© 2013AOAC INTERNATIONAL
minimize easily ionizable element (EIE) effects and to correct for
physical and chemical interferences.
F. Instrumentation
(
Note
: ICP-OESequipmentsmustbeusedbyqualified laboratory
personnel who are familiar with the operation andmaintenance of
analytical systems and must followmanufacturer’s directions for
safety risk, safety environment, and use of instruments.)
(
a
)
ICP-OES spectrometer
.—Instrument with
axial, radial,
or dual view grating configurations and autosampler, capable of
determining multiple wavelengths for each element of interest
with the required sensitivity. A 3-channel peristaltic pump with
or without appropriate in-line addition system (e.g., T connector)
are linked between the peristaltic pump and nebulizer to avoid
having to manually add ionization buffer and internal standards
to each sample solution. A thermostated cyclonic spray chamber
equipped with a micro-concentric nebulizer or other components
designed to optimize aerosol and maximize precision was used.
Followmanufacturer’s recommendations. Select peristaltic pump
rotation speed, sample, and internal standardpump tubes of similar
size tomaximize mixing accuracy while maintaining the required
detection levels.
Ionizationbuffer (cesium chloride) is combinedwith the internal
standard solution to compensate EIEs effects (e.g., K, Na, andCa)
in the plasma since certain food materials can contain substantial
concentrationsof theseelements.Thisprovides a significant source
of electrons in the plasma. The presence of ionization buffer in
all samples and standards will minimize the effects of varying
concentrations of EIEs in the sample. The solution presented to
the nebulizer contains amaximumof 5000mg/kg cesium for high-
Table 2011.14F. Interlaboratory study results formanganese
Matrix
Mean, mg/kg Rec.,% S
r
a
RSD
r
b
,% S
R
c
, ng/g RSD
R
d
,% HorRat
No. of labs
e
Outlier labs
f
Chocolatemilk powder
7.54
NA
h
0.14
1.88
0.67
8.82
0.75
9
NS
g
Dieteticmilk powder 2
0.40
99
0.01
2.56
0.0197
4.89
0.27
8
2C
Infant cereal
16.74
NA 1.14
6.79
1.44
8.61
0.82
9
NS
Peanut butter NISTSRM2387 15.85
(16.0)
i
99
0.45
2.86
1.32
8.31
0.79
9
NS
Wheat glutenNISTRM8418
12.87
(14.3)
1
90
0.23
1.75
1.13
8.75
0.80
9
NS
a
S
r
=Standarddeviation for repeatability (within laboratory).
b
RSD
r
=
Relative standard deviation for repeatability.
c
S
R
=Standarddeviation for reproducibility (among laboratories).
d
RSD
R
=Relative standard deviation for reproducibility.
e
Reporting laboratoriesminus outliers.
f
C=Cochran outlier; SG=SingleGrubbs outlier; DG=DoubleGrubbs outlier.
g
NS=Not significant.
h
NA=Not available.
i
Value in parentheses =Certified or reference values.
Table 2011.14G. Interlaboratory study results for sodium
Matrix
Mean, mg/kg Rec.,% S
r
a
RSD
r
b
,% S
R
c
, ng/g RSD
R
d
,% HorRat
No. of labs
e
Outlier labs
f
Chocolatemilk powder
1927.84
97
43.30
2.25
51.07
2.65
0.52
9
NS
g
Dieteticmilk powder 2
1769.19
96
18.64
1.05
33.39
1.89
0.36
9
NS
Infant cereal
992.41
95
37.67
3.80
39.72
4.00
0.71
8
6SG
Peanut butter NISTSRM2387 4924.12
(4890)
h
101 158.61 3.22
158.61
3.22
0.72
9
NS
Wheat glutenNISTRM 8418
1346.82
(1420)
h
95
19.56
1.45
26.85
1.99
0.37
8
6SG
a
S
r
=Standarddeviation for repeatability (within laboratory).
b
RSD
r
=
Relative standard deviation for repeatability.
c
S
R
=Standarddeviation for reproducibility (among laboratories).
d
RSD
R
=Relative standard deviation for reproducibility.
e
Reporting laboratoriesminus outliers.
f
C=Cochran outlier; SG=SingleGrubbs outlier; DG=DoubleGrubbs outlier.
g
NS=Not significant.
h
Value in parentheses =Certified or reference values.
MTE-01
FORWORKINGGROUP/ERPUSEONLY
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