CNC-1: Cellulose Nanocrystal Powder Certified Reference Material

This Certified Reference Material is intended primarily for use in the validation of procedures and development of methods for the determination of trace metals in cellulosic nanomaterials or those of a similar matrix. It has been gamma sterilized to support studies of environmental health and safety and nanotoxicology. CNC-1 also serves as a stable and homogeneous representative test material to foster development and validation of international consensus-based standards to further rigorous physico-chemical characterization of CNC and similar or related cellulosic-based nanomaterials. Parameters of interest include elemental/molecular composition, specific surface area, surface chemistry, particle size and distribution, morphology/shape/form, surface charge and crystal structure.

A unit of CNC-1 CRM consists of a bottle containing approximately 1 g of spray-dried cellulose nanocrystals.

Table 1 summarizes those trace metals for which certified values have been established for this material. Certified values are based on data generated at NRC. The expanded uncertainty (UCRM) in the certified value is equal to UCRM = kuc where uc is the combined standard uncertainty calculated according to the JCGM Guide Footnote 1 and k is the coverage factor. It is intended that UCRM accounts for every aspect that reasonably contributes to the uncertainty of the measurement Footnote 2. A coverage factor of 2 was applied for all elements. The table below lists certified values for CNC-1, expressed on a dry mass basis.

Table 1: Certified Mass Fraction Values for CNC-1

Element Mass fraction, mg/kg
As (a) <0.035 Table 1 note 1
Cd (a,b) 0.009 ± 0.003
Cr (b,c) 0.79 ± 0.09
Cu (a,b) 0.481 ± 0.059
Fe (b,c) 20.8 ± 2.5
Hg (a,b) 0.01 ± 0.007
Ni (b,c) 4.51 ± 0.25
Pb (a,b) 0.919 ± 0.067

Table notes

Table 1 note 1

for the purposes of uncertainty propagation, this value (x) could be interpreted as x/2 ± x/(2√3) where the uncertainty value is derived assuming a rectangular distribution within the interval 0 to X.

Return to table 1 note 1 referrer

Coding

Coding refers to the applied instrumental method of analysis.

  • a - inductively coupled plasma mass spectrometry; method of additions
  • b - isotope dilution inductively coupled plasma mass spectrometry
  • c - inductively coupled plasma atomic emission spectrometry; method of additions

Table 2: Reference Value for Specific Surface Area (dry mass basis)

Surface Area Table 2 note a, m2/g
1.29 ± 0.10 Table 2 note b

Table notes

Table 2 note a

An average adsorbate (nitrogen) area per molecule of 0.162 nm2 is used for the determination.

Return to table 2 note a referrer

Table 2 note b

Uncertainty is an expanded uncertainty (k=2) about the mean (n=5) and accounts for all sources that reasonably contribute to the uncertainty of the measurement.

Return to table 2 note b referrer

Table 3: Reference value for mass fraction of sulfur

Mass Fraction, mg/g
6.63 ± 0.54 Table 3 note 1

Table notes

Table 3 note a

Uncertainty is an expanded uncertainty (k=2) about the mean (n=2) calculated by combining between-method and within-method variances following; dry mass basis

Return to table 3 note a referrer

Table 4: Reference values derived from DLS measurements of CNC-1

Parameter Value Table 4 note c
Z-average size, nm 95.3 ± 13.6 Table 4 note a
Polydispersity index 0.22 ± 0.08 Table 4 note b

Table notes

Table 4 note a

Z-average size is an intensity-weighted harmonic mean diameter of an equivalent sphere as determined by cumulants analysis of DLS measurements.

Return to table 4 note a referrer

Table 4 note b

Polydispersity index is a dimensionless parameter determined by cumulants analysis of DLS measurements. Uncertainty is an expanded uncertainty (k=2) about the mean (n=3), calculated by combining between-method and within-method variances following

Return to table 4 note a referrer

Table 5: Reference values for particle length and height of CNC-1

Parameter Value, nm
Length AFM 133 ± 100 Table 5 note a Table 5 note c
Length TEM 108 ± 34 Table 5 note a Table 5 note d
Height AFM 4.1 ± 3.2  Table 5 note b Table 5 note c

Table notes

Table 5 note a

Length is the longest dimension of a particle deposited on a substrate measured along a direction parallel to the substrate. Value presented is the arithmetic mean and uncertainty corresponds to the standard deviation.

Return to table 5note a referrer

Table 5 note b

Height is the arithmetic mean of a short dimension of a particle deposited on a substrate measured along a direction perpendicular to the length and parallel to the substrate normal. Uncertainty corresponds to the standard deviation of analysis of 32 individual particles.

Return to table 5 note b referrer

Table 5 note c

Value derived from image analysis of 32 individual particles.

Return to table 5 note c referrer

Table 5 note d

Value derived from image analysis of 1672 individual particles.

Return to table 5 note d referrer

Table 6: Reference Value for Zeta potential for CNC-1

Zeta potential, mV
-(39.3 ± 5.8) Table 6 note a

Table notes

Table 6 note a

Uncertainty is an expanded uncertainty (k=2) about the mean (n=2) calculated by combining between-method and within-method variances following

Return to table 6 note a referrer

Table 7: Reference thermogravimetry-derived values for CNC-1

Parameter Value Table 7 note a
Oxidation temperature
Peak 1, °C 299.55 ± 0.36
Peak 2, °C 400.03 ± 6.59
Residual mass Table 7 note b mg/g 13.7 ± 2.1

Table notes

Table 7 note a

Uncertainty is the standard deviation of results of 10 replicate measurement cycles.

Return to table 7 note a referrer

Table 7 note b

Dry mass basis.

Return to table 7 note b referrer

Date of issue: May 2013
Date of expiry: May 2023
Revised: March 2016 (editorial update), July 2017 (Storage and Sampling section), March 2018 (date of expiry extended)

Date modified: