NASS-7: Seawater Certified Reference Material for Trace Metals and other Constituents

The following tables show those constituents for which certified, reference and information values have been established for this seawater 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 for all elements. It is intended that UCRM accounts for every aspect that reasonably contributes to the uncertainty of the measurement. The density of NASS‑7 is 1.021 g/mL at 21°C

Table 1: Certified values for NASS‑7

Element Mass Fraction,
μg/kg
Mass Concentration,
μg/L
International recognition
of measurement
capability (CMC)
boron (a,b) 3670 ± 120 3750 ± 120 -
cadmium (a,b,c) 0.0157 ± 0.0016 0.0161 ± 0.0016 TEW20
cobalt (b,c) 0.0143 ± 0.0014 0.0146 ± 0.0014 TEW22
copper (a,b,c) 0.195 ± 0.014 0.199 ± 0.014 TEW23
iron (a,c) 0.344 ± 0.026 0.351 ± 0.026 TEW24
manganese (b,c) 0.74 ± 0.06 0.75 ± 0.06 TEW26
molybdenum (a,b,c) 9.10 ± 0.40 9.29 ± 0.40 TEW27
nickel (a,b,c) 0.243 ± 0.018 0.248 ± 0.018 TEW28
lead (a,b,c) 0.0025 ± 0.0008 0.0026 ± 0.0008 TEW25
uranium (a,b,c) 2.81 ± 0.16 2.87 ± 0.16 -
zinc (a,b,c) 0.41 ± 0.08 0.42 ± 0.08 TEW30

Table 2: Reference values for NASS‑7

Element Mass Fraction,
μg/kg
Mass Concentration,
μg/L
International recognition
of measurement
capability (CMC)
arsenic (b,c) 1.23 ± 0.06 1.26 ± 0.06 TEW19
chromium (a,c) 0.105 ± 0.016 0.107 ± 0.016 TEW21
vanadium (b,c) 1.27 ± 0.08 1.30 ± 0.08 TEW29

Table 3: Information values for NASS‑7

Compound Mass Fraction,
μg/kg
Mass Concentration,
μg/L
lanthanum (c) 0.006 0.006
cerium (c) 0.003 0.003
praseodymium (c) 0.002 0.002
neodymium (c) 0.003 0.003
samarium (c) 0.002 0.002
europium (c) 0.0006 0.0006
gadolinium (c) 0.0014 0.0014
terbium (c) 0.0003 0.0003
dysprosium 0.0013 0.0013
holmium (c) 0.0010 0.0010
erbium (c) 0.0012 0.0012
thulium (c) 0.000 11 0.000 11
ytterbium (c) 0.0010 0.0010
lutetium (c) 0.0002 0.0002

Table 3 (continued): Information values for NASS‑7

Element Mass Fraction,
μg/kg
Mass Concentration,
μg/L
inorganic arsenic (d) 0.83 0.85
monomethylarsenic (as As) (d) 0.018 0.019
dimethylarsenic (as As) (d) 0.190 0.190
trimethylarsenic (as As) (d) 0.013 0.013

Coding

Coding

  • a - Isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS)
  • b - Standard addition inductively coupled plasma mass spectrometry (SA-ICP-MS)
  • c - Inductively coupled plasma mass spectrometry (ICP-MS)
  • d - Hydride generation cryo-trapping ICP-MS

Intended use

This certified reference material is primarily intended for use in the calibration of procedures and the development of methods used for the analysis of seawater for trace metals. A minimum sample volume of 10 mL is recommended.

Uncertainty

Included in the overall combined uncertainty estimate (uc) are uncertainties in the batch characterization (uchar), uncertainties related to possible between-bottle variation (uhom), and uncertainties related to inconsistency between the various measurement methods (umethod). Expressed as standard uncertainties, these components are listed in Table 4.

Table 4: Uncertainty components for NASS‑7

Element uc,
μg/kg
uchar,
μg/kg
uhom,
μg/kg
umethod,
μg/kg
boron 60 50 30 0
cadmium 0.0008 0.0004 0.0003 0.0006
cobalt 0.0007 0.0006 0.0003 0.0000
copper 0.007 0.006 0.003 0.003
iron 0.013 0.011 0.000 0.007
manganese 0.03 0.02 0.02 0.01
molybdenum 0.20 0.15 0.13 0.00
nickel 0.009 0.005 0.007 0.000
lead 0.0004 0.0002 0.0003 0.0000
uranium 0.08 0.06 0.05 0.00
zinc 0.04 0.03 0.02 0.00

Table 4 (continued): Uncertainty components for NASS‑7

Element uc,
μg/kg
uchar,
μg/kg
uhom,
μg/kg
umethod,
μg/kg
arsenic 0.03 0.03 0.01 0.01
chromium 0.008 0.004 0.006 0.004
vanadium 0.04 0.03 0.00 0.02

Date of issue: February 2016
Date of expiry: December 2024
Revised: March 2016 (editorial update); January 2017 (inorganic arsenic), August 2018 (date of expiry extended)

Date modified: