Materials
(
a
)
Volumetric flasks
.—Glass, 50, 100, 500, 1000 mL
(SLV, testsMD1 andMD2) or equivalent (testsMD3,MD4,
andRT).
(
b
)
Erlenmeyer flask for slurry preparation
.—Glass,
100mL(SLV, testsMD1andMD2)orequivalent (testsMD3,
MD4, andRT).
(
c
)
Sample tubes
.—Polyethyleneor polystyrene, tubes 15
or 50 mL with caps (Falcon) for ICP analysis (SLV, tests
MD1 andMD2) or equivalent (testsMD3,MD4, andRT).
(
d
)
Filters
.—Ashless filter papers, quantitative (SLV,
tests MD1 and MD2), Whatman 589/1 (diameter 125 mm
and/or 90 mm; Schleicher & Schuell, Whatman, Dassel,
Germany), or equivalent (testsMD3,MD4, andRT).
(
e
)
Pipets
.—Macropipet, variable volume 0.5–5.0 mL;
micropipet, variable volume 50–200 L and 200–1000 L;
electronic digital pipet 50–1000 L (SLV, tests MD1 and
MD2), or equivalent (testsMD3,MD4, andRT).
(
f
)
Samples
.—Certified and standard reference materials
fromNational Institute of Standards andTechnology (NIST;
Gaithersburg, MD) and National Metrology Institute (LGC
standards, Teddington, UK), in-house reference available
samples (from internal proficiency tests), and rawmaterials
(Table 2) were used for the SLV, ruggedness tests MD1,
MD2,MD3, andMD4and internalRT, includingdairy-based
products, milk, and cereals-based products, chocolate and
dietetic milk powders, refrigeratedmeals, pet food, and raw
materials, suchaswholeeggpowder,wheatgluten, cornbran,
and added food-grade salts (calcium carbonate, calcium
phosphate tribasic, calcium citrate tribasic, potassium
chloride, magnesium carbonate, magnesium chloride,
manganese sulfate, and sodiumchloride).
ChemicalsandReferenceSolutions
(
a
)
High grade water, H
2
O (18 M )
.—MilliQ
™
Plus
system(Millipore, Bedford,MA).
(
b
)
Nitric acid (HNO
3
)
.—65%(w/v), Suprapure.
(
c
)
Nitric acid (HNO
3
)
.—65%(w/v), analytical grade.
(
d
)
Hydrochloric acid
.—37%(w/v), analytical grade.
(
e
)
Hydrogenperoxide.—
97%(w/v), analytical grade.
(
f
)
Multistandard.—
CPI International (Santa Rosa, CA).
Composition of the CPI standard solution, in mg/L: Ca =
7500;Cu=50;Fe=250;K=10000;Mg=2500;Mn=1.25;
Na=5000; P=5000; Zn=100.
(
g
)
Calcium standard solution.—
10000 mg/L (Merck,
Darmstadt, Germany).
1486
P
OITEVINETAL.
: J
OURNALOF
AOACI
NTERNATIONAL
V
OL
. 92,N
O
. 5, 2009
Table 2. Rawmaterials, certified, and in-house referencematerialsused forSLVandRT
Material type
Sample reference
AOAC food trianglesector
a
Test code
Sterilizedcream
LGCRM7104
1
SLV
Bakingchocolate
NISTSRM2384
2
SLV
Peanut butter
NISTSRM2387
3
RT
Wholeeggpowder
NISTRM8415
4
SLV
Chocolatemilkpowder
CMP
5
SLV
b
-RT
Infant cereals
IC
5
SLV
b
-RT
Baby foodcomposite
NISTSRM2383
5
SLV
Cornbran
NISTRM8433
5
SLV
b
Dieteticmilkpowder 1
DMP1
6
SLV
b
Dieteticmilkpowder 2
DMP2
6
RT
Pet food
PET
6
SLV
b
Nonfatmilkpowder
NISTSRM1549
7
SLV
b
Wheat gluten
NISTRM8418
9
RT
Calciumcarbonate
CASNo. 471-34-1
NA
c
SLV
Calciumphosphate tribasic
CASNo. 7758-84-4
NA
SLV
Calciumcitrate tribasic
CASNo. 5785-44-4
NA
SLV
Potassiumchloride
CASNo. 7447-40-7
NA
SLV
Magnesiumcarbonate
CASNo. 546-93-0
NA
SLV
Magnesiumchloride
CASNo. 7791-18-6
NA
SLV
Manganesesulfate
CASNo. 10034-96-5
NA
SLV
Sodiumchloride
CASNo. 7647-14-5
NA
SLV
a
Sector number (1 to9) of the food triangle (27).
b
SLV, including ruggedness tests (MD).
c
NA=Not applicable.
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