ASTM D8469-22

Standard Test Method for Analysis of Multiple Elements in Cannabis Matrices by Inductively Coupled Plasma Mass Spectrometry (ICP-MS)

SIGNIFICANCE AND USE
5.1 Medical and/or recreational marijuana (cannabis) has been legalized for adult use in many countries and states within the USA (5). Many jurisdictions that permit the use of medicinal and recreational marijuana require testing of cannabis and associated products to ensure safety from contaminants, especially the toxic “big four” elements such as As, Cd, Hg, and Pb (6), and other metals worthy of consideration (6). These heavy metals can accumulate in plants grown in polluted soils or contamination can occur during the manufacturing process (7). In addition to ensuring product safety, the analysis of mineral and other trace elements is required for labeling purposes when these products are sold as nutritional supplements. Trace element analysis of plant and nutritional supplement materials is a well-established application (8). Following acidic digestion to break down the plant-based samples' primary components, ICP-MS is often used for quantitative analysis because of its multi-element capability, high sensitivity, speed, robustness, and wide dynamic range.  
5.2 This test method covers the rapid determination of multiple elements in cannabis sample digests. The elements include the priority toxic elements (As, Cd, Hg, and Pb), as well as elements required by some states and elements of interest in the cannabis community (V, Cr, Cu, Zn, Sb, Ba, Se, Ag, Na, Al, K, Mn, Fe, Co, Ni, Mo, Tl, Th, and U). Irrespective of the number of elements being measured, test times are approximately a few minutes per test specimen, and detectability for most elements is in the low- to sub-ppb range.
SCOPE
1.1 This test method uses inductively coupled plasma mass spectrometry (ICP-MS) to determine multiple trace elements in cannabis and cannabis-related matrices following sample preparation using microwave-assisted acid digestion. This test method is applicable to the quantification of trace levels of elements in dried plant materials, concentrates, oils, extracts, tinctures of cannabis and cannabis-related products. Other matrices may be added provided that the lab validates the extra matrices using Practice D8282. Details are provided on the validation of both the sample preparation procedure and analytical method using certified reference materials (CRMs) and validation of the analytical method using spike recovery testing of several cannabis based samples.  
1.2 This test method should be used by analysts experienced in the use of microwave digestion and ICP-MS, matrix interferences, and procedures for their correction or reduction, and should only be used by personnel trained in the handling, preparation, and analysis of samples for the determination of trace elements in cannabis and cannabis products (1).2 This test method was developed using a single quadrupole ICP-MS equipped with a collision/reaction cell (CRC) that can be pressurized with helium (He) gas for the removal of polyatomic interferences using kinetic energy discrimination (KED). This test method can also be run using a triple quadrupole or “tandem” mass spectrometer (MS/MS) ICP-MS instrument, which is fitted with CRC technology. The ICP-MS method accounts for polyatomic interferences, which are the most common spectral overlaps in ICP-MS, isobaric interferences, and any potential doubly-charged ion interferences (M2+) that may arise from the presence of rare earth elements (REEs) in the samples, as the REE2+ ion interferences can affect the accuracy of the measurement of arsenic (As) and selenium (Se) in the samples. Table 1 lists elements for which the test method applies along with recommended analytical masses, and secondary masses for some elements. The priority toxic elements arsenic (As), cadmium (Cd), mercury (Hg), and lead (Pb), also sometimes referred to as the “big four” toxic trace elements are listed separately because of their toxicity, as discussed in 5.1.  
1.3 Certified reference materials (CRMs) should be matrix matc...

General Information

• Status: Published
• Publication Date: 31-Jul-2022
• ICS: 11.120.99 - Other standards related to pharmaceutics
• ICS: 65.020.20 - Plant growing
• Technical Committee: D37 - Cannabis
• Drafting Committee: D37.03 - Laboratory

Relations

• Refers: ASTM D8282-19 - Standard Practice for Laboratory Test Method Validation and Method Development
• Effective Date: 01-Sep-2019
• Refers: ASTM E177-14 - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-May-2014
• Refers: ASTM E691-13 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-May-2013
• Refers: ASTM E177-13 - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-May-2013
• Refers: ASTM E691-11 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-Nov-2011
• Refers: ASTM E177-10 - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-Oct-2010
• Refers: ASTM E177-08 - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-Oct-2008
• Refers: ASTM E691-08 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-Oct-2008
• Refers: ASTM E177-06b - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 15-Nov-2006
• Refers: ASTM E177-06a - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-Nov-2006
• Refers: ASTM D1193-06 - Standard Specification for Reagent Water
• Effective Date: 01-Mar-2006
• Refers: ASTM E691-05 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-Nov-2005
• Refers: ASTM E177-04 - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-Nov-2004
• Refers: ASTM E177-04e1 - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-Nov-2004
• Refers: ASTM E177-06 - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-Nov-2004

Overview

ASTM D8469-22 is an international standard developed by ASTM for the rapid determination of multiple elements in cannabis and cannabis-related matrices using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). This method addresses the need for safety and quality assurance in cannabis products, especially as the legalization and medicinal use of cannabis expand globally. ICP-MS offers high sensitivity and the ability to measure a wide range of elements simultaneously, providing accurate analysis for regulatory compliance, consumer safety, and product labeling.

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Key Topics

• Scope of Analysis
  The standard specifies a test method for quantifying trace elements in various forms of cannabis, including dried plant material, concentrates, oils, extracts, tinctures, and other cannabis-related products.

• Elements Covered
  Analysis focuses on the "big four" toxic elements (arsenic, cadmium, mercury, and lead) frequently regulated due to their health risks, as well as other elements such as vanadium, chromium, copper, zinc, antimony, barium, selenium, silver, sodium, aluminum, potassium, manganese, iron, cobalt, nickel, molybdenum, thallium, thorium, and uranium.

• Sample Preparation
  Method uses microwave-assisted acid digestion to break down complex cannabis matrices before ICP-MS analysis.

• Interferences and Accuracy
  The standard addresses and mitigates common analytical interferences (polyatomic, isobaric, and physical) using collision/reaction cell (CRC) technology and internal standards to ensure accurate trace element measurement.

• Validation and Quality Assurance
  Results are validated using certified reference materials (CRMs) and spike recovery testing. The method is intended for use by experienced analysts familiar with sample preparation and ICP-MS instrumentation.

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Applications

• Regulatory Compliance and Public Safety
  Supports laboratories and manufacturers in meeting state, federal, and international regulatory requirements for heavy metals and contaminants in cannabis products.

• Nutritional Supplement Labeling
  Used for the quantification of minerals and trace elements in cannabis-derived products sold as nutritional supplements, ensuring accurate product labeling.

• Quality Control in Manufacturing
  Assures product consistency and consumer safety by detecting contamination from soil, water, or processing environments.

• Research and Product Development
  Enables detailed profiling of elemental content in cannabis for research, cultivar development, and health risk assessment studies.

• Versatile Matrix Analysis
  Method allows for future expansion to other product matrices, so long as additional validation is performed as per referenced laboratory practices.

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Related Standards

• ASTM D8270 – Terminology Relating to Cannabis
  Defines key terms used in cannabis testing and analysis.

• ASTM D8282 – Practice for Laboratory Test Method Validation and Method Development
  Guidance for validating additional matrices and ensuring laboratory best practices.

• ASTM D1193 – Specification for Reagent Water
  Specifies water quality for reagent preparation.

• EPA Methods 200.8 and 6020B
  Widely used methods for elemental analysis by ICP-MS in environmental samples.

• FDA EAM 2.2
  Guidance on food homogenization relevant for cannabis sample preparation.

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Keywords: ASTM D8469-22, cannabis testing, ICP-MS, heavy metals, trace elements, cannabis matrices, product safety, regulatory compliance, certified reference materials, microwave-assisted digestion, collision/reaction cell, cannabis industry standards, laboratory best practices

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Practical Value:
ASTM D8469-22 provides a standardized, validated approach for laboratories and manufacturers to accurately and efficiently quantify elemental contaminants and nutrients in cannabis products, supporting consumer safety, regulatory adherence, and quality control across the expanding global cannabis market.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D8469 − 22
Standard Test Method for
Analysis of Multiple Elements in Cannabis Matrices by
Inductively Coupled Plasma Mass Spectrometry (ICP-MS)
This standard is issued under the fixed designation D8469; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope masses, and secondary masses for some elements.The priority
toxicelementsarsenic(As),cadmium(Cd),mercury(Hg),and
1.1 This test method uses inductively coupled plasma mass
lead (Pb), also sometimes referred to as the “big four” toxic
spectrometry(ICP-MS)todeterminemultipletraceelementsin
trace elements are listed separately because of their toxicity, as
cannabis and cannabis-related matrices following sample
discussed in 5.1.
preparation using microwave-assisted acid digestion. This test
method is applicable to the quantification of trace levels of
1.3 Certified reference materials (CRMs) should be matrix
elements in dried plant materials, concentrates, oils, extracts,
matched as closely as possible to the cannabis/plant matrix.
tinctures of cannabis and cannabis-related products. Other
In-house reference materials (RMs) are acceptable if no CRM
matricesmaybeaddedprovidedthatthelabvalidatestheextra
is available and/or the in-house RM is well characterized, but
matrices using Practice D8282. Details are provided on the
CRMs are preferred. NIST 1575a Pine Needles, NRC
validation of both the sample preparation procedure and
HEMP-1, and a NIST hemp sample (NIST number not
analytical method using certified reference materials (CRMs)
assigned yet) were analyzed to verify method bias. The
and validation of the analytical method using spike recovery
RM/CRMs should have a recovery between 80% to 120 %
testing of several cannabis based samples.
when concentrations are above the limit of quantification
(LOD) or within the concentration uncertainty (converted to
1.2 Thistestmethodshouldbeusedbyanalystsexperienced
in the use of microwave digestion and ICP-MS, matrix percent relative uncertainty) supplied on the certificate, which-
ever is greater. If acceptable values are not obtained, the
interferences, and procedures for their correction or reduction,
and should only be used by personnel trained in the handling, analytical solution may be reanalyzed once. If acceptability is
still not met, recalibrate and reanalyze the entire analytical
preparation, and analysis of samples for the determination of
traceelementsincannabisandcannabisproducts (1). Thistest sequence and/or prepare and digest new analytical portions.
method was developed using a single quadrupole ICP-MS
1.4 Multi-laboratory Validation (MLV)—This test method
equipped with a collision/reaction cell (CRC) that can be
was tested by analyzing an NRC hemp CRM, a NIST hemp
pressurized with helium (He) gas for the removal of poly-
SRM, and a NIST plant control sample (NIST 1575a Pine
atomic interferences using kinetic energy discrimination
Needles)byfourlaboratorieseachrunningasinglequadrupole
(KED). This test method can also be run using a triple
ICP-MS.
quadrupole or “tandem” mass spectrometer (MS/MS) ICP-MS
instrument, which is fitted with CRC technology.The ICP-MS
1.5 Gravimetric dilution (weight/weight), volumetric dilu-
method accounts for polyatomic interferences, which are the
tion (volume/volume), or a combination of the two techniques
most common spectral overlaps in ICP-MS, isobaric
(weight/volume) are acceptable methods for ICP-MS sample
interferences, and any potential doubly-charged ion interfer-
preparation.
2+
ences (M ) that may arise from the presence of rare earth
2+ 1.6 Units—The values stated in SI units are to be regarded
elements(REEs)inthesamples,astheREE ioninterferences
as the standard. No other units of measurement are included in
canaffecttheaccuracyofthemeasurementofarsenic(As)and
this standard.
selenium (Se) in the samples. Table 1 lists elements for which
the test method applies along with recommended analytical
1.7 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
This test method is under the jurisdiction of ASTM Committee D37 on
Cannabis and is the direct responsibility of Subcommittee D37.03 on Laboratory. mine the applicability of regulatory limitations prior to use.
Current edition approved Aug. 1, 2022. Published October 2022. DOI: 10.1520/
1.8 This international standard was developed in accor-
D8469-22.
dance with internationally recognized principles on standard-
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
this standard. ization established in the Decision on Principles for the
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D8469 − 22
TABLE 1 Recommended Masses for Each Element and Some
3.2.2 calibration blank (CalBK), n—volume of Type 1
Secondary Masses
reagent water containing the same amount of acid matrix as is
Recommended Secondary Analytical
in the calibration standards.
Priority Elements
Analytical Mass Masses
Arsenic (As) 75 . 3.2.3 calibration standards (CalSTD), n—a standard having
Cadmium (Cd) 111 114
an accepted value (reference value) for use in calibrating a
A
Lead (Pb) 208 .
measurement instrument or system.
Mercury (Hg) 201 200, 202
Recommended
3.2.4 calibration stock solution, n—solution prepared from
Other Elements
Analytical Mass
thestockstandardsolution(s)toverifytheinstrumentresponse
Sodium (Na) 23 .
Aluminum (Al) 27 .
with respect to analyte concentration.
Potassium (K) 39 .
3.2.5 cannabidiol (CBD), n—acannabinoidfoundincanna-
Vanadium (V) 51 .
Chromium (Cr) 52 53
bis plants.
Manganese (Mn) 55 .
3.2.6 collision/reaction cell (CRC), n—device used to re-
Iron (Fe) 56 54
Cobalt (Co) 59 .
move polyatomic interfering ions through reaction or collision
Nickel (Ni) 60 58, 62
with a gas added to the cell.
Copper (Cu) 63 65
Zinc (Zn) 66 67, 68
3.2.7 interlaboratory study (ILS) or multi lab validation
Selenium (Se) 78 77, 80
(MLV), n—study in which collaborators in multiple laborato-
Molybdenum (Mo) 95 98
ries use a defined method of analysis to analyze identical
Silver (Ag) 107 .
Antimony (Sb) 121 .
portions of homogeneous materials to assess the performance
Barium (Ba) 137 .
characteristics obtained for that method of analysis.
Thallium (Tl) 205 .
Thorium (Th) 232 .
3.2.8 internal standard (ISTD), n—pure element(s), which
Uranium (U) 238 .
is not one of the analyte elements and is not present in the
A
Leadismeasuredasthesumofthethreemostabundantisotopes,206,207,and
sample, added in known amount(s) to a solution.
208: (208) = M(206) + M(207) + M(208).
3.2.9 laboratory duplicate (DUP), n—two aliquots of the
same sample taken in the laboratory and analyzed separately
with identical procedures; analyses of laboratory duplicate 1
and laboratory duplicate 2 indicate precision associated with
Development of International Standards, Guides and Recom-
laboratory procedures, but not with sample collection,
mendations issued by the World Trade Organization Technical
preservation, or storage procedures.
Barriers to Trade (TBT) Committee.
3.2.10 limit of detection (LOD), n—the minimum concen-
2. Referenced Documents tration of an analyte that can be identified, measured, and
reportedwith99%confidencethattheanalyteconcentrationis
2.1 ASTM Standards:
greater than zero.
D1193Specification for Reagent Water
D8270Terminology Relating to Cannabis 3.2.11 method blank (MBK), n—use 0.5 g Type 1 water for
method blanks.
D8282Practice for Laboratory Test Method Validation and
Method Development
3.2.12 relative standard deviation (RSD), n—themeasureof
E177Practice for Use of the Terms Precision and Bias in
deviation of the measured analytical concentrations around the
ASTM Test Methods
mean—used to express the precision of the results.
E691Practice for Conducting an Interlaboratory Study to
3.2.13 spike solution, n—an aliquot of cannabis sample to
Determine the Precision of a Test Method
which known quantities of the method analytes are added in
2.2 Other Standards:
order to check if the sample matrix contributes bias to the
U.S. Environmental Protection Agency (EPA) standard
analytical results; the background concentrations of the ana-
methods 200.8 and 6020B (2, 3)
lytes in the sample matrix must be determined in a separate
FDA EAM 2.2Food Homogenization (4)
aliquotandthemeasuredvaluesinthespikedsamplecorrected
for background concentrations—see 14.2.
3. Terminology
3.2.14 tuning solution, n—a solution which is used to
3.1 For definitions of terms related to cannabis, see Termi-
determine acceptable instrument performance before calibra-
nology D8270.
tion and sample analyses—see 13.1.
3.2 Definitions:
3.2.1 analytical solution, n—a cannabis sample that has 4. Summary of Test Method
been prepared for analysis per 11.3.
4.1 This test method describes the multi-element determi-
nation of multiple trace elements by ICP-MS in cannabis and
cannabis-based samples and matrices. The digested sample is
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
introduced into the ICP (plasma) as an aerosol by passing the
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
liquid sample through a simple pneumatic nebulizer. The
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. largest aerosol droplets are removed from the gas stream by a
D8469 − 22
spray chamber, and about 2% to 3 % of the remaining smaller nutritional supplement materials is a well-established applica-
dropletsaresweptintothecentralchanneloftheplasmaviathe tion (8). Following acidic digestion to break down the plant-
torch. It is recommended to use a thermoelectric (Peltier)
basedsamples’primarycomponents,ICP-MSisoftenusedfor
cooledspraychambertoreducesignaldriftcausedbylocalized quantitative analysis because of its multi-element capability,
temperature change. A cooled spray chamber also reduces the
high sensitivity, speed, robustness, and wide dynamic range.
water vapor content of the aerosol, resulting in a hotter plasma
5.2 This test method covers the rapid determination of
and so improving matrix tolerance, increasing ionization,
multiple elements in cannabis sample digests. The elements
reducing suppression, and reducing formation of oxides and
include the priority toxic elements (As, Cd, Hg, and Pb), as
other matrix based polyatomic ion overlaps. The sample
well as elements required by some states and elements of
aerosol enters the plasma, which is generated in a stream of
interest in the cannabis community (V, Cr, Cu, Zn, Sb, Ba, Se,
argoncontainedinatorch.Thetorchissurroundedbyacoilor
Ag,Na,Al,K,Mn,Fe,Co,Ni,Mo,Tl,Th,andU).Irrespective
plate to transfer RF energy into the plasma. The argon plasma
of the number of elements being measured, test times are
temperature (up to 10000 K maximum and around 7500 K in
approximatelyafewminutespertestspecimen,anddetectabil-
the central channel) rapidly dries the aerosol droplets, which
ity for most elements is in the low- to sub-ppb range.
are then decomposed, vaporized, atomized, and ionized by the
removal of one electron from each atom. The positively
6. Interferences
charged ions that are produced in the plasma are extracted into
the vacuum system via a series of interface cones.To maintain
6.1 Spectral Interferences—Polyatomic ions that have the
the high vacuum around the mass spectrometer, the orifices of
same m/z as an analyte ion are the main source of spectral
the cones are small, typically 1mm diameter or less. An ion
interferences in ICP-MS.Alist of typical polyatomic ions that
focusing system or “lens” is used to focus the ions into the
are derived from the plasma gas (Ar), reagents, or sample
entrance aperture of a quadrupole mass spectrometer (MS).
matrix is shown in Table 2. If a high plasma temperature is
The quadrupole uses a combination of DC (direct current) and
maintained, the level of many polyatomic interferences will be
AC (alternating current) electrical fields to separate the ions
reduced. The robustness of the plasma can be determined by
based on their mass-to-charge ratio (m/z). The electron multi-
measuring the CeO/Ce ratio. The oxide ratio shows the
plier (EM) detector detects each ion as it exits the quadrupole.
plasma’s ability to break apart the Ce-O molecule. Since the
+
Singly charged ions (M ) with an m/z equal to the ion’s mass
Ce-O molecule is strongly bound, it is a good indicator of
aredetectedbytheEMdetector.Thedetectorelectronicscount
decomposition of the sample matrix and other molecular ions.
and store the total signal for each mass (m/z), creating a mass
+ +
Comparing the signal for CeO at m/z 156 to Ce at m/z 140
spectrum.
allows a quick assessment of the plasma’s capability to
4.2 Aweighed portion (approximately 0.5g is typical) of a
decompose the matrix. A more robust plasma (lower CeO/Ce
thoroughly homogenized cannabis sample is digested using a
ratio) is beneficial for analyzing the high and variable matrix
mixture of HNO and HCl using closed-vessel digestion
3 levels encountered in typical batches of cannabis samples.The
apparatus. The digests are then diluted using Type 1 reagent
typical CeO/Ce ratio that can be achieved varies for different
waterto50g.BlanksandCRMsarepreparedinthesameway.
ICP-MS designs, but operators should be aware of the analyti-
Internal standards are added to the solutions to compensate for
cal benefits of better matrix tolerance, higher ionization, and
variations in sample introduction efficiency and element ion-
lower levels of polyatomic interferences that are provided by
ization efficiency in the plasma. The solutions are typically
optimizingtoalowerCeO/Ceratio,ideallyascloseaspossible
introduced to the ICP-MS instrument via an autosampler. By
to 1%. Often polyatomic ion interferences can be avoided by
comparing measured m/z peak intensities of elements in the
the selection of an alternative analytical isotope. If that is not
sample with m/z peak intensities measured with the calibration
appropriate, some ICP-MS systems provide a simple and
standards, the concentrations of elements in the sample can be
reliable solution to resolve common polyatomic interferences
calculated.
using a CRC that is operated in helium collision mode, often
referred to as He mode. He mode uses KED to filter out
5. Significance and Use
polyatomicionswhileallowingatomicionstopassthroughthe
cell to the detector. KED is a physical process that makes use
5.1 Medical and/or recreational marijuana (cannabis) has
of the fact that polyatomic (molecular) ions have a larger ionic
beenlegalizedforadultuseinmanycountriesandstateswithin
cross-sectionthantheatomicionsatthesame m/z.Duetotheir
the USA (5). Many jurisdictions that permit the use of
larger size, the polyatomic ions collide more frequently with
medicinal and recreational marijuana require testing of canna-
the helium cell gas, and so lose more energy than the (smaller)
bis and associated products to ensure safety from
analyte ions do. Because of their greater energy loss during
contaminants, especially the toxic “big four” elements such as
As, Cd, Hg, and Pb (6), and other metals worthy of consider- passage through the cell, the polyatomic ions can be rejected
using a bias voltage at the cell exit. He mode is effective for
ation (6). These heavy metals can accumulate in plants grown
in polluted soils or contamination can occur during the many polyatomic ion overlaps, so it works for many elements,
anditcanbeappliedtoawiderangeoftypicalICP-MSsample
manufacturing process (7). In addition to ensuring product
safety, the analysis of mineral and other trace elements is types, even varied samples with complex and unknown matri-
ces. Common, matrix-based polyatomic interferences are
required for labeling purposes when these products are sold as
nutritional supplements. Trace element analysis of plant and removed, allowing access to the preferred isotopes of all
D8469 − 22
TABLE 2 Common Polyatomic and Potential Elemental Interferences in Typical Cannabis Matrix Samples
Priority Analytes Polyatomic Interferences Elemental Interferences
75 40 34 40 35 150 ++ 150 ++
As Ar SH, Ar Cl, Sm , Nd
40 35 37
Ca Cl, Cl H
111 95 16 94 16
Cd Mo O, Zr OH .
206, 207, 208 190 16 191 16 192 16
Pb Pt O, Ir O, Pt O .
Hg . .
Other Analytes Polyatomic Interferences Elemental Interferences
23 7 16 46 ++
Na Li O Ti
27 12 15 13 14 12 14
Al C N, C N, H C N .
39 38 78 ++
K ArH Se
51 35 16 37 l14 34 16
V Cl O, C N, S OH .
52 36 16 40 12 35 16 37 14 34 18
Cr Ar O, Ar C, Cl OH, Cl NH, S O .
55 37 18 23 32 23 31 110 ++
Mn Cl O, Na S, Na PH Cd
56 40 16 40 16 112 ++
Fe Ar O, Ca O Cd
59 40 18 43 16 23 35 118 ++
Co Ar OH, Ca O, Na ClH Sn
60 44 16 23 37 120 ++ 120 ++
Ni Ca O, Na Cl Sn , Te
63 40 23 12 16 35 12 14 37 31 32 126 ++ 126 ++
Cu Ar Na, C O Cl, C N Cl, P S, Te , Xe
31 16
P O
66 34 16 32 34 33 48 18 132 ++ 132 ++
Zn S O , S S, S , Ca O Xe , Ba
2 2
78 40 38 62 16 78 156 ++ 156 ++
Se Ar Ar, Ni O Kr, Gd , Dy
95 40 39 16 79 16
Mo Ar K O, Br O .
107 91 16
Ag Zr O .
121 105 16
Sb Pd O .
137 97 40
Ba Mo Ar .
Tl . .
Th . .
238 201 37
U Hg Cl .
150 ++
typical analytes. He mode also removes the common poly- ion interference from the REE, samarium ( Sm ) and
150 ++
atomic overlaps on secondary isotopes. Measuring secondary neodymium ( Nd ). Other examples of potential elemental
isotopes can be used to confirm the result reported using the interferences are listed in Table 2. Some instrument manufac-
primary isotope. For severe background interferences, a reac- turer’s software includes an automatic software routine to
tive cell gas may be suitable as an alternative to He collision correct for doubly-charged ion interferences.The same correc-
mode. However, reactive cell gases need to be treated with tion can be set up manually, following manufacturer guide-
caution on single quadrupole ICP-MS, as their use can lead to lines.
analyte signal loss, and the creation of unpredictable new
6.3 Physical Interferences—Physical interferences occur
cell-formed product ion overlaps, unless the CRC mass stabil-
during sample introduction, processes in the plasma, and the
ity boundaries and reactive gas flows are optimized correctly.
transmission of ions through the instrument’s interface and
But a reaction gas may give more complete removal of certain
may lead to differences in instrument responses for the sample
predictable and consistent interferences, such as Ar on Se at
and the calibration standards. Physical interferences can occur
mass 78 and 80. Correction equations within ICP-MS instru-
when the viscosity and surface tension of a sample solution is
ment software can also be used to correct for polyatomic
different compared to the low matrix, synthetic calibration
interferences, although they can be less reliable than using a
standards. The difference can cause variation in the solution
CRC in KED/He mode of operation. Interference equations
flow through the uptake tubing, the nebulization (aerosol
involve determining the signal for another isotope of the
droplet formation) process, and the transport and evaporation
interferingelementandsubtractingtheappropriatesignalfrom
rate of the aerosol droplets. These variations lead to a change
the analyte isotope signal.
in the overall transport of aerosol droplets to the plasma and
6.2 Isobaric Molecular and Doubly-charged Ion therefore a change in the overall signal. Since these effects
Interferences—Isobaric molecular and doubly-charged ion in- influence all elements the same, internal standard correction
terferencescanaffectICP-MSmeasurementsofsomeanalytes, can be used to effectively compensate for the signal differ-
as shown in Table 2. Isobaric overlaps occur when an analyte ences. If samples contain high levels of total dissolved solids
is measured at an isotope mass where an isotope of a different (TDS) and the plasma is not optimized for good robustness,
element is also present. Most isobaric interferences that could undissociated sample matrix material may deposit on the
affect ICP-MS determinations have been well studied in the interface cones, affecting ion transmission. Typically, for ICP-
literature and are not unique to this method (1, 2). These MS, it is advised that TDS should not exceed 0.2 % (w/v), so
overlaps are easy to avoid by choosing the default, preferred samples that contain higher TDS levels would typically be
analyticalisotopeforeachelementofinterest.Doubly-charged diluted before being analyzed. However, instruments that are
ions can affect quadrupole ICP-MS measurements because a equipped with aerosol dilution technology use an additional
quadrupole mass spectrometer separates ions based on their argon gas flow to dilute the aerosol before it reaches the torch.
m/z,ratherthantheirtrueatomicmass.So,ifanatomlosestwo This technology enables samples with percent levelTDS to be
2+
electrons—givingitadouble-positivecharge(M )ratherthan analyzed routinely by ICP-MS over extended periods of time.
+
the usual single-positive charge (M ), it will appear at half its Internalstandardizationorstandardadditionmaybeeffectively
true mass. For example, arsenic can suffer a doubly-charged used to compensate for many physical interference effects and
D8469 − 22
long term drift. Internal standards should have similar analyti- 8. Reagents and Materials
cal behavior to the elements being determined.
8.1 Purity of reagents—Reagent grade chemicals shall be
6.4 Memory Interferences—To minimize carryover of iso-
used in all tests. Unless otherwise indicated, it is intended that
topes of elements in one sample contributing to the signals of
all reagents shall conform to the specifications of the commit-
subsequent samples, ensure that the elements are stabilized in
