CNCS-1: Cellulose Nanocrystal Suspension 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. CNCS-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 CRM CNCS-1 consists of a bottle containing approximately 25 mL of a stable aqueous suspension of cellulose nanocrystals at a mass fraction of 67.9 ± 0.3 mg/g.

Table 1 summarizes those elements for which certified values have been established for this suspension. 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 and k is the coverage factor. It is intended that UCRM accounts for every aspect that reasonably contributes to the uncertainty of the measurement. A coverage factor of 2 was applied for all elements. The table below lists certified values for CNCS-1, expressed as mg/kg of suspension.

Table 1: Certified Mass Fraction Values

Element Mass fraction, (mg/kg)
As (a) <0.002 Table 1 note *
Cd (a,b) 0.0022 ± 0.0021
Cr (b,c) 0.048 ± 0.012
Cu (a,b) 0.017 ± 0.002
Fe (b,c) 0.224 ± 0.075
Hg (a,b) <0.002 Table 1 note *
Ni (b) 0.261 ± 0.032
Pb (a,b) 0.007 ± 0.002

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 (uniform) 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 mass fraction of sulfur

Mass Fraction Unit
0.50 ± 0.08 Table 2 note a mg/g

Table notes

Table 2 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 2 note a referrer

Table 3: Reference values derived from DLS measurements

Parameter Value Table 3 note c Unit
Z average size, nm 80.1 ± 5.6 Table 3 note a nm
Polydispersity index 0.181 ± 0.039 Table 3 note b -

Table notes

Table 3 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 3 note a referrer

Table 3 note b

Polydispersity index is a dimensionless parameter determined by cumulants analysis of DLS measurements

Return to table 3 note b referrer

Table 3 note c

Results are shown as X̄ ± Up(X̄), where is an equally weighted arithmetic average of the participating laboratories Z average size values and Up (X̄) is an expanded uncertainty with p=95%. Effective degrees of freedom were estimated to be 18.5 and 4.4 for Z average size and polydispersity, respectively.

Return to table 3 note c referrer

Table 4: Reference values for particle length and height

Parameter Value, nm
Length AFM 115 ± 28 Table 4 note a Table 4 note e
Length TEM 84 ± 14 Table 4 note b Table 4 note f
Height AFM 4.91 ± 0.61 Table 4 note c Table 5 note e
Height TEM 5.6 ± 1.1 Table 4 note d Table 4 note f

Table notes

Table 4 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. A dispersion, the standard deviation of the dimension distribution for AFM length measurement, of 49 ± 15 nm was obtained.

Return to table 4 note a referrer

Table 4 note b

Length is the longest dimension of a particle deposited on a substrate measured along a direction parallel to the substrate.

Return to table 4 note b referrer

Table 4 note c

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. A dispersion, the standard deviation of the dimension distribution for AFM height measurement, of 1.61 ± 0.31 nm was obtained.

Return to table 4 note c referrer

Table 4 note d

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 (an assumption is made in this case that the measured width is equivalent to the height).

Return to table 4 note d referrer

Table 4 note e

Results are shown as X ̅±U_p (X ̅ ), where X ̅ is an equally weighted average value of the measurand and U_p (X ̅ ) is an expanded uncertainty with p=95%. Results from 2 laboratories were combined in accordance with. Effective degrees of freedom were 13.0 and 7.7 for length mean and dispersion, respectively, and 13.5 and 6.6 for height mean and distribution, respectively.

Return to table 4 note e referrer

Table 4 note f

Results are shown as X ̅±U_p (X ̅ ), where X ̅ is an average value of the measurand and U_p (X ̅ ) is an expanded uncertainty with p=95%. Results from 2 laboratories were combined in accordance with Footnote 3. Effective degrees of freedom were estimated to be 5.9 and 6.5 for length and width mean, respectively.

Return to table 4 note f referrer

Table 5: Reference thermogravimetry-derived values

Parameter Value Table 5 note a
Peak 1, °C 261.4 ± 2.2
Peak 2, °C 480.9 ± 4.6
Residual mass Table 5 note b , mg/g 50 ± 28

Table notes

Table 5 note a

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

Return to table 5 note a referrer

Table 5 note b

Dry mass basis.

Return to table 5 note b referrer

Table 6: Reference Value for Zeta potential for CNCS 1

Zeta potential, mV
-(46.7 ± 12.8) Table 6 note a

Table notes

Table 6 note a

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 6 note a referrer

Date of issue: May 2013
Date of expiry: May 2023
Revised: March 2016 (editorial update), March 2018 (date of expiry extended)

Date modified: