CNC1: 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. CNC1 also serves as a stable and homogeneous representative test material to foster development and validation of international consensusbased standards to further rigorous physicochemical characterization of CNC and similar or related cellulosicbased 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 CNC1 CRM consists of a bottle containing approximately 1 g of spraydried 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 (U_{CRM}) in the certified value is equal to U_{CRM} = ku_{c} where u_{c} is the combined standard uncertainty calculated according to the JCGM Guide Footnote 1 and k is the coverage factor. It is intended that U_{CRM} 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 CNC1, expressed on a dry mass basis.
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.
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
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 nm^{2} is used for the determination.
 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.
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 betweenmethod and withinmethod variances following; dry mass basis
Parameter  Value 

Zaverage 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

Zaverage size is an intensityweighted harmonic mean diameter of an equivalent sphere as determined by cumulants analysis of DLS measurements.
 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 betweenmethod and withinmethod variances following
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.
 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.
 Table 5 note c

Value derived from image analysis of 32 individual particles.
 Table 5 note d

Value derived from image analysis of 1672 individual particles.
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 betweenmethod and withinmethod variances following
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.
 Table 7 note b

Dry mass basis.
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)
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