Monitor the pH for at least 15 minutes with stirring, as indicated in the method. This will help to ensure that the herbicide is in its acid form.
- Ensure that after addition of acetone, mixing continues for at least 20 minutes. Acetone needs sufficient interaction time with the matrix to penetrate the pore space of the solid material and solvate both herbicides and water (field moisture).
- Ensure that at least 75 percent of the extraction solvent is recovered after the third extraction cycle. There likely will be some herbicide partitioned into retained solvent; with consecutive extractions portioning will be favorable for removal of most of the constituent mass. Three successive extractions have shown to be good in general.
- Ensure that during separatory‐funnel extraction the pH of the aqueous phase is less than 2; the herbicide must be in its acid form to partition into the organic extraction solvent efficiently.
- Following separatory‐funnel extraction, there should be no acetone remaining since the acetone is more soluble in the aqueous phase (polar) than in the organic phase (diethyl ether, non‐polar).
- Ensure that the final extract is completely dry using anhydrous sodium sulfate prior to blow‐down. It should be dried as described in Section 7.3.6. Water will interfere with the derivatization efficiency.
- Hydrolysis samples should be processed in a water bath at 60‐65°C. Lower temperatures can cause problems.
- To check methylation, obtain a reference standard in the acid form and methylate this without extraction.
- If LCS spikes are in the acid form, check to see if you are losing herbicides in the alkaline hydrolysis step by comparing results with and without the hydrolysis step.
- Make sure that all glassware, sodium sulfate, and filter media are acid-rinsed.
Is it acceptable to use SW-846 3535A for all aqueous samples that are destined to be run by 8270D?
Method 3535A only references TCLP extracts for 8270. Is it acceptable to use 3535A for all aqueous samples that are destined to be run by 8270D?
Use of 3535A for preparing aqueous samples for analysis by 8270D is allowed. The application table in 3535A merely states those are the applications that have performance data and have been evaluated thus far. It does not preclude laboratories from other applications of the method. Also, see Section 1.2 of Method 8270D regarding the use of Method 3535.
Solid-Phase Extraction (SPE) works well for preparing aqueous samples for analysis of PAH and BNA compounds, PCBs, pesticides, and total petroleum hydrocarbons. It does not work as well for phenols and some nitro-aromatics, although new types of cartridges and disks are always being developed by vendors that may improve performance. As long as adequate performance for the project's data quality objectives can be demonstrated, use of the methods is allowed.
Other Category: 3000 Series
Low recovery of styrene and several other compounds in soil organics analysis (VOA) samples.
We have observed low recovery of styrene and several other compounds in some soil VOA samples. After conducting some research, we found that the sodium bisulfate preservative is likely to be responsible for the low recoveries.
Chapter 4 – Table 4‐1 of SW‐846 recommends that a second set of samples without acid preservatives be collected and analyzed as soon as possible if the compounds (e.g., vinyl chloride, styrene, and 2-chloroethyl vinyl ether) are analytes of interest. EPA 5035 does not provide another preservation option, aside from sodium bisulfate, for low concentration soil method unless the sample is effervescent.
An updated Method 5035A (Draft Revision 1, July 2002) is available and posted on the “Validated Test Methods Recommended for Waste Testing” page.
The information provided in Appendix A of Method 5035A was based on EPA’s evaluation of currently available data and technology as applied to the most appropriate sample handling and preservation procedures in order to minimize the loss of volatile organic compounds (VOCs) during the collection and analysis of aqueous and solid materials. The intended users of this Appendix guidance are those individuals and organizations involved in the collection and preparation of samples for VOC analyses during the characterization of solid materials under the Resource Conservation and Recovery Act (RCRA). See Appendix A for guidance on selecting an appropriate sample collection and preservation technique that are suitable for VOC analyses to meet the data quality requirements or objectives for the intended use of the results.
Table A-1 in Appendix A of 5035A recommends VOC Sample Preservation Techniques and Holding Times with a variety options using physical and chemical preservations and compound applicability.
Ultimately, holding times and preservation requirements are typically set by the regulator or data user in a project-specific QAPP.
Other Category: Holding Time & Preservation
Holding time and preservation requirements for volatile organics analysis (VOA).
SW‐846 Chapter 4 recommends that for aqueous samples for 5030/8260 VOA when analysis for vinyl chloride and styrene are target compounds, an unpreserved vial be used and the holding time becomes within 7 days of collection. Our lab routinely analyzes aqueous MS/MSD samples from a large variety of sources (effluents, groundwater, surface water, etc.) that are preserved at a pH <2 with HCl with recoveries for these compounds well within 70‐130 percent. Because we typically spike the MS/MSD samples less than 48 hours from analysis we don’t have long-term stability data of these two compounds in preserved vials. Field samples are collected in 2 preserved vials and 2 unpreserved vials and we have analyzed samples that have detections of vinyl chloride and styrene from both preserved and unpreserved vials with statistically similar results.
The previous version of SW-846 Chapter 4 Table 4-1 recommended, for aqueous samples with no residual chlorine present, that "If vinyl chloride, styrene, or 2‐chloroethyl vinyl ether are analytes of interest, collect a second set of samples without acid preservatives and analyze as soon as possible."
In Update V, Chapter 4 (July 2014 rev 5) Table 4-1, that same recommendation was revised to "If compounds that readily degrade in acidified water (e.g., 2‐chloroethyl vinyl ether) are analytes of interest, collect a second set of samples without acid preservatives and analyze as soon as possible."
The reason for this change followed discussion in the Workgroup regarding the requirement of a second set of unpreserved vials for analysis of styrene and vinyl chloride. Stability studies were conducted and the stability data for vinyl chloride and styrene were felt to be reasonably comparable by the group. Therefore, the Workgroup dropped the unpreserved requirement for those two compounds, but not for 2‐chloroethylvinyl ether, as the study data did not address 2‐chloroethylvinyl ether. It is still the recommended guidance that unpreserved samples be run for 2‐chloroethylvinyl ether.
Other Category: Holding Time & Preservation
What are the guidelines for the hydrolysis step in SW-846 Method 8151A for environmental samples?
What are the guidelines for the hydrolysis step in 8151A for environmental samples? Shouldn't hydrolysis always be performed?
Most chlorinated herbicides in the 8151A list come in numerous formulations including acids, esters, and salts. The purpose of the hydrolysis step in method 8151A is to convert all of the ester herbicides into acid form. While the esters have a half-life of about a week in soil matrices, they are stable enough to be detected by the method when the hydrolysis step is performed. Therefore, not performing the hydrolysis step would not detect fresh applications of ester formulations. Given that it seems to be a relatively rare situation when esters are not required analytes, it seems most practical to always perform the hydrolysis step.
How to find unique peaks for Aroclors in SW-846 Method 8082A.
Method 8082A states in section 126.96.36.199, "For each Aroclor, the set of 3-5 peaks should include at least one peak that is unique to that Aroclor". Since AR1016, AR1232, AR1242, and AR1248 all have exactly the same peaks (just in different height/area ratios), how do you find a peak that is unique to each one? The same case exists for AR1260 and AR1262.
The method states at least one peak that is unique to that Aroclor should be included. However, since many of the Aroclors have the same peaks, but with different area ratios, it is not practical to do so on samples that contain similar congeners. For PCBs that do have different congeners, for example 1016 and 1260, unique peaks can be chosen.
Choosing peaks that have the best response and the least inferences is recommended. Pattern matching is probably the most important part of the PCB analysis, which can become difficult if more than one Aroclor is present or if weathering has occurred. By choosing five peaks or more for quantitation, the analyst can choose the peaks that correspond closely with one another (in concentration) and remove the values that are affected by inferences and weathering.
How should the lower limit of quantitation (LLOQ) for total Xylenes be reported for SW-846 test methods?
How should the lower limit of quantitation (LLOQ) for total Xylenes be reported, i.e., a sum of the LLOQ for the 3 isomers?
Unless a separate integration for total xylenes is performed, the xylene isomer LLOQs should be added together. Similarly, when reporting total xylenes, the results of m&p xylene and o-xylene should be added together. It is important to point out that m- and p-xylene are difficult to chromatographically separate under the conditions described in methods 8015 and 8260, while separation of the o-xylene peak from m+p-xylenes is easier to achieve. If both m- and p-xylenes are present in a mixed stock solution at the same concentration, then the calibration range for the peak representing m- and p-xylene would be twice as high as for other target analytes. Along with their corresponding lower limit of quantitation (based on the low standard concentration).
Other category: Detection & Quantitation