388 / 670
(
g
)
AgNO
3
solution, 0.025M (optional)
.
—
Into a 1000 mL volumetric flask, pipet 250 mL AgNO
3
95
solution, 0.1 M [
C
c or
D
a]. Make up to the mark with water.
96
Prepare freshly before use
.
Then check the titer by titration of 25 mL against 0.025 M NaCl
97
solution.
98
(
h
)
NaCl solution, 0.025M (optional)
.
—
Into a 100 mL volumetric flask pipet 25 mL NaCl
99
solution, 0.1M [
D
b]. Make up to the mark with water.
Prepare freshly before use.
100
(
i
)
KNO
3
solution, 1 M.
—
Weigh 10.11 g potassium nitrate [
C
j] into a 100 mL volumetric flask.
101
Add about 80mL water and place it in an ultrasonic cleaner [
B
m] to dissolve with ultrasound and
102
heating until dissolved thoroughly. Cool down to room temperature and make up to the mark
103
with water. Filter using a 0.45 membrane disposable syringe before use.
104
105
E. Sample Preparation
106
Milk product, infant formula and adult/pediatric nutritional
.
—
Mix well to ensure that sample is
107
homogeneous.
108
Reconstitute powder samples by dissolving 25 g powder sample in 200 mL warm water (40 °C).
109
F. Extraction
110
For high protein samples requiring additional protein precipitation than that accomplished by
111
addition of nitric acid solution perform [
a-c
]. Otherwise begin with step [
d
].
112
(a)
Weigh an appropriate aliquot of Ready-to-feed (RTF) or reconstituted powder (e.g. 25g)
113
(accurate to 0.1 mg) into a 50 mL centrifuge tube.
Note: For samples with a high chloride content, weigh
114
a smaller test portion e.g. 5 g of reconstituted or RTF product.
115
(b)
Transfer 2.5 mL precipitating solution I [
D
c] and 2.5 mL precipitating solution II [
D
d] into
116
the tube
.
Complete to 50 mL with water. Mix well. If foam impacts the constant volume, one or
117
two drops of defoaming agent ([
C
l]) shall be used.
118
(c)
Centrifuge at 12000 x
g
for 5 min at 4°C. Then equilibrate to room temperature.
119
(d)
Accurately transfer either 10 mL supernatant from steps [a-c] or weigh an appropriate aliquot
120
of RTF or reconstituted powder (e.g. 25g) (accurate to 0.1 mg).
Note: For samples with a high chloride
121
content, weigh a smaller test portion e.g. 5 g of reconstituted or RTF product.
122
2015.07/2015.08 (February 2016)
Chlor-02/Chlor-04
FOR ERP USE ONLY
DO NOT DISTRIBUTE