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3000, 3500, and 3600 Series

EPA received many questions about hazardous waste test methods. The questions and responses for this category are listed below.

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In SW-846 Method 3620C Section 11.13.4, is 0.035 the correct elution amount for acetonitrile?

Section 11.13.4 of Method 3620C states, "Elute the column with 60 mL of methylene chloride / acetonitrile / hexane (50/0.035/49.65, v/v/v), collecting the eluate in a second flask. This is Fraction 2." If the middle number were 0.35 instead of 0.035, the total of the three would be 100. Is this just a typo?

That is a typo, which was corrected in the Update V version of the method. The correct entry for acetonitrile should be 0.35, not 0.035.

Other Category: General

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Meeting performance checks in SW-846 Method 3620B when using Florisil cartridges.

We are using the Florisil cartridges described in Method 3620B and we cannot find any that meet the performance checks described in Sec. 8 of the method. Specifically, we cannot get the recovery of trichlorophenol to be less than 5%.

While the use of the Florisil cartridges may require a bit of practice, the root cause of your problem may be the result of an editorial error in the "B" version of this method. At some point during the development of Method 3620B, the units for the cartridge check solution in Sec. 5.11 were changed to milligrams per liter when the units should be micrograms per liter (mg/L versus ug/L). As a result, the cartridge check solution is 1000 times more concentrated than intended and may overload the cartridges, allowing the trichlorophenol to break through. This editorial error was corrected in the latest version of the method, 3620C, which is available in Update V.

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Is SW-846 Method 3050B appropriate for the digestion of coal ash?

We are trying to determine whether EPA 3050B is appropriate for the digestion of coal ash. Section 1.2 of the method states, "This method is not a total digestion technique for most samples. It is a very strong acid digestion that will dissolve almost all elements that could become "environmentally available.” By design, elements bound in silicate structures are not normally dissolved by this procedure as they are not usually mobile in the environment. If absolute total digestion is required use Method 3052."

Since coal ash could contain silicas, would EPA 3050B be an appropriate digestion method for all of the metals listed in section 1.1 of EPA 6010C? Could you also provide a more detailed explanation of Section 1.2 and the statement above?

Method 3050B is based on a very strong acid digestion that leaches elements from the sample that could become environmentally available. The premise is if this strong acid leach cannot remove the element from the sample and bring it into solution, then there is no further worry about the sample from an environmental standpoint. If the element is associated with the silicate matrix, which is not broken down in the environment, then the element cannot be mobilized and it is not of environmental concern.

In order to release elements contained in the silicate matrix of the soil or coal ash, the silicate matrix must be destroyed. This is done with hydrofluoric acid (HF). Method 3052 employs HF to destroy the silicate matrix, along with the strong mineral acids in a high pressure microwave vessel. As such, it completely destroys the sample and releases all elements. It is considered an absolute total digestion. Such numbers might be needed in case of material balance studies, or comparison to other types of true total analyses, but they are not generally necessary from an environmental release standpoint.

If the study goal is to evaluate the coal-ash contaminated soil or remediated soil to see if it releases elements of environmental concern, then Method 3050B would be appropriate. If the study goal is to determine whether all the ash has been removed, an element or multiple elements that are unique to the ash and not the soil must be identified. The remediated soil should then be digested by Method 3050B to see if the ash marker elements are still being released. If they are under a particular threshold, the soil could be considered remediated.

Other Category: Inorganic

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What is the basis for the reduction from 10% to 1% weight loss value for discarding samples from SW-846 Methods 3015 and 3051 to Methods 3015A and 3051A?

SW-846 Methods 3015 and 3051 specify that the sample is to be discarded when weight loss exceeds 10%. Methods 3015A and 3051A specify that the sample is to be discarded when weight loss exceeds 1%. This seems to be a rather dramatic reduction, what is the basis for this?

When Methods 3015 and 3051 were drafted, the state of the art for vessel technology was different than it is today. At that time, it was determined that some loss of mass was inevitable, since the sealing and pressure relief components were largely composed of PTFE, which is somewhat soft and tends to flow under compression. Ten percent loss was a compromise between the ability to maintain integrity of the seal and the number of individual vessels that would fail to meet the maximum loss criterion in any individual run. Microwave technology was less advanced as well; even with rotating carousels the homogeneity of microwave energy in the cavity absorbed by individual vessels varied and resulted in uneven heating.

Advances in technology have resulted in improved sealing mechanisms and improved microwave performance. In reviewing performance data generated for Methods 3015A and 3051A, the ORCR Workgroup likely determined that a 1‐percent mass loss represented an acceptable upper bound when comparing analyte recoveries with digestion throughput.

Other Category: Inorganic

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Can SW-846 Method 3005A be used for mercury analysis by Method 6020A, Inductively Coupled Plasma-Mass Spectrometry (ICP-MS)?

Can EPA Method 3005A be used for mercury analysis by ICP-MS (Method 6020A), if the lab demonstrates acceptable precision, accuracy, and sensitivity? Mercury is listed in the analyte list for Method 6020A, but is not listed in 3005A.

Acid digestion itself is not sufficient for mercury, so permanganate should be added to the final acid digest until a persistent purple color is obtained. Then the extract can be analyzed by CVAA as described in the Hg 7000 series. This is a key step if Method 3005A is used for preparing mercury samples for analysis by CVAA.

