GB/T 5009.14-2003 (GB/T5009.14-2003)

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GB/T 5009.14-2003: PDF in English (GBT 5009.14-2003)

GB/T 5009.14-2003
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 67.040
C 53
Replacing GB/T 5009.14-1996
Determination of Zinc in Foods
ISSUED ON. AUGUST 11, 2003
IMPLEMENTED ON. JANUARY 01, 2004
Issued by. Ministry of Health of the People's Republic of China;
Standardization Administration of the People's Republic of
China.
Table of Contents
Foreword ... 3 
1 Scope ... 4 
2 Normative references ... 4 
3 Principle ... 4 
4 Reagents ... 4 
5 Instrument ... 5 
6 Analysis steps ... 5 
7 Result calculation ... 6 
8 Precision ... 6 
9 Principle ... 7 
10 Reagents ... 7 
11 Instrument ... 8 
12 Analysis steps ... 8 
13 Result calculation ... 9 
14 Precision ... 9 
15 Principle ... 10 
16 Reagents ... 10 
17 Instrument ... 10 
18 Analysis steps ... 10 
19 Result calculation ... 11 
Foreword
This Standard replaces GB/T 5009.14-1996 “Method for Determination of Zinc in Foods”.
Compared with GB/T 5009.14-1996, the major changes of this Standard are as follows.
- The Chinese name of the standard is changed to be "Determination of Zinc in Foods";
- According to GB/T 20001.4-2001 “Rules for Drafting Standards - Part 4. Methods for
Chemical Analysis”, the structure of the previous standard is changed.
This Standard was proposed by and shall be under the jurisdiction of the Ministry of Health
of the People's Republic of China.
Method I of this Standard was responsibly drafted by Guizhou Province Health and Anti-
Epidemic Station, and Guangxi Zhuang Autonomous Region Health and Anti-Epidemic
Station.
Method II of this Standard was responsibly drafted by Hunan Province Health and Anti-
Epidemic Station, and Tianjin Municipality Health and Anti-Epidemic Station.
Method III of this Standard was responsibly drafted by Guangxi Zhuang Autonomous
Region Health and Anti-Epidemic Station.
This Standard was first-time released in 1990, and first-time revised in 1996; this is the
second revision.
Determination of Zinc in Foods
1 Scope
This Standard specifies the methods for the determination of zinc in foods.
This Standard applies to the determination of zinc in foods.
The detection limits of this Standard. for atomic absorption method, it is 0.4 mg/kg; for
dithizone colorimetry method, it is 2.5 mg/kg.
2 Normative references
The provisions in the following documents become the provisions of this Standard through
the reference of this Standard. For the dated reference documents, the subsequent
amendments (excluding corrigendum) or revisions do not apply to this Standard. However,
all parties who reach an agreement according to this Standard are encouraged to discuss
whether the latest editions of these documents can be applied. For the undated reference
documents, their latest editions apply to this Standard.
GB/T 5009.11- 2003 Determination of Total Arsenic and Inorganic Arsenic in Foods
Method I Atomic Absorption Spectrometry
3 Principle
After the sample is treated, IMPORT into the atomic absorption spectrophotometer; after
atomization, ABSORB 213.8 nm resonance line. Its absorption value is proportional to the
zinc content; compare and quantify with the standard series.
4 Reagents
4.1 4-methyl amyl ketone -2 (MIBK, also known as methyl isobutyl ketone).
4.2 Phosphoric acid (1 + 10).
4.3 Hydrochloric acid (1 + 11). measure 10 mL of hydrochloric acid, add to an appropriate
amount of water and then dilute to 120 mL.
4.4 Mixed acid. nitric acid + perchloric acid (3 + 1).
4.5 Zinc standard solution. weigh accurately 0.500 g of metal zinc (99.99%) to dissolve in
10 mL of hydrochloric acid; then evaporate on a water bath until nearly dry; use a small
amount of water to dissolve before transferring to a 1000 mL volumetric flask; use
water to dilute to the scale mark; store in a polyethylene bottle. Per mL of this solution
is equivalent to 0.50 mg of zinc.
4.6 Zinc standard solution. draw 10.0 mL of zinc standard solution; place into a 50 mL
