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GB 14883.10-2016: Examination of radioactive materials for foods -- Determination of cesium-137
GB 14883.10-2016
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
National Food Safety Standard - Examination of
Radioactive Materials for Foods - Determination of
Cesium-137
ISSUED ON: AUGUST 31, 2016
IMPLEMENTED ON: MARCH 1, 2017
Issued by: National Health and Family Planning Commission of the
People’s Republic of China
Table of Contents
Foreword ... 3 
1 Scope ... 4 
Method-1 --  Spectrometry ... 4 
2 Principle ... 4 
3 Reagents and Materials ... 4 
4 Instruments and Equipment ... 4 
5 Analytical Procedures ... 5 
6 Expression of Analytical Result ... 7 
7 Others ... 8 
Method-2 -- Ammonium Phosphomolybdate Method ... 8 
8 Principle ... 8 
9 Reagents and Materials ... 8 
10 Instruments and Equipment ... 10 
11 Analytical Procedures ... 10 
12 Expression of Analytical Result ... 13 
13 Others ... 13 
Method-3 -- Cobalt Potassium Ferricyanide ... 14 
14 Principle ... 14 
15 Reagents and Materials ... 14 
16 Instruments and Equipment ... 14 
17 Analytical Procedures ... 14 
18 Expression of Analytical Result ... 15 
19 Others ... 15 
Appendix A Total Correction Factor of 137Cs Measurement Efficiency at Different
Heights and Apparent Densities ... 16 
Appendix B Lower Detection Limit of 137Cs Radioactivity ... 17 
National Food Safety Standard - Examination of
Radioactive Materials for Foods - Determination of
Cesium-137
1 Scope
This Standard is applicable to the determination of cesium-137 (137Cs) in various foods.
Method-1 --  Spectrometry
2 Principle
Directly, or after certain pre-treatment, load fresh food samples into a certain shape
and volume of sample box. On  spectrometer, measure the -ray characteristic peak
full energy peak net area of 137Cs in the sample at 661.6 keV. Compare it with a
standard radioactive source whose activity is already known. Calculate the
concentration of 137Cs radioactivity. When cesium-134 (134Cs) exists in the sample, this
method shall be applied to the determination of 137Cs.
3 Reagents and Materials
137Cs radioactive standard solution: specific activity is around 1,000 Bq/mL; it shall be
calibrated by a national statutory metrology department; it shall have an inspection
certificate signed by a legally recognized organization.
4 Instruments and Equipment
4.1 Low Background  Spectrometer System
Low background  spectrometer system shall satisfy the following requirements:
a) Detector: coaxial high-purity germanium or germanium (lithium) detector. In
terms of 60Co 1332.5 keV -ray full energy peak, its energy resolution shall be
less than 3 keV; its relative efficiency shall be higher than 15%.
b) Shield: the primary shield shall be multi-layer material heavy metal shield,
5.1.1 Energy scale
In accordance with energy scale, use  radioactive source (4.4) to conduct energy
scale of the low background  spectrometer system (4.1). Record the characteristic -
ray energy of the scale source, and corresponding full energy peak location. Through
computer processing, or drawing on a cartesian coordinate paper, or conducting the
least square fitting of the data, a graph of the relations between energy and the location
may be obtained.
5.1.2 Full energy peak detection efficiency scale
Measure 137Cs standard radioactive source. In order to reduce system errors, the net
area of the full energy peak being measured shall at least be more than 100,000 counts.
In accordance with Formula (1), calculate its detection efficiency at 661.6 keV -ray full
energy peak.
Where,
E---detection efficiency of 137Cs standard radioactive source at 661.6 keV -ray full
energy peak;
N---net area of 661.6 keV -ray full energy peak, expressed in (count);
A---activity of 137Cs standard radioactive source, expressed in (Bq);
T---measured time of 137Cs standard radioactive source, expressed in (s);
B---branch ratio of 137Cs 661.6 keV -ray, 84.62%.
5.2 Sampling
Sampling shall comply with the stipulations in GB 14883.1.
5.3 Preparation of Sample for Measurement
5.3.1 Grain sample: take 500 g of sample, then, evenly spread it in an enameled plate
or a stainless-steel plate. Place it in the oven, at around 70 °C, dry it for around 5 h.
Then, weigh it; calculate the dry mass/fresh mass ratio. In terms of granular grain, dry
it, then, directly place it into a sample box, which is already cleaned on the outside and
the inside; tamp it. In terms of finely powdered grain, use a sampler to press it, so that
the height of the sample is the same as the height of 137Cs standard radioactive source.
Record the dry sample mass and the height of the sample to be determined; calculate
its apparent density.
5.3.2 Vegetable sample: take around 3 kg of sample; remove the inedible part. Wash
E---same as Formula (1);
F---total correction factor of measurement efficiency, %, please refer to Appendix A;
please refer to GB/T 16145 for more accurate calculation methods;
B---branch ratio of 137Cs 661.6 keV -ray, 84.62%;
W---equivalent fresh sample mass of the sample being measured, expressed in (kg)
or (L);
---137Cs’s disintegration constant, expressed in (a-1);  = 0.693/T0, T0 is 137Cs’
radioactive half-life, 30 a;
t---time interval from sampling to measurement, expressed in (a).
7 Others
The lower detection limit of 137Cs radioactivity may be calculated in accordance with
Appendix B and the practical situation.
Method-2 -- Ammonium Phosphomolybdate Method
8 Principle
Use nitro-hydrochloride to leach food ash. Through adsorption separation of
ammonium phosphomolybdate, under citric acid masking, use iodine bismuth salt to
deposit and purify cesium. Use low background -ray meter to measure  radioactivity
of 137Cs.
9 Reagents and Materials
Unless it is otherwise stipulated, all reagents used in this method shall be analytically
pure. Water shall be Grade-1 water stipulated in GB/T 6682.
9.1 Reagents
9.1.1 Diammonium hydrogen phosphate [(NH4)2HPO4].
9.1.2 Ammonium nitrate (NH4NO3).
9.1.3 Ammonium molybdate [(NH4)6Mo7O244H2O].
9.1.4 Bismuth trioxide (Bi2O3).
9.3.1 137Cs standard solution: around 1  103 disintegrations / (minmL), contains 0.1
mol/L hydrochloric acid solution of 0.1 mgCs+/mL.
9.3.2 Cesium carrier solution (10 mgCs+/mL): weigh-take 12.67 g of cesium chloride,
then, place it in a small beaker. Add water to dissolve it, then, add 3 drops of
concentrated hydrochloric acid. Quantitatively transfer it into 1 L volumetric flask; use
water to dilute to the scale. Calibration may use one of the following two methods:
a) Calibration method 1 -- cesium perchlorate method: accurately absorb 4.00 mL
of cesium carrier solution, then, place it in a 125 mL conical flask. Add 1 mL of
nitric acid and 5 mL of perchloric acid. Evaporate it, till it emits white smoke for
a few minutes. Take it down, then, cool it down to the room temperature. Add
15 mL of absolute ethanol, shake it up. Then, in ice bath, cool it down for a few
minutes. Extract and filter the sediment in G4 sand core glass crucible, which
is already weighed. Use 10 mL of absolute ethanol to rinse it once, then, at
105 °C, dry it for 15 min. Cool it down in the dryer, then, weigh it.
b) Calibration method 2 -- tetraphenylboron-cesium method: take 2.00 mL of
cesium carrier solution, then, place it in a 100 mL beaker. Add 20 mL of water
and 1 mL of 6 mol/L acetic acid solution; mix it up. Add 10 mL of 3% sodium
tetraphenylborate solution; sli...