If mercury will be analyzed by ICP‐AES (method 6010) or ICP-MS (method 6020), addition of permanganate is not recommended. In such cases, we recommend another oxidizing agent that works at a lower concentration and does not interfere with any of the target analytes. We have successfully used 3005A and other metals digestion methods for mercury, and stabilized the mercury with 2 ppm gold chloride, followed by ICP‐AES or ICP‐MS detection. As long as the digest has a pH of 2 or less and has 2 ppm Au+3 ions, the mercury will remain oxidized and stay in solution over a long period (e.g., NIST trace‐level mercury in water reference materials prepared in this manner will still give the reference value, even though they were prepared in the 1970s). The gold also eliminates the long washout times mercury would require in an ICP system if gold were not used. Note, the gold must be at the same level in the calibration standards and samples. Also, the gold does not cause any interferences on any target analytes when using ICP‐AES or ICP‐MS.

The higher level of chlorides from a 3005A digestion can make analysis for arsenic and selenium by ICP‐MS more challenging. Use of collision cell or dynamic reaction cell technology to lower molecular ion interferences is recommended.

We recommend adding the gold under acidic conditions for any digestion, whether closed or open digestion when determining mercury by ICP-MS or ICP‐AES. It prevents deposition of mercury in the sample introduction system and prevents long wash‐out times between samples. Simply stated, gold does an excellent job as a strong oxidizer keeping mercury oxidized in its ionic state. As long as mercury is kept in its ionic state, it behaves like any other dissolved metal and will remain in solution over long periods and will not be lost due to heat or being open to the atmosphere. Without gold or another strong oxidizer like permanganate, mercury can reduce to elemental mercury at active sites on vessel walls (especially plastic) or soil particles and become vapor which may be lost through the vessel walls or in the headspace above the liquid. HCl does not totally stabilize mercury like gold does.

Other Category: Inorganic

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Is it acceptable to use SW-846 3535A for all aqueous samples that are destined to be run by 8270D?

Method 3535A only references Toxicity Characteristic Leaching Procedure (TCLP, Method 1311) 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. This method does not have to be used for only TCLP leachates. Both Methods 8270D and 3535A are to be used as guidance and do not have to be followed prescriptively. 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 the footnote in the application table 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 SPE is allowed.

Other Category: 8000 series

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Are there any further updates regarding the EPA ORCR August 5, 2010 memo concerning the spiking issue in SW-846 organic extraction methods?

Are there any further updates or clarifications/decisions regarding the EPA ORCR August 5, 2010 memo concerning when the spiking of soil samples should occur relative to the addition of the drying agent (e.g., sodium sulfate)?

There are no further updates or changes since the August 5, 2010 memo "Memorandum Regarding the Spiking Issue in SW-846 Organic Extraction Methods" was released. The guidance in that memo still holds.

Other Category: General

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In SW-846 3550C Section 11.0, does “prior to use” mean before the sonicator is put in service?

SW-846 3550C Section 11.0 states, "The horn must be properly maintained, including tuning according to the manufacturer's instructions prior to use, and inspection of the horn tip for excessive wear."

Does “prior to use” mean before the sonicator is put in service? If not, how often does the lab need to tune the sonicator? Does this mean every day of use?

Prior to use in this case means prior to use each day. Most modern sonicators have an autotune feature that adjusts for temperature, load, etc. This should be run each day prior to use.

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Spiking surrogates for SW-846 Methods 3510C and 3520C.

Methods 3510C and 3520C state to spike surrogates into the graduated cylinder or sample bottle and mix well. Multiple transfers introduces potential for losses and mixing well in a graduated cylinder is difficult.

Would it be acceptable to transfer the sample to a separatory funnel for 3510C then add the surrogates? This minimizes the possibility of cross-contamination from the graduated cylinders.

Knowing that it is important to already have solvent in the continuous liquid/liquid extraction (CLLE) body before the addition of the sample or the water will get into the boiling flask, would it be acceptable to add the surrogates to the upper (aqueous) phase in the CLLE?

It would be acceptable to add the surrogate spiking solution directly to the separatory funnel rather than to a graduated cylinder or the sample container. Even though the cylinder and container are solvent rinsed, there is a remote chance a portion of the surrogates could be retained on the glass walls. Should you choose to spike directly into the sample volume in the separatory funnel, be sure to perform this step prior to pH adjustment and the first solvent addition.

It would also be acceptable to set up the sample and methylene chloride in the CLLE and then spike directly into the upper aqueous phase, provided your spike is in a water miscible solvent.

However, since the final decision on whether this change is acceptable will come from your regulatory agency/accrediting body, it would be advisable to contact them first.

Other Category: QA/QC

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What does “other systems and other types of vessels” mean in SW-846 Method 3546 Section 1.1?

Method 3546 Section 1.1 states, “Other systems and other types of vessels may be used, provided that the analyst demonstrates appropriate performance for the specific application.”

What does “other systems and other types of vessels” mean? Does it mean other microwave systems or any other heating system?

The method is specific regarding the use of microwave energy as a heating source using closed vessels at high temperature and pressure (i.e., 100-115 °C and 50-175 psi) to facilitate solvent extraction. So long as the general approach incorporates these specifications, selection of the microwave unit and vessels is left to the user. Other heating systems, like block heaters which do not utilize microwave energy, are not described in the method and should not reference 3546 or claim equivalency to 3546.

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