Task Group Co-Chairs Debra Kaiser, NIST Aleks Stefaniak, NIOSH Contributing Task Group Members (to date) Keana Scott, Tinh Nguyen, and Rick Davis, NIST Jurg Schutz, CSIRO, Australia Frank von der Kammer, University of Vienna, Austria Dermont Bouchard, EPA Technical Experts Consulted (to date) Robert Cook, Frank DelRio, Jeffrey Fagan, Justin Gorham, Angela Hight-Walker, Elijah Petersen, Keana Scott (NIST); Jeff Simpson (Towson University) Task Group 1 : Methods NanoRelease Consumer Products: Multi-Wall Carbon Nanotube (MWCNT) in Polymers Steering Committee Workshop May 16-17, 2013
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Task Group Co-Chairs Debra Kaiser, NIST Aleks Stefaniak, NIOSH Contributing Task Group Members (to date) Keana Scott, Tinh Nguyen, and Rick Davis, NIST.
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Task Group Co-ChairsDebra Kaiser, NIST
Aleks Stefaniak, NIOSH
Contributing Task Group Members (to date)Keana Scott, Tinh Nguyen, and Rick Davis, NIST
Jurg Schutz, CSIRO, AustraliaFrank von der Kammer, University of Vienna, Austria
Dermont Bouchard, EPA
Technical Experts Consulted (to date)Robert Cook, Frank DelRio, Jeffrey Fagan, Justin Gorham, Angela Hight-Walker, Elijah Petersen, Keana Scott (NIST); Jeff Simpson
(Towson University)
Task Group 1 : Methods
NanoRelease Consumer Products: Multi-Wall Carbon Nanotube (MWCNT) in Polymers
Steering Committee Workshop
May 16-17, 2013
Work Flow
2
Methods:• Generation of released material• Representative sampling
• Sample preparation for measurement
• Measurement of released materialTG 1: Methods May16-17, 2013NanoRelease Steering Committee
• Detection: presence (yes or no) of MWCNTs; detection limit
• Quantification: number or mass concentration of MWCNTs in released material per unit volume or area of composite
• Characterization: determination of characteristics and properties of MWCNTs and fragments
Measurement “Hierarchy”*
* Adapted from von der Kammer et al., Trends Anal. Chem. 2011, 30, 425-436 (note: identification combined with detection)
Measurement methods include instrument specification , procedures or well-defined protocols, data analysis and representation, and data compilation in a common format
* Adapted from von der Kammer et al., Trends Anal. Chem. 2011, 30, 425-436 (note: identification combined with detection)
Qualitative vs. Quantitative Measurements• Qualitative
• ranges from, e.g., “the sample does or does not contain MWCNTs” to “the sample contains about 50% MWCNTs” per unit area or volume examined
• relative uncertainty in the estimate is large• Semi-Quantitative
• measurement of, e.g., number of MWCNTs as “counted” in a sample• not all MWCNTs present may be measured (e.g., encased MWCNTs)• difficult to perform measurements that are statistically significant
Number or mass concentration of MWCNTs in fragments (quantification)
Physico-chemical characteristics or properties of MWCNTs in fragments, e.g., average size (diameter and length), size distribution, and surface composition
Relative amounts of fragments that contain MWCNTs vs. fragments that do not contain MWCNTs (by number or mass)
Average size and size distribution of the fragments
Shape of fragments
All of the same to the left Presence of unbound MWCNTs in sample
(detection) Relative amounts of fragments vs.
unbound MWCNTs in sample Number or mass concentration of
unbound MWCNTs in sample Physico-chemical characteristics or
properties of unbound MWCNTs in sample, e.g., average size (diameter and length), size distribution, and surface composition
QL , qualitative: yes/no or rough estimateSQ, semi-quantitative: can get a numerical result that is a good estimate, uncertainty is medium to high, dependent on numerous factorsQN, quantitative: get a numerical result with low uncertainty
High: statistically relevant sample size; minimal sample preparation; broadly available commercial instrument; measurement requires minimal expertise and timeMedium: unlikely that sample size is statistically relevant; moderate sample preparation; moderate availability of instruments, may contract measurements; skilled expertise and significant measurement timeLow: sample size not statistically relevant; difficult sample preparation; few instruments available at e.g., user facilities; exceptional expertise and measurement time
For detection (D), quantification (Q), and characterization (C)High: easy to detect, quantitative result for Q and CMedium: difficult to detect; semi-quantitative result for Q and CLow: not used for detection; qualitative result for Q and C
• Must first prioritize and select key characteristics and properties of MWCNTs, in fragments and unbound, and fragments
• More than one method is required to determine a characteristic or property
• Numerous methods for detection of MWCNTs, unbound and in fragments
• Most methods for quantification (concentration of MWCNTs) are semi-quantitative at best, i.e., may get a numerical result that is a reasonable estimate, uncertainty is medium to high
• Most methods for characterization are semi-quantitative at best:• Tedious to measure a large enough amount of material for
statistically relevant results• For many methods, cannot measure MWCNTs encased in a
fragment• Validated protocols and reference materials essential for
accurate measurements• Validation of methods and data are difficult and time-
Presence of MWCNTs (detection) Number or mass concentration of
MWCNTs on surface (quantification) Physico-chemical characteristics or
properties of MWCNTs , e.g., average size (diameter and length), size distribution, spatial distribution (degree of dispersion), and surface composition
Presence of MWCNTs in release media (detection)
Number or mass concentration of unbound MWCNTs per volume of media
Physico-chemical characteristics or properties of unbound MWCNTs in media, e.g., average size (diameter and length), size distribution, and surface composition
Tangled network of MWCNTs
Potential release of unbound MWCNTs
Prioritization and selection of what to measure is the essential first step More than one measurement method is required for quantification and
characterization Sample large enough to yield a statistically relevant result (quantitative
measurements)
Release media (dependent on lifecycle stage and mode of consumer use):
8 published studies• Polymer: epoxy (2); PA (3), PU (2), POM* (1)
• Methods identified below considered only tangled network resulting from polymer degradation (not subsequent release of MWCNTs or fragments by further action)
* Polymers not considered by TG2: POM = polyoxymethlene
High: statistically relevant sample size; minimal sample preparation; broadly available commercial instrument; measurement requires minimal expertise and time
Medium: unlikely that sample size is statistically relevant; moderate sample preparation; moderate availability of instruments, may contract measurements; skilled expertise and significant measurement time
Low: sample size not statistically relevant; difficult sample preparation; few instruments available at e.g., user facilities; exceptional expertise and measurement time
For detection (D), quantification (Q), and characterization (C)High: easy to detect, quantitative result for Q and CMedium: difficult to detect; semi-quantitative result for Q and CLow: not used for detection; qualitative result for Q and C
Table completed with input from NIST experts; additional input is welcome
• Start with a pilot study involving a few labs with great expertise in the topic
• Possible to design a pilot test and eventually an ILS for:• Generation of released material in a controlled manner• Representative sampling of released material
• Very difficult to design a pilot test for measuring MWCNTs in polymer composites that would yield reproducible results
• Start with protocol development• Generation of released material by one or more specific
methods• Sampling or sample preparation protocols• Protocols for qualitative or semi-quantitative measurements
Standardization of Methods • Too early!• Requires well-defined, validated protocols for any methodTG 1: Methods May16-17, 2013NanoRelease Steering Committee