This standard specifies the reagents, instruments, operating procedures and result calculation methods for the determination of copper, iron, manganese, zinc, calcium, magnesium and other elements in various cereals and cereal products by atomic absorption spectrophotometry. This standard is applicable to various cereals and cereal products. GB/T 14609-1993 Determination of copper, iron, manganese, zinc, calcium and magnesium in cereals Atomic absorption method GB/T14609-1993 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Method for determination of Cu,Fe,Mn,Zn,Ca,Mg in cereals by atomic absorptionspectrophotometry
1 Subject content and scope of application
GB/T 14609--93
This standard specifies the reagents, instruments, operating procedures and result calculation methods for the determination of copper, iron, manganese, zinc, calcium, magnesium and other elements in various cereals and cereal products by atomic absorption spectrophotometry. This standard is applicable to various cereals and cereal products. 2 Reference standards
GB5497 Determination of moisture content in grains and oilseeds 3 Principle
After burning and ashing, the cereal samples are treated with hydrochloric acid and diluted to a reasonable concentration range. Use an atomic absorption spectrophotometer to measure the absorption value of each element, and then calculate the content of each element. If the calcium content is to be determined, dilute it with a hydrochloric acid solution containing lanthanum to an appropriate concentration.
4 Instruments (The glass instruments used in this standard must be soaked in 1:1 HNO: overnight before use) 4.1 Atomic absorption spectrophotometers of various models are acceptable. 4.2 Copper, iron, manganese, zinc, calcium, and magnesium hollow cathode lamps can be used with the atomic absorption spectrophotometer (4.1). 4.3 Air-acetylene flame system can be used with the atomic absorption spectrophotometer (4.1). 4.4 Muffle furnace.
4.5 Analytical balance
Sensitivity 0.1 mg.
4.6 Temperature-controlled electric furnace or electric heating plate.
4.7 Quartz or porcelain crucibles If porcelain pots are used, the porcelain surface must be smooth, without cracks or cracks. 4.8 Volumetric flask 100ml.
4.9 Beaker 250ml.
4.10 Pipette 1.0ml, 2.0ml, 5.0ml, 50ml. 4.11
Micropipette 500μL.
5 Reagents
The reagents listed in this standard are all analytical grade or equivalent, and the working water is deionized water. Hydrochloric acid (GB622)
Approved by the State Administration of Technical Supervision on September 5, 1993 and implemented on July 1, 1994
GB/T14609-93
5.26mol/L hydrochloric acid Pipette 500ml of hydrochloric acid (5.1) and mix with 500ml of water. 5.30.1mol/L hydrochloric acid 2 Pipette 16ml of hydrochloric acid (5.2) and dilute to 1000ml with water. 5.4 0.5 mol/L hydrochloric acid Take 80 mL of hydrochloric acid (5.2) and dilute to 1000 mL with water. 5.5 Lanthanum stock solution containing 50 g of lanthanum and about 25% hydrochloric acid (5.1) per liter Dissolve 58.65 g of oxide (La20, 99.99%) in 250 ml of concentrated hydrochloric acid and dilute to 1000 mL with water. 5.6 Standard stock solution
5.6.1 Copper standard stock solution containing 1000 μg/ml of copper Dissolve 1.000 g of spectrally pure copper flakes in a small amount of nitric acid (about 5-10 mL), add 5 ml of hydrochloric acid (5.1), evaporate to near dryness, and dilute to 1000 mL with hydrochloric acid (5.3).
5.6.2 Iron standard stock solution containing 1000μg/mL of iron Dissolve 1.000g of spectrally pure iron wire in 30mL of boiling 6mol/L hydrochloric acid (5.2), and dilute to 1000mL with 0.1mol/L hydrochloric acid (5.3).
5.6.3 Manganese standard stock solution containing 1000μg/mL of manganese Dissolve spectrally pure manganese dioxide (MnOz.99.99%) in 30mL of 6mol/L hydrochloric acid (5.2), boil for several minutes to drive out chlorine, and dilute to 1000mL
5.6.4 Zinc standard stock solution containing 1000μg/mL of zinc Dissolve 1.000g of spectrally pure metallic zinc in 10mL of 6mol/L hydrochloric acid (5.2), and dilute to 1000mL with water. 5.6.5 Magnesium standard stock solution containing 1000μg/mL of magnesium Dissolve 1.000g of spectrally pure magnesium in 50mL of water, slowly add 10mL of hydrochloric acid (5,1), and dilute to 1000mL with 0.1mol/L hydrochloric acid (5.3).
