GB/T 5009.86-2003 Determination of total ascorbic acid in vegetables, fruits and their products (fluorescence method and 2,4-dinitrophenylhydrazine method)

This standard specifies the determination of ascorbic acid in food by fluorescence method and 2,4-dinitrophenylhydrazine colorimetric method. This standard is applicable to the determination of total ascorbic acid in vegetables, fruits and their products. GB/T 5009.86-2003 Determination of total ascorbic acid in vegetables, fruits and their products (fluorescence method and 2,4-dinitrophenylhydrazine method) GB/T5009.86-2003 Standard download decompression password: www.bzxz.net

ICS67.040
National Standard of the People's Republic of China
GB/T5009.86—2003
Replaces GB/T12392-1990
Determination of total ascorbic acid in fruitsvegetables and derived products-Flourometricmethod and colorimetric methodPublished on August 11, 2003
Ministry of Health of the People's Republic of China
Standardization Administration of the People's Republic of China
Implemented on January 1, 2004
GB/T5009.86-2003
The first method of this standard corresponds to ISO6557-1:1986 "Determination of ascorbic acid in vegetables, fruits and their products" and AOAC967.22 "Microfluorimetric determination of total vitamin C in vitamin products". The consistency of this standard with ISO6557-1 and AOAC967.22 is not equivalent. This standard replaces GB/T12392-1990 "Determination of total ascorbic acid in vegetables, fruits and their products (fluorimetric method and 2,4-dinitrophenylhydrazine method)".
Compared with GB/T12392-1990, this standard has been modified as follows: - The Chinese name of the standard has been modified, and the Chinese name of the standard has been changed to "Determination of total ascorbic acid in vegetables, fruits and their products (fluorescence method and 2,4-dinitrophenylhydrazine method)";
The structure of the original standard has been modified according to GB/T20001.4-2001 "Standard Preparation Rules Part 4: Chemical Analysis Methods".
This standard is proposed and managed by the Ministry of Health of the People's Republic of China. This standard is drafted by the Institute of Nutrition and Food Hygiene, Chinese Academy of Preventive Medicine. The main drafters of this standard are: Wang Guangya, Yang Xiaoli, Tian Lixin. The original standard was first issued in 1990, and this is the first revision. 624
1 Scope
GB/T5009.86—2003Www.bzxZ.net
Determination of total ascorbic acid in vegetables, fruits and their products (fluorescence method and 2,4-dinitrophenylhydrazine method) This standard specifies the determination of ascorbic acid in food by fluorescence method and 2,4-dinitrophenylhydrazine colorimetric method. This standard is applicable to the determination of total ascorbic acid in vegetables, fruits and their products. The detection limit of this method is 0.022μg/mL for fluorescence method and 0.1ug/mL for 2,4-dinitrophenylhydrazine colorimetric method. Linear range: 5μg/mL~20μg/mL for fluorescence method and 1μg/mL~12μg/mL for 2,4-dinitrophenylhydrazine colorimetric method. Method 1 Fluorescence method
2 Principle
After the reduced ascorbic acid in the sample is oxidized to dehydroascorbic acid by activated carbon, it reacts with o-phenylenediamine (OPDA) to generate fluorescent quinoxaline, whose fluorescence intensity is proportional to the concentration of ascorbic acid under certain conditions, so as to determine the total amount of ascorbic acid and dehydroascorbic acid in food.
Dehydroascorbic acid can form a complex with boric acid without reacting with OPDA, thereby eliminating the interference caused by fluorescent impurities in the sample. 3 Reagents
3.1 Metaphosphoric acid-acetic acid solution: Weigh 15g metaphosphoric acid, add 40mL glacial acetic acid and 250mL water, heat, stir, and gradually dissolve it. After cooling, add water to 500mL. It can be stored in a refrigerator at 4℃ for 7d to 10d. 3.2 0.15mol/L sulfuric acid: Take 10mL sulfuric acid, carefully add it to water, and then dilute it to 1200mL with water. 3.3 Metaphosphoric acid-acetic acid-sulfuric acid solution: Use 0.15 mol/L sulfuric acid solution as diluent, and prepare the rest as in 3.1. 3.4 Sodium acetate solution (500 g/L): Weigh 500 g sodium acetate (CHCOONa·3H,O), and add water to 1000 mL. 3.5 Boric acid-sodium acetate solution: Weigh 3 g boric acid and dissolve it in 100 mL sodium acetate solution (3.4). Prepare before use. 3.6 o-phenylenediamine solution (200 mg/L): Weigh 20 mg o-phenylenediamine and dilute it to 100 mL with water before use. 3.7 Ascorbic acid standard solution (1 mg/mL) (prepare before use): Accurately weigh 50 mg ascorbic acid, dissolve it in a 50 mL volumetric flask with metaphosphoric acid-acetic acid solution (3.1), and dilute to the mark. 3.8 Ascorbic acid standard solution (100 μg/mL): Take 10 mL of ascorbic acid standard solution and dilute it to 100 mL with metaphosphoric acid-acetic acid solution. Test the pH value before dilution. If the pH value is > 2.2, dilute it with metaphosphoric acid-acetic acid-sulfuric acid solution (3.3). 3.9 0.04% thymol blue indicator solution: Weigh 0.1 g of thymol blue, add 0.02 mol/L sodium hydroxide solution, grind in a glass mortar until dissolved. The amount of sodium hydroxide used is about 10.75 mL. After grinding, dilute to 250 mL with water. Color change range:
pH value equal to 1.2
pH value equal to 2.8
pH value greater than 4
3.10 Activation of activated carbon: Add 200g of carbon powder to 1L of hydrochloric acid (1+9), heat and reflux for 1h~2h, filter, wash with water until there is no iron ion in the filtrate, place in an oven at 110℃~120℃ to dry, and set aside. 4 Instruments
4.1 Common laboratory equipment.
GB/T5009.86—2003
4.2 Fluorescence spectrophotometer or fluorometer with wavelengths of 350nm and 430nm. 4.3 Pulverizer.
5 Analysis steps
5.1 Preparation of samples
Weigh 100g of fresh sample, add 100mL of metaphosphoric acid-acetic acid solution (3.1), pour into a blender to make a homogenate, and use thymol blue indicator to adjust the pH of the homogenate. If it is red, dilute it with metaphosphoric acid-acetic acid solution. If it is yellow or blue, dilute it with metaphosphoric acid-acetic acid-sulfuric acid solution to make its pH 1.2. The amount of homogenate should be determined according to the content of ascorbic acid in the sample. When the sample solution content is between 40μg/mL and 100μg/mL, generally take 20g of homogenate, dilute it to 100mL with metaphosphoric acid-acetic acid solution, filter, and set aside the filtrate. 5.2 Determination
5.2.1 Oxidation treatment: Take 100 mL of the sample filtrate (5.1) and the standard working solution (3.8) respectively in a 200 mL Erlenmeyer flask with a lid, add 2 g of activated carbon, shake vigorously for 1 min, filter, discard the first few milliliters of filtrate, and collect all the remaining filtrates, namely the sample oxidation solution and the standard oxidation solution, for determination.
5.2.2 Take 10 mL of the standard oxidation solution in two 100 mL volumetric flasks, and mark them as "standard" and "standard blank" respectively. 5.2.3 Take 10 mL of the sample oxidation solution in two 100 mL volumetric flasks, and mark them as "sample" and "sample blank" respectively. 5.2.4 Add 5 mL of boric acid-sodium acetate solution to the "standard blank" and "sample blank" solutions, mix and shake for 15 min, dilute with water to 100 mL, place in a 4°C refrigerator for 2h~3h, and take out for use. 5.2.5 Add 5 mL of 500 g/L sodium acetate solution to each of the "sample" and "standard" solutions, dilute to 100 mL with water, and set aside. 5.3 Preparation of standard curve
Take 0.5, 1.0, 1.5 and 2.0 mL of the above "standard" solution (5.2.5) (ascorbic acid content 10 μg/mL), take two portions and place them in 10 mL capped test tubes, and then add water to 2.0 mL. Perform the fluorescence reaction according to 5.4. 5.4 Fluorescence reaction
Take the "standard blank" solution, "sample blank" solution and 5.2.4.5. Add 2 mL of each "test sample" solution into 10 mL test tubes with caps. Quickly add 5 mL of o-phenylenediamine solution to each tube in a dark room, shake and mix, react at room temperature for 35 minutes, and measure the fluorescence intensity at an excitation wavelength of 338 nm and an emission wavelength of 420 nm. The fluorescence intensity of the standard series minus the fluorescence intensity of the standard blank is used as the ordinate, and the corresponding ascorbic acid content is used as the abscissa. Draw a standard curve or perform related calculations, and its linear regression equation is used for calculation. 6. Calculation of results
See formula (1).
Where:
×F×1000
X is the total content of ascorbic acid and dehydroascorbic acid in the sample, in milligrams per 100 grams (mg/100g); c is obtained from the standard curve or by The concentration of the sample solution is calculated by the regression equation in micrograms per milliliter (pg/mL); m is the mass of the sample in grams (g);
V is the sample volume used for the fluorescence reaction in milliliters (mL); F is the dilution factor of the sample solution.
The calculation result is expressed to one decimal place. 7 Precision
The absolute difference between two independent measurement results obtained under repeatability conditions shall not exceed 10% of the arithmetic mean. 626
8 Principle
Method 2: 2,4-Dinitrophenylhydrazine colorimetric method
GB/T5009.86—2003
Total ascorbic acid includes reduced, dehydrogenated and diketogulonic acid. The reduced ascorbic acid in the sample is oxidized to dehydrogenated ascorbic acid by activated carbon. Ascorbic acid, then reacts with 2,4-dinitrophenylhydrazine to generate red color. The content in the sulfuric acid solution is proportional to the ascorbic acid content, and colorimetric quantification is performed.
9 Reagents
9.14.5mol/L sulfuric acid: Carefully add 250mL sulfuric acid (relative density 1.84) to 700mL water, cool and dilute to 1000mL with water
9.285% sulfuric acid: Carefully add 900mL sulfuric acid (relative density 1.84) to 100mL water. 9.32,4-dinitrophenylhydrazine solution (20g/L): Dissolve 2g2,4-dinitrophenylhydrazine in 100mL4.5mol/L sulfuric acid and filter. Store in the refrigerator when not in use and must be filtered before each use. 9.4 Oxalic acid solution ( 20g/L): Dissolve 20g oxalic acid (HC,O) in 700mL water and dilute to 1000mL. 9.5 Oxalic acid solution (10g/L): Take 500mL oxalic acid solution (9.4) and dilute to 1000mL. 9.6 Thiourea solution (10g/L): Dissolve 5g thiourea in 500mL oxalic acid solution (9.5). 9.7 Thiourea solution (20g/L): Dissolve 10g thiourea in 500mL oxalic acid solution (9.5). 9.8 1mol/L hydrochloric acid: Take 100mL hydrochloric acid, add it to water and dilute to 1200mL. 9.9 Ascorbic acid standard solution: Weigh 100mg pure ascorbic acid and dissolve it in 100mL oxalic acid solution (9.4). Each milliliter of this solution is equivalent to 1mg ascorbic acid.
9.10 Activated carbon: Add 100g of activated carbon to 750mL of 1mol/L hydrochloric acid, reflux for 1h2h, filter, wash with water several times until there is no iron ion (Fe+) in the filtrate, and then place it in a 110℃ oven for drying. Method for testing iron ions: Use Prussian blue reaction. Mix 20g/L potassium ferrous nitride and 1% hydrochloric acid in equal amounts, and drop the above filtrate into the solution. If there is iron ion, a blue precipitate will be produced. 10 Instruments
10.1 Constant temperature box: 37℃±0.5℃.
10.2 Visible-ultraviolet spectrophotometer.
10.3 Pulverizer.
11 Analysis steps
11.1 Preparation of samples
The entire experimental process should be protected from light.
11.1.1 Preparation of fresh sample: weigh 100g of fresh sample and absorb 100mL of 20g/L oxalic acid solution, pour into a masher to make a slurry, take 10g~40g of the slurry (containing 1mg~2mg ascorbic acid) and pour into a 100mL volumetric flask, dilute to the mark with 10g/L oxalic acid solution, and mix well. 11.1.2 Preparation of dry sample: weigh 1g~4g of dry sample (containing 1mg~2mg ascorbic acid) and put it into a mortar, add 10g/L oxalic acid solution to grind into a slurry, pour into a 100mL volumetric flask, dilute to the mark with 10g/L oxalic acid solution, and mix well. 11.1.3 Filter the solutions in 11.1.1 and 11.1.2, and set aside the filtrate. Samples that are difficult to filter can be centrifuged in a centrifuge, pour out the supernatant, filter, and set aside.
11.2 Oxidation treatment
Take 25mL of the above filtrate, add 2g of activated carbon, shake for 1min, filter, and discard the first few milliliters of filtrate. Take 10mL of this oxidation extract, add 10mL of 20g/L sulfur gland solution, mix, and this sample is the diluent. 627
GB/T5009.86—2003
11.3 Color reaction
11.3.1 Add 4mL of diluent (11.2) to each of the three test tubes. One test tube is used as a blank, and 1.0mL of 20g/L 2,4-dinitrophenylhydrazine solution is added to the remaining test tubes. Put all the test tubes in a 37℃±0.5℃ constant temperature box or water bath and keep warm for 3h. 11.3.2 Take out after 3h, and put all the test tubes except the blank tube in ice water. After the blank tube is taken out, cool it to room temperature, then add 1.0mL 20g/L 2.4-dinitrophenylhydrazine solution, place it at room temperature for 10min~15min, and then place it in ice water. The rest of the steps are the same as the sample. 11.4 85% sulfuric acid treatment
After the test tube is placed in ice water, add 5mL 85% sulfuric acid to each test tube. The dropwise addition time should be at least 1min, and the test tube should be shaken while adding. Take the test tube out of the ice water, place it at room temperature for 30min, and then compare the color. 11.5 Colorimetry
Use a 1cm colorimetric cup, adjust the zero point with the blank solution, and measure the absorbance at a wavelength of 500nm. 11.6 Drawing of the standard curve
11.6.1 Add 2g of activated carbon to 50mL of the standard solution, vibrate for 1min, and filter. 11.6.2 Take 10 mL of the filtrate and place it in a 500 mL volumetric flask, add 5.0 g of sulfur gland, and dilute to the mark with 10 g/L oxalic acid solution. The ascorbic acid concentration is 20 μg/mL.
11.6.3 Take 5, 10, 20, 25, 40, 50, and 60 mL of the dilutions and place them in 7 100 mL volumetric flasks, respectively, and dilute to the mark with 10 g/L sulfur gland solution. The ascorbic acid concentrations in the final dilutions are 1, 2, 4, 5, 8, 10, and 12 g/mL, respectively. 11.6.4 Form a knee and perform colorimetry according to the sample determination steps. 11.6.5 Draw a standard curve with the absorbance value as the ordinate and the ascorbic acid concentration (μg/mL) as the abscissa. 12 Calculation of results
See formula (2).
Wherein?
X—total ascorbic acid content in the sample, in milligrams per 100 grams (mg/100g); (2)
—the concentration of total ascorbic acid in the "sample oxidation solution" obtained from the standard curve or calculated by the regression equation, in micrograms per milliliter (μg/mL);
the volume of the sample fixed with 10g/L oxalic acid solution, in milliliters (mL). F—the dilution factor during the sample oxidation process; m—the mass of the sample, in grams (g). The calculated result is expressed to two decimal places. 13 Precision
The absolute difference between two independent determination results obtained under repeatability conditions shall not exceed 10% of the arithmetic mean. 6286Thiourea solution (10g/L): Dissolve 5g of thiourea in 500mL of oxalic acid solution (9.5). 9.7Thiourea solution (20g/L): Dissolve 10g of thiourea in 500mL of oxalic acid solution (9.5). 9.81mol/L hydrochloric acid: Take 100mL of hydrochloric acid, add it to water, and dilute to 1200mL. 9.9Ascorbic acid standard solution: Weigh 100mg of pure ascorbic acid and dissolve it in 100mL of oxalic acid solution (9.4). Each milliliter of this solution is equivalent to 1mg of ascorbic acid.
9.10Activated carbon: Add 100g of activated carbon to 750mL of 1mol/L hydrochloric acid, reflux for 1h2h, filter, wash with water several times until there is no iron ion (Fe+) in the filtrate, and then place it in a 110℃ oven to dry. Method for testing iron ions: Use Prussian blue reaction. Mix 20g/L potassium ferrous nitride and 1% hydrochloric acid in equal amounts, and drip the filtrate above. If there are iron ions, a blue precipitate will be produced. 10 Instruments
10.1 Constant temperature box: 37℃±0.5℃.
10.2 Visible-ultraviolet spectrophotometer.
10.3 Masher.
11 Analysis steps
11.1 Preparation of samples
The whole experimental process should be protected from light.
11.1.1 Preparation of fresh samples: Weigh 100g of fresh sample and absorb 100mL of 20g/L oxalic acid solution, pour into the masher to make a slurry, take 10g~40g of the slurry (containing 1mg~2mg ascorbic acid) and pour into a 100mL volumetric flask, dilute to the scale with 10g/L oxalic acid solution, and mix well. 11.1.2 Sample preparation: weigh 1g~4g of dry sample (containing 1mg~2mg ascorbic acid) and put it into a mortar, add 10g/L oxalic acid solution and grind it into a homogenate, pour it into a 100mL volumetric flask, dilute it to the mark with 10g/L oxalic acid solution, and mix it. 11.1.3 Filter the solutions in 11.1.1 and 11.1.2, and set aside the filtrate. Samples that are difficult to filter can be centrifuged, and the supernatant can be poured out, filtered, and set aside.
11.2 Oxidation treatment
Take 25mL of the above filtrate, add 2g of activated carbon, shake for 1min, filter, and discard the first few milliliters of filtrate. Take 10mL of this oxidation extract, add 10mL of 20g/L sulfur gland solution, mix, and this sample is the dilution. 627
GB/T5009.86—2003
11.3 Color reaction
11.3.1 Add 4 mL of diluent (11.2) to each of the three test tubes. One test tube is used as a blank. Add 1.0 mL of 20 g/L 2,4-dinitrophenylhydrazine solution to the remaining test tubes. Place all test tubes in a 37°C ± 0.5°C constant temperature box or water bath and keep warm for 3 hours. 11.3.23 hours later, take out the test tubes and place all test tubes except the blank tube in ice water. After taking out the blank tube, cool it to room temperature, then add 1.0 mL of 20 g/L 2,4-dinitrophenylhydrazine solution, place it at room temperature for 10 minutes to 15 minutes, and then place it in ice water. The rest of the steps are the same as the test sample. 11.485% sulfuric acid treatment
After the test tubes are placed in ice water, add 5mL of 85% sulfuric acid to each test tube. The dripping time should be at least 1min, and the test tubes should be shaken while adding. Take the test tubes out of the ice water and place them at room temperature for 30min before colorimetry. 11.5 Colorimetry
Use a 1cm colorimetric cup, adjust the zero point with blank solution, and measure the absorbance at a wavelength of 500nm. 11.6 Drawing of standard curve
11.6.1 Add 2g of activated carbon to 50mL of standard solution, shake for 1min, and filter. 11.6.2 Take 10mL of filtrate and place it in a 500mL volumetric flask, add 5.0g of sulfur gland, and dilute to the scale with 10g/L oxalic acid solution. The ascorbic acid concentration is 20μg/mL.
11.6.3 Take 5, 10, 20, 25, 40, 50, 60 mL of the dilution solution and place them in 7 100 mL volumetric flasks respectively. Dilute to the mark with 10 g/L sulfur gland solution so that the concentration of ascorbic acid in the final dilution is 1, 2, 4, 5, 8, 10, 12 g/mL respectively. 11.6.4 Form a knee and compare colors according to the sample determination steps. 11.6.5 Draw a standard curve with the absorbance value as the ordinate and the ascorbic acid concentration (μg/mL) as the abscissa. 12 Calculation of results
See formula (2).
Wherein?
X—total ascorbic acid content in the sample, in milligrams per 100 grams (mg/100g); (2)
—the concentration of total ascorbic acid in the "sample oxidation solution" obtained from the standard curve or calculated by the regression equation, in micrograms per milliliter (μg/mL);
the volume of the sample fixed with 10g/L oxalic acid solution, in milliliters (mL). F—the dilution factor during the sample oxidation process; m—the mass of the sample, in grams (g). The calculated result is expressed to two decimal places. 13 Precision
The absolute difference between two independent determination results obtained under repeatability conditions shall not exceed 10% of the arithmetic mean. