usp talc methods expert panel update - overview...expert panel that will conclude at the end of the...

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USP Talc Methods Expert Panel Update- Overview

Martin S. Rutstein, Ph.D. Co-chair, Talc Methods Expert Panel

March 13, 2020

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Disclaimer

This presentation reflects the current work and recommendations of the USP Talc Expert Panels.

The content and views expressed do not necessarily reflect the policies of the U.S. Pharmacopeial Convention or the USP Council of Experts.

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Agenda

Background – Talc usage and Test forAsbestos in Pharmaceutical Talc

Overview of FDA (CDER) Request to USP

Overview of USP Talc Expert Panels (#1 and#2) and published Stimuli articles to date

Overview of the Expert Panel #2 phasedapproach to test method selection, detection,and planned publication of future Stimuliarticle

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ore TALC powder

SEM image TALC

ASBESTOS, variety

chrysotile

pharmaceuticals

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Background - Talc Usage Very Widespread

Our focus

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Background – Test for Asbestos in Pharmaceutical Talc

Characterizing the Productfor

“PURITY”

How do we measure & characterize the

elongateD “stuff” in

talcproducts?

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Background – The USP Talc Monograph

USP publishes their standards in the United States Pharmacopeia-National Formulary (USP-NF).

The quality standards contained in USP–NF monographs apply to any articles that are marketed in the U.S. that are intended or labeled for use as drugs or as ingredients in drugs.

The USP Talc monograph contains requirements applicable to talc for pharmaceutical applications.

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Background – FDA Interactions with USP

FDA-

Enforces USP standards for drug substances, drug products and excipients under the Federal Food, Drug, and Cosmetic Act.

– Note USP has no role in enforcement per USP General Notices 2.30 Legal Recognition.

Participates in USP’s standards-setting process and engages in research and development works.

Works with USP’s Expert Committees, workshops and stakeholder forums.

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Overview – FDA request to USP Nov. 16, 2010

The FDA Monograph Modernization Task Group (MMTG) sent a letter to USP requesting USP to modernize the USP Talc monograph as a high priority.

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Overview – FDA request to USP Nov. 16, 2010

The request for a revision was stated as follows:

–“Labeling should be revised to match the statements that are provided in the Talc FCC monograph, thereby assuring that Talc is not sourced from mines that are known to contain asbestos. Also, USP should consider revising the current tests for asbestos to ensure adequate specificity.”

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Urgency to update USP Talc Monograph

FDA requested USP to modernize the Talc monograph for Asbestos testing and labeling as “high urgency” because:

– High impact on public health.

This effort reflects the resolutions adopted by USP in 2010 convention and re-affirmed in 2015 Convention. The Excipient’s Expert Committee included this revision in their work plan.

Part of the work plan of the Pharmacopeial Discussion Group (PDG), represented by USP, Ph. Eur. and JP.

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Deficiency of the current Talc Monograph –Absence of Asbestos Test

Deficiency of the current test for “Absence of Asbestos”-

FibersPresent?

Light Microscopy (LM)

AsbestosPresent

No

Yes

AsbestosNot

Present

AsbestosNot

Present

Yes

either Infrared (IR)

Amphibole or SerpentineDetected?

No

or X-ray Diffraction (XRD)IR and XRD may haveFalse-Negative

LM may haveFalse-Positive

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Deficiency of the current Talc Monograph –Absence of Asbestos Test

Analysts are given the option to perform:

- Procedure 1: infrared spectroscopy [Identification Tests–General <197>]

- OR - Procedure 2: x-ray diffraction

[Characterization of Crystalline and Partially Crystalline Solids by X-Ray Powder Diffraction (XRPD) <941>]

If either test gives a positive result, then

- Procedure 3: optical microscopy [Optical Microscopy <776>] must be performed to confirm.

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Deficiency of the current Talc Monograph –Absence of Asbestos:SUMMARY

The infrared spectroscopy (IR) and x-ray diffraction (XRD) methods,

if used alone,

could lead to False-Negative results,

which could allow

talc samples with asbestos contamination

to pass

the Absence of Asbestos test

of

the current USP Talc monograph.

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Deficiency of the current Talc Monograph –Absence of Asbestos: SUMMARY

After applying the current USP microscopy method,

the analyst cannot rule out

the presence of asbestos in the sample.

The lack of particulate/particle

identification procedures

in the optical microscopy section

could lead to

false results.

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Deficiency of the current Talc Monograph –Absence of Asbestos

Talc Expert Panel #2 General Comments on Current Monograph Method

IR absorption spectroscopy and X-ray diffraction cannot distinguish asbestos (i.e., shapes) from non-asbestos forms of the same mineral. So, in case of positive answer by one of these methods, the morphology of the mineral should be examined using polarized light optical microscopy.

It is difficult to set the detection limit of this method since the Absence of Asbestos standard is dependent on the particle-size distribution of the pharmaceutical grade&Not all pharmaceutical grades share the same particle-size distribution.

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Overview – USP Talc Expert Panels and published Stimuli Articles

Talc Expert Panel #1 (Cycle 2010-2015)

The Talc Expert Panel (EP #1) was formed to address the request submitted in a letter from the FDA MMTG (dated November 16, 2010) to modernize the high priority USP-NF Talc monograph.

The Talc EP#1 was charged with modernizing the USP Talc monograph to ensure that the tests contained in the Absence of Asbestos have adequate specificity.

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Overview – USP Talc EP #1 and Stimuli #1

Talc Panel #1 Stimuli Paper

Pharmacopeial Forum (PF) 40(4) [Jul – Aug 2014]

Note Stimuli articles do not necessarily reflect the policies of the USPC or the USP Council of Experts

available at: https://www.uspnf.com/pharmacopeial-forum

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Overview – USP Talc EP #1 and Stimuli #1

The Expert Panel #1 recommendation for revision of the test for Absence of Asbestos included

omission of the infrared spectroscopy test &

inclusion of a revised x-ray diffraction procedure, in combination with one or more microscopic evaluations

polarized-light microscopy, transmission electron microscopy or scanning electron microscopy

Also recommended were additional sample preparation/concentration methods.

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Talc EP #1 Recommendations on the Deficiencies

FibersPresent?

Light Microscopy (LM)

AsbestosPresent

No

Yes

AsbestosNot

Present

AsbestosNot

Present

Yes

either Infrared (IR)


No

or X-ray Diffraction (XRD) IR and XRD may haveFalse–NegativeEP#1 Recommendations:

1) Delete IR

2) Improve XRD

3) Combination with

one or more microscopic

evaluations

LM may haveFalse –Positive

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FDA request (2010)

“Labeling should be revised to match the statements that are provided in the Talc FCC monograph, thereby assuring that Talc is not sourced from mines that are known to contain asbestos.

Description in the FCC Talc monograph:

“….Talc derived from deposits that are known to contain associated asbestos is not food grade. It is insoluble in water and in solutions of alkali hydroxides, but is slightly soluble in dilute mineral acids.”

Labeling – USP Talc Expert Panel #1 (Stimuli #1)

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Labeling in the existing USP Talc monograph:

“The label states, where applicable, that the substance is suitable for oral or topical administration. The certificate of analysis states the absence of asbestos. It also indicates which method specified in the test for Absence of Asbestos was used for analysis.”

Stimuli article #1 (2014)“It is the conclusion of the Talc Expert Panel that mine suitability as a source of talc is not subject to USP quality standards. Rather, it is the responsibility of the talc supplier to supply a product that is asbestos free and can meet the USP compendial standards.

Based on the above, the panel #1 recommended updating statements in the definition and/or labeling sections to indicate that talc containing (detectable) asbestos is not pharmaceutical grade.

Labeling – USP Talc Expert Panel #1 (Stimuli #1)

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Overview – USP Talc Methods Expert Panel (EP #2)

Talc Expert Panel #2 (Revision Cycle 2015-2020)

The 2010-2015 Excipient Monograph committee concluded that USP should create a Talc Methods Expert Panel to address the task of identifying appropriate analytical methods and Reference Standards (RS's) for testing Absence of Asbestos in Talc.

The new Expert Panel #2 would develop and optimize Talc analytical methods and develop RS based on knowledge gained from the Talc Expert Panel that will conclude at the end of the 2010-2015 Cycle.

EP #2 would also review, evaluate and generate proposals, procedures, and data to modernize of the test for asbestos, and will provide recommendations to the relevant Expert Committees.

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Key Tasks for Expert Panel #2 Derive a workable set of analytical procedures based on scientific principles that will satisfy the FDA request to USP to consider revising the current tests for asbestos to ensure adequate specificity & allow talc suppliers to strive to ensure that talc products used in medicines are not harmful to human health.

Recognize: state-of-art methodspracticality in industry population size detection limitquantificationprecision & accuracy

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Major Issues Facing Talc EP#2

1. Develop analytical procedures for industry that meet FDA and public confidence. Test methods should strike an appropriate balance between the need to address a significant quality issue and the industry’s ability to perform requisite testing.2. Remain neutral in health effects talc litigation. (Focus on Science)3. Focus on minerals with record of harmful health effects that could occur with talc ores.4. Clarify and standardize terminology.

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Issues Dealt with by Talc EP#2

Analytical Methods Protocols sample preparation and testing protocols Phased Testing Sequencing What analytes to test for?? What is Positive for Presence of Asbestos? What is Negative for Presence of Asbestos? Detection limits QA/QC Interpreting data Reporting results Round robin to test protocols Definitions/Nomenclature

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Overview – USP Talc EP #2 Stimuli articles

Stimuli article #2:“USPC Responses to Comments on Stimuli Article “Modernization of Asbestos Testing in USP Talc”, PF 43(4) [Jul-Aug 2017].

Planning Stimuli article #3:“Modernization of Asbestos Testing in USP Talc - Part 2”, Targeting to publish in PF 46(5) [Sep-Oct 2020].

1. Introduction2. What particles to consider for the proposed revision3. X-Ray diffraction4. Polarized light microscopy5. Ambiguities and interferences, detection limits and

measurement uncertainty6. Conclusions and recommendations

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“Asbestos” and Mineral Nomenclature

Many different definitionsof

asbestos,asbestiform,

fiber…

Word meanings can change with time!

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Scientifically rigorousConsistent with regulatory practices

Particle Identificationby

Chemical CompositionShape/MorphologyCrystal Structure

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“transitional”

talc

fibroustalc

amphiboles asbestiform amphiboles

overgrowths

domains

How to treat

a mixed box?

“Talc” can be a complex mixture of minerals and morphologies

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Talc, Asbestos,

Amphiboles&

Numerous Minerals

One can often find “something”

elongate in almost all rocks!

** Ref. - See Gunter et al, 2016Buzon & Gunter, 2016, esp. for sepiolite

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SHAPE (“morphology” & aspect ratio)

chrysotile

The “easier” stuff, especially ACBM (building materials)

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Modified from US Bureau of Mines Report No. IC 8751, “Selected Silicate Minerals and their Asbestiform Varieties”. Campbell, 1977

Aspect ratio most agree on!

Disagreement

ASPECT RATIO &

”Federal Fiber”PopulationHow many particulates to count to confirm a Positive?

“Federal Fiber”

Population number

ofparticles

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The Big Issues

Measurement & regulation of “elongate”particles (EMP’s)

oftalc? tremolite? anthophyllite? chrysotile?

(& some other minerals, esp. sepiolite)

cleavage fragments(broken crystals)

acicular/prismatic shapes(long & narrow crystals & fragments)

asbestiform minerals(fibers formed by crystal growth)

“WE” PREFER NOT TO USE THE TERMSFibrous Talc

Asbestiform Talc

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The Big Issues

Measurement & regulation of “elongate”particles (EMP’s)

TALC

“WE” PREFER NOT TO USE OR LIMIT USAGE of the

TERMSFibrous Talc

(use ribbon talc)

Asbestiform Talcgiven the possible confusion

with regulatory asbestos

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Recommendations:Our “Dictionary”

Particle instead of particulate

Elongate rather than elongated

Change “Absence of Asbestos”

To“Test for Asbestos”

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Overview – USP Talc EP #2 adopted the following definition

For the purposes of the USP “Absence of Asbestos”

[Test for Asbestos]” method,

The definition of asbestos will include the six regulated asbestos phases:serpentine (chrysotile) and five amphiboles (amosite, crocidolite, actinolite-asbestos, tremolite-asbestos, and anthophyllite-asbestos).

and in addition,

other asbestiform amphiboles with a focus on those known to cause asbestos-related disease.

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Overview – USP Talc EP #2 adopted the following definition

EPA considered that “asbestiform” includes aspects of morphology visible in the polarizing light microscope and described it as follows: “Said of a mineral that is like asbestos, i.e., crystallized with the habit of asbestos. Some asbestiform minerals may lack the properties which make asbestos commercially valuable, such as long fiber length and high tensile strength. With the light microscope, the asbestiform habit is generally recognized by the following characteristics:Mean aspect ratios ranging from 20:1 to 100:1 or higher for fibers longer than 5 µm. Aspect ratios should be determined for fibers, not bundles.Very thin fibrils, usually less than 0.5 micrometers in width, andTwo or more of the following:

Parallel fibers occurring in bundles,Fiber bundles displaying splayed ends,Matted masses of individual fibers, and/orFibers showing curvature

U.S. Environmental Protection Agency. Test Method EPA/600/R-93/116, 1993, Method for the Determination of Asbestos in Bulk Building Materials. Perkins, R.L. and B. W. Harvey.

EPA-600/M4-82-020, 1982, Test Method- Interim Method for the determination of asbestos in bulk insulation samples. 12 pp

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Identification IssuesSamplingTesting

Interpretation

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The ideal goal is to strive

dispassionately for

PROOF!

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X-ray Diffraction (XRD) – Round robin 1 & 2 studies

– Three labs participated in the study within the Expert Panel.

– Focused on the instrument/experimental parameters and detection and resolution

– Results of the improved XRD method• detection and resolution of tremolite and anthophyllite at 0.25% and 1% levels

• detection of serpentine at 0.25% and 1% levels without chlorite interference• detection of serpentine at 1% level with 1% chlorite interference.

Round Robin Studies

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Polarized Light Microscopy (PLM) – Round robin study

Five labs participated in the study within the Expert Panel.

Thirteen levels of samples used, including pure talc, spiked non-asbestos tremolite, chrysotile, tremolite-asbestos

at 1ppm, 10 ppm, 100 ppm and 1000 ppm analyte levels, respectively.

All labs successfully detected asbestos at the level of 100 ppm[0.01% (w/w) based on the spiked samples].

Asbestiform and non-asbestiform can be differentiated using PLM.

Round Robin Studies

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YesYes

Concentration Method?

1. Evaluate the >5 um size fraction

Recommended Changes to USP Monograph:“Test for Asbestos”A Phased Approach

No

EM (SEM, TEM)

Amphibole/SerpentineDetected?

AsbestosDetected

(>0.01%)Yes Amphibole/

SerpentineAsbestos?

UnidentifiedSuspectFibers?

PLM

Wet Sieve Concentration

XRD Positive?

XRD Analysis

2. Evaluate the <5 um size fraction(Pending Phase II Evaluation)

No

No

Phase I Phase II Proposal

Report AsbestosContent

(Empirical DetectionLimit To be

Determined)


AsbestosNot Detected

(<0.01%)

XRD Negative?



(<0.01%)

PLM


No

Yes

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Definition of asbestos will include the six regulated asbestos phases, which include one serpentine (chrysotile) and five amphiboles (amosite, crocidolite, actinolite-asbestos, tremolite-asbestos, and anthophyllite-asbestos). & other asbestiform amphiboles with a focus on those known to cause asbestos-related disease.

Conclusions and Recommendations of EP #2

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Methodology – Phased approach Phase I: XRD and PLM (mandatory) – supported by successful round robin studiesPhase II: evaluate electron microscopy methods, such as TEM (with EDS and SAED), and SEM, etc., considering round robin studies.


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Reporting “Pass/Fail”, focusing on the six regulated asbestos phases, but also asbestiform amphiboles known to cause asbestos-related disease.

Recommends changing the name of the USP Talc monograph test from

“Absence of Asbestos” to “Test for Asbestos”


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Phone | Social Media | Email

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USP Talc Methods Expert Panel Update- X-Ray Diffraction

Gary TomainoMember, Talc Methods Expert PanelMarch 13, 2020

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Disclaimer



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Outline

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ore TALC powder

SEM image TALC

chrysotile

“pharma”

X-Ray DIFFRACTION (XRD)

- XRD Overview

- Talc Expert Panel #1 RECOMMENDATIONS

- Talc Methods Expert Panel #2 OBJECTIVES

XRD ROUND ROBIN (RR) STUDIES

- XRD RR #1

- XRD RR #2- Confirmation of initial blending- Examples of participating labs- Examples of quantification

- General findings/ Findings of RR #1 and 2

XRD ROUND ROBIN # 3 (Future study recommendation)

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1) primary analysis technique and an important tool for any mineral and material characterizations qualitatively and when applicable quantitatively to the method

2) critical to identification of phases present in the talc product

3) determine overall purity of a talc product and its accessory minerals, that ensures compliance with the USP Talc monograph.

4) applied to end consumer product can provide identification of other mineral additives to a formulation and provide an alert to laboratory as to some unknown adulteration

5) provide qualitatively and quantitatively, total amphibole and total serpentine of talc product, end use product

6) cannot distinguish morphology and therefore cannot be used to exclusively determine presence of asbestiform amphibole or asbestiform serpentine; as noted used in conjunction with another microscopy method.

X-Ray Diffraction (XRD) OVERVIEW

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TALC EXPERT PANEL (EP) #1 RECOMMENDATIONS

The infrared (IR) spectroscopy test for absence of asbestos should be omitted in favor of XRD.

Any “stopping rule” following an XRD evaluation and determination of no detectable amphibole or serpentine would not be acceptable and was deficient in the characterization of a talc product.

AND

At least one or more microscopy techniques (PLM or TEM-EDS-SAED or SEM-EDS) is necessary to provide specificity to the attribute modifications.

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Procedure 2 (XRD) limited evaluation conditions: amphibole and serpentine.

Amphibole diagnostic diffraction peak at ~10.50 2θ was noted for tremolite however the amphibole diagnostic peak for anthophyllite at ~10.70 2θ was not considered (Cu radiation).

Partial or full overlap of chlorite group minerals with serpentine minerals was not addressed within the confines of the two specific serpentine scan regions

higher detection limits for serpentine leading to false-positives for serpentine

A given analyst/laboratory should understand that XRD provides total amphibole ortotal serpentine content and does not distinguish the morphology of asbestiform and non-asbestiform amphiboles or serpentine

TALC EP #1 RECOMMENDATIONS for XRD

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ROUND ROBIN #1

INSTRUMENT AND SAMPLE ALIGNMENT, MINERALOGICAL IDENTIFICATION

PRIMARY NIST REFERENCE(S), SECONDARY TALC REFERENCE MATERIAL (NOT PHARMA-TALC)

ROUND ROBIN #2

RESOLUTION TESTS AND RELATIVE DETECTION LIMITS

TREMOLITE versus ANTHOPHYLLITE

SERPENTINE versus CHLORITE

ROUND ROBIN # 3 (Recommend for future study)

LIMIT OF QUANTIFICATION AND LIMIT OF DETECTION (BELOW 0.25%)

TREMOLITE versus ANTHOPHYLLITE

SERPENTINE versus CHLORITE

TALC EP #2 XRD Round Robin Objectives

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XRD ROUND ROBIN STUDIES

XRD Round Robin #1

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1) general instrument and full 2θ scan conditions at a minimum over the range 4-55 or higher 2θ (minimum)

2) instrument and sample alignment checks for achieving and for providing a qualitative mineralogical profile including identification of amphibole and serpentine in addition to other minerals present

chlorite, carbonates (magnesite, calcite, dolomite), quartz, feldspars, apatite

provides user on the purity of the talc

Recommendations to incorporate calibration standards and reference materials as routine part of the lab procedures

TALC EP #2 XRD ROUND ROBIN #1

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NIST STANDARDS RECOMMENDED (one or more) PRIMARY CRM SPECIFIC TO XRD

INSTRUMENT ALIGNMENT PRECISION

1976----------Alumina plate---Instrument Sensitivity Standard for XRD

660a---------LaB6, line position/line profile standard for XRD

640B/C/D/E--------- Si metal, line position/line profile standard for XRD

SAMPLE ALIGNMENT PRECISION PACKING TECHNIQUE

675---------Low 2 theta (large d-spacing) for XRD; Fluorophlogopite

640B/C--------- Si metal, line position/line profile standard for XRD

ANALYST COMPETENCY FOR SAMPLE PACKING ALIGNMENT

674b--------Intensity Set* for XRD; TiO2, ZnO, Cr2O3, CeO2;

*peak position two-theta tables for each phase

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ISO 17025 QUALITY PROGRAM-COMPETENCY ANALYST NIST 640C SILICON POWDER

NIST VALUES d-Spacing

AN

ALY

ST

VA

LU

ES

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ADDITIONAL Reference Materials (TALC)

PRIMARY REFERENCE MATERIALS--BRAMMER CERTIFIED REFERENCE

JAPANESE CERAMIC RM 901, 902, 903

[PURCHASED AS A SET OF 3]50 grams each; $1250/set

SECONDARY REFERENCE MATERIAL--BRAMMER CERTIFIED REFERENCE

BCS 203a RM

RM 100 grams; $255(TOMAINO TO PROVIDE TO SUB-GROUP USP/ASTM)

IN-HOUSE TALC REFERENCES (PHARM-PRODUCTS)

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QUALITATIVE SCAN

TALC MAJOR

CHLORITE TRACE

QUARTZ TRACE

DOLOMITE TRACE

MAGNESITE MINOR

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9.3559.335 9.347 9.339

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PA

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REPLICATE RUN

TALC SAMPLE ALIGNMENT-IDENTIFICATION

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TALC SAMPLE ALIGNMENT-IDENTIFICATION

PDF 19-7703.12 +/-0.01

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XRD Round Robin #2

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1) GENERAL INSTRUMENT and QUANTITATIVE 2θ scan conditions

TREMOLITE, ANTHOPHYLLITE, SERPENTINE, CHLORITE

2) RESOLUTION and DETECTION of TREMOLITE and ANTHOPHYLLITE

0.25% and 1% levels

3) RESOLUTION and DETECTION of SERPENTINE without CHLORITE INTERFERENCE

0.25% and 1% levels

4) RESOLUTION and DETECTION of SERPENTINE with CHLORITE INTERFERENCE

1% Serpentine/1% Chlorite levels


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RESOLUTION and RELATIVE DETECTION LIMIT IN TALC

1% TREMOLITE-NA 1% ANTHOPHYLLITE-A (A-181; AS RECEIVED) 1% SERPENTINE/CHRYSOTILE (#1422 WCD, AS RECEIVED)

0.25% TREMOLITE-NA 0.25% ANTHOPHYLLITE-A (A-181; AS RECEIVED) 0.25% SERPENTINE/CHRYSOTILE (#1422 WCD, AS RECEIVED)

1% Serpentine/Chrysotile (#1422 WCD, AS RECEIVED)1% Chlorite (highly crystalline spike-fine powder)

BASE LINE TALC [NO CHLORITE, CARBONATES; MACRO-CRYSTALLINE FORM]


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3) TREMOLITE AND ANTHOPHYLLITE START ANGLE (2-THETA): RECOMMENDED 9.8

END ANGLE (2-THETA): RECOMMENDED 11.2

STEP-SIZE (2-THETA): RECOMMENDED 0.02

COUNT TIME/STEP RECOMMENDED SECONDS 100

4) ANTHOPHYLLITE START ANGLE (2-THETA): RECOMMENDED 28.8




5) SERPENTINE AND CHLORITE START ANGLE (2-THETA): RECOMMENDED 11




6) SERPENTINE AND CHLORITE START ANGLE (2-THETA): RECOMMENDED 23.5




QUANTITATIVE

SCAN

CONDITIONS

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CONFIRMATION OF INITIAL BLENDING (RR #2)


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QUALITATIVE SCAN CONDITIONS

1% TREMOLITE

1% ANTHOPHYLLITE

1% SERPENTINE

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QUANTITATIVE SCAN CONDITIONS

1% TREMOLITE

1% ANTHOPHYLLITE

1% SERPENTINE

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CONE AND QUARTER, GRAB TESTING

GOOD REPLICATION OF THE BLENDS

RE-COMBINE, MIX, SUB-SAMPLE

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© 2019 USP


CONE AND QUARTER, GRAB TESTING

GOOD REPLICATION OF THE BLENDS

RE-COMBINE, MIX, SUB-SAMPLE

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CONFIRMATION OF FINAL BLENDING ROUND ROBIN #2

TEN (10) REPLICATE SUB-SAMPLES TAKEN

1% TREMOLITE-ANTHOPHYLLITE-SERPENTINE

0.25% TREMOLITE-ANTHOPHYLLITE-SERPENTINE

SEVEN (7) REPLICATE SUB-SAMPLES TAKEN

1% SERPENTINE WITH 1% CHLORITE INTERFERENCE


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REPLICATE OVERLAY

BASELINE

0.25% T-A-S

1% T-A-S


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10 REPLICATES OVERLAY

0.25% T-A-S

TREMOLITE -ANTHOPHYLLITE


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0.25% T-A-S

SERPENTINE


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© 2019 USP


1% SERPENTINE

1% CHLORITE


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© 2019 USP

EXAMPLES OF

PARTICIPATING LABS


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0.25% T-A-SLAB RR#2


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© 2019 USP

1% T-A-SLAB RR#2


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© 2019 USP

1% SERPENTINE1% CHLORITELAB RR#2


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© 2019 USP

EXAMPLES OF

QUANTIFICATION


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EXAMPLES OF QUANTIFICATION 1% TREMOLITE 1% ANTHOPHYLLITE

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© 2019 USP


EXAMPLES OF QUANTIFICATION 0.25% TREMOLITE 0.25% ANTHOPHYLLITE

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EXAMPLES OF QUANTIFICATION PEAK HEIGHT 1% AND 0.25% T-A

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EXAMPLES OF QUANTIFICATION PEAK AREA 1% AND 0.25% T-A

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XRD Round Robin Findings

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TALC EP #2 XRD ROUND ROBIN 1 and 2

GENERAL FINDINGS:

XRD Round Robin 1 and 2

1) provide the analyst-laboratory with the ability to identify and if needed quantify for total amphibole and total serpentine in a pharmaceutical talc product.

2) microscopic technique(s) utilized following the XRD evaluation should correlate/trend with relative levels of amphibole or serpentine, if detected

3) microscopic technique(s) should not find and should not state amphibole or serpentine levels at substantially higher than the XRD level

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FINDINGS:

XRD Round Robin 1 and 2

1) acceptable resolution and detection of tremolite and anthophyllite at 0.25%

2) easily resolved and detected tremolite and anthophyllite at 1%

3) acceptable detection of serpentine at 0.25% without chlorite interference

4) easily detected serpentine at 1% without chlorite interference

5) acceptable resolution and detection of serpentine at 1% with chlorite at 1%

TALC EP #2 XRD ROUND ROBIN 1 and 2

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REPORTING LEVELS BASED ON RR#2

For the data thus far collected in the round robin, it is recommended the XRD portion of the asbestos attribute state:

1) if no detectable peak for tremolite or anthophyllite then “none detected < 0.2%”

2) if no detectable peak for serpentine without chlorite interference then “none detected < 0.2%”

3) if no detectable peak for serpentine with 1% chlorite interference then “none detected < 0.5%”

note: chlorite levels above 1% up to 10-15% would increase the detection limit of serpentine to 1%

TALC EP #2 XRD ROUND ROBIN 2

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RECOMMENDATIONS TALC EP#2

While the XRD round robin study used samples prepared with known amphibole and serpentine amounts to determine a relative limit of detection for XRD:

It would be the analyst or laboratory’s responsibility to perform the confirmation of a properly calibrated instrument and confirmation of the XRD evaluation on a set of talc reference materials

Compliance with the compendia standard for the mandatory XRD reporting:

need only be a Pass-Fail result-limit and not a quantitative result

TALC EP #2 XRD ROUND ROBIN 2

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TALC EP #2 Recommendation on XRD ROUND ROBIN #3

1) Round Robin 3 be conducted to confirm if amphibole levels should be set at 0.1%.2) However, each laboratory performing the test would need to verify individual

detection limits.

0.5% TREMOLITE-NA 0.5% ANTHOPHYLLITE-A (A-181; MILLED) 0.5% SERPENTINE/CHRYSOTILE (#1422 WCD, AS RECEIVED)



BASE LINE TALC(s) [TO BE DETERMINED]

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QUANTITATIVE ANALYSES METHOD OF ADDITIONS ASTM TALC

QUANTITATIVE

SCAN

0.16% TREMOLITE

ADDITION

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© 2019 USP

QUANTITATIVE ANALYSES METHOD OF ADDITIONS ASTM TALC

QUANTITATIVE

SCAN

0.16% TREMOLITE

ADDITION

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USP Talc Monograph Update – Polarized Light Microscopy

Julie PierCo-chair, Talc Methods Expert PanelMarch 13, 2020

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Disclaimer



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Agenda – USP Talc Monograph UpdatePolarizing Light Microscopy (PLM)

Phased Approach

– What Phase I tells us

– Example

PLM Methodology

– What PLM tells us

– Conducting the Round Robin

– Results/Conclusions

– Creation of spiked materials for study

Next steps

– Phase II methods validation

– Things to consider/Discussion

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YesYes


1. Evaluate the >5 µm size fraction

Recommended Changes to USP Monograph:“Test for Asbestos”Phased Approach

No

EM (SEM, TEM)


AsbestosDetected(>0.01%)

Yes Amphibole/SerpentineAsbestos?


PLM


XRD Positive?

XRD Analysis

2. Evaluate the finer size fraction(Pending Phase II Evaluation)

No

No




Determined)



(<0.01%)

XRD Negative?



(<0.01%)

PLM


No

Yes

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© 2019 USP

Phased Approach

As no one method gives the complete picture, the phased approach proposes complementary methodology to evaluate the full particle size spectrum:

– Larger (>5 µm) size fraction/Phase I (XRD/PLM)

– Smaller size fraction (not resolved by PLM)/Phase II (SEM/TEM)

Why start with Phase I?

– The phased approach builds on the original USP Monograph protocol (with recommended improvements and determination of an empirical detection limit).

– Asbestos, if present, should present itself over the full particle size distribution of a ground mineral mixture (see example).

– The larger particles of asbestos are easier to identify and characterize as asbestos as they display characteristic attributes.

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Particle Size Distribution of Talc Products

0

2

4

6

8

10

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0.1 1 10 100

Vo

lum

e %

Particle Size (um)

TEM

Roller Milled Product (Cosmetic size)Median Particle Size = 12 um

"AFG" Product(Alpine Fine Grind)Median Particle Size = 5 um

Light Microscopy (PLM)

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© 2019 USP


0

2

4

6

8

10

12

0.1 1 10 100

Vo

lum

e %

Particle Size (um)

TEM




Unlikely that asbestos would only be here:

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0

2

4

6

8

10

12

0.1 1 10 100

Vo

lum

e %

Particle Size (um)

TEM




More likely that asbestos would cover the full range:

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© 2019 USP

Asbestos, if present, tends to concentrate in the larger size range of a talc/asbestos mixture.

– Asbestos resists grinding due to its high tensile strength and flexibility.

– Talc is easy to grind (softest mineral known)

– Amphibole and serpentine have higher hardness values than talc (4 – 6 vs. 1).

– Differential grinding profile causes preferential enrichment toward the larger sizes.

Years ago, grinding (to get rid of non-asbestos particles) and sieving (to concentrate asbestos) was the purification process for commercially produced asbestos.

Conclusion: if talc and asbestos are milled together, talc gets smaller while asbestos holds its strength. Therefore, it is very unlikely that asbestos would only be in the smallest size fraction of a ground talc/asbestos mixture.

Rather, the opposite is true.

Particle Size Distribution of Asbestos

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Example:

Ground sample had a median particle size of 1-2 um– Finer than pharma and cosmetic talc.

– Likely contained both an asbestos and a non-asbestos component (as it was not a commercial asbestos product).

Suspect particles were identified by:1. Wet sieve isolation of the larger particles (+400 mesh = 38 um)

2. Analysis by XRD, PLM, and SEM

3. A separate (on-concentrated) sample was analyzed by TEM.

Conclusions:1. Asbestos/amphibole was present in all size fractions.

2. The asbestos component was more readily identified by PLM/SEM.

A finely ground “natural” talc ore sample with a trace level of amphibole asbestos(i.e. not spiked)

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Example: XRD

Amphibole*

Talc Quantitative XRD scan

*Detected by quantitative scan only

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Example: PLM (material retained on the sieve)

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Example: SEM (material retained on the sieve)

400 X

1000 X

=TEM FOV

=TEM FOV

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Example: TEM

*Analysis performed at 20,000X magnification

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Existing StandardsPLM Asbestos Analysis in Bulk Materials

Bulk Building Materials– EPA 600/M4-82-020 (1982) and 600/R-93/116 (1993)

– NIOSH 9002

– OSHA ID191

– NY ELAP 198.1 and 198.6

Bulk Minerals– ISO 22262-1, A22262-2

– ASTM Draft (Work Item WK30024523)

– CTFA J4-1

– USP (Current Monograph) – LM only

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Recommendations for PLM

Phase I recommendations:

– Drop FTIR

– Require microscopy (not conditional)

– Upgrade LM to PLM

– Investigate sieve concentration preparation

– Establish detection level

FibersPresent?

Light Microscopy

AsbestosPresent

No

Yes

AsbestosNot

Present

AsbestosNot

Present

Yes

XRD Analysis


No

FTIR Analysis - Or -

Existing Talc Monograph Procedure:

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© 2019 USP

Amphibole Asbestos Analysis by PLM

Refractive index liquid of 1.605 used for screening.

Dispersion staining technique:– Amphibole = yellow/magenta– Talc = pale blue

Refractive index > liquid confirmed by Becke line.

Conclusive ID can be accomplished by use of additional RI liquids (if necessary).

Amphibole asbestos spiked into talc

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Chrysotile (Asbestos) Analysis by PLM

Refractive index liquid of 1.55 used for screening

Dispersion staining technique:– Chrysotile = blue/magenta– Talc = pale yellow

Refractive index ≈ liquid confirmed by relief.

Original hypothesis (that PLM would be difficult for chrysotile) was proven to be incorrect.

Chrysotile (asbestos) spiked into talc

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© 2019 USP

Wet sieving isolates the larger size range

– Capturing the larger particles (i.e. >400 Mesh), to concentrates all harder-to-grind materials (i.e. quartz, mica, asbestos – if present).

– Removes interfering small particles

This technique capitalizes on known asbestos attributes to assist in the analysis (labs participating in the Round Robin found this technique helpful).

Identification is easier because the larger particles more readily show observable attributes of asbestos.

The smaller size fraction can sometimes be ambiguous.

Wet Sieve Concentration Option Mandatory

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Polarizing Light Microscopy (PLM)

0.001% (10 ppm) Chrysotile Spiked in Talc 0.001% (10 ppm) Tremolite Asbestos Spiked in Talc

PLM Advantage is morphology characterization

Observable asbestiform morphology preserved, even though aggressively ground and present at trace levels.

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© 2019 USP

EPA Definition of “Asbestiform”(i.e. how to recognize it in an optical microscope)

From EPA 600/R-93/116 (similar to ISO 22262-1):

Mean aspect ratios ranging from 20:1 to 100:1 or higher for fibers longer than 5 µm. Aspect ratios should be determined for fibers, not bundles.

Very thin fibrils, usually less than 0.5 micrometers in width, and

Two or more of the following:– Parallel fibers occurring in bundles,*– Fiber bundles displaying splayed ends,*– Matted masses of individual fibers, and/or– Fibers showing curvature*

These characteristics refer to the population of fibers as observed in a bulk sample. It is not unusual to observe occasional particles having aspect ratios of 10:1 or less, but it is unlikely that the asbestos component(s) would be dominated by particles (individual fibers) having aspect ratios of <20:1 for fibers longer than 5 µm. If a sample contains a fibrous component of which most of the fibers have aspect ratios of <20:1 and that do not display the additional asbestiform characteristics, by definition the component should not be considered asbestos.

0.001% (10 ppm) Tremolite Asbestos spiked into talc

*Features observed in particles from the Round Robin study, even at trace levels.

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Spiked Samples

TremoliteAsbestos

ChrysotileAsbestos

Tremolite(Non-Asbestiform)

0% (Un-spiked Talc)

0.0001% (1 ppm) 0.0001% (1 ppm) 0.0001% (1 ppm)

0.001% (10 ppm) 0.001% (10 ppm) 0.001% (10 ppm)

0.01% (100 ppm) 0.01% (100 ppm) 0.01% (100 ppm)

0.1% (1000 ppm) 0.1% (1000 ppm) 0.1% (1000 ppm)

• 13 samples per set• 8 sets created (including a reference set)• 104 samples total• Many hours contributed by Expert Panel #2 members

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© 2019 USP

PLM Round Robin Results – Non-spiked Talc

No false positives in the non-spiked talc sample

Spike Level Lab Vial Asbestos Detected (Yes/No)

Asbestos Mineral Found

Amount Found

Non-spikedTalc

D D-11 No --- ---

E E-12 No --- ---

F F-5 No --- ---

G G-9 No --- ---

H H-11 No --- ---

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PLM Round Robin Results – Tremolite Asbestos

One lab detected 0.001%

Four labs detected 0.01%

All labs detected 0.1%

One lab identified anthophyllite asbestos (test will not require amphibole speciation)

Amount not consistent (test will be positive/negative)

One false positive for chrysotile (single particle = contamination?)

Spike Level Lab VialAsbestos Detected?

Asbestos Mineral Amount

0.0001%Tremolite Asbestos

(1 ppm)

D D‐6 No ‐‐‐ ‐‐‐

E E‐11 No ‐‐‐ ‐‐‐

F F‐13 No ‐‐‐ ‐‐‐

G G‐1 No ‐‐‐ ‐‐‐

H H‐7 No ‐‐‐ ‐‐‐


(10 ppm)

D D‐4 Yes Tremolite asbestos 0.0011

E E‐6 No ‐‐‐ ‐‐‐

F F‐10 No ‐‐‐ ‐‐‐

G G‐8 No ‐‐‐ ‐‐‐

H H‐1 No ‐‐‐ ‐‐‐


(100 ppm)


E E‐13 Yes Tremolite asbestos 0.02

F F‐3 Yes Tremolite asbestos 0.002

G G‐12 No ‐‐‐ ‐‐‐

H H‐3 YesAnthophyllite asbestos

Chrysotile (1)0.03549


(1000 ppm)


E E‐8 Yes Tremolite asbestos 0.40

F F‐6 Yes Tremolite asbestos 0.019

G G‐11 Yes Tremolite asbestos 0.00893

H H‐9 Yes Anthophyllite asbestos 0.00130

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© 2019 USP

PLM Round Robin Results – Chrysotile

One lab detected 0.0001%

Two labs detected 0.001%

All labs detected 0.01% and 0.1%

Amount not consistent (test will be positive/negative)

Consistent chrysotile detection by PLM unexpected

Spike Level Lab Vial Asbestos Detected?

Asbestos Mineral

Amount

0.0001% Chrysotile(1 ppm)

D D‐10 No ‐‐‐ ‐‐‐

E E‐9 No ‐‐‐ ‐‐‐

F F‐4 No ‐‐‐ ‐‐‐

G G‐4 No ‐‐‐ ‐‐‐

H H‐2 Yes Chrysotile 0.00190

0.001%Chrysotile(10 ppm)

D D‐7 Yes Chrysotile 0.0007

E E‐5 No ‐‐‐ ‐‐‐

F F‐9 No ‐‐‐ ‐‐‐

G G‐13 Yes Chrysotile 0.03015

H H‐6 No ‐‐‐ ‐‐‐


D D‐2 Yes Chrysotile 0.0028

E E‐1 Yes Chrysotile 0.02

F F‐1 Yes Chrysotile 0.029




D D‐3 Yes Chrysotile Quant. not attempted

E E‐3 Yes Chrysotile 0.33

F F‐2 Yes Chrysotile 0.238



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PLM Round Robin Results – Non-asbestiform Tremolite

Differentiation between non-asbestos tremoliteand tremoliteasbestos is achievable by PLM.

One false “positive” (chrysotile single particle = contamination?).

Spike Level Lab Vial Asbestos Detected?

Asbestos Mineral

Amount

0.0001%Non‐asbestiform Tremolite

(1 ppm)

D D‐5 No ‐‐‐ ‐‐‐

E E‐2 No ‐‐‐ ‐‐‐

F F‐12 No ‐‐‐ ‐‐‐

G G‐6 No ‐‐‐ ‐‐‐

H H‐8 No ‐‐‐ ‐‐‐


(10 ppm)

D D‐1 No ‐‐‐ ‐‐‐

E E‐10 No ‐‐‐ ‐‐‐

F F‐11 No ‐‐‐ ‐‐‐

G G‐10 No ‐‐‐ ‐‐‐

H H‐4 No ‐‐‐ ‐‐‐


(100 ppm)

D D‐9 No ‐‐‐ ‐‐‐

E E‐4 No ‐‐‐ ‐‐‐

F F‐7 No ‐‐‐ ‐‐‐

G G‐7 No ‐‐‐ ‐‐‐

H H‐12 No ‐‐‐ ‐‐‐


(1000 ppm)

D D‐13 No ‐‐‐ ‐‐‐

E E‐7 No ‐‐‐ ‐‐‐

F F‐8 No ‐‐‐ ‐‐‐

G G‐3 No ‐‐‐ ‐‐‐

H H‐5 Yes Chrysotile (1) 0.00074

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© 2019 USP

Results/Observations

Particles showed classic asbestiform morphology attributes (bundles, splayed ends, flexibility), even though aggressively ground to product size specifications.

No false positives in talc-only samples.

No false positives in non-asbestiform tremolite spikes.

False negatives for 1 ppm, and some 10 ppm samples (perhaps due to ability to create homogenous standards – or – limitation of method).

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Method Limiting Observations

Two cases of single particle chrysotile detected in non-chrysotile sample (contamination?).

Anthophyllite vs. tremolite identification

– Tremolite asbestos has anomalous parallel extinction (could be confused with anthyphyllite?)

– Refractive indices overlap in some amphibole species

Concentrations were not consistent.

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© 2019 USP

Conclusions/Summary

Working detection level will be 0.01% (100 ppm).

Result will remain positive/negative (vs. a quantified result).

Sieve prep step will be mandatory.

Minimum of 5 microscope slide preps will be required (or minimum weight).

Speciation of amphiboles will not be required.

A single particle is not distinguishable from background/contamination.

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Challenges with Creating Spikes for Round Robin

Asbestos does not behave as a typical analyte.

Dispersion of asbestos (fiber) into matrix talc (powder) is difficult.

Particle size distribution is different between talc and asbestos.

Talc and asbestos have differential grinding profiles.

Tremolite Asbestos:

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© 2019 USP

Procedure for Creating Spikes for Round Robin Study

Start with talc “chips” (unground raw ore provided by one talc supplier).

Mix a known amount of analyte (chrysotile, tremolite asbestos, and non-asbestiform tremolite) to produce a stock mixture (i.e. 1%).

Aggressively co-mill stock talc + analyte to reach typical talc product specification.

Dilute to desired concentration using a mixture of various talc raw materials provided by FDA. FDA received these raw material samples from talc suppliers as part of survey conducted in 2010.

Mix diluted samples to thoroughly disperse the stock mixture.

Result: simulated talc product with trace levels of asbestos (NOT simply adding commercial grade asbestos to already ground talc powder).

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Mixture of talc for dilution

2010 FDA Talc Survey (https://www.fda.gov/media/122418/download)

– Included 27 raw material talc samples from various suppliers.

– Both major US talc suppliers were represented.

– All samples tested negative for asbestos by PLM and TEM* applying a gravimetric reduction method to prepare 3 specimens of each sample.

A mixture of various talc products from several suppliers participating in this survey were used to dilute the spiked base material (talc + analyte) to various concentrations.

Using this material, samples could not be traced to any one supplier.

*See e.g. NY ELAP 198.4; TEM average limit of detection quoted as 0.021 ppm ± 0.001.

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© 2019 USP

Crushed Talc + 100 ppm amphibole asbestos

Approach: Co-milling Asbestos and Crushed Talc Base Material

~100% recovery

McCrone® Micronizing Mill

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Analyte spiked into Talc Base Material @1%:- Homogeneity checked on 3 replicates using XRD

0

5000

10000

24 24.50 25 25.50 26

RLH806636-1 3154127c 1%NA Trem in Talc_chrys RLH806636-1 3154127b 1%NA Trem in Talc_chrys RLH806636-1 3154127a 1%NA Trem in Talc_chrys

0

5000

10000

11 12 13

RLH806636-1 3154127c 1%NA Trem in Talc_trem RLH806636-1 3154127b 1%NA Trem in Talc_trem RLH806636-1 3154127a 1%NA Trem in Talc_trem

ChrysotileTremolite Asbestos

2-theta2-theta

X-r

ay C

ount

s

X-r

ay C

ount

sReplicate 1Replicate 2Replicate 3

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© 2019 USP

Mixing of talc base material + talc product mixture – for dilution to various concentrations

Final samples were thoroughly mixed:– Ground, spiked base material (talc + analyte), mixed with– Material used for diluting to appropriate concentration (mixture of various talc raw materials

received from suppliers which all tested negative for asbestos by TEM in 2010 FDA Survey.)

Flacktek® Speedmixer

Mixing efficiency demonstrated using Playdough®- From Flacktek® website

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PLM Round Robin was a “Double-Blind” Study

Two-Step Approach

– Third party lab not involved with Expert Panel performed initial blinding and distribution of samples.

– USP received and compiled all results to maintain confidentiality between participants.

Significant time was expended to identify appropriate lab for blinding process and coordination of samples.

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© 2019 USP

Next Steps…

Finalize draft method/General Chapters

Complete Stimuli Article

Begin Phase II evaluation of electron microscopy methods (TEM/SEM)

EM will be evaluated for potential false negative resolution; however, a systematic, scientific method validation will be performed before recommendation takes place.

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YesYes


1. Evaluate the >5 um size fraction

Recommended Changes to USP Monograph:“Test for Asbestos”Phased Approach

No

EM (SEM, TEM)


AsbestosDetected(>0.01%)

Yes Amphibole/SerpentineAsbestos?


PLM


XRD Positive?

XRD Analysis

2. Evaluate the finer size fraction(Pending Phase II Evaluation)

No

No




Determined)



(<0.01%)

XRD Negative?



(<0.01%)

PLM


No

Yes

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To Be Considered (Phase II): Detection Limit

From EPA 600/R-93/116:

Detection Limit - The smallest concentration/amount of some component of interest that can be measured by a single measurement with a stated level of confidence.

Considerations regarding confidence in the measurement:

– Reproducibility

– Difference from background

– Unambiguous interpretation

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To Be Considered: Background levels of asbestos

Lab blank programs indicate non-zero background levels.

100 blanks done with same parameters as analysis is required to prove 1 – 3 fibers is different than background (ASTM D6620).

Sources of contamination:– Earth’s crust is ~5% amphibole & serpentine is

common (state rock of California).

– Inorganic component of dust is similar to weathering products of rocks in the crust.

– Industrial use of asbestos (historic and present); asbestos is persistent.

– Safe drinking water standard allows 7 million asbestos fibers per liter of water.

– Air in rural areas = 10 fibers/m3*

– Air in urban areas = 100 fibers/m3*

*U.S. ATSDR: “10 fibers are typically presentin a cubic meter (fibers/m3 ) of outdoor air in rural areas. A cubic meter is about the amount of air that you breathe in 1 hour.”

ATSDR = Agency for Toxic Substances and Disease Registry

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To Be Considered: Standard Reference Materials

Standard reference materials need to be developed

NIST standards for asbestos are no longer available

Reference talc base material should be defined

A low but detectable concentration should be created (by labs doing the analysis?) so that analysts can practice using the actual analyte in the actual matrix material.

0.1% or 0.05% (for PLM)?

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Summary of Phase I Outcomes

XRD Result (Amphibole/Serpentine)

PLM Result Phase I Outcome

Not detected Amphibole/serpentine not detected <100 ppm

Not detected Asbestos not detected…and…Unidentified suspect fibers not detected

<100 ppm

Not detected Asbestos not detected…but…Unidentified suspect fibers detected

EM recommended(Phase II)

Not detected Asbestos detected >100 ppm

Detected Amphibole/serpentine not detected EM recommended(Phase II)

Detected Asbestos not detected…and…Unidentified suspect fibers not detected

<100 ppm

Detected Asbestos not detected…but…Unidentified suspect fibers detected

EM recommended(Phase II)

Detected Asbestos detected >100 ppm

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usp talc methods expert panel update - overview...expert panel that will conclude at the end of the...

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