Determination of copper，iron，zinc，calcium，magnesium and phosphorus content in vegetables and derived products
Some standard content:
ICS 67. 080. 20
National Standard of the People's Republic of China
GB/T23375-—2009
Determination of copper, iron, zinc, calcium, magnesium and phosphorus content in vegetables and derived products2009-03-28 Issued
General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of ChinaStandardization Administration of China
2009-10-01Implementation
This standard is proposed and managed by the Ministry of Agriculture of the People's Republic of China. Foreword
The drafting unit of this standard is Food Quality Supervision, Inspection and Testing Center of the Ministry of Agriculture (Jinan). GB/T23375—2009
The main drafters of this standard are Ren Fengshan, Zhang Bingchun, Wang Lei, Zhao Pingjuan, Zhu Aiguo, Teng Dai, Meng Lihong, Nie Yan, Gu Xiaohong. http://w
rww.foodmate.net
1 Scope
Determination of copper, iron, zinc, calcium, magnesium and phosphorus in vegetables and their products
This standard specifies the determination method of copper, iron, zinc, calcium, magnesium and phosphorus in vegetables and their products. This standard is applicable to the determination of copper, iron, zinc, calcium, magnesium and phosphorus in vegetables and their products. GB/T 23375—2009
The detection limit of this method is: copper, 0.05mg/L, iron, 0.10mg/L; zinc, 0.05mg/L. Calcium, 0.25tg/L; magnesium, 0.05mg/L; phosphorus, 0.05mg/L. Linear range, copper, 0.1mg/L~10mg/L; iron, 0.2mg/L~10mg/L; zinc, 0.1mg/L~2.0mg/L; calcium, 0.2mg/L~20mg/L; magnesium, 0.01mg/L~~1.0mg/L; phosphorus, 0.1mg/L~10mg/L.2 Normative references
The clauses in the following documents become the clauses of this standard through reference in this standard. For all dated referenced documents, all subsequent amendments (excluding errata) or revisions are not applicable to this standard. However, the parties who reach an agreement based on this standard are encouraged to study whether the latest versions of these documents can be used. For all undated referenced documents, the latest versions are applicable to this standard. GB/T6682 Specifications and test methods for water in analytical laboratories 3 Principle
After acid digestion, the sample is introduced into an atomic absorption spectrophotometer. After atomization, steel, iron, zinc, calcium, and magnesium in the test solution absorb 324.8mml, 248.3nm213.8nm422.7mm.285.2nm resonance lines respectively. Within a certain concentration range, the absorbance (value) is proportional to its concentration and is quantitatively compared with the standard series.
After the sample is acid digested, phosphorus combines with ammonium molybdate under acidic conditions to form ammonium phosphomolybdate. This compound is reduced to a blue compound - molybdenum blue by hydroquinone and sodium sulfite. The absorbance (value) of blue is measured at a wavelength of 660nm using a spectrophotometer. Its absorbance (value) is proportional to the phosphorus content and is quantitatively compared with the standard series.
4 Reagents
Unless otherwise specified, analytical reagents and water of grade 2 or above specified in GB/T6682 are used in the analysis. 4.1 Hydrochloric acid solution [(HCI+H,0)=1+1]
Measure 50mL hydrochloric acid and 50mL water respectively, and mix. 4. 2 Nitric acid-perchloric acid mixed solution [(HNO, +HCIO,) =4 + 1]Measure 80mL nitric acid and 20mL perchloric acid respectively, and mix. 4.3 Lanthanum oxide solution: 50g/L
Weigh 29.32g lanthanum oxide (LazO,) and moisten it with 25mL water, then slowly add 125mL hydrochloric acid (4.1) to dissolve it, transfer it to a 500mL volumetric flask with water, and dilute to the scale. 4.4 Sulfuric acid solution [(H2S0,)15%]
Pipette 15mL sulfuric acid and slowly add it to 80mL water, mix, and dilute to 100mL with water after cooling. 4.5 Ammonium molybdate solution. 50g/L
Weigh 5g ammonium molybdate [(NH4,),Mo4O4H4O] and dilute to 100mL with sulfuric acid solution (4.4). 4.6 Sodium sulfite solution: 200g/L
Weigh 20g sodium sulfite (Na4SO4) and dissolve in 100mL water. This solution should be prepared immediately before use. Apricot can make the lead blue solution turbid. 1
GB/T23375—2009
4.7 Hydroquinone solution: 5g/L
Weigh 0.5g hydroquinone [CH, (OH)] and dissolve it in 100mL water, and add a drop of sulfuric acid (to slow down the oxidation) 4.8 Standard stock solution
4.8.1 Copper standard purchase solution: 1000mg/L
National certified copper standard solution or prepare it according to the following method: Accurately weigh (1.0000±0.0001)g spectrally pure copper in a beaker, add 40mL hydrochloric acid solution (4.1) and 50mL water, heat to boil, cool and transfer to a 1000mL volumetric flask, and dilute to the scale with water. 4.8.2 Iron standard preparation solution: 1000mg/L
National certified iron standard solution or prepare as follows: Accurately weigh (1.0000±0.0001)g spectrally pure metallic iron in a beaker, add 40mL hydrochloric acid solution (4.1) and 50mL water, heat to boil, cool and transfer to a 1000mL volumetric flask and dilute to scale with water. 4.8.3 Zinc standard stock solution: 1000mg
National certified zinc standard solution or prepare as follows: Accurately weigh (1.0000
and transfer to a 1000mL volumetric flask and dilute to scale with water. 4.8.4 Calcium standard stock solution 1000mg/l
|National certified calcium standard volume or prepare
10mL hydrochloric acid solution according to the following
method. 1) Heat slightly to dissolve, cool and standard calcium carbonate (CaCO) in a beaker with hydrochloric acid solution (4.1). 0mL dissolve, accurately weigh (2.
bottle with water 4963±0.0001
and dilute to the scale
and transfer to 1000mL
4.8.5 Magnesium standard purchase
1000mg/1
National certified magnesium standard recommended
solution or prepare
according to the following method. Put optically pure metallic magnesium in a beaker, slowly add 50mL water and 50mL hydrochloric acid solution and accurately weigh (1.
±0.0001)g
(4 .1), dissolve it with water and transfer it to a 1000mL volumetric flask, and dilute it to the scale. 4.8.6 Phosphorus standard stock solution: 100mg/L National certified phosphorus standard nutrient solution or prepare it according to the following method Accurately weigh (0.43.0001) standard potassium monoxide (KHO) dried at 105%, place it in a beaker, dissolve it with water and transfer it to 10000mL volumetric flasks, and dilute it to the scale. 4.9 Standard working solution 4.9.1 Copper standard working solution Dilute it step by step to 5.0μg copper per milliliter. Use water to make copper standard stock solution 4.9.2 Iron standard working solution: 25.0m
Dilute the iron standard stock solution (4.8.2) with water to 25.0 g iron per ml. 4.9.3 Zinc standard working solution: 5.00 mg/L
Dilute the zinc standard stock solution (4.8.3) with water to 5.0 ug zinc per ml. 4.9.4 Calcium standard working solution: 50.0 mg/L
Dilute the calcium standard stock solution (4.8.4) with water to 50.0 g calcium per ml. 4.9.5 Magnesium standard working solution: 5.00 mg/L
Dilute the magnesium standard stock solution (4.8.5) with water to 5.0 μg magnesium per ml. 4.9.6 Phosphorus standard working solution: 10.0 mg/L
Dilute the phosphorus standard stock solution (4.8.6) with water to 10.0 pg phosphorus per ml. 5 Instruments
All glass containers used are soaked in nitric acid (10%~20%) for more than 24 hours, rinsed repeatedly with tap water, then washed and dried. The utensils used should avoid contact with metal or rubber products to prevent contamination. 5.1 Atomic absorption spectrophotometer: with flame atomizer and copper, iron, zinc, calcium, magnesium hollow cathode lamps. 5.2 Visible spectrophotometer.
5.3 Balance: sensitivity 0.0001g.
5.4 Tissue crusher and ball mill
5.5 Adjustable electric heating plate.
6 Sample preparation
GB/T23375—2009
Rinse fresh vegetables with tap water, then rinse with water to remove surface moisture. Use the quartering method to chop the edible part, mash it into a homogenate, and set aside.
