Inorganic

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

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Should a used oil marketer use SW-846 Method 1311 (TCLP) to determine whether used oil meets the specification levels for arsenic, cadmium, chromium and lead?

Should a used oil marketer use the Toxicity Characteristic Leaching Procedure (TCLP) to determine whether used oil meets the specification levels for arsenic, cadmium, chromium and lead?

When determining the levels of arsenic, cadmium, chromium, and lead in used oil that will be burned for energy recovery, the TCLP is not the appropriate test. The TCLP was developed to simulate leaching in a landfill, addressing the degree of mobility of waste streams (61 FR 11798, 11809; March 29, 1990). This attribute of the used oil is irrelevant if the used oil will be burned for energy recovery rather than land disposed. Instead of a TCLP, a totals analysis should be performed on the used oil. Chapter Two of "Test Methods for Evaluating Solid Waste, Physical/Chemical Methods (SW-846)" offers guidance on selecting appropriate test methods for specific constituents in different matrices, such as used oil. For example, Table 2-39 of Chapter Two lists testing options for various metals, including arsenic, cadmium, chromium, and lead.

Other Category: Hazardous Waste Characteristics

What EPA SW-846 test methods are available for use in detecting the presence of mercury?

These following test methods are described in detail in EPA's publication SW-846, which is the Office of Resource Conservation and Recovery's (ORCR) official compendium of analytical methods that are available for use in complying with Resource Conservation & Recovery Act (RCRA) regulations.

Method 7470A, Mercury in Liquid Waste (Manual Cold-Vapor Technique)

Method 7471B, Mercury in Solid or Semisolid Waste (Manual Cold-Vapor Technique)

Method 7472, Mercury in Aqueous Samples and Extracts by Anodic Stripping Voltammetry (ASV)

Method 7473, Mercury in Solids and Solutions by Thermal Decomposition, Amalgamation, and Atomic Absorption Spectrophotometry

Method 7474, Mercury in Sediment and Tissue Samples by Atomic Fluorescence Spectrometry

Method 6010D, Inductively Coupled Plasma-Atomic Emission Spectrometry

Method 6020B, Inductively Coupled Plasma-Mass Spectrometry

Can digests from SW-846 Methods 3015A and 3051A be used directly on an automated mercury analyzer without any further sample treatment?

Mercury is listed as an analyte in both Method 3015A and Method 3051A. Can digests from those two methods be used directly on an automated mercury analyzer without any further sample treatment (elimination of the aqua-regia and permanganate digestions)?

Sec. 1.1 of Method 3015A lists mercury, as does Sec. 1.1 of Method 3051A and Sec. 1.1 of Method 3052. Samples containing mercury may be digested using the conditions described in these methods (i.e., without aqua-regia and permanganate digestions). Data from validation of the microwave procedures may be found in the methods.

What is the holding time for soil samples analyzed for hexavalent chromium by SW-846 Method 7196A?

What is the holding time for soil samples analyzed for hexavalent chromium by Method 7196A? The method appears to say 24 hours; however, I understand that there is guidance in the SW‐846 manual that the holding time is 30 days to extraction and then 7 days from extraction to analysis.

Method 7196A is meant for TCLP extracts and groundwaters for which the hold time is 24 hours as the method specifies. These types of samples are not as stable and need to be analyzed more quickly. However, for soils there is a separate extraction step before the analytical steps described in 7196A. The extraction method gives a more stable extract than groundwater or a TCLP extract, hence the holding time can be longer before analysis. The extraction method is 3060A where Section 6.4 says, "hexavalent chromium has been shown to be quantitatively stable in field moist soil samples for 30 days from sample collection. In addition Cr(VI) has also been shown to be stable in the alkaline digest for up to 168 hours (7 days) after extraction from soil." Guidance is also given in SW-846 Chapter 3, Table 3-2 where it says aqueous samples have a holding time of 24 hours and solids have 30 days to extraction and 7 days from extraction to analysis.

In summary, for waters or TCLP extracts, the holding time is 24 hours to analyze by Method 7196A or Method 7199. For soils, the holding time is up to 30 days from sample collection before extracting by Method 3060A, then up to another 7 days to analyze the 3060A extracts by Method 7196A (colorimetry) or Method 7199 (ion chromatography).

Other Category: Holding Time & Preservation

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: 3000 Series

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: 3000 Series

SW-846 Test Methods 9012B and 9010C and compliance with 40 CFR 268.40 footnote 7.

40 CFR 268.40 footnote 7 for cyanide analysis states you may use the test Methods 9010C or 9012B with the sample weight of 10 g with the distillation time of 1 hour and 15 minutes. Can a lab run test Method 9012B or 9010C and use 1 gram sample weight using the midi‐vap distillation and still be compliant with footnote 7?

Both Methods 9012B and 9010C are method defined parameters (MDPs) and must be followed prescriptively as written, with no exceptions. The text “are to be” in footnote 7 is synonymous with “must”. Therefore, use of a 10 gram of sample and distilling for 1 hour and 15 minutes is required to be compliant.

Other Category: 9000 series

Does ORCR observe the same holding time and preservations for SW-846 Method 7199 for hexavalent chromium allowed under 40 CFR 136?

There appears to be a discrepancy in EPA 7199 Revision 0 for analysis of hexavalent chromium. The method and Chapter Three of SW-846 both state that the hold time is 24 hours, yet the method indicates the use of a preservative to achieve a pH of 9‐9.5. 40 CFR Chapter 136 allows the use of EPA 218.6 in which using a buffer and adjusting the pH to 9.3‐9.7 extends the hold time to 28 days. The fact that 7199 mentions the buffer but then does not extend the hold time seems like an error. Does the Office of Resource Conservation and Recovery observe the same holding time and preservations for hexavalent chromium allowed under 40 CFR 136?

The holding times and sample preservation information found in SW-846 Chapter 3 and Method 7199 are intended as guidance. Holding times and preservation requirements a lab has to follow are typically set by data users (e.g., a regulator) or specified in a project-specific QAPP. They may specify the method be followed exactly as written, or they may allow the 28-day hold time mentioned in footnote 20 in 40 CFR Part 136.3, Table II to be followed. The footnote is reproduced below but it contains a caveat that prevents the use of the 28 day holding time as a default value in all circumstances:

"20To achieve the 28-day holding time, use the ammonium sulfate buffer solution specified in EPA Method 218.6. The allowance in this footnote supersedes preservation and holding time requirements in the approved hexavalent chromium methods, unless this supersession would compromise the measurement, in which case requirements in the method must be followed."

The caveat "unless this supersession would compromise the measurement" is important and some would argue it's intention is to use the shorter hold-time guidance in 7199 or shorter hold time specification in 218.6 unless it is proven that the longer hold time does not compromise the measurement for samples from a given site. This proof would require analyzing an aliquot of sample(s) from a site within the shorter hold time, then rerun another aliquot of the same samples later within the longer hold time and see if they had any significant change. If there is no change, the longer holding time would be acceptable. If there is a change, the laboratory is in a precarious situation if they used the longer holding time for the reported samples (i.e., the data would have to be qualified, and possibly rejected). A regulator, data user, or QAPP may choose the safest approach and just specify the shorter hold times.

Other Category: Holding Time & Preservation

Extraction fluids for SW-846 Method 1312 (SPLP) analyses of samples that may contain cyanide.

According to Method 1312, Section 5.4.3, extraction fluid #3 is used to determine cyanide. Also, Section 7.1.4.3 states for cyanide containing wastes and/or soils, extraction fluid #3 must be used because leaching of cyanide containing samples under acidic conditions may result in the formation of hydrogen cyanide gas. How is this to be interpreted when analyzing both cyanide and metals on an SPLP extraction? Is fluid #3 to be used for all SPLP analyses which may contain cyanide, or is one extraction done with fluid #3 for cyanide and another extraction with the appropriate fluid for metals.

Section 5.4 of Method 1312 indicates that Extraction fluid #3 is to be used for cyanide and volatiles. Extraction fluid #1 and #2 are supposed to be used for other analytes: Extraction fluid #1 for sites east of the Mississippi River and #2 for sites west of the Mississippi River. Therefore, if metals and cyanide analyses are needed, two separate sample aliquots would be extracted with two different fluids.

Other Category: Hazardous Waste Characteristics

How do you interpret the mass calibration criteria for Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) as described in SW-846 Method 6020A?

I’d like to know how to interpret the mass calibration criteria for ICP‐MS as described in Method 6020A:

If the mass calibration differs more than 0.1 amu from the true value, then the mass calibration must be adjusted to the correct value.

Does this mean ± 0.05 amu or ± 0.1 amu from the true value?

The method does not specify direction, but "differs more than 0.1 amu from the true value" means outside of 0.1 amu above or below the true value or ± 0.1 amu from the true value.

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: 3000 Series

Is SW-846 Method 7199 intended for the determination of dissolved or total hexavalent chromium?

Our laboratory has a client requesting for both dissolved and total hexavalent chromium by EPA 7199. We normally report the results as dissolved hexavalent chromium since the method calls for filtration of the aqueous sample using a 0.45 μm filter.

Is the method intended for determination of dissolved Cr6+ only? Or, does the way Section 6.2 is written, i.e., “For the determination of dissolved Cr(VI)…”, imply that EPA 7199 is intended for both dissolved and total Cr6+? If the method is intended for both total and dissolved, how should analysis of total hexavalent chromium be carried out?

Although the method is not perfectly clear on this matter, Section 6.1 states that the sample should be filtered and pH-adjusted at the time of collection or as soon as possible. Section 6.2 then describes the procedure for filtering and preserving mentioned in 6.1 and clarifies that this is for dissolved hexavalent chromium. Therefore, only dissolved hexavalent chromium can be analyzed by this method.

What are the filtration and headspace requirements for SW-846 Method 6850?

Method 6850 calls for filtering in the field with a 0.2 micron filter. The laboratory prep calls for a 0.45 micron filtration. Is the 0.2 micron filter a requirement? Can we use a 0.45 micron filter? If no filtration is performed in the field, should the sample be collected with or without headspace? The method requires headspace.

Whenever possible, field filtration of water samples using sterile 0.2 μm PTFE filter membranes is recommended to remove perchlorate‐reducing bacteria (PRB) that could potentially introduce low bias due to biodegradation, as well as to remove filterable organic carbon (an electron donor) that may act as a nutrient for PRB under anoxic conditions. The 0.45 μm filtration criteria are to both ensure that there is no potential for occluding the high‐performance liquid chromatography (HPLC) column with suspended material and to generate a sample whose suspended solids content is representative of water quality within an underground aquifer composed of fine‐grained materials. Although not specifically required by the method, also consider cooling the samples to <4°C to further inhibit microbial growth.

If not field‐filtered, the sample should be filtered as soon as possible following receipt at the laboratory. There is some ambiguity here regarding whether to filter to 0.2 or 0.45 μm; typical filter media used in the laboratory prior to analysis are 0.45 μm syringe filter cartridges. If the samples are not analyzed relatively soon following receipt, the laboratory should filter using a 0.2 μm filter.

In any case, the samples should be collected with residual headspace in the containers, since this (ambient air) will help minimize growth of the anaerobic PRB.

For SW-846 Method 6020A, is the serial dilution to be performed on the sample or is the post-digestion spiked sample to be serially diluted?

Method 6020A states to run a post-digestion spike if the matrix spike (MS)/matrix spike duplicate (MSD) recoveries are unacceptable and if the post-digestion spike fails a serial dilution is to be performed. Is the serial dilution to be performed on the sample or is the post-digestion spiked sample to be serially diluted?

The purpose of the post-digestion spike is to determine if the unacceptable MS/MSD results are due to the digestion part of the procedure or the analysis part of the procedure. An acceptable post-digestion spike tells you the unacceptable MS/MSD results were caused by the digestion (this is very typical for analytes like antimony in soil samples). An unacceptable post-digestion spike tells you the problem may be with the analysis stage due to matrix interferences. By doing a dilution, matrix interferences can be reduced. If the dilution test passes, it indicates that there is a matrix interference during analysis that is responsible for the unacceptable MS/MSD results. However, in order to do a meaningful dilution test, enough analyte present must be present in the undiluted sample such that the diluted results are still quantifiably detected. That is more likely if a spiked sample is diluted, which in this case is the post-digestion spike. 6020A Section 9.11.2 dilution test is usually meant to be run on the post-digest spike. There are situations where there are sufficient analytes in the native sample digest that running the diluted native sample digest would give meaningful data. Diluting that digest instead of a post-digestion spiked sample would answer whether matrix interferences are responsible for unacceptable MS/MSD results.

Method 6020B, which was recently released with SW-846 Update V, has been revised to better clarify the purpose of the dilution test and the post-digest matrix spike test.

What is the recommended frequency for the frequency of analysis of the Interference Check Samples (ICS) for SW-846 Method 6010C?

Method 6010C does have a clear recommendation for the frequency of analysis of the Interference Check Samples (ICS). Our lab had been analyzing at the beginning of each run, but an auditor had mentioned that this was inadequate. What is the recommended frequency when you do not apply corrections, but use the ICS to show absence of interference?

EPA Method 6010C provides different guidance for analysis of interference check solutions depending on if interelement corrections are applied.

Sections 4.2.8, 4.2.9, and 10.1.5.6 discuss procedures for when interelement corrections are applied. Section 10.1.5.6 of Method 6010C recommends verifying the interference correction routine by analyzing interference check standards after instrument optimization and before analyzing samples. Section 4.2.9 recommends verifying interelement corrections daily with interference check solutions but does not specify when during the run. Section 4.2.8 explains how to identify if a correction routine is not operating properly and recommends analyzing interference check solutions more than once to confirm a correction factor change has occurred.

When interelement corrections are not used, Section 4.2.10.2 recommends verifying the absence of interferences by analyzing an interference check solution on a continuing basis. The method does not specify the definition of “continuing basis”; however, the industry standard is generally to bracket sample results with good QC, so it seems appropriate to at least analyze the interference check solution at the beginning of the batch and again at the end of the batch. Of course, some instruments are more drift-prone and more frequent interference check solution analyses may have to be performed.

Decay equation for Radium-228 in SW-846 Method 9320.

I was recently recalculating laboratory results for Ra‐228 from a laboratory using a slightly modified version of 9320, using the calculation on page 5. Using this equation, I was not able to duplicate the results that the laboratory reported. However, when I multiplied the t1 and t3 time by the decay constant, I was able to duplicate the results.

The equation in older versions of SW-846 Method 9320 is misprinted. The error has been fixed in the Update V version of the method, "Method 9320: Radium 228, part of Test Methods for Evaluating Solid Waste, Physical/Chemical Methods". Any decay equation requires the incorporation of the decay constant, lambda, which is ln2/half-life.

Other categories: 9000 Series, General

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Last updated on October 24, 2024