5.6.6 Calcium standard stock solution containing 25ug/mL of calcium Dissolve 1.249g of spectrally pure calcium carbonate (CaCO3, 99.99%) in a small amount of 6mol/L hydrochloric acid (5.2), and dilute to 1000ml with water. Pipette 50ml of the solution into a 1000mL volumetric flask and dilute to the mark with 0.5mol/L hydrochloric acid (5.4). 5.7 Working standard solutions
5.7.1 Working standard solutions of calcium
Put 0, 5, 10, 15, and 20 mL of calcium standard stock solution (5.6.6) in 25 mL volumetric flasks, add 5 mL of lanthanum stock solution (5.5) to each flask, and make up to 25 mL.
5.7.2 Working standard solutions of other elements
Use 0.1 mol/L hydrochloric acid (5.3) to dilute the standard stock solutions listed in 5.6.1, 5.6.2, 5.6.3, 5.6.4, and 5.6.5 to form standard solutions of 4 concentration levels. The concentration of each element should be within the working range of the instrument. 6 Operation steps
6.1 Sample preparationbzxz.net
6.1.1 Uniformly select the sample to be tested and grind it in a grinder until it passes through a 40-mesh sieve (0.45mm), not less than 50g. Determine the sample moisture according to GB5497, and the measured results are calculated on a dry basis. 6.1.2 Accurately weigh 10g of the sample to be tested into a crucible and carbonize it on a hot plate until there is no smoke. Then place it in a muffle furnace preheated to 500C and ash it until there are no carbon particles. If the ash is not complete, it can be taken out, cooled and moistened with a few drops of concentrated nitric acid, dried at low temperature and then ashed again. 6.1.3 Take out the ash-treated sample (in order to prevent the crucible from breaking due to sudden cooling, the muffle furnace can be turned off overnight), dissolve the residue with 10mL of concentrated hydrochloric acid (5.1), boil it on a hot plate and evaporate it to nearly. 6.1.4 Add 20mL 0.5mol/L hydrochloric acid (5.4) to dissolve the residue (6.1.3) and filter it into a 100mL volumetric flask with quick filter paper. Wash the filter paper and residue thoroughly with water, combine the filtrate, dilute 100mL, and shake well. 6.1.5 If calcium is to be determined, 20mL lanthanum stock solution (5.5) should be added to the solution (6.1.4) to make the final solution contain 1% lanthanum. If the concentration of a certain element to be determined in the solution is high, it should be further diluted to the concentration range allowed by the instrument. 428
6.2 Determination
GB/T14609—93
6.2.1 Adjust the instrument to the optimal conditions according to the instrument manual. Due to the differences in the design of each instrument, this standard only provides basic parameters, see the table below:
Basic parameter table
Wavelength, nm
Flame type
Air-acetylene
Air-acetylene
Air-acetylene
Air-acetylene
Air-acetylene
Air-acetylene
Concentration range, mg/ml.
2～10
6.2.2 Read the absorption value of each element to be measured by aspirating solution (6.1.4) or (6.1.5) on the adjusted instrument. Before and after the sample is measured, the readings of four standard solutions within the analysis range should be read at least twice. Before each measurement, water should be aspirated to clean the burner, and the absorption zero point should be determined each time.
6.2.3 Draw the concentration-absorption curve based on the average reading of each standard solution before and after the sample measurement. 6.2.4 According to the measured sample absorption value, find the sample concentration on the curve (6.2.3) and calculate. 6.3 Result calculation
The sample content is expressed as micrograms of the element contained in each gram of sample, and one decimal place is retained. The content of a certain element in the sample is calculated according to the following formula: Element content (μg/g) = (CC.) × N
Where: C——Concentration-absorption value curve. The concentration corresponding to the sample absorption value. C. —The concentration corresponding to the blank absorption value in the concentration-absorption value curve. N-dilution multiple.
WWeighing weight.g.
6.4 Allowable difference
The allowable difference between two consecutive determination results by the same analyst shall not exceed: 10% of the average value of calcium samples (relative difference). 10% of the average value of magnesium samples (relative difference). Copper 0.5 μg/g (absolute difference).
Iron 4.0μg/g (absolute difference).
Manganese 1.5μg/g (absolute difference).
Zinc 1.5ug/g (absolute difference).
Additional Notes:
GB/T14609-93
This standard is proposed by the Ministry of Commerce of the People's Republic of China. This standard is under the jurisdiction of the Grain Storage and Transportation Bureau of the Ministry of Commerce. This standard is drafted by the Institute of Cereal Oil Chemistry of the Ministry of Commerce. The main drafter of this standard is Lei Ting.
This standard is equivalent to the approved method AACC40-70 "Determination of Various Elements in Cereals by Atomic Absorption Spectrophotometry" of the American Association of Cereal Chemists.
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