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GB 5009.92-2016

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GB 5009.92-2016 英文版 355 购买 现货,9秒内自动发货PDF,有增值税发票。 食品安全国家标准 食品中钙的测定 作废

   
标准详细信息 GB 5009.92-2016; GB5009.92-2016
中文名称: 食品安全国家标准 食品中钙的测定
英文名称: Determination of calcium in foods
行业: 国家标准
中标分类: X09
发布日期: 2016-12-23
实施日期: 2017-06-23
旧标准 (被替代): GB/T 5009.92-2003; GB 5413.21-2010 Partly; GB/T 23375-2009 Partly; GB/T 14609-2008 Partly; GB/T 14610-2008; GB/T 9695.13-2009; NY/T 82.19-1988 Partly
标准依据: National Health and Family Planning Commission Notice No.17 of 2016

GB 5009.92-2016
National Food Safety Standard -- Determination of Calcium in Foods
中华人民共和国国家标准
食品安全国家标准
食品中钙的测定
2016-12-23发布
2017-06-23实施
中华人民共和国国家卫生和计划生育委员会
国 家 食 品 药 品 监 督 管 理 总 局 发 布
前言
本标准代替GB/T5009.92-2003《食品中钙的测定》、GB5413.21-2010《食品安全国家标准婴
幼儿食品和乳品中钙、铁、锌、钠、钾、镁、铜和锰的测定》、GB/T 23375-2009《蔬菜及其制品中铜、铁、
锌、钙、镁、磷的测定》、GB/T 14609-2008《粮油检验 谷物及其制品中铜、铁、锰、锌、钙、镁的测定 火
焰原子吸收光谱法》、GB/T 14610-2008《粮油检验谷物及制品中钙的测定》、GB/T 9695.13-2009《肉
与肉制品 钙含量测定》和NY82.19-1988《果汁测定方法 钙和镁的测定》中钙的测定方法。
本标准与GB/T 5009.92-2003相比,主要变化如下.
---标准名称修改为“食品安全国家标准食品中钙的测定”;
---增加了微波消解、压力罐消解;
---修改了火焰原子吸收光谱法和EDTA滴定法;
---增加了电感耦合等离子体发射光谱法;
---增加了电感耦合等离子体质谱法。
食品安全国家标准
食品中钙的测定
1 范围
本标准规定了食品中钙含量测定的火焰原子吸收光谱法、滴定法、电感耦合等离子体发射光谱法和
电感耦合等离子体质谱法。
本标准适用于食品中钙含量的测定。
第一法 火焰原子吸收光谱法
2 原理
试样经消解处理后,加入镧溶液作为释放剂,经原子吸收火焰原子化,在422.7nm处测定的吸光度
值在一定浓度范围内与钙含量成正比,与标准系列比较定量。
3 试剂和材料
除非另有规定,本方法所用试剂均为优级纯,水为GB/T 6682规定的二级水。
3.1 试剂
3.1.1 硝酸(HNO3)。
3.1.2 高氯酸(HClO4)。
3.1.3 盐酸(HCl)。
3.1.4 氧化镧(La2O3)。
3.2 试剂配制
3.2.1 硝酸溶液(5+95).量取50mL硝酸,加入950mL水,混匀。
3.2.2 硝酸溶液(1+1).量取500mL硝酸,与500mL水混合均匀。
3.2.3 盐酸溶液(1+1).量取500mL盐酸,与500mL水混合均匀。
3.2.4 镧溶液(20g/L).称取23.45g氧化镧,先用少量水湿润后再加入75mL盐酸溶液(1+1)溶解,
转入1000mL容量瓶中,加水定容至刻度,混匀。
3.3 标准品
碳酸钙(CaCO3,CAS号471-34-1).纯度>99.99%,或经国家认证并授予标准物质证书的一定浓度
的钙标准溶液。
3.4 标准溶液的配制
3.4.1 钙标准储备液(1000mg/L).准确称取2.4963g(精确至0.0001g)碳酸钙,加盐酸溶液(1+1)
溶解,移入1000mL容量瓶中,加水定容至刻度,混匀。