volumetric flask; use hydrochloric acid (0.1 mol/L) to dilute to the scale mark. Per mL of
this solution is equivalent to 100.0 µg of zinc.
5 Instrument
Atomic absorption spectrophotometer.
6 Analysis steps
6.1 Sample Processing
6.1.1 Grains. remove debris and dust; remove chaff if necessary; grind, pass through 40
mesh sieve, and mix well. Weigh about 5.00 g ~ 10.00 g to place into a 50 mL porcelain
crucible; carbonize on small fire until smokeless; transfer to a muffle furnace; take out of
the crucible after about 8 h of ashing at 500°C ± 25°C; cool down; add a small amount of
mixed acid; heat on small fire to prevent drying up; add a little mixed acid if necessary;
repeat the process until the residue contains no carbon granule; add 10 mL of hydrochloric
acid (1 + 11) when the crucible is slightly cooled; dissolve the residue and transfer to a 50
mL volumetric flask; use hydrochloride acid (1 + 11) to wash the crucible repeatedly; merge
the washing into the volumetric flask; dilute to the scale mark; mix well for later use.
Take the same amount of mixed acid and hydrochloric acid (1 + 11) as that of sample
treatment; carry out reagent blank test according to the same operation method.
6.1.2 Vegetables, fruits and legumes. take the edible parts; use water to wash and dry up;
cut up or smash well. Weigh 10.00 g ~ 20.00 g to place into a porcelain crucible; add 1 mL
of phosphoric acid (1 + 10); carbonize on small fire; then operate according to 6.1.1,
starting from " transfer to a muffle furnace ..."
6.1.3 Poultry, eggs, fish and dairy products. take the edible parts and mix well. Weigh 5.00
g ~ 10.00 g to place into a porcelain crucible; carbonize on small fire; then operate
according to 6.1.1, starting from " transfer to a muffle furnace ..."
Measure 50 mL of milk; after mixing well, place into a porcelain crucible; add 1 mL of
phosphoric acid (1 + 10); evaporate on a water bath to dry up; carbonize on small fire; then
operate according to 6.1.1, starting from " transfer to a muffle furnace ..."
Method II Dithizone Colorimetry
9 Principle
After the sample is digested, zinc ions and dithizone form a purple complex at pH 4.0 ~
5.5; dissolve in carbon tetrachloride; add sodium thiosulfate; prevent the interference of
copper, mercury, lead, bismuth, silver, cadmium and other ions; compare and quantify with
the standard series.
10 Reagents
10.1 Sodium acetate solution (2 mol/L). weigh 68 g of sodium acetate (CH3COONa • 3H2O);
add water to dissolve before diluting to 250 mL.
10.2 Acetate (2 mol/L). measure 10.0 mL of glacial acetic acid; add water to dilute to 85
mL.
10.3 Acetic acid - acetate buffer. mix equal volume of sodium acetate solution (2 mol/L)
and acetic acid (2 mol/L); the pH value of the solution is about 4.7.
Use dithizone-carbon tetrachloride solution (0.1 g/L) to extract for several times, 10 mL
each time; remove zinc content until the green of carbon tetrachloride layer remains
unchanged; discard the carbon tetrachloride layer; then use carbon tetrachloride to extract
the excess dithizone in acetic acid-acetate buffer until carbon tetrachloride becomes
colorless; discard the carbon tetrachloride layer.
10.4 Ammonia (1 + 1).
10.5 Hydrochloric acid (2 mol/L). measure 10 mL of hydrochloric acid; add water to dilute
to 60 mL.
10.6 Hydrochloric acid (0.02 mol/L). draw 1 mL of hydrochloric acid (2 mol/L); add water to
dilute to 100 mL.
10.7 Hydroxylamine hydrochloride solution (200 g/L). weigh 20 g of hydroxylamine
hydrochloride; add 60 mL of water; add dropwise aqueous ammonia (1 + 1); adjust the pH
to 4.0 to 5.5; then use dithizone-carbon tetrachloride solution (0.1 g/L) for processing
according to 10.3.
10.8 Sodium thiosulfate solution (250 g/L). use acetic acid (2 mol/L) to adjust the pH to 4...
......
 
(Above excerpt was released on 2016-08-26, modified on 2021-06-07, translated/reviewed by: Wayne Zheng et al.)
Source: https://www.chinesestandard.net/PDF.aspx/GBT5009.14-2003