Vegetable sauces and liquid products should be fully reviewed and directly sampled. Frozen and canned products should be thawed in a dense container in advance, all poured out, and the edible part should be made into a homogenate. Self-sieve, set aside.
7 Analysis steps
7.1 Sample decomposition
Carbonization.
The use of perchloric acid in digestion is explosive
pg or dry sample
Weigh 5g of fresh sample (accurate to 0.00) on a hot plate. Heat the sample slowly at low temperature. Wait for the effect to ease before heating to continue digestion. Cool and add nitric acid
or the color becomes darker, take
to avoid carbonization. After the final product is cooked and white smoke is emitted, remove the remaining nitric acid from the solution. When the liquid in the conical flask is close to M, wash it into the volumetric flask with
decomposition solution 50m
|Replace the sample with water#
7.2 Determination
7.2.1 Instrument conditions
Be careful not to boil it dry, and strictly prevent
150mL conical flask, containing ethanol or dioxide mixed acid (4.2) Cover with a small funnel and place for a while, when the liquid is about 5mL, there is still undecomposed substance
5mL. Digest to 5
Observe, repeat until there is no above phenomenon, pay attention to the color, then digestion is complete. Add a few milliliters
colorless and transparent or slightly yellow
water, heat to remove excess
mL, remove and cool
mL hydrochloric acid solution (4
1) slightly heated, the sample
Wash the flask once, add the washing liquid into the volumetric flask, and dilute to the scale. 1. Operation method: At the same time as the reagent
Adjust the instrument performance to
the fastest set, use air-acetylene flame, and introduce the flame atomizer for measurement. Due to the different designs of various instrument models, this standard only provides this parameter, and the reference measurement conditions are shown in Table 1. Table 1 Reference measurement conditions
7.2.2 Drawing of standard curve
Wavelength/nm
Lamp current/mA
7.2.2.1/Pick 0.00mL, 2.00mL, 4.00mL, 6.00mL of copper, iron, and zinc standard solutions (4.9.1, 4.9.2, and 4.9.3) respectively. .00ml, 8.00ml, 10.00ml in a 50ml volumetric flask, add 2.0ml hydrochloric acid solution (4.1), and dilute to the mark with water. The concentrations of each standard series are: copper, 0.00mg/L, 0.20mg/L, 0.40mg/L, 0.60mg/L, 0.80mg/L, 1.00mg/L; iron, 0.00mg/L, 1.00mg/L, 2.00mg/L, 3.00mg/L, 4.00mg/L5.00mg/L, zinc, 0.00mg/L0.20mg/L, 0.40mg/L, 3
http://foodmate.netGB/T 23375—2009
0.60mg/L.0.80mg/L.1.00mg/L
7.2.2.2 Take 0.00mL, 2.00mL, 4.00mL, 6.00mL, 8.00mL, 10.00mL of calcium and magnesium standard working solutions (4.9.4, 4.9.5) respectively into a 50mL volumetric flask, add 2.0mL of hydrochloric acid solution (4.1), 1.0nL of oxidized ion solution (4.3), and dilute to the mark with water. The concentrations of each standard series are: calcium, 0.00mg/L, 2.00mg/L, 4.00mg/L, 6.00mg/L, 8.00mg/L, 10.00mg/L. Magnesium, 0.00mg/L, 0.20mg/L, 0.40mg/L, 0.60mg/L, 0.80mg/L, 1.00mg/L. Introduce the solutions in 7.2.2.1 and 7.2.2.2 into the flame atomizer respectively and measure their absorbance (value). Take the concentration of each element as the horizontal axis and the absorbance (value) as the vertical axis, calculate the linear regression equation of each element or draw a standard curve. 7.2.2.3 Take 0.00mL, 2.50ml, 5.00mL, 10.00mL, 15.00mL, and 20.00mL of phosphorus standard solution (4.9.6) respectively, place them in a 50mL container, add 4.0mL of ammonium hydroxide solution (4.5) in turn, shake well. Let it stand for a few seconds. Add 2.0mL of sodium sulfite solution (4.6) and 2.0mL of hydroquinone solution (4.7), shake well, and dilute with water to the scale. The concentrations of the standard series are: 0.00mg/L, 0.50mg/L, 1.00 mg/L, 2.00 mg/L, 3.00 mg/L, and 4.00 mg/L. After leaving it at room temperature above 20℃ for 30 minutes, use 1 cm colorimetric cup, adjust the zero point with the zero tube solution, and measure the absorbance (value) at a wavelength of 660 Ⅱ И on the spectrophotometer. With phosphorus content as the horizontal axis and absorbance (value) as the vertical axis, calculate the linear regression equation or draw a standard curve. 7.2.3 Sample determination
7.2.3.1 Determination of copper, iron and zincWww.bzxZ.net
While determining the standard series solution, introduce the sample decomposition solution (7.1) and the reagent blank solution into the flame atomizer to measure the absorbance of each element respectively. Then calculate the concentration of copper, iron or zinc in the sample decomposition solution by the linear regression equation of each element or check the working curve.
7.2.3.2 Determination of calcium and magnesium
Accurately pipette 2.00mL~5.00mL of the sample decomposition solution (7.1) and the blank solution of the same amount, place them in 50mL volumetric flasks, add 2.0mL of hydrochloric acid solution (4.1) and 1.0mL of lanthanum oxide solution (4.3), and dilute to the scale with water. While the standard series solutions are being prepared, the above solutions are introduced into the flame atomizer to measure the absorbance (value) of each element. Then the concentrations of calcium and magnesium in the sample solution are calculated from the linear regression equation of each element or obtained from the working curve. 7.2.3.3 Determination of phosphorus
Accurately pipette 1.00mL~5.00mL of the sample decomposition solution (7.1) and the same amount of blank solution into 50mL volumetric flasks respectively. Then add 4.0mL of the sample solution (7.1) in sequence according to 7.2.2.3. mL ammonium molybdate solution (4.5) shake well and operate according to the law. The phosphorus content in the sample solution is calculated by the linear regression equation or by the standard curve using the measured absorbance (value). If the absorbance (value) of the sample solution is greater than the absorbance (value) of the highest point in the standard series, the solution should be diluted and re-measured. 8 Calculation
8.1 The copper, iron or zinc content in the sample is expressed as mass fraction zw, expressed in milligrams per kilogram (mg/kg), and calculated according to formula (1). w= (ep)×V
***-(1 )
The calculation result is expressed to three significant figures. When the content is less than 1mg/kg, it is expressed to two significant figures. 8.2 The calcium or magnesium content in the sample is expressed as mass fraction w, expressed in percentage (%), and calculated according to formula (2). ()×V
The calculation result is expressed to three significant figures. When the content is less than 0.1%, it is expressed to two significant figures. 8.3 The phosphorus content in the sample is expressed as mass fraction w, expressed in percentage (%), and calculated according to formula (3). w=exx
The calculated result is expressed to three significant figures. When the content is less than 0.1%, it is expressed to two significant figures. In formula (1), formula (2), and formula (3): the mass concentration of copper, iron, zinc, calcium or magnesium in the sample test solution, in milligrams per liter (g/IL); 4
the mass concentration of copper, iron, zinc, calcium or magnesium in the reagent blank solution, in milligrams per liter (mg/L); the fixed volume of the sample decomposition solution, in milliliters (mL): - the mass of the sample, in grams (g);
the fixed volume of the sample test solution, in milliliters (mL); V2
the volume of the sample decomposition solution taken for determination, in milliliters (nL); the mass liquid of phosphorus in the sample test solution, in milligrams per liter (IIg/L); V—the color development volume of the sample test solution, in milliliters (mL). If the test solution is diluted, the dilution factor should be added to the calculation. Precision
GB/T 23375—2009
The absolute difference between two independent determination results obtained under repeated conditions should not exceed 10 of the arithmetic mean.5 Adjustable electric heating plate.
6 Sample preparation
GB/T23375—2009
Rinse fresh vegetables with tap water, then rinse with water to remove surface moisture. Use the quartering method to chop the edible part, mash it into a homogenate, and set aside.
Vegetable sauces and liquid products should be fully reviewed and directly sampled. Frozen and canned products should be thawed in a dense container in advance, all poured out, and the edible part should be made into a homogenate. Self-sieve and set aside.
7 Analysis steps
7.1 Sample decomposition
Carbonization.
The use of perchloric acid in digestion is explosive
pg or dry sample
Weigh 5g of fresh sample (accurate to 0.00) on a hot plate. Heat the sample slowly at low temperature. Wait for the effect to ease before heating to continue digestion. Cool and add nitric acid
or the color becomes darker, take
to avoid carbonization. After the final product is cooked and white smoke is emitted, remove the remaining nitric acid from the solution. When the liquid in the conical flask is close to M, wash it into the volumetric flask with
decomposition solution 50m
|Replace the sample with water#
7.2 Determination
7.2.1 Instrument conditions
Be careful not to boil it dry, and strictly prevent
150mL conical flask, containing ethanol or dioxide mixed acid (4.2) Cover with a small funnel and place for a while, when the liquid is about 5mL, there is still undecomposed substance
5mL. Digest to 5
Observe, repeat until there is no above phenomenon, pay attention to the color, then digestion is complete. Add a few milliliters
colorless and transparent or slightly yellow
water, heat to remove excess
mL, remove and cool
mL hydrochloric acid solution (4
1) slightly heated, the sample
Wash the flask once, add the washing liquid into the volumetric flask, and dilute to the scale. 1. Operation method: At the same time as the reagent
Adjust the instrument performance to
the fastest set, use air-acetylene flame, and introduce the flame atomizer for measurement. Due to the different designs of various instrument models, this standard only provides this parameter, and the reference measurement conditions are shown in Table 1. Table 1 Reference measurement conditions
7.2.2 Drawing of standard curve
Wavelength/nm
Lamp current/mA
7.2.2.1/Pick 0.00mL, 2.00mL, 4.00mL, 6.00mL of copper, iron, and zinc standard solutions (4.9.1, 4.9.2, and 4.9.3) respectively. .00ml, 8.00ml, 10.00ml in a 50ml volumetric flask, add 2.0ml hydrochloric acid solution (4.1), and dilute to the mark with water. The concentrations of each standard series are: copper, 0.00mg/L, 0.20mg/L, 0.40mg/L, 0.60mg/L, 0.80mg/L, 1.00mg/L; iron, 0.00mg/L, 1.00mg/L, 2.00mg/L, 3.00mg/L, 4.00mg/L5.00mg/L, zinc, 0.00mg/L0.20mg/L, 0.40mg/L, 3
http://foodmate.netGB/T 23375—2009
0.60mg/L.0.80mg/L.1.00mg/L
7.2.2.2 Take 0.00mL, 2.00mL, 4.00mL, 6.00mL, 8.00mL, 10.00mL of calcium and magnesium standard working solutions (4.9.4, 4.9.5) respectively into a 50mL volumetric flask, add 2.0mL of hydrochloric acid solution (4.1), 1.0nL of oxidized ion solution (4.3), and dilute to the mark with water. The concentrations of each standard series are: calcium, 0.00mg/L, 2.00mg/L, 4.00mg/L, 6.00mg/L, 8.00mg/L, 10.00mg/L. Magnesium, 0.00mg/L, 0.20mg/L, 0.40mg/L, 0.60mg/L, 0.80mg/L, 1.00mg/L. Introduce the solutions in 7.2.2.1 and 7.2.2.2 into the flame atomizer respectively and measure their absorbance (value). Take the concentration of each element as the horizontal axis and the absorbance (value) as the vertical axis, calculate the linear regression equation of each element or draw a standard curve. 7.2.2.3 Take 0.00mL, 2.50ml, 5.00mL, 10.00mL, 15.00mL, and 20.00mL of phosphorus standard solution (4.9.6) respectively, place them in a 50mL container, add 4.0mL of ammonium hydroxide solution (4.5) in turn, shake well. Let it stand for a few seconds. Add 2.0mL of sodium sulfite solution (4.6) and 2.0mL of hydroquinone solution (4.7), shake well, and dilute with water to the scale. The concentrations of the standard series are: 0.00mg/L, 0.50mg/L, 1.00 mg/L, 2.00 mg/L, 3.00 mg/L, and 4.00 mg/L. After leaving it at room temperature above 20℃ for 30 minutes, use 1 cm colorimetric cup, adjust the zero point with the zero tube solution, and measure the absorbance (value) at a wavelength of 660 Ⅱ И on the spectrophotometer. With phosphorus content as the horizontal axis and absorbance (value) as the vertical axis, calculate the linear regression equation or draw a standard curve. 7.2.3 Sample determination
7.2.3.1 Determination of copper, iron and zinc
While determining the standard series solution, introduce the sample decomposition solution (7.1) and the reagent blank solution into the flame atomizer to measure the absorbance of each element respectively. Then calculate the concentration of copper, iron or zinc in the sample decomposition solution by the linear regression equation of each element or check the working curve.
7.2.3.2 Determination of calcium and magnesium
Accurately pipette 2.00mL~5.00mL of the sample decomposition solution (7.1) and the blank solution of the same amount, place them in 50mL volumetric flasks, add 2.0mL of hydrochloric acid solution (4.1) and 1.0mL of lanthanum oxide solution (4.3), and dilute to the scale with water. While the standard series solutions are being prepared, the above solutions are introduced into the flame atomizer to measure the absorbance (value) of each element. Then the concentrations of calcium and magnesium in the sample solution are calculated from the linear regression equation of each element or obtained from the working curve. 7.2.3.3 Determination of phosphorus
Accurately pipette 1.00mL~5.00mL of the sample decomposition solution (7.1) and the same amount of blank solution into 50mL volumetric flasks respectively. Then add 4.0mL of the sample solution (7.1) in sequence according to 7.2.2.3. mL ammonium molybdate solution (4.5) shake well and operate according to the law. The phosphorus content in the sample solution is calculated by the linear regression equation or by the standard curve using the measured absorbance (value). If the absorbance (value) of the sample solution is greater than the absorbance (value) of the highest point in the standard series, the solution should be diluted and re-measured. 8 Calculation
8.1 The copper, iron or zinc content in the sample is expressed as mass fraction zw, expressed in milligrams per kilogram (mg/kg), and calculated according to formula (1). w= (ep)×V
***-(1 )
The calculation result is expressed to three significant figures. When the content is less than 1mg/kg, it is expressed to two significant figures. 8.2 The calcium or magnesium content in the sample is expressed as mass fraction w, expressed in percentage (%), and calculated according to formula (2). ()×V
The calculation result is expressed to three significant figures. When the content is less than 0.1%, it is expressed to two significant figures. 8.3 The phosphorus content in the sample is expressed as mass fraction w, expressed in percentage (%), and calculated according to formula (3). w=exx
The calculated result is expressed to three significant figures. When the content is less than 0.1%, it is expressed to two significant figures. In formula (1), formula (2), and formula (3): the mass concentration of copper, iron, zinc, calcium or magnesium in the sample test solution, in milligrams per liter (g/IL); 4
the mass concentration of copper, iron, zinc, calcium or magnesium in the reagent blank solution, in milligrams per liter (mg/L); the fixed volume of the sample decomposition solution, in milliliters (mL): - the mass of the sample, in grams (g);
the fixed volume of the sample test solution, in milliliters (mL); V2
the volume of the sample decomposition solution taken for determination, in milliliters (nL); the mass liquid of phosphorus in the sample test solution, in milligrams per liter (IIg/L); V—the color development volume of the sample test solution, in milliliters (mL). If the test solution is diluted, the dilution factor should be added in the calculation. Precision
GB/T 23375—2009
The absolute difference between two independent determination results obtained under repeated conditions should not exceed 10 of the arithmetic mean.5 Adjustable electric heating plate.
6 Sample preparation
GB/T23375—2009
Rinse fresh vegetables with tap water, then rinse with water to remove surface moisture. Use the quartering method to chop the edible part, mash it into a homogenate, and set aside.
Vegetable sauces and liquid products should be fully reviewed and directly sampled. Frozen and canned products should be thawed in a dense container in advance, all poured out, and the edible part should be made into a homogenate. Self-sieve and set aside.
7 Analysis steps
7.1 Sample decomposition
Carbonization.
The use of perchloric acid in digestion is explosive
pg or dry sample
Weigh 5g of fresh sample (accurate to 0.00) on a hot plate. Heat the sample slowly at low temperature. Wait for the effect to ease before heating to continue digestion. Cool and add nitric acid
or the color becomes darker, take
to avoid carbonization. After the final product is cooked and white smoke is emitted, remove the remaining nitric acid from the solution. When the liquid in the conical flask is close to M, wash it into the volumetric flask with
decomposition solution 50m
|Replace the sample with water#
7.2 Determination
7.2.1 Instrument conditions
Be careful not to boil it dry, and strictly prevent
150mL conical flask, containing ethanol or dioxide mixed acid (4.2) Cover with a small funnel and place for a while, when the liquid is about 5mL, there is still undecomposed substance
5mL. Digest to 5
Observe, repeat until there is no above phenomenon, pay attention to the color, then digestion is complete. Add a few milliliters
colorless and transparent or slightly yellow
water, heat to remove excess
mL, remove and cool
mL hydrochloric acid solution (4
1) slightly heated, the sample
Wash the flask once, add the washing liquid into the volumetric flask, and dilute to the scale. 1. Operation method: At the same time as the reagent
Adjust the instrument performance to
the fastest set, use air-acetylene flame, and introduce the flame atomizer for measurement. Due to the different designs of various instrument models, this standard only provides this parameter, and the reference measurement conditions are shown in Table 1. Table 1 Reference measurement conditions
7.2.2 Drawing of standard curve
Wavelength/nm
Lamp current/mA
7.2.2.1/Pick 0.00mL, 2.00mL, 4.00mL, 6.00mL of copper, iron, and zinc standard solutions (4.9.1, 4.9.2, and 4.9.3) respectively. .00ml, 8.00ml, 10.00ml in a 50ml volumetric flask, add 2.0ml hydrochloric acid solution (4.1), and dilute to the mark with water. The concentrations of each standard series are: copper, 0.00mg/L, 0.20mg/L, 0.40mg/L, 0.60mg/L, 0.80mg/L, 1.00mg/L; iron, 0.00mg/L, 1.00mg/L, 2.00mg/L, 3.00mg/L, 4.00mg/L5.00mg/L, zinc, 0.00mg/L0.20mg/L, 0.40mg/L, 3
http://foodmate.netGB/T 23375—2009
0.60mg/L.0.80mg/L.1.00mg/L
7.2.2.2 Take 0.00mL, 2.00mL, 4.00mL, 6.00mL, 8.00mL, 10.00mL of calcium and magnesium standard working solutions (4.9.4, 4.9.5) respectively into a 50mL volumetric flask, add 2.0mL of hydrochloric acid solution (4.1), 1.0nL of oxidized ion solution (4.3), and dilute to the mark with water. The concentrations of each standard series are: calcium, 0.00mg/L, 2.00mg/L, 4.00mg/L, 6.00mg/L, 8.00mg/L, 10.00mg/L. Magnesium, 0.00mg/L, 0.20mg/L, 0.40mg/L, 0.60mg/L, 0.80mg/L, 1.00mg/L. Introduce the solutions in 7.2.2.1 and 7.2.2.2 into the flame atomizer respectively and measure their absorbance (value). Take the concentration of each element as the horizontal axis and the absorbance (value) as the vertical axis, calculate the linear regression equation of each element or draw a standard curve. 7.2.2.3 Take 0.00mL, 2.50ml, 5.00mL, 10.00mL, 15.00mL, and 20.00mL of phosphorus standard solution (4.9.6) respectively, place them in a 50mL container, add 4.0mL of ammonium hydroxide solution (4.5) in turn, shake well. Let it stand for a few seconds. Add 2.0mL of sodium sulfite solution (4.6) and 2.0mL of hydroquinone solution (4.7), shake well, and dilute with water to the scale. The concentrations of the standard series are: 0.00mg/L, 0.50mg/L, 1.00 mg/L, 2.00 mg/L, 3.00 mg/L, and 4.00 mg/L. After leaving it at room temperature above 20℃ for 30 minutes, use 1 cm colorimetric cup, adjust the zero point with the zero tube solution, and measure the absorbance (value) at a wavelength of 660 Ⅱ И on the spectrophotometer. With phosphorus content as the horizontal axis and absorbance (value) as the vertical axis, calculate the linear regression equation or draw a standard curve. 7.2.3 Sample determination
7.2.3.1 Determination of copper, iron and zinc
While determining the standard series solution, introduce the sample decomposition solution (7.1) and the reagent blank solution into the flame atomizer to measure the absorbance of each element respectively. Then calculate the concentration of copper, iron or zinc in the sample decomposition solution by the linear regression equation of each element or check the working curve.
7.2.3.2 Determination of calcium and magnesium
Accurately pipette 2.00mL~5.00mL of the sample decomposition solution (7.1) and the blank solution of the same amount, place them in 50mL volumetric flasks, add 2.0mL of hydrochloric acid solution (4.1) and 1.0mL of lanthanum oxide solution (4.3), and dilute to the scale with water. While the standard series solutions are being prepared, the above solutions are introduced into the flame atomizer to measure the absorbance (value) of each element. Then the concentrations of calcium and magnesium in the sample solution are calculated from the linear regression equation of each element or obtained from the working curve. 7.2.3.3 Determination of phosphorus
Accurately pipette 1.00mL~5.00mL of the sample decomposition solution (7.1) and the same amount of blank solution into 50mL volumetric flasks respectively. Then add 4.0mL of the sample solution (7.1) in sequence according to 7.2.2.3. mL ammonium molybdate solution (4.5) shake well and operate according to the law. The phosphorus content in the sample solution is calculated by the linear regression equation or by the standard curve using the measured absorbance (value). If the absorbance (value) of the sample solution is greater than the absorbance (value) of the highest point in the standard series, the solution should be diluted and re-measured. 8 Calculation
8.1 The copper, iron or zinc content in the sample is expressed as mass fraction zw, expressed in milligrams per kilogram (mg/kg), and calculated according to formula (1). w= (ep)×V
***-(1 )
The calculation result is expressed to three significant figures. When the content is less than 1mg/kg, it is expressed to two significant figures. 8.2 The calcium or magnesium content in the sample is expressed as mass fraction w, expressed in percentage (%), and calculated according to formula (2). ()×V
The calculation result is expressed to three significant figures. When the content is less than 0.1%, it is expressed to two significant figures. 8.3 The phosphorus content in the sample is expressed as mass fraction w, expressed in percentage (%), and calculated according to formula (3). w=exx
The calculated result is expressed to three significant figures. When the content is less than 0.1%, it is expressed to two significant figures. In formula (1), formula (2), and formula (3): the mass concentration of copper, iron, zinc, calcium or magnesium in the sample test solution, in milligrams per liter (g/IL); 4
the mass concentration of copper, iron, zinc, calcium or magnesium in the reagent blank solution, in milligrams per liter (mg/L); the fixed volume of the sample decomposition solution, in milliliters (mL): - the mass of the sample, in grams (g);
the fixed volume of the sample test solution, in milliliters (mL); V2
the volume of the sample decomposition solution taken for determination, in milliliters (nL); the mass liquid of phosphorus in the sample test solution, in milligrams per liter (IIg/L); V—the color development volume of the sample test solution, in milliliters (mL). If the test solution is diluted, the dilution factor should be added in the calculation. Precision
GB/T 23375—2009
The absolute difference between two independent determination results obtained under repeated conditions should not exceed 10 of the arithmetic mean.When 1%, it indicates two significant figures. In formula (1), formula (2), and formula (3): the mass concentration of copper, iron, zinc, calcium or magnesium in the sample solution, in milligrams per liter (g/IL); 4
the mass concentration of copper, iron, zinc, calcium or magnesium in the reagent blank solution, in milligrams per liter (mg/L); the fixed volume of the sample decomposition solution, in milliliters (mL): - the mass of the sample, in grams (g):
the fixed volume of the sample solution, in milliliters (mL); V2
the volume of the sample decomposition solution taken for determination, in milliliters (nL); the mass concentration of phosphorus in the sample solution, in milligrams per liter (Ⅱg/L); V—the color development volume of the sample solution, in milliliters (mL). If the solution is diluted, the dilution factor is added to the calculation. Precision
GB/T 23375—2009
The absolute difference between two independent determination results obtained under repeated conditions should not exceed 10 of the arithmetic mean.
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