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食品安全国家标准 食品接触材料及制品 木质材料中二氧化硫的测定
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GB 31604.32-2016
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标准编号: GB 31604.32-2016 (GB31604.32-2016)
中文名称: 食品安全国家标准 食品接触材料及制品 木质材料中二氧化硫的测定
英文名称: Food contact materials for export -- Wood materials -- Determination of sulfur dioxide
行业: 国家标准
中标分类: X09
字数估计: 8,852
发布日期: 2016-10-19
实施日期: 2017-04-19
旧标准 (被替代): SN/T 2827-2011部分
标准依据: 国家卫生和计划生育委员会公告2016年第15号
GB 31604.32-2016: 食品安全国家标准 食品接触材料及制品 木质材料中二氧化硫的测定
GB 31604.32-2016 英文名称: Food contact materials for export -- Wood materials -- Determination of sulfur dioxide
1 范围
本标准规定了食品接触木(竹)质材料中二氧化硫滴定法和比色法的测定方法。
本标准适用于木(竹)筷、木(竹)碗、木(竹)勺、木(竹)铲中二氧化硫的测定。
第一法 滴定法
2 原理
在密闭容器中对试样进行酸化并加热蒸馏,以释放出其中的二氧化硫,释放物用乙酸铅溶液吸收。
吸收后用浓盐酸酸化,再以碘标准溶液滴定,根据所消耗的碘标准溶液量计算出试样中二氧化硫的
含量。
3 试剂和材料
除非另有说明,本方法所用试剂均为分析纯,水为GB/T 6682规定的三级水。
3.1 试剂
3.1.1 盐酸(HCl)。
3.1.2 乙酸铅[Pb(CH3COO)2·3H2O]。
3.1.3 碘(I2)。
3.1.4 可溶性淀粉[(C6H10O5)n]。
3.2 试剂配制
3.2.1 盐酸溶液(1+1,体积比):取盐酸100mL小心加入100mL水中,混匀。
3.2.2 乙酸铅溶液(20g/L):称取20g乙酸铅,溶于少量水中并稀释至1000mL。
3.2.3 淀粉指示剂(10g/L):称取1g可溶性淀粉,用少许水调成糊状后,再缓缓倾入100mL沸水中,
随加随搅拌,煮沸2min,冷却至室温,备用,此溶液现用现配。
3.3 标准品
碘标准溶液按GB/T 601配制与标定或商品化产品。
3.4 标准溶液配制
碘标准滴定溶液[(12I2)=0.01mol/L]:吸取10.0mL碘标准溶液,置于100mL容量瓶中,用水稀
释定容至刻度。
4 仪器和设备
4.1 分析天平:感量0.1mg。
4.2 全玻璃蒸馏器。
4.3 酸式滴定管。
4.4 碘量瓶。
4.5 电刨或电锯。
4.6 粉碎机。
5 分析步骤
5.1 试样制备
将抽取的样品,用电刨或电锯取其表面3mm厚,粉碎,装入洁净容器内。密封作为试样,标明标
记。在制样的操作过程中,应防止样品受到二氧化硫的污染。
5.2 蒸馏
称取试样5g(精确至0.01g),置于500mL圆底烧瓶。在圆底烧瓶中加入250mL水,为防止样液
暴沸,可加入少许玻璃珠。装上冷凝装置,冷凝管下端插入碘量瓶中的25mL乙酸铅溶液(20g/L)中,
然后在蒸馏瓶中加入10mL盐酸溶液(1+1,体积比),立即盖上塞子,加热蒸馏。当蒸馏液约达
200mL时,使冷凝管下端离开液面,再继续蒸馏1min。用少量蒸馏水冲洗插入乙酸铅溶液(20g/L)的
装置部分。在检测试样的同时做空白试验,空白试验的测定从“在圆底烧瓶中加入250mL水”做起。
5.3 滴定
向取下的碘量瓶中依次加入10mL盐酸、1mL淀粉指示剂(10g/L),摇匀后用碘标准滴定溶液
(0.01mol/L)滴定至溶液变蓝且在30s内不褪色为止。
6 分析结果的表述
试样中二氧化硫的含量按式(1)计算:
7 精密度
在重复性条件下获得的两次独立测定结果的绝对差值不得超过算术平均值的10%。
8 其他
方法检出限为10mg/kg。
第二法 比色法
9 原理
在密闭容器中对试样进行酸化并加热蒸馏,以释放出其中的二氧化硫,二氧化硫被四氯汞钾吸收后
形成稳定的络合物,再与甲醛及盐酸副玫瑰苯胺作用生成玫瑰紫色化合物,比色定量。
10 试剂和材料
除非另有说明,本方法所用试剂均为分析纯,水为GB/T 6682规定的三级水。四氯汞钾液有剧毒
性,操作时应戴橡胶手套,若溅到皮肤上,立即用水冲洗。
10.1 试剂
10.1.1 氯化汞(HgCl2)。
10.1.2 乙二胺四乙酸二钠盐(Na2·EDTA)。
10.1.3 氯化钾(KCl)。
10.1.4 氨基磺酸(H3NO3S)。
10.1.5 甲醛(HCHO):含量36%~38%。
10.1.6 盐酸副玫瑰苯胺(C19H18ClN3;CASNo.569-61-9):纯度不得低于95%。
10.1.7 盐酸(HCl)。
10.1.8 磷酸(H3PO4)。
10.2 试剂配制
10.2.1 四氯汞钾吸收液(0.04mol/L):称取10.86g氯化汞、0.066g乙二胺四乙酸二钠盐、5.96g氯化
钾,溶于水中并稀释至1000mL。
10.2.2 氨基磺酸溶液(6g/L):称取0.6g氨基磺酸,溶于100mL水中,临用配制。
10.2.3 甲醛溶液(2g/L):吸取1mL甲醛,用水稀释至200mL,储存在具塞玻璃瓶中,临用配制。
10.2.4 盐酸溶液(1mol/L):取盐酸90mL用水稀释到1000mL。
10.2.5 盐酸溶液(1+1):取盐酸100mL小心加入100mL水中。
10.2.6 磷酸溶液(3mol/L):取20.5mL磷酸用水稀释到100mL。
10.2.7 盐酸副玫瑰苯胺储备液(2g/L):精确称取0.2g盐酸副玫瑰苯胺,溶于100mL盐酸溶液中。
10.2.8 盐酸副玫瑰苯胺工作液(0.16g/L):取20mL盐酸副玫瑰苯胺储备液和25mL磷酸溶液于
250mL容量瓶中,用水稀释至刻度,此溶液于暗处保存可放置6个月。
10.3.1 二氧化硫标准溶液:配制见附录A。
10.3.2 二氧化硫标准使用液:按标定计算结果,用四氯汞钾吸收液(10.2.1)将二氧化硫标准溶液
(10.3.1)稀释成1mL相当于5μg二氧化硫,于0℃~4℃下可保存1个月。
11 仪器和设备
11.1 紫外可见分光光度计。
11.2 分析天平:感量0.1mg。
11.3 全玻璃蒸馏器。
11.4 碘量瓶。
11.5 电刨或电锯。
11.7 水浴锅。
12 分析步骤
12.1 试样制备
将抽取的样品,用电刨或电锯取其表面3mm厚,粉碎,装入洁净容器内。密封作为试样,标明标
记。在制样的操作过程中,应防止样品受到二氧化硫的污染。
12.2 蒸馏
称取试样5g(精确至0.01g)(试样量视产品二氧化硫含量高低而定),置于500mL圆底烧瓶。在
圆底烧瓶中加入250mL水,为防止样液暴沸,可加入玻璃珠少许,装入冷凝装置,冷凝管下端应插入碘
量瓶中的25mL四氯汞钾吸收液(10.2.1)中,然后在蒸馏瓶中加入10mL盐酸溶液(10.2.5),立即盖上
插入四氯汞钾吸收液(10.2.1)的装置部分。将蒸馏液转移至250mL容量瓶中,用新煮沸放冷的水加至
刻度。在检测试样的同时做空白试验,空白试验的测定从“在圆底烧瓶中加入250mL水”做起。
GB 31604.32-2016
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
National food safety standard -
Food contact materials and products -
Determination of sulfur dioxide in wood materials
ISSUED ON. OCTOBER 19, 2016
IMPLEMENTED ON. APRIL 19, 2017
Issued by. National Health and Family Planning Commission of the PRC
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Principles ... 4
3 Reagents and materials ... 4
4 Instrument and equipment ... 5
5 Analytical procedures ... 5
6 Analysis results expression ... 6
7 Precision ... 7
8. Others ... 7
9 Principles ... 7
10 Reagents and materials ... 7
11 Instrument and equipment ... 9
12 Analytical procedures ... 9
13 Analysis results expression ... 10
14 Precision ... 11
15 Others ... 11
Appendix A Preparation of sulfur dioxide standard solution ... 12
Foreword
This standard replaces the determination of sulfur dioxide in SN/T 2827-2011
“Food contact materials for export - Wood materials - Determination of sulfur
dioxide”.
Compared with SN/T 2827-2011, the main changes of this standard are as
follows.
-- The standard name has been changed to “National food safety standard -
Food contact materials and products - Determination of sulfur dioxide in
wood materials”;
-- Modify "method summary" in Method I into "principles";
-- Modify "results calculation and expression" in Method I into "analysis
results expression";
-- Modify the formula in Method I;
-- Modify "method summary" in Method II into "principles" and revise the
text;
-- Modify "results calculation and expression" in Method II into "analysis
results expression" and revise the text.
National food safety standard -
Food contact materials and products -
Determination of sulfur dioxide in wood materials
1 Scope
This standard specifies the determination methods for titration and colorimetry
of sulfur dioxide in food contact wood (bamboo) materials.
This standard applies to the determination of sulfur dioxide in wood (bamboo)
chopsticks, wood (bamboo) bowls, wood (bamboo) spoons and wood (bamboo)
shovels.
Method I Titration
2 Principles
Acidify the sample in a closed vessel; heat and distill it to release sulfur dioxide
therein. Use lead acetate solution to absorb the released substance. After
absorption, use concentrated hydrochloric acid to acidify and then titrate with
iodine standard solution. According to the consumed amount of iodine
standard solution, calculate the content of sulfur dioxide in the sample.
3 Reagents and materials
Unless otherwise indicated, the reagents used in this method are analytical
grade, the water is the grade-3 water specified in GB/T 6682.
3.1 Reagents
3.1.1 Hydrochloric acid (HCl).
3.1.2 Lead acetate [Pb(CH3COO)2.3H2O].
3.1.3 Iodine (I2).
3.1.4 Soluble starch [(C6H10O5)n].
V2 - The volume of iodine standard titration solution used for titration reagent
c - The concentration of iodine standard titration solution, in mole per liter
(mol/L);
0.032 - 1mL iodine standard solution [(( 2
1 I2 = 1.0mol/L] equivalent to the
mass of sulfur dioxide, in grams per mole (g/mol);
1000 - Conversion factor;
m - The mass of the sample, in grams (g).
The calculation result is retained with three significant figures.
7 Precision
under repeatability conditions shall not exceed 10% of the arithmetic mean.
8. Others
The method detection limit is 10mg/kg.
Method II Colorimetry
9 Principles
Acidify the sample in a closed vessel; heat and distill it to release sulfur dioxide
therein. Sulfur dioxide is absorbed by potassium mercuric tetrachloride to form
stable complex, which is then reacted with formaldehyde and pararosaniline
hydrochloride to form rose-purple compound for colorimetric determination.
Unless otherwise indicated, the reagents used in this method are analytical
grade, the water is the grade-3 water specified in GB/T 6682. The potassium
mercuric tetrachloride solution is highly toxic. Wear rubber gloves when
handling. If it splashes on the skin, rinse immediately with water.
solution into 250mL volumetric flask; USE water to dilute it to the mark. This
solution can be stored in dark place for 6 months...
10.3 Standard solution preparation
10.3.1 Sulfur dioxide standard solution. See Appendix A for preparation.
10.3.2 Sulfur dioxide standard working solution. According to the calculation
solution (10.2.1) to dilute sulfur dioxide standard solution (10.3.1) to 1mL which
is equivalent to 5μg of sulfur dioxide; STORE it at 0°C~4°C for 1 month.
11 Instrument and equipment
11.1 UV-visible spectrophotometer.
11.2 Analytical balance. Sensitivity is 0.1mg.
11.3 All-glass distiller.
11.4 Iodine volumetric flask.
11.5 Electric planer or chainsaw.
11.6 Crusher.
12 Analytical procedures
12.1 Sample preparation
USE electric planer or chainsaw to take 3mm thick out of the surface of the
sample; CRUSH; PLACE it in a clean container. SEAL it as the sample and
INDICATE the mark. During the operation of sample preparation, the sample
shall be protected from sulfur dioxide contamination.
12.2 Distillation
WEIGH 5g of sample (accurate to 0.01g) (the amount of sample depends on
the level of sulfur dioxide content of the product); PLACE it in 500mL
order to prevent the sample solution from boiling, ADD a few glass beads.
INSTALL condensing device and INSERT the lower end of the condenser into
the 25mL of potassium mercuric tetrachloride absorber solution (10.2.1) in
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