tee onAnalytical Reagents of theAmerican Chemical Society,
solution (for example, by adding HCl) and flush the system
where such specifications are available (9). Other grades may
with a rinse blank(s) between samples. Blanks should be
be used, provided it is pure enough to be used without
analyzed periodically to check that they are free from memory
lessening the accuracy of the determination.
effects. The possibility of memory effects should be
8.2 Purity of water—Unless otherwise indicated, references
acknowledged, and suitable rinse times should be employed.
to water shall be understood to mean reagent water as defined
The required rinse time for a particular element varies and
by Type 1 of Specification D1193.
should be determined before the analysis. This can be done by
8.3 Purity of acids—Trace metal grade or better chemicals
aspirating the highest calibration standard containing the ele-
of nitric acid and hydrochloric acid should be used for
mentsofinterestforanormalsampleanalysisperiod,followed
microwave digestion and preparing diluted acid for sample
by analysis of the rinse blank multiple times afterwards.Track
preparation and analysis.
the rinse blank for any carry-over. The length of time required
toreduceanalytesignalstowithinafactorof10ofthelimitof
8.4 Diluent—Made with 1 % (v/v) HNO /0.5 % (v/v) HCl
detection should be noted. If available, an intelligent rinse
solution in Type 1 water.
function can be used to optimize rinse times by monitoring the
8.5 ICP-MS tuning, calibration, and internal standards—
elemental signals and terminating the rinse step early if the
The stock standards used for tuning and calibrating the
monitored element signals fall below a set threshold. If the
ICP-MS, and the internal standard solution used for the
analytical solution concentrations are higher than the highest
preparation of the samples are detailed in Table 3.
standard concentration, dilute the analytical solution. The new
8.5.1 Blank solutions—Prepare calibration blank (1 %
concentration should ideally be at the midpoint of the calibra-
HNO /0.5 % HCl inASTMType 1Water or2%HNO /0.5 %
3 3
tion curve for that element. If the concentration of the injected
HCl in ASTM Type 1 Water) and a rinse blank (same
unknown sample is higher than the highest calibration
composition as calibration blank) solutions on the same day as
standard, then check all samples following that high sample.
analysis.
Make sure to check for carry-over by checking the RSD of
8.5.1.1 Method blanks (MBK)—A minimum of two MBKs
replicate concentrations of all samples following the sample
must be included in each digestion batch to verify the absence
that was higher than the highest calibration curve. If RSD
of contamination that may arise from the vessels.
exceeds 10 %, determine if it is due to carry-over and remedy
before proceeding.
Reagent Chemicals, American Chemical Society Specifications, American
7. Apparatus
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
7.1 Balance—Toploadingoranalytical,withautomatictare,
listed by the American Chemical Society, see Analar Standards for Laboratory
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
capable of weighing to 0.0001g, with sufficient capacity to
and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
weigh prepared solutions.
MD.
7.2 Volumetric tubes—Forvolumetricdilution,use15mLor
50mLtubesthatareclassAcalibrated,sothevolumemarkcan
TABLE 3 Solutions Used in Method Development
be used for final dilution in the vials.
Solution Elements
7.3 Inductively coupled plasma mass spectrometer (ICP-
Initial Calibration Verification 10 µg/mL of Ag, Al, As, Ba, Be, Cd,
Standard (Second source Co, Cr, Cu, Mn, Mo, Ni, Pb, Sb, Se,
MS)—The ICP-MS must be capable of scanning m/z range 5µ
standard from the Environmental Tl, V, Zn, Th, U;
to 240µ with a minimum resolution better than 0.5 µ at 10 %
Calibration Standard) 1000 µg/mL of Fe, K, Ca, Na, Mg, Sr
peak height. The ICP-MS should be equipped with a CRC or
Environmental Spike Mix 100 µg/mLAg, Al, As, Ba, Be, Cd, Co,
equivalent that provides consistent and reliable control of
Cr, Cu, Mn, Mo, Ni, Pb, Sb, Se, Tl, V,
typical polyatomic ion overlaps. In many routine applications,
Zn, U.
the CRC is pressurized with helium, acting as a collision gas.
1000 µg/mL Fe, K, Ca, Na, Mg
Polyatomic overlaps on analyte ions are removed through the
Environmental Calibration 10 µg/mL of Ag, Al, As, Ba, Be, Cd,
physical process of KED. On single quadrupole ICP-MS
Standard Co, Cr, Cu, Mn, Mo, Ni, Pb, Sb, Se,
instruments, reactive cell gases may be suitable for addressing
Tl, V, Zn, Th, U;
1000 µg/mL of Fe, K, Ca, Na, Mg
some spectral overlaps. See manufacturers’ instruction manual
for operation of the ICP-MS.
Internal Standard 100 µg/mL of Li, Sc, Ge, Lu, In, Tb,
7.3.1 The instrument should be configured with a typical Rh, Bi
sampleintroductionsystemsuchasanebulizer,spraychamber,
Tuning Stock Solution 10 µg/mL of Li, Co, Ce, Y, Tl
quartz torch, and interface cones. Sample uptake and introduc-
tion to the ICP-MS is done with a peristaltic pump. Mercury (Hg) 1000 µg/mL of Hg
7.4 Microwave digestion system—A microwave capable of
Hg Calibration Solution 10 µg/mL of Hg
reaching 210 °C should be used.
D8469 − 22
8.5.2 Calibration standard solutions—Prepare these weekly 8.5.4.6 Laboratory duplicates (DUP)—Select a sample
in a 50-mL polypropylene centrifuge tube: Working Environ- from the batch to be analyzed. Remove two 15 mLaliquots of
thesamplesolutionandplaceeachaliquotinaseparate50mL
mental Calibration Standard: 1 mg/LAg, Al, As, Ba, Be, Cd,
polypropylene test tube.
Co,Cr,Cu,Mn,Mo,Ni,Pb,Sb,Se,Tl,V,Zn,Th,U.100mg/L
Fe, K, Ca, Na, Mg in 1 % (v/v) HNO and 0.5 % (v/v) HCl 8.5.4.7 Spike solution—Prepare the spike solutions and add
to the chosen cannabis samples before closed-vessel micro-
solution. Add 5 mL of Environmental Calibration Standard to
wave digestion. Prepare the standards on the same day as
45 mL of 1 % (v/v) HNO and 0.5 % (v/v) HCl solution.
sample digestion. One spiked analytical solution per sample
Mercury (Hg) Stock Calibration StandardA: 10 mg/LHg in 1
type is recommended.
%(v/v)HNO and0.5%(v/v)HClsolution.Preparebyadding
8.5.4.8 Mercury (Hg) Spike Stock Solution A—100mg/LHg
0.5 mL of 1000 µg/mL Hg Standard to 49.5 mL of 1 % (v/v)
in 1% (v/v) HNO solution. Prepare by adding 5 mL of 1000
HNO and 0.5 % (v/v) HCl solution. Mercury (Hg) Working
mg/LHgStandardto45mLof2%(v/v)HNO solutionina50
SolutionA: 0.1 mg/Lin 1 % (v/v) HNO and 0.5 % (v/v) HCl
mL polypropylene test tube. The Hg spike stock solution is
solution. Prepare by adding 0.5 mL of Hg Stock Calibration
preparedwithoutHClandshouldthereforebefreshlyprepared
StandardA(see previous text) to 49.5 mL of 1 % (v/v) HNO
each month or more frequently if the stability of the standard
and 0.5 % (v/v) HCl solution.
cannot be confirmed.
8.5.3 Calibration standards—Prepare the multi-element
8.5.4.9 Working spike solution – High—1 mg/LAg,Al,As,
calibration standards listed in Section 12 from the calibration
Ba,Be,Cd,Co,Cr,Cu,Hg,Mn,Mo,Ni,Pb,Sb,Se,Tl,V,Zn,
stock solutions. Prepare the standards on the same day as
Th, U. 10 mg/L Fe, K, Ca, Na, Mg. in 2 % (v/v) HNO
sampleanalysis,makeeachstandardina50mLpolypropylene
solution. Prepare by adding 0.5 mL of Environmental Spike
