CNCD‑1: Cellulose Nanocrystal Powder Certified Reference Material

The following tables show those constituents for which certified, reference and information values have been established for this cellulose nanocrystal certified reference material (CRM).

The expanded uncertainty (UCRM) in the certified value is equal to U = kuc where uc is the combined standard uncertainty calculated according to the JCGM Guide [1] and k is the coverage factor. A coverage factor of two (2) was applied. It is intended that UCRM accounts for every aspect that reasonably contributes to the uncertainty of the measurement.

Table 1: Certified value for mass fraction of elemental sulfur in CNCD‑1

Mass fraction,Table 1 note aTable 1 note b
mg/kg
8720  ± 140Table 1 note c

Table notes

Table 1 note a

Measured by standard addition inductively-coupled plasma atomic emission spectroscopy (ICP-AES).

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Table 1 note b

Expressed on a dry mass basis.

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Table 1 note c

The expanded uncertainty of the weighted mean from 2 laboratory results was calculated by the BOB method [2].

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Table 2: Reference value for massic amount of sulfate half ester in CNCD‑1

Massic amount,Table 2 note aTable 2 note b
mmol/kg
253.6  ± 7.5Table 2 note cTable 2 note d

Table notes

Table 2 note a

Measured by conductometric titration for CNCD‑1 that has been dialysed and protonated with strong acid cation exchange resin.

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Table 2 note b

Expressed on a dry mass basis.

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Table 2 note c

The expanded uncertainty of equally weighted mean of 2 laboratory means calculated by BOB method [2].

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Table 2 note d

For comparison, the massic amount of sulfate half ester in CNCD‑1 corresponds to an elemental sulfur mass fraction (as sulfate half ester) of 8132  ± 240 mg/kg.

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Table 3: Reference values for CNCD‑1 suspension from dynamic light scattering (DLS) measurementsTable 3 note a

Quantity Value
Z-averageTable 3 note b, nm 70.0  ± 1.4Table 3 note d
polydispersityTable 3 note c 0.18

Table notes

Table 3 note a

A 0.5 mg/g suspension of CNCD‑1 in 5 mM NaCl.

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Table 3 note b

Z-average is the intensity-weighted equivalent spherical hydrodynamic diameter obtained by cumulants analysis.

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Table 3 note c

Polydispersity is a dimensionless parameter determined by cumulants analysis of DLS measurements; information value.

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Table 3 note d

Expanded uncertainty of the mean calculated by unbalanced ANOVA.

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Table 4: Reference values for CNCD‑1 from atomic force microscopy measurements aTable 4 note a

Quantity Value, nm
Mean height 3.4  ± 0.8bTable 4 note b
Width of height distribution 1.1  ± 0.4bTable 4 note b

Table notes

Table 4 note a

Samples were prepared by spin coating a dilute CNC suspension on poly-lysine coated mica and were imaged dry; 5 independently prepared samples were imaged with analysis of approximately 300 individual CNCs/sample, excluding aggregates. The maximum particle height is reported.

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Table 4 note b

Expanded uncertainties of the equally weighted mean of 5 measurement means of height and width of height distribution were calculated with k = 2.8 and k = 2.1, respectively.

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Table 5: Information values for CNCD‑1 from microscopy measurements

Method Quantity Value, nm
AFMTable 5 note a Mean length 76Table 5 note b
AFM Width of length distribution 32Table 5 note b
TEMTable 5 note cTable 5 note d Mean length 87Table 5 note e
TEM Width of length distribution 35Table 5 note f

Table notes

Table 5 note a

Samples were prepared by spin coating a dilute CNC suspension on poly-lysine coated mica and were imaged dry; 5 independently prepared samples were imaged with analysis of approximately 300 individual CNCs/sample, excluding aggregates. The maximum length along the long axis of the particle is reported.

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Table 5 note b

Standard deviation of sample means of 5 samples was 5 nm for both length and the width of the length distribution.

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Table 5 note c

Samples were prepared by depositing a dilute CNC suspension on a carbon-coated copper grid and staining with uranyl acetate. Data from two labs are reported (5 samples, 1909 particles; 3 samples, 600 particles). Only individual CNCs were analyzed.

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Table 5 note d

A mean width of 7.3 nm was obtained by TEM. The difference between the TEM width and AFM height may be due to lateral aggregation of particles.

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Table 5 note e

Mean of 2 laboratory means: 82 and 92 nm with standard deviations of 5 and 19 nm, respectively.

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Table 5 note f

Mean of 2 laboratory means: 36 and 33 nm with standard deviations of 5 and 6 nm, respectively.

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Table 6: Information value for zeta potential for CNCD‑1 suspension Table 6 note a

Method Value, mV
Electrophoretic mobility –37bTable 6 note b

Table notes

Table 6 note a

A 0.5 mg/g suspension of CNCD‑1 in 5 mM NaCl.

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Table 6 note b

A standard deviation s = 2 mV was obtained for 22 measurements.

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Table 7: Information values for crystalline fraction for CNCD‑1

Method Value
Solid state NMRTable 7 note a 0.59Table 7 note b
X-ray diffractionTable 7 note c 0.88Table 7 note d

Table notes

Table 7 note a

The crystalline fraction is measured by 13C cross polarization magic angle spinning solid state NMR and is the ratio of the broad signal from disordered C4 to the total C4 signal (disordered + crystalline); note that surface glucose units are included in the disordered fraction [3].

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Table 7 note b

A standard deviation s = 0.01 was obtained for 5 measurements, each on a different sample.

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Table 7 note c

A thin film sample was prepared from a CNCD‑1 suspension. The crystalline fraction is obtained as the ratio of the total intensity of crystalline regions divided by the sum of crystalline and amorphous regions in the X-ray diffraction spectrum, with deconvolution using Ruland-Rietveld analysis [4].

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Table 7 note d

A standard deviation s = 0.02 was obtained for 5 measurements, each on a different subsample.

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Table 8: Information values obtained by thermogravimetric analysis for CNCD‑1

Peak IDTable 8 note a Temperature,
°CTable 8 note b
Mass loss,
g/(100 g)
1 88 1.8
2 296 52.7Table 8 note c
3 305
4 350 23.2Table 8 note d
5 454
6 734 2.5
Residual mass   19.8

Table notes

Table 8 note a

Samples were heated between 25 and 800 °C in an argon atmosphere. Data were obtained by fitting the thermograms to a 6 asymmetric peak model and are mean values for 5 samples.

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Table 8 note b

The temperatures correspond to the maxima of the deconvoluted asymmetric Fraser-Suzuki peaks of the differential thermogravimetric curves. Standard deviations (°C) for the temperatures are 1, 2, 2, 2, 7 and 1 for peaks 1-6.

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Table 8 note c

Mass loss for peaks 2 and 3.

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Table 8 note d

Mass loss for peaks 4 and 5.

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Intended use

This certified reference material is primarily intended for use in the validation of procedures and the development of methods for the characterization of cellulose nanocrystals. It also serves as a stable test material to foster development and validation of international consensus-based standards for CNC. CNCD‑1 has been gamma sterilized and is suitable for studies of environmental health and safety. A minimum sample mass of 250 mg is recommended for elemental sulfur, 50 mg for dispersion of CNCD‑1 and 150 mg for the conductometric titration.

Date of issue: April, 2016
Date of expiry: April, 2021

Date modified: