Fruit and vegetable products-Determination of copper content-Photometric method

This standard specifies the method for determining the copper content of fruit and vegetable products. This method is applicable to the determination of copper content in fruit and vegetable products, including various sauces, purees, fruit juices and vegetable juices. GB/T 12284-1990 Determination of copper content in fruit and vegetable products - Photometric method GB/T12284-1990 Standard download decompression password: www.bzxz.net
This standard specifies the method for determining the copper content in fruit and vegetable products. This method is applicable to the determination of copper content in fruit and vegetable products, including various sauces, purees, fruit juices and vegetable juices.

National Standard of the People's Republic of ChinabZxz.net
Fruit and vegetable products-Determination of copper content --Photometric method
Fruit and vegetable products-Determination of copper content --Photometric methodGB12284-90
This standard is equivalent to the international standard ISO3094-1974 "Determination of copper content in fruit and vegetable products-Subject content and scope of application
This standard specifies the method for the determination of copper content in fruit and vegetable products. --Photometric method".
This method is applicable to the determination of copper content in fruit and vegetable products, including various sauces, purees, fruit juices and vegetable juices. Note: Bismuth and tellurium interfere with the determination of this method.
2. .Reference Standard
GB12283 Decomposition Method of Organic Matter in Fruits, Vegetables and Products3 Principle
After the organic matter in the sample is decomposed, the acid solution during decomposition is neutralized with an alkaline solution. The copper ions in the sample react with sodium ethyldithiocarbamate to form a brown-yellow complex. The copper complex is extracted with chloroform or carbon tetrachloride, and the color intensity of the complex is measured.4 Reagents
All reagents are analytically pure. Distilled water or water of the same purity is used. 4.1 Chloroform or carbon tetranitride (GB682 or GB688), without carbonic acid. 4.2 Hydromethanol (GB683).
4.3 Ammonia water (GB 631), specific gravity 0.88g/mL. 4.4 Ammonium citrate-sodium ethylenediaminetetraacetic acid solution Dissolve 20g ammonium citrate (Q/HG12--256) and 5g sodium ethylenediaminetetraacetic acid (GB1401) in water and dilute to 100mL.
4.5 Sodium diethyl dithiocarbamate (HG3-962) solution 5g/L Heating in a 25~30℃ water bath can accelerate the dissolution of the reagent. This solution should be used within one week and stored in a refrigerator. 4.6 Copper standard solution equivalent to 0.01g/L
Dissolve 0.196g copper sulfate (CuSO·5H,O) in water, add a few drops of sulfuric acid with a specific gravity of 1.84g/mL, dilute to 500mL with water, and mix well. Take another 10mL and dilute to 100mL with water. This solution contains 10μg/mL of copper. 4.7 Thymol blue indicator (C27H2gOSNa) Dissolve 0.1g thymol blue in 8.6mL of 0.1mol/L sodium hydroxide solution and 10mL of 96% (u/) ethanol with heating, and dilute to 250mL with 20% (v/) ethanol.
Approved by the State Administration of Technical Supervision on March 29, 1990 140
Implemented on December 1, 1990
5 Instruments and equipment
5.1 Short-necked separatory funnel*
5.2 Spectrophotometer
GB12284—90
Equipped with 10 or 20mm colorimetric cup, measured at a wavelength of 435nm. 6 Analysis steps
6.1 Sample collection and organic matter decomposition
See GB12283.
Before decomposing organic matter, avoid using copper equipment when grinding and sieving samples. 6.2 Formation and extraction of copper complexes
When the copper content in the sample is expected to be less than 50μg, use the entire solution (6.1). When the copper content in the sample is expected to be higher, dilute the solution (6.1) with water to 100mL and take an appropriate amount from it. After the decomposition solution is cooled, dilute the solution with 30-40mL of water, transfer the solution to a separatory funnel (5.1), and add 20mL of ammonium citrate-ethylenediaminetetraacetic acid sodium salt (EDTA) solution (4.4), 5mL of ammonia solution (4.3), 2 drops of thymol blue indicator (4.7) and enough ammonia solution (4.3) in sequence to change the color of the solution from yellow to blue (pH 8 to 9.6). Cool in running water, loosening the stopper of the separatory funnel from time to time. Add 2 mL of sodium diethyldithiocarbamate solution (4.5), accurately add 10 mL of chloroform or carbon tetrachloride (4.1), shake for 5 minutes, and let stand to separate. Wipe the funnel with filter paper or cotton wool. Place the chloroform or carbon tetrachloride extract containing the copper complex in a test tube and store it away from light. Leave it for a while to allow trace water to come out, and filter it through filter paper into another test tube to remove trace water. Add 0.5 mL of anhydrous methanol (4.2), and place it in a dark place for 2 hours and in a bright place for 1 hour before measurement (avoid direct light). 6.3 Blank test
Carry out the sample determination method in 6.1 and 6.2 at the same time, but without adding sample. 6.4 Determination
Use a spectrophotometer (5.2) and use the blank test (6.3) as a control to determine the color intensity of the copper complex in the chloroform or carbon tetrachloride extract (see 6.2) at 435 nm. 6.5 Drawing of standard curve
After decomposing organic matter, take 1, 2, 3, 4, 5 mL of copper standard solution (4.6), containing 10, 20, 30, 40, 50 μg of copper respectively, and treat them in the same way as the sample and measure them respectively. Draw a standard curve with the absorbance value and the corresponding microgram of copper. At the same time, prepare a blank solution according to 6.3 and measure according to 6.4. When the standard curve and the sample solution are prepared at the same time, there is no need to make a blank solution separately. 7 Result expression
7.1 Calculation method and formula
Convert the measured value of 6.4 into micrograms of copper according to the standard curve. The copper content (mg/kg) in the sample is calculated as follows: Copper (mg/kg)
Where: U
The volume used for measurement from the solution (6.1), mL; the copper content found on the standard curve, ug; the mass of a sample, g.
Take the arithmetic mean of the two times as the analysis result. 7.2 Allowable difference
same--The difference between the results of two determinations made by the analyst simultaneously or in rapid succession shall not exceed 141
GB1228490
.0.2mg/kg when the copper content is less than or equal to 5mg/kg, and the average value shall not exceed 5% when the copper content is higher. Additional remarks:
This standard was proposed by the Ministry of Agriculture of the People's Republic of China. This standard was drafted by the Analysis and Testing Center of the Chinese Academy of Agricultural Sciences. The main drafters of this standard were Li Weige, Chen Bifang and Gu Junhua. 142
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