3.4.2 钙标准中间液(100mg/L).准确吸取钙标准储备液(1000mg/L)10mL于100mL容量瓶中,
加硝酸溶液(5+95)至刻度,混匀。
3.4.3 钙标准系列溶液.分别吸取钙标准中间液(100mg/L)0mL,0.500mL,1.00mL,2.00mL,
4.00mL,6.00mL于100mL容量瓶中,另在各容量瓶中加入5mL镧溶液(20g/L),最后加硝酸溶液
(5+95)定容至刻度,混匀。此钙标准系列溶液中钙的质量浓度分别为0mg/L、0.500mg/L、1.00mg/L、
2.00mg/L、4.00mg/L和6.00mg/L。
注.可根据仪器的灵敏度及样品中钙的实际含量确定标准溶液系列中元素的具体浓度。
4 仪器设备
注.所有玻璃器皿及聚四氟乙烯消解内罐均需硝酸溶液(1+5)浸泡过夜,用自来水反复冲洗,最后用水冲洗干净。
4.1 原子吸收光谱仪.配火焰原子化器,钙空心阴极灯。
4.2 分析天平.感量为1mg和0.1mg。
4.3 微波消解系统.配聚四氟乙烯消解内罐。
4.4 可调式电热炉。
4.5 可调式电热板。
4.6 压力消解罐.配聚四氟乙烯消解内罐。
4.7 恒温干燥箱。
4.8 马弗炉。
5 分析步骤
5.1 试样制备
注.在采样和试样制备过程中,应避免试样污染。
5.1.1 粮食、豆类样品
样品去除杂物后,粉碎,储于塑料瓶中。
5.1.2 蔬菜、水果、鱼类、肉类等样品
样品用水洗净,晾干,取可食部分,制成匀浆,储于塑料瓶中。
5.1.3 饮料、酒、醋、酱油、食用植物油、液态乳等液体样品
将样品摇匀。
5.2 试样消解
5.2.1 湿法消解
准确称取固体试样0.2g~3g(精确至0.001g)或准确移取液体试样0.500mL~5.00mL于带刻度
消化管中,加入10mL硝酸、0.5mL高氯酸,在可调式电热炉上消解(参考条件.120℃/0.5h~120℃/1h、
化液呈无色透明或略带黄色。取出消化管,冷却后用水定容至25mL,再根据实际测定需要稀释,并在
稀释液中加入一定体积的镧溶液(20g/L),使其在最终稀释液中的浓度为1g/L,混匀备用,此为试样
待测液。同时做试剂空白试验。亦可采用锥形瓶,于可调式电热板上,按上述操作方法进行湿法消解。
5.2.2 微波消解
准确称取固体试样0.2g~0.8g(精确至0.001g)或准确移取液体试样0.500mL~3.00mL于微波
消解罐中,加入5mL硝酸,按照微波消解的操作步骤消解试样,消解条件参考附录A。冷却后取出消
解罐,在电热板上于140℃~160℃赶酸至1mL左右。消解罐放冷后,将消化液转移至25mL容量瓶
中,用少量水洗涤消解罐2次~3次,合并洗涤液于容量瓶中并用水定容至刻度。根据实际测定需要稀
释,并在稀释液中加入一定体积镧溶液(20g/L)使其在最终稀释液中的浓度为1g/L,混匀备用,此为
5.2.3 压力罐消解
准确称取固体试样0.2g~1g(精确至0.001g)或准确移取液体试样0.500mL~5.00mL于消解内
罐中,加入5mL硝酸。盖好内盖,旋紧不锈钢外套,放入恒温干燥箱,于140℃~160℃下保持4h~
5h。冷却后缓慢旋松外罐,取出消解内罐,放在可调式电热板上于140℃~160℃赶酸至1mL左右。
冷却后将消化液转移至25mL容量瓶中,用少量水洗涤内罐和内盖2次~3次,合并洗涤液于容量瓶中
并用水定容至刻度,混匀备用。根据实际测定需要稀释,并在稀释液中加入一定体积的镧溶液(20g/L),
使其在最终稀释液中的浓度为1g/L,混匀备用,此为试样待测液。同时做试剂空白试验。
5.2.4 干法灰化
准确称取固体试样0.5g~5g(精确至0.001g)或准确移取液体试样0.500mL~10.0mL于坩埚
试样,加数滴硝酸,小火加热,小心蒸干,再转入550℃马弗炉中,继续灰化1h~2h,至试样呈白灰状,
冷却,取出,用适量硝酸溶液(1+1)溶解转移至刻度管中,用水定容至25mL。根据实际测定需要稀释,
并在稀释液中加入一定体积的镧溶液,使其在最终稀释液中的浓度为1g/L,混匀备用,此为试样待测
液。同时做试剂空白试验。
5.3 仪器参考条件
参考条件见附录B。
5.4 标准曲线的制作
将钙标准系列溶液按浓度由低到高的顺序分别导入火焰原子化器,测定吸光度值,以标准系列溶液
中钙的质量浓度为横坐标,相应的吸光度值为纵坐标,制作标准曲线。
在与测定标准溶液相同的实验条件下,将空白溶液和试样待测液分别导入原子化器,测定相应的吸
光度值,与标准系列比较定量。
6 分析结果的表述
试样中钙的含量按式(1)计算.
X=
(ρ-ρ0)×f×V
(1)
式中.
X ---试样中钙的含量,单位为毫克每千克或毫克每升(mg/kg或mg/L);
ρ0 ---空白溶液中钙的质量浓度,单位为毫克每升(mg/L);
f ---试样消化液的稀释倍数;
V ---试样消化液的定容体积,单位为毫升(mL);
m ---试样质量或移取体积,单位为克或毫升(g或mL)。
当钙含量≥10.0mg/kg或10.0mg/L时,计算结果保留三位有效数字,当钙含量<10.0mg/kg或
10.0mg/L时,计算结果保留两位有效数字。
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
为1.5mg/kg(或1.5mg/L)。
第二法 EDTA滴定法
9 原理
在适当的pH范围内,钙与EDTA(乙二胺四乙酸二钠)形成金属络合物。以EDTA滴定,在达到
当量点时,溶液呈现游离指示剂的颜色。根据EDTA用量,计算钙的含量。
10 试剂和材料
除非另有规定,本方法所用试剂均为分析纯,水为GB/T 6682规定的三级水。
10.1 试剂
10.1.1 氢氧化钾(KOH)。
10.1.3 柠檬酸钠(Na3C6H5O7·2H2O)。
10.1.4 乙二胺四乙酸二钠(EDTA,C10H14N2O8Na2·2H2O)。
10.1.5 盐酸(HCl).优级纯。
10.1.6 钙红指示剂(C21O7N2SH14)。
10.1.7 硝酸(HNO3).优级纯。
10.1.8 高氯酸(HClO4).优级纯。
10.2 试剂配制
10.2.1 氢氧化钾溶液(1.25mol/L).称取70.13g氢氧化钾,用水稀释至1000mL,混匀。
10.2.2 硫化钠溶液(10g/L).称取1g硫化钠,用水稀释至100mL,混匀。
10.2.4 EDTA溶液.称取4.5gEDTA,用水稀释至1000mL,混匀,贮存于聚乙烯瓶中,4℃保存。使
用时稀释10倍即可。
10.2.5 钙红指示剂.称取0.1g钙红指示剂,用水稀释至100mL,混匀。
10.2.6 盐酸溶液(1+1).量取500mL盐酸,与500mL水混合均匀。
10.3 标准品
碳酸钙(CaCO3,CAS号471-34-1).纯度>99.99%,或经国家认证并授予标准物质证书的一定浓度
的钙标准溶液。
10.4 标准溶液配制
钙标准储备液(100.0mg/L).准确称取0.2496g(精确至0.0001g)碳酸钙,加盐酸溶液(1+1)溶
11 仪器设备
注.所有玻璃器皿均需硝酸溶液(1+5)浸泡过夜,用自来水反复冲洗,最后用水冲洗干净。
11.1 分析天平.感量为1mg和0.1mg。
11.2 可调式电热炉。
11.3 可调式电热板。
11.4 马弗炉。
12 分析步骤
12.1 试样制备
同5.1。
12.2.1 湿法消解
同5.2.1。
12.2.2 干法灰化
同5.2.4。
12.3 滴定度(T)的测定
吸取0.500mL钙标准储备液(100.0mg/L)于试管中,加1滴硫化钠溶液(10g/L)和0.1mL柠檬
酸钠溶液(0.05mol/L),加1.5mL氢氧化钾溶液(1.25mol/L),加3滴钙红指示剂,立即以稀释10倍
的EDTA溶液滴定,至指示剂由紫红色变蓝色为止,记录所消耗的稀释10倍的EDTA溶液的体积。
根据滴定结果计算出每毫升稀释10倍的EDTA溶液相当于钙的毫克数,即滴定度(T)。
分别吸取0.100mL~1.00mL(根据钙的含量而定)试样消化液及空白液于试管中,加1滴硫化钠
溶液(10g/L)和0.1mL柠檬酸钠溶液(0.05mol/L),加1.5mL氢氧化钾溶液(1.25mol/L),加3滴钙
红指示剂,立即以稀释10倍的EDTA溶液滴定,至指示剂由紫红色变蓝色为止,记录所消耗的稀释
10倍的EDTA溶液的体积。
13 分析结果的表述
试样中钙的含量按式(2)计算.
