CNCS1: 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. CNCS1 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 CRM CNCS1 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 (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 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. A coverage factor of 2 was applied for all elements. The table below lists certified values for CNCS1, expressed as mg/kg of suspension.
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.
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
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 betweenmethod and withinmethod variances following.
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 intensityweighted harmonic mean diameter of an equivalent sphere as determined by cumulants analysis of DLS measurements.
 Table 3 note b

Polydispersity index is a dimensionless parameter determined by cumulants analysis of DLS measurements
 Table 3 note c

Results are shown as X̄ ± U_{p}(X̄), where X̄ is an equally weighted arithmetic average of the participating laboratories Z average size values and U_{p} (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.
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.
 Table 4 note b

Length is the longest dimension of a particle deposited on a substrate measured along a direction parallel to the substrate.
 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.
 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).
 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.
 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.
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.
 Table 5 note b

Dry mass basis.
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 betweenmethod and withinmethod variances following.
Date of issue: May, 2013
Date of expiry: May, 2018
Revised: March 2016 (editorial update)
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