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GB 5009.91-2017: Food safety national standard -- Determination of potassium and sodium in food
GB 5009.91-2017
GB
NATIONAL STANDARD
OF THE PEOPLE’S REPUBLIC OF CHINA
National food safety standard
Determination of potassium and sodium in foods
ISSUED ON. APRIL 06, 2017
IMPLEMENTED ON. OCTOBER 06, 2017
Issued by. National Health and Family Planning Commission of the PRC;
State Food and Drug Administration
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Table of contents
Foreword ... 3 
1 Scope ... 4 
2 Principle... 4 
3 Reagents and materials ... 4 
4 Instruments and equipment ... 6 
5 Analytical procedures ... 6 
6 Expression of analytical results ... 9 
7 Precision... 9 
8 Others ... 9 
9 Principles ... 10 
10 Reagents and materials... 10 
11 Instruments and equipment ... 11 
12 Analytical procedures ... 12 
13 Expression of analytical results ... 12 
14 Precision ... 13 
15 Others ... 13 
Appendix A Sample determination reference condition ... 14 
Foreword
This standard replaces the potassium and sodium determination part in GB/T
5009.91-2003 “Determination of potassium and sodium in foods”, GB/T
15402-1994 “Fruits, vegetables and derived products – determination of
sodium and potassium”, NY 82.18-1988 “Determination of potassium and
sodium in fruit juice”, GB 5413.21-2010 “National food safety standard –
Determination of calcium, iron, zinc, sodium, potassium, magnesium, copper
and manganese in foods for infants and young children, milk and milk
products”, GB/T 18932.11-2002 “Method for determination of potassium,
phosphorus, iron, calcium, zinc, aluminum, sodium, magnesium, boron,
manganese, copper, barium, titanium, vanadium, nickel, cobalt and chromium
in honey - Inductively coupled plasma atomic emission spectrometry (ICP-AES
method”, GB/T 18932.12-2002 “Method for determination of potassium,
sodium, calcium, magnesium, zinc, iron, copper, manganese, chromium, lead
and cadmium contents in honey - Atomic absorption spectrometry”, AND NY/T
1653-2008 “Determination for mineral elements in vegetables, fruits, and
derived products by ICP-AES method”.
As compared with the above standards, the main changes are as follows.
- CHANGE the standard name into “National food safety standard -
Determination of potassium and sodium in foods”;
- MODIFY the flame atomic absorption spectrometry method as the first
method, the flame atomic emission spectrometry method as the second
method, the inductively coupled plasma emission spectroscopy method
as the third method, AND the inductively coupled plasma mass
spectrometry as the fourth method;
- MODIFY some part of the sample preparation;
- MODIFY some part of the sample digestion;
- INCREASE the method detection limit and quantitative limit;
- ADD appendix.
National food safety standard
Determination of potassium and sodium in foods
1 Scope
This standard specifies four methods for the determination of potassium and
sodium in food. the flame atomic absorption spectrometry, the flame atomic
emission spectrometry, the inductively coupled plasma emission spectroscopy,
AND the inductively coupled plasma mass spectrometry.
This standard applies to the determination of potassium and sodium in food.
Method I. Flame atomic absorption spectrometry
2 Principle
After digestion, the sample is injected into the atomic absorption spectrometer.
After the flame atomization, the potassium and sodium respectively absorb the
766.5 nm and 589.0 nm resonance line. AND within a concentration range, its
absorption value is proportional to the contents of potassium and sodium, AND
it is quantified through comparison with standard series.
3 Reagents and materials
Unless otherwise specified, the reagents used in this method are excellent
grade pure, AND the water is level II water as specified in GB/T 6682.
3.1 Reagents
3.1.1 Nitric acid (HNO3).
3.1.2 Perchloric acid (HClO4).
3.1.3 Cesium chloride (CsCl).
3.2 Reagent preparation
3.2.1 Mixed acid [perchloric acid + nitric acid (1 + 9)]. TAKE 100 mL of
perchloric acid; slowly ADD it into 900 mL of nitric acid; MIX it uniformly.