X=
T×(V1-V0)×V2×1000
m×V3
式中.
X ---试样中钙的含量,单位为毫克每千克或毫克每升(mg/kg或mg/L);
T ---EDTA滴定度,单位为毫克每毫升(mg/mL);
V1 ---滴定试样溶液时所消耗的稀释10倍的EDTA溶液的体积,单位为毫升(mL);
V0 ---滴定空白溶液时所消耗的稀释10倍的EDTA溶液的体积,单位为毫升(mL);
V2 ---试样消化液的定容体积,单位为毫升(mL);
1000---换算系数;
m ---试样质量或移取体积,单位为克或毫升(g或mL);
V3 ---滴定用试样待测液的体积,单位为毫升(mL)。
14 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%。
15 其他
以称样量4g(或4mL),定容至25mL,吸取1.00mL试样消化液测定时,方法的定量限为
100mg/kg(或100mg/L)。
第三法 电感耦合等离子体发射光谱法
见GB 5009.268。
第四法 电感耦合等离子体质谱法
见GB 5009.268。
微波消解升温程序参考条件
微波消解升温程序参考条件见表A.1。
表A.1 微波消解升温程序参考条件
步骤
设定温度
升温时间
min
恒温时间
min
火焰原子吸收光谱法参考条件
火焰原子吸收光谱法参考条件见表B.1。
表B.1 火焰原子吸收光谱法参考条件
元素
波长
nm
狭缝
nm
灯电流
燃烧头高度
mm
空气流量
L/min
乙炔流量
L/min
钙 422.7 1.3 5~15 3 9 2

GB 5009.92-2016
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
National food safety standard -
Determination of calcium in foods
食品安全国家标准
食品中钙的测定
ISSUED ON. DECEMBER 23, 2016
IMPLEMENTED ON. JUNE 23, 2017
Issued by. National Health and Family Planning Commission of the
People’s Republic of China;
China 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 ... 5
5 Analysis procedure ... 6
6 Expression of analysis results .. 8
7 Precision .. 9
8 Others ... 9
9 Principle ... 9
10 Reagents and materials ... 9
11 Instruments and equipment .. 10
12 Analysis procedure ... 10
13 Expression of analysis results ... 11
14 Precision ... 12
15 Others .. 12
Annex A Microwave digestion temperature rise program reference conditions .. 13
Annex B Flame atomic absorption spectrometry reference conditions ... 14
Foreword
This Standard replaces the determination method for calcium in GB/T 5009.92-2003
“Determination of calcium in foods”, 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
23375-2009 “Determination of copper , iron , zinc , calcium , magnesium and
phosphorus content in vegetables and derived products”, GB/T 14609-2008
“Inspection of grain and oils - Determination of copper, iron, manganese, zinc, calcium,
magnesium in cereals and derived products by atomic absorption and flame
spectrophotometry”, GB/T 14610-2008 “Inspection of grain and oils - Determination of
calcium in cereals and cereal products”, GB/T 9695.13-2009 “Meat and meat products
- Method for Determination of calcium content” and NY 82.19-1988 “Determination of
fruit juice - Determination of calcium and magnesium”.
Compare this Standard with GB/T 5009.92-2003, the main changes are as follows.
- MODIFY the standard name TO "National food safety standard - Determination of
calcium in foods";
- ADD the microwave digestion, pressure tank digestion;
- MODIFY the flame atomic absorption spectrometry and EDTA titration;
- ADD the inductively coupled plasma emission spectrometry;
- ADD the inductively coupled plasma mass spectrometry.
National food safety standard -
Determination of calcium in foods
1 Scope
This Standard specifies the determination of calcium in foods by flame atomic
absorption spectrometry, titration, inductively coupled plasma atomic emission
spectrometry and inductively coupled plasma mass spectrometry.
This Standard applies to the determination of calcium content in foods.
Method I Flame atomic absorption spectrometry
2 Principle
After the sample is digested, add lanthanum solution as the releasing agent, atomize
by atomic absorption flame, and measure the absorbance value at 422.7 nm, which is
proportional to the calcium content in a certain concentration range. Compare with the
standard series.
3 Reagents and materials
and the water is Grade 2 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 Hydrochloric acid (HCl).
3.1.4 Lanthanum oxide (La2O3).
3.2 Preparation of reagents
3.2.1 Nitric acid solution (5 + 95). MEASURE 50 mL of nitric acid; ADD 950 mL of water;
MIX well.
mL of water.
3.2.3 Hydrochloric acid solution (1 + 1). MEASURE 500 mL of hydrochloric acid; MIX
well with 500 mL of water.
3.2.4 Lanthanum solution (20 g/L). WEIGH 23.45 g of lanthana; firstly, MOISTEN with
a small amount of water and then ADD 75 mL of hydrochloric acid solution (1 + 1) to
dissolve; TRANSFER to a 1000 mL volumetric flask; ADD water to the mark; MIX well.
3.3 Standard
Calcium carbonate (CaCO3, CAS No. 471-34-1). Purity > 99.99 %, or calcium standard
solution at a certain concentration certified by the state and awarded the standard
3.4 Preparation of standard solutions
3.4.1 Calcium standard stock solution (1000 mg/L). accurately WEIGH 2.4963 g (to
the nearest 0.0001 g) of calcium carbonate; ADD hydrochloric acid solution (1 + 1) to
dissolve; TRANSFER to a 1000 mL volumetric flask; ADD water to the mark; MIX well.
3.4.2 Calcium standard intermediate solution (100 mg/L). accurately PIPETTE 10 mL
of calcium standard stock solution (1000 mg/L) into a 100 mL volumetric flask; ADD
nitric acid solution (5 + 95) to the mark; MIX well.
3.4.3 Calcium standard series solutions. respectively PIPETTE 0 mL, 0.500 mL, 1.00
mL, 2.00 mL, 4.00 mL and 6.00 mL of calcium standard intermediate solution (100
volumetric flask; and finally ADD nitric acid solution (5 + 95) to the mark; MIX well. The
concentrations of calcium in standard calcium series solutions are 0 mg/L, 0.500 mg/L,
1.00 mg/L, 2.00 mg/L, 4.00 mg/L and 6.00 mg/L, respectively.
NOTE. It may determine the specific concentration of elements in the standard solution series
according to the sensitivity of the instrument and the actual content of calcium in the sample.
4 Instruments and equipment
NOTE. All glassware and polytetrafluoroethylene digestion inner tank must be soaked in nitric
acid solution (1 + 5) overnight, washed repeatedly with tap water, and finally rinsed with water.
4.1 Atomic absorption spectrometer. with flame atomizer, calcium hollow cathode lamp.
4.3 Microwave digestion system. with polytetrafluoroethylene digestion inner tank.
4.4 Adjustable electric furnace.
5.2.2 Microwave digestion
Accurately WEIGH 0.2 g ~ 3 g (to the nearest 0.001 g) of solid sample or accurately
PIPETTE 0.500 mL ~ 3.00 mL of liquid sample in a microwave digestion tank; ADD 5
mL of nitric acid. DIGEST the sample according to procedure of the microwave
digestion, refer to Annex A for digestion conditions. REMOVE the digestion tank after
cooling; PLACE it on the electric hot plate to get rid of acid to about 1 mL at 140 °C ~
160 °C. After the digestion tank is cool, TRANSFER the digestion solution to a 25 mL
water; COLLECT the washing liquid in the volumetric flask and ADD water to the mark.
DILUTE according to the actual measurement needs; and ADD a certain volume of
lanthanum solution (20 g/L) in the diluted solution, so that its concentration in the final
diluted solution is 1 g/L; MIX for use, this is the sample solution to be tested. At the
same time, carry out the reagent blank test.
5.2.3 Pressure tank digestion
Accurately WEIGH 0.2 g ~ 1 g (to the nearest 0.001 g) of solid sample or accurately
PIPETTE 0.500 mL ~ 5.00 mL of liquid sample in a digestion inner tank; ADD 5 mL of
nitric acid. COVER the inner cap; TIGHTEN the stainless-steel outer tank; PLACE into
LOOSEN the outer tank after cooling; REMOVE the digestion inner tank; PLACE it on
the adjustable electric hot plate to get rid of acid to about 1 mL at 140 °C ~ 160 °C.
After cooling, TRANSFER the digestion solution to a 25 mL volumetric flask; WASH
the inner tank and the inner cap twice or three times with a small amount of water;
COLLECT the washing liquid in the volumetric flask and ADD water to the mark; MIX
well for use. DILUTE according to the actual measurement needs; and ADD a certain
volume of lanthanum solution (20 g/L) in the diluted solution, so that its concentration
in the final diluted solution is 1 g/L; MIX for use, this is the sample solution to be tested.
At the same time, carry out the reagent blank test.
Accurately WEIGH 0.5 g ~ 5 g (to the nearest 0.001 g) of solid sample or accurately
PIPETTE 0.500 mL ~ 10.0 mL of liquid sample in a crucible; HEAT with low flame;
CARBONIZE to smokeless. TRANSFER to a muffle furnace; ASH at 550 °C for 3 h ~
4 h. COOL and REMOVE. For incompletely-ashed sample, ADD a few drops of nitric
acid; HEAT with low flame; carefully EVAPORATE to dryness; TRANSFER to a muffle
furnace at 550 °C; continue to ASH for 1 h ~ 2 h until the sample is grayish white;
COOL and REMOVE; DISSOLVE with an appropriate amount of nitric acid solution (1
+ 1) and TRANSFER to a graduated tube; ADD water to 25 mL. DILUTE according to
the actual measurement needs; and ADD a certain volume of lanthanum solution in
for use, this is the sample solution to be tested. At the same time, carry out the reagent
blank test.
10.2.1 Potassium hydroxide solution (1.25 mol/L). WEIGH 70.13 g of potassium
hydroxide; DILUTE with water to 1000 mL; MIX well.
10.2.2 Sodium sulfide solution (10 g/L). WEIGH 1 g of sodium sulfide; DILUTE with
water to 100 mL; MIX well.
10.2.3 Sodium citrate solution (0.05 mol/L). WEIGH 14.7 g of sodium citrate; DILUTE
with water to 1000 mL; MIX well.
10.2.4 EDTA solution. WEIGH 4.5 g of EDTA; DILUTE with water to 1000 mL; MIX well.
10.2.5 Calcium red indicator. WEIGH 0.1 g of calcium red indicator; DILUTE with water
to 100 mL; MIX well.
10.2.6 Hydrochloric acid solution (1 + 1). MEASURE 500 mL of hydrochloric acid; MIX
well with 500 mL of water.
10.3 Standard
Calcium carbonate (CaCO3, CAS No. 471-34-1). with purity > 99.99 %, or calcium
standard solution at a certain concentration certified by the state and awarded the
standard substance certificate.
10.4 Preparation of standard solution
nearest 0.0001 g) of calcium carbonate; ADD hydrochloric acid solution (1 + 1) to
dissolve; TRANSFER to a 1000 mL volumetric flask; ADD water to the mark; MIX well.
11 Instruments and equipment
NOTE. All glassware and polytetrafluoroethylene digestion inner tank must be soaked in nitric
acid solution (1 + 5) overnight, washed repeatedly with tap water, and finally rinsed with water.
11.1 Analytical Balance. with the division of 1 mg and 0.1 mg.
11.2 Adjustable electric furnace.
11.3 Adjustable electric hot plate.
11.4 Muffle furnace.
12.1 Sample preparation
V1 - the volume of 10-fold diluted EDTA solution that is consumed when titrating the
sample solution, in milliliters (mL);
V0 - the volume of 10-fold diluted EDTA solution that is consumed when titrating the
blank solution, in milliliters (mL);
V2 - the constant volume of the sample digestion solution, in milliliters (mL);
1 000 - the conversion factor;
m - the mass of the sample weighed or the volume pipetted, in grams or milliliters
(g or mL);
The calculation results retain three significant figures.
14 Precision
The absolute difference between two independent determination results obtained
under repeatability conditions shall not exceed 10 % of the arithmetic mean.
15 Others
When weighing 4 g (or 4 mL) of sample, diluting to the constant volume of 25 mL and
pipetting 1.00 mL of sample digestion solution for determination, the limit of
quantification for...
   
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