P
oitevin
:
J
ournalof
AOAC I
nternational
V
ol
.
95, N
o
. 1, 2012
183
using only one internal standard line. Following is the list of
wavelengths for each element (and its appropriate internal
standard), in priority order, that have been found acceptable for
main foodstuffs:Wavelength (nm): Ca: 317.933 (In: 303.936);
Cu:324.754 (In:303.936);Fe:259.94 (Sr:338.071);K:766.491
(Sr: 460.733); Mg: 285.213 (In: 303.936); Mn: 257.610 (Sr:
338.071); Na: 589.592 (Sr: 460.733); P: 213.618 (In: 303.936);
andZn: 213.857 (Sr: 338.071).
Other wavelengths that are acceptable for both elements and
internal standards couldbeusedas confirmatoryanalytical lines
or alternatewavelengths as certain recommended linesmaynot
be available on some ICP-OES systems:Wavelength (nm): Ca:
317.933 (Y: 371.028); Cu: 324.754 (Y: 371.028), 327.395 (In:
303.936orY: 371.028);Fe: 259.94 (Y: 371.028orCr: 283.563);
Mg: 285.213 (Y: 371.028), 279.028 (In: 303.936);Mn: 257.610
(Sr: 460.733 or Y: 371.028); P: 178.222 (Sr: 460.733 or Y:
371.028); andZn: 213.857 (Sr: 460.733 orY: 371.028).
Other lines of appropriate sensitivity, free of interferences or
corrected for interferences in specific matrixes, may be just as
acceptable.
G. Reagents
(
a
)
Ionization buffer/internal standard solution
.—Weigh
1.27 g cesium chloride into a 1000mL acid-washed volumetric
flask.
Note
: This cesium 0.1% (w/v) solution was tested as the
minimal recommended concentration required for element
analysis in most food matrixes. Cs solution 1% (w/v) is
recommended if an element is present at low concentration
in high-salted food raw materials, e.g., culinary products or
tastemakers, or if it isanalyzedasan impurity in food-grade salts.
Add40mL indium1000mg/kgand10mLeachof strontium,
yttrium, and chromium 1000mg/kg stock standard solutions as
internal standards. Add 10 mL HNO
3
. Dilute to volume with
H
2
O, mix, and transfer to an acid-washed polyethylene bottle.
Note
: Reagent concentrations assume the use of same pump
tubing internal diameter for both internal standard/ionization
buffer and sample pump tubes using automatic addition.
(
b
)
Stock standard solution
.—Working standards can be
prepared from ICP-grade individual element 1000 mg/kg
(e.g., for copper, iron, manganese and zinc) and 10000mg/kg
Table 2011.14J. Suggestedconcentrationof thesix standardsolutions,mg/kg
Element
Std0
Std1
Std2
Std3
Std4
Std5
Std6
Ca
0
7.5
15
30
75
150
225
Cu
0
0.05
0.1
0.2
0.5
1.0
1.5
Fe
0
0.25
0.5
1.0
2.5
5
7.5
K
0
10
20
40
100
200
300
Mg
0
2.5
5
10
25
50
75
Mn
0
0.00125
0.0025
0.005
0.0125
0.025
0.0375
Na
0
5
10
20
50
100
150
P
0
5
10
20
50
100
150
Zn
0
0.1
0.2
0.4
1.0
2.0
3.0
Table 2011.14I. Interlaboratory study results for zinc
Matrix
Mean, mg/kg Rec.,% S
r
,mg/kg
a
RSD
r
,%
b
S
R
, mg/kg
c
RSD
R
,%
d
HorRat No. of labs
e
Outlier labs
f
Chocolatemilk powder
18.06
NA
g
0.396 2.19
0.95
5.24
0.51
8
5–SG
Dieteticmilk powder 2
53.65
105 1.43 2.66
2.36
4.40
0.50
9
NS
h
Infant cereal
36.51
NA 0.92 2.25
1.27
3.44
0.37
9
NS
Peanut butter
NISTSRM 2387
26.64 (26.3)
i
101 1.06 3.96
1.78
6.69
0.69
9
NS
Wheat gluten
NISTRM 8418
49.30 (53.8)
i
92
0.96
1.95
3.19
6.46
0.73
9
NS
a
S
r
=SD for repeatability (within laboratory).
b
RSD
r
=RSD for repeatability.
c
S
R
=SD for reproducibility (among laboratories).
d
RSD
R
=RSD for reproducibility.
e
Reporting laboratoriesminus outliers.
f
SG=SingleGrubbs outlier.
g
NA=Not available.
h
NS=Not significant.
i
Certifiedor reference values.
MTE-01
FORWORKINGGROUP/ERPUSEONLY
DONOTDISTRIBUTE