3.2.2 Nitric acid solution (1 + 99). TAKE 10 mL of nitric acid; slowly ADD it into
990 mL of water; MIX it uniformly.
3.2.3 Cesium chloride solution (50 g/L). DISSOLVE 5.0 g of cesium chloride in
water; USE water to dilute it to 100 mL.
3.3 Standard substance
3.3.1 Potassium chloride standard substance (KCl). its purity is greater than
99.99%.
3.3.2 Sodium chloride standard substance (NaCl). its purity is greater than
99.99%.
3.4 Preparation of standard solution
3.4.1 Potassium and sodium standard stock solution (1000 mg/L). PLACE the
potassium chloride or sodium chloride in the oven at 110 °C ~ 120 °C to dry it
for 2 h. Accurately WEIGH 1.9068 g of potassium chloride or 2.5421 g of
sodium chloride; respectively DISSOLVE it into water; TRANSFER it into a
1000 mL volumetric flask; DILUTE it to the mark; MIX it uniformly; STORE it in
a polyethylene bottle; PRESERVE it at 4 °C; or otherwise USE the standard
solution which had been certified and awarded with the standard substance
certificate by the state.
3.4.2 Potassium and sodium standard working solution (100 mg/L). accurately
PIPETTE 10.0 mL of potassium or sodium standard stock solution in a 100 mL
volumetric flask; USE water to dilute it to the mark; STORE it in a polyethylene
bottle; PRESERVE it at 4 °C.
3.4.3 Potassium and sodium standard series working solution. accurately
PIPETTE 0 mL, 0.1 mL, 0.5 mL, 1.0 mL, 2.0 mL, and 4.0 mL of potassium
standard working solution in 100 mL volumetric flask; ADD 4 mL of cesium
chloride solution; USE water to make its volume reach to the mark; MIX it
uniformly. The concentration of potassium in this standard series working
solution is 0 mg/L, 0.100 mg/L, 0.500 mg/L, 1.00 mg/L, 2.00 mg/L, and 4.00
mg/L, respectively; AND it may, in accordance with the potassium
concentration in the actual sample solution, appropriately adjust the
concentration range of the standard solution. Accurately PIPETTE 0 mL, 0.5
mL, 1.0 mL, 2.0 mL, 3.0 mL, and 4.0 mL of sodium standard working solution in
100 mL volumetric flask; ADD 4 mL of cesium chloride solution; USE water to
make its volume reach to the mark; MIX it uniformly. The concentration of
sodium in the standard series working solution is 0 mg/L, 0.500 mg/L, 1.00
mg/L, 2.00 mg/L, 3.00 mg/L, and 4.00 mg/L, respectively; AND it may, in
WEIGH 0.5 g ~ 5 g (accurate to 0.001 g) of sample in the glass OR Teflon
pressure digestion tank; as for the samples containing ethanol or carbon
dioxide, PLACE it on the heating plate to heat it at low temperature to remove
ethanol or carbon dioxide; ADD 10 mL of mixed acid; COVER and PLACE it for
1 h or overnight; PLACE it in the adjustable temperature control electric
heating plate or furnace for digestion; if it changes into dark brown, COOL it
down and ADD the mixed acid, until white smoke is generated AND the
digestion solution is in colorless transparent OR in light yellow; COOL it down;
USE water to make its volume reach to 25 mL or 50 mL; MIX it uniformly to
prepare for use; and meanwhile MAKE blank test.
5.2.4 Dry digestion method
WEIGH 0.5 g ~ 5 g (accurate to 0.001 g) of sample in the crucible; MAKE it
subject to carbonization in the electric furnace at small fire to make it
smokeless; PLACE it into the 525 °C ± 25 °C muffle furnace for ashing for 5 ...