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Determination of boric acid in foods
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GB/T 21918-2008: PDF in English (GBT 21918-2008) GB/T 21918-2008
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 67.040
X 04
Determination of Boric Acid in Foods
ISSUED ON. MAY 16, 2008
IMPLEMENTED ON. NOVEMBER 01, 2008
Issued by.
General Administration of Quality Supervision, Inspection
and Quarantine 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
Method I Ethohexadiol-trichloromethane Extraction Turmeric Colorimetry ... 4
3 Principles ... 4
4 Reagents ... 5
5 Instruments and equipment ... 5
6 Analysis steps ... 6
7 Degree of precision ... 7
Method II Inductively Coupled Plasma Atomic Emission Spectrometry and
Inductively Coupled Plasma Mass Spectrometry ... 8
8 Principles ... 8
9 Reagents ... 8
10 Instruments and equipment ... 9
11 Analysis steps ... 9
12 Calculation ... 11
13 Degree of precision ... 11
Annex A ... 12
Annex B ... 13
Foreword
Annex A and annex B of this Standard are informative.
This Standard was proposed by and shall be under the jurisdiction of National Food Safety
Emergency Standardization Working Group.
Drafting organization of method I in this Standard. Shanghai Institute of Quality Inspection
and Technical Research.
Drafting organization of method II in this Standard. Product Quality Supervision and
Inspection Station of Haidian District, Beijing (National Food Quality Supervision and
Inspection Center).
Main drafters of method I in this Standard. Chao qiangguo, Zhou Zelin, Ge Yu, Li Qin,
Zhang Yanqin, and Lin Lin.
Main drafters of the second method II in this Standard. Lin Li, Zhou Anfei, Yang Yanli,
Wang Zhaohui, and Cao Hong.
Determination of Boric Acid in Foods
1 Scope
This Standard specifies the determination method of boric acid in foods.
This Standard applies to the determination of boric acid in aquatic products, meat
products (e.g. meat balls, fish balls), beans, cooked wheaten food, dried bean curd sticks,
traditional Chinese rice-pudding, cakes, soy sauce, and other foods.
This Standard’s detection limit. 2.50 mg/kg for method I ethohexadiol-trichloromethane
extraction turmeric colorimetry; 1.00 mg/kg for method II inductively coupled plasma
atomic emission spectrometry (ICP-AES); 0.20 mg/kg for inductively coupled plasma
mass spectrometry (ICP-MS) method.
2 Normative references
The articles contained in the following documents have become part of this document
when they are quoted herein. For the dated documents so quoted, all subsequent
modifications (Including all corrections) or revisions made thereafter do not apply to this
Standard. However, the parties who reach an agreement according to this Standard are
encouraged to study whether the latest versions of these documents may be used. For
the undated documents so quoted, the latest versions (including all modification sheets)
apply to this document.
GB/T 6682 Water for laboratory use; Specifications (GB/T 6682-1992, neq ISO 3696.
1987)
Method I Ethohexadiol-trichloromethane Extraction
Turmeric Colorimetry
3 Principles
Gather and extract boric acid in samples through ethohexadiol-trichloromethane solution;
remove the impact of coexisting salts; use protonated turmeric generated from the mixture
of concentrated sulfuric acid and turmeric to react with boric acid to generate red products.
Shade of solution color is in direct proportion to the content of boric acid in sample, which
may be determined through colorimetry. In acidic conditions, borax exists in the form of
5.5 150 mL plastic beaker.
5.6 25 mL or 50 mL lidded plastic test tube.
5.7 Vortex oscillator.
6 Analysis steps
6.1 Preparation of standard curve
Accurately measure 0.00, 1.00, 2.00, 3.00, 4.00 and 5.00 mL of standard solutions; place
into 25 mL plastic tubes; add water to 5 mL respectively. Add 1 mL of sulfuric acid (1+1)
solution; oscillate to mix; then add 5.00 mL of EHD-CHCl3 solution; put the cover; put into
vortex oscillator to operate for about 2 min; stand still for layering; draw under layer’s
EHD-CHCl3 solution; filter through Ø7cm dried fast filter paper.
Respectively take 1.00 mL of filtrate; place into 50 mL plastic tube; successively add 1.0
mL of turmeric-glacial acetic acid solution and 5 mL of concentrated sulfuric acid; oscillate
uniformly; stand still for 30 min; add 25 mL of anhydrous alcohol; after standing still for 10
min, measure absorbance at 550nm with 1 cm cuvette. Take standard series boric acid
amount (μg) as abscissa, and absorbance as ordinate; draw the standard curve.
6.2 Determination
6.2.1 Sample treatment
Solid samples. Weigh 2.00 g~10.00 g (accurate to 0.01 g) of samples; use high-speed
masher to mash; add 40 mL~60 mL of water and mix well; slowly add 2 mL of
concentrated sulfuric acid drop-by-drop; apply ultrasound for 10 min to promote the
dissolution and mixing. Add 5 mL of zinc acetate solution and 5 mL of potassium
ferrocyanide solution; add water to a fixed volume 100 mL; use as sample solution after
filtration. Take 1.00 mL~3.00 mL of sample solution according to the content of sample;
place into a 25 mL plastic tube; add water to 5 mL. Add 1 mL of sulfuric acid (1 + 1)
solution; oscillate to mix well. Then add 5.00 mL of EHD-CHCl3 solution; put the cover;
oscillator operates for 2 min; stand still for layering; draw under layer’s EHD-CHCl3
solution; filter through Ø7cm dried fast filter paper.
Liquid samples. Weigh 2.00 g~10.00 g of samples (accurate to 0.01 g); add water to a
constant volume 100 mL as sample solution. For liquid samples with high protein or fat
content, 5 mL of zinc acetate solution may be added to the samples; add water to a
constant volume 100 mL and use it as sample solution. Take 1.00 mL~3.00 mL of sample
solution according to sample content; place into a 25 mL plastic tube; add water to 5 mL;
add 1 mL of sulfuric acid (1+1) solution; oscillate to mix well. Then add 5.00 mL of
EHD-CHCl3 solution; put the cover; vertex oscillator operates for about 2 min; stand still
for layering; draw under layer’s EHD-CHCl3 solution; filter through Ø7 cm dried fast filter
volumetric flask; use 5% nitric acid solution to dilute and fix to constant volume;
concentration of this standard stock solution is equal to 10μg of boron per milliliter.
Prepared solution shall be timely transferred to a plastic bottle and be stored in
refrigerator at 0°C~4°C for 3 months.
9.10 Scandium standard working solution. 1.00 mg/L.
Draw 1.00 mL of scandium standard working solution and place into a 100 mL plastic
volumetric flask; use 5% nitric acid solution and fix to constant volume; each milliliter in
volumetric flask is equivalent to 1.00μg of scandium.
Solution prepared shall be timely transferred to a plastic bottle and be stored in
refrigerator at 0°C~4°C for 3 months.
9.11 Preparation of series standard solution. Respectively draw 0.0, 0.5, 3.0, 10.0 and
20.0 mL of boron standard working solutions (9.9); place into 100 mL volumetric flasks;
then accurately add 1.00 mL of yttrium element standard stock solution (9.7); use 5% nitric
acid solution to fix volume to scale; concentrations of solutions in volumetric flasks are
equivalent to 0.00, 0.05, 0.30, 1.00 and 2.00 μg of boron per milliliter. Solution prepared
shall be transferred to a plastic bottle timely.
Note. Yttrium element standard stock solution is not added to the standard solution tested
through ICP-MS.
When ICP-MS is adopted for determination, adopt yttrium standard working solution (9.10)
online internal standard adding.
10 Instruments and equipment
10.1 All containers used in test are plastic.
10.2 Ultrapure water preparation system.
10.3 Sample smashing device.
10.4 Microwave digestion system.
10.5 Inductively coupled plasma atomic emission spectrometer (ICP-AES) and inductively
coupled plasma mass spectrometer (ICP-MS). All containers used have been soaked
overnight with 20% nitric acid.
11 Analysis steps
11.1 Preparation of samples
There is a need to pay special attention to prevent all kinds of...
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Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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