centrifuge tube.
Mix and 0.5 mLof Hg Spike SolutionA(see above) to 49 mL
8.5.4 Internal standard and QC standards—Prepare the
of 2 % (v/v) HNO solution in a 50 mL polypropylene test
following standard solutions and sample solutions in 50 mL
tube.
polypropylene centrifuge tubes:
8.5.4.10 Working spike solution – Low—100 µg/L Ag, Al,
8.5.4.1 Internal standard (ISTD) working solution for on- As,Ba,Be,Cd,Co,Cr,Cu,Hg,Mn,Mo,Ni,Pb,Sb,Se,Tl,V,
line addition—2 mg/L Li, Sc, Ge, Lu, In, Tb, Rh, Bi in 1 % Zn, Th, U. 0.1 mg/L Fe, K, Ca, Na, Mg. in 2 % (v/v) HNO
solution. Prepare by adding 5 mLofWorking Spike Solution –
HNO .Preparebyadding1mLofInternalStandardMixto49
High(seeabove)to45mL2%(v/v)HNO solutionina50mL
mL of 1 % (v/v) HNO and 0.5 % (v/v) HCl solution. ISTD
polypropylene test tube.
solution may be prepared volumetrically.The exact concentra-
tion is less important than the same concentration over an
9. Hazards
entire analytical sequence.
8.5.4.2 Mercury (Hg) working solution B—1.0 mg/L Hg in
9.1 The use of laboratory equipment and chemicals exposes
1 % (v/v) HNO and 0.5 % (v/v) HCl solution. Prepare by
the analyst to several potential hazards. Good laboratory
technique and safety practices should be used at all times.
adding5.0mLof10µg/mLHgStandardto45mLof1%(v/v)
Safety glasses and acid resistant gloves should be worn at all
HNO and 0.5 % (v/v) HCl solution. Prepare independent
times when handling samples or reagents, or when near others
solutions from Working Hg Solution A. Use independent Hg
handling these items, especially when handling standards
standard from Hg Stock Calibration Standard A.
containing elements such as As, Cd, Hg, Pb, Cr, Cu, Zn, Sb,
8.5.4.3 Initial calibration verification (ICV) solution—0.05
Ba,Se,Ag,Na,Al,K,Mn,Fe,Co,Ni,Mo,Tl,Th,andU.Also,
mg/LAg,Al,As, Ba, Be, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Sb,
proper ventilation and other physical safeguards should be in
Se,Sr,Tl,V,Zn,Th,U.5mg/LFe,K,Ca,Na,Mg.0.001mg/L
place when handling these standards.Analysts should consult,
Hg in 1 % (v/v) HNO and 0.5 % (v/v) HCl solution. Prepare
and must be familiar with, their laboratory’s chemical hygiene
by adding 0.25 mL of Initial Calibration Verification Standard
and safety plan and Safety Data Sheets for all reagents and
and 0.05 mLof 1 mg/LWorking Hg Solution B to 49.7 mLof
standards listed.
1 % (v/v) HNO and 0.5 % (v/v) HCl solution. Prepare
9.2 ICP-MS instruments require a supply of argon gas that
independent solutions from the Continuing Calibration Verifi-
can be provided from compressed argon gas cylinders or
cation solution.
bottles, or from a liquid argon Dewar. Liquid argon represents
8.5.4.4 Continuing calibration verification (CCV)
a potential cryogenic and suffocation hazard and leaks from a
solution—Use a mid-level calibration standard (Std 5 in
compressed argon cylinder can also represent a suffocation
Section 12).
hazard. Safe handling procedures should be employed at all
8.5.4.5 Certified reference materials (CRM)—Add the de-
times when handling compressed gas cylinders, liquid argon
tailsoftheCRMyourlaboratoryhasselectedandfillintheQC
tanks, and fittings, and appropriate gas monitoring equipment
information in the ICP-MS software. Analyze at least one
should be installed in laboratories where such gases are stored
CRM sample such as NIST 1547a Peach Leaves, NIST 1573a
and used. Many ICP-MS instruments are fully interlocked to
Tomato Leaves, NIST 1575a Pine Needles, NRC HEMP-1, or
prevent user exposure to harmful electrical voltages, radio
NIST Hemp SRM (available in 2022). Digest them with the
frequency emissions, ultraviolet radiation, high temperatures,
other samples. andotherhazards.Theoperatorshouldneverattempttodisable
D8469 − 22
TABLE 5 Example ICP-MS Parameters
these interlocks or operate the instrument if any safety inter-
locks are suspected to have been disabled. Refer to instrument Parameter Value
manuals for safety precautions regarding use. RF power (W) 1600
Sampling depth (mm) 10
9.3 All additional company safety practices and procedures
Carrier gas (L/min) 0.80
Aerosol dilution gas (L/min) 0.15
should be followed at all times. Spilled samples and reagents
Aerosol dilution setting 4
should be cleaned up from instrument and laboratory surfaces
Helium cell gas (mL/min) 4.3
immediately. Acid spills should be neutralized with sodium
Energy discrimination (V) 3.0
bicarbonate solution before cleanup. The acidification of
samples containing reactive materials may result in the release
TABLE 6 Example Microwave Digestion Parameters
of toxic gases, such as cyanides or sulfides.Acidification (and
disposal) of samples should be done in a fume hood.
Example Digestion
Sample weight 0.5 g
HNO 9mL
10. Sampling, Test Specimens, and Test Units
HCl 1 mL
10.1 The method was developed and tested on the cannabis Oven Program
Ramp (to 210 °C) 20 min
and hemp samples listed in Table 4.
Hold (at 210 °C) 15 min
Cool down 10 min
10.2 Sample Homogenization—This test method assumes
Final Dilution
that all samples have been collected and homogenized accord-
Reagent water Add to 50 g
ingly per production batch size and physical form of the
Total dilution factor 100×
product. The aim of sample collection is to obtain a represen-
tative sample of the entire production batch while the aim of
homogenizationistoobtainananalyticalsamplerepresentative
of the collected sample. Follow state protocol for cannabis
sampling and homogenization, or refer to ASTM Committee
achieved. In most cases, a clear and colorless solution upon
D37 Sample Preparation Group documents (under develop-
dilution with no particulate constitutes a complete digestion.
ment)forreferenceonhomogenizationapproaches.Depending
Check for matrix enhancements and suppressions by monitor-
onthetypeofsample,thehomogenizationprocedureshouldbe
ingspikerecoverydataandbyexaminingtheinternalstandard
such that it provides uniform and repeatable results using
signal.
instrumentationthatiseasytocleanandmaintain,isadaptedto
holdvarioussamplesizes,and,preferably,thatismetalfree,to
12. Calibration and Standardization
reduce the risk of contamination of the sample.
12.1 The ICP-MS system should be calibrated using a
calibration blank and a minimum of four calibration standards
11. Preparation of Apparatus
using a linear curve fit. Up to seven multi-element standards
11.1 ICP-MS—Consult the manufacturer’s instructions for
wereusedinthistestmethod(Table7).Usingpipettestomake
operating the instrument.
calibration standards, and then recording the weights is com-
11.2 The ICP-MS operating parameters used for verifying
mon.
thismethodfortheanalysisofcannabisandhemp-matricesare
12.2 Calibration—At the beginning of the analysis of each
shown in Table 5. Optimal operating parameters for this test
batch of samples, perform a calibration consisting of the blank
method may vary by specific ICP-MS system models. The
and all calibration standards appropriate for the range. Use the
instrument used included a CRC operating in helium collision
CCV check standard to determine if each element is in
modeandaerosoldilutiontechnology.SeeSection13formore
calibration.WhentheresultsobtainedwiththeCCVarewithin
details.
10 % of the expected concentrations for all elements to be
11.3 Typical microwave digestion operating parameters
analyzed, proceed with test specimen analyses. Otherwise,
used for the preparation of cannabis and hemp-matrices are
make any adjustments to the instrument that are necessary and
shown in Table 6. Optimal operating parameters for this
repeat the calibration for those elements that failed the QC
method may vary by specific microwave digestion system
check. Repeat this procedure with the check standard every 10
models.Thesedigestionconditionswereoptimizedforbatches
to 20 samples.
of mixed samples of various degrees of decomposition diffi-
12.3 ICP-MS instruments use software that automatically
culty. If digesting only plant material, for example, less acid
performsthecalculationstoestablishthecalibrationcurve.See
volume may be used. When using less acid volume or lower
Section 15 for details of the calculations.
digestion temperatures, a complete digestion should still be
12.4 The limits of detection (LODs) are calculated by
TABLE 4 Cannabis Sample Categories and Samples
analyzingalow-levelspikesolution:LOD=3×SD(low-level
Sample Category Sample spike) × 100 (dilution factor). Analytical limits will vary
Inhaled Hemp flower depending on the specific instrumentation, dilution factor, and
Oral Hemp butter
blank quality. Achieving the lowest analytical limits requires
Topical Cannabis-based pain relief cream
careful attention to operating conditions and the highest level
Manufacturing CBD crude extract
of quality control.
D8469 − 22
TABLE 7 Example Calibration Standards
Volume to Add
Solution
A A
Std 1 Std 2 Std 3 Std 4 Std 5 Std 6 Std 7
Working Environmental 0 5 µL 25 µL 50 µL 500 µL 2500 µL 5000 µL
Calibration Standard
(1 mg/L trace, 100 mg/L
major)
Working Hg solution, A 0 5 µL 25 µL 50 µL 500 µL 2500 µL 5000 µL
(0.1 mg/L Hg)
Calibration blank added to 50.00 mL 50.00 mL 50.00 mL 50.00 mL 50.00 mL 50.00 mL 50.00 mL
make up final volume
Final concentrations
Trace elements (µg/L) 0 0.1 0.5 1 10 50 100
Major elements (µg/L) 0 10 50 100 1000 5000 10 000
Hg (µg/L) 0 0.01 0.05 0.1 1 5 10
A
Std 6 and Std 7 are for optional use if any of the element concentrations prove higher than 5 µg/L, or 10 µg/L for Hg.
13. Procedure 13.2.2 Polyatomic ion overlaps were controlled through a
combination of a robust, high temperature plasma and the use
13.1 Instrument startup routine and initial checks should be
of a CRC set up to control typical matrix-based polyatomic
performed per the manufacturer’s recommendations. Ignite the
ions.
plasma and start the peristaltic pump. Allow the plasma and
system to stabilize per the manufacturer’s recommendations. 13.2.3 Unknown plant materials may contain REEs and
TunetheICP-MSinstrumentaccordingtotheguidelinesinthe
barium (Ba) at a high enough concentration to interfere with
manufacturer’s tuning guide. During the tuning step, the
As, Se, and Zn. To simplify setup of the method for the
2+
internal standard tubing is placed in Type 1 water. Optimize
analysis, “REE Correction” can be selected in the ICP-MS
2+
plasma parameters for best sensitivity (Mcps/ppm), while
instrument software if available. If automated REE correc-
maintaining acceptable oxide and doubly-charged ratios per
tion is not available in the instrument’s software, users should
manufacturer recommendations. The instrument must meet
ensure they manually define an appropriate set of equations to
minimum manufacturer specifications. Perform a daily check
correct for these overlaps. Whether defined automatically or
for instrument sensitivity, detection limits, oxide formation 2+
setup manually, the basis of the REE correction is to use
ratios, doubly-charged element formation ratios, background,
increased quadrupole resolution to enable the measurement of
and stability.This daily check can be done automatically using
the signal for doubly charged ions formed from odd numbered
the instrument’s pre-run performance check routine, as recom-
REE isotopes, which appear at a half mass positions, since
mended by the manufacturer. If the performance check is not
doubly-charged ions appear at a m/z equal to half their true
satisfactory, additional optimization or maintenance actions
mass. Based on the natural isotopic abundances of the REEs
may be necessary per manufacturer recommendations.
2+ 2+
(which are retained in the REE ions), the half mass REE
2+
13.2 If using aerosol dilution technology to dilute the
signalsareusedtocalculatethesignalintensitiesfortheREE
samplesusingargongas,unknownhighmatrixsamplescanbe
ions (formed from even numbered REE isotopes), that overlap
analyzed without the need for matrix matched calibrations,
the analytes of interests. For example, for As at m/z 75, the
enabling the samples and the standards to be analyzed in the 2+ 150 2+ 150 2+
overlapping REE ions are Sm and Nd and the
same batch. If aerosol dilution technology is not available on
2+
uninterfered (half mass) REE isotopes that are measured to
the ICP-MS, it would be necessary to dilute high matrix
2+ 2+
calculate the Nd and Sm contributions on m/z 75 are
samplesusingconventionalliquiddilution.Equivalencycanbe
145 ++ 147 ++
Nd at m/z 75.5 and Sm at m/z 73.5. Based on the
ensured when all quality control parameters listed in this
150 145
isotopic abundance ratio for Nd, ( Nd/ Nd = 5.6/8.3), the
procedure are met.
150 2+
signal intensity for Nd can be calculated as 0.6747 times
13.2.1 For verification of this test method, an aerosol
145 2+
that of Nd . Similarly, based on the isotopic abundance
dilution factor of 4 was used. This dilution gas reduces the
150 147
ratio for Sm ( Sm/ Sm = 7.38/14.99), the signal intensity
aerosol density and fragments the droplets, leading to higher
150 2+ 147 2+
for Sm can be calculated as 0.4923 times that of Sm .
plasmatemperature,bettermatrixdecomposition,loweroxides
Using this information and the measured signal intensities as
and other interferences, and reduced maintenance. In this
m/z 72.5 and 73.5, a correction equation can be defined to
context, “matrix” refers to the composition of the major
150 2+
calculate and subtract the contribution that Sm and
elements in the samples. If different acid levels are used to
150 2+
Nd make to the total counts at m/z 75 as shown below:
prepare samples and standards, aerosol dilution will help to
reduce the suppression effects from the sample matrix and the 21 75
REE interferencecorrectionequationfor As:
(1)
different acid composition. However, large differences in
Mc~75! 5M~75! 2M~72.5! 30.6747 2M~73.5! 30.4923
matrix and acid levels can lead to physical sample transport
A similar approach is used to correct for the contributions
and nebulization effects that will need to be corrected using
appropriate internal standards. from the REE (and Ba) isotopes that overlap Se and Zn.
D8469 − 22
13.2.4 Normally in ICP-MS measurements, the quadrupole Interferencecorrectionequationfor Cd:
(5)
is operated with a peak width of about 0.7µ at 10% peak Mc 111 5M 111 2M 108 31.181M 106 30.712
~ ! ~ ! ~ ! ~ !
145 2+
height, so peaks measured at half masses (such as Nd at
95 +
where the last two terms correct for any MoO contribu-
147 2+
m/z 72.5 and Sm at m/z 73.5) would be overlapped by the
tion at m/z 111 and for any Pd that may be present.
“tails” of the adjacent peaks (at m/z 72, 73 and 74).When half
2+
14.5 Isobaric interferences in ICP-MS are caused by iso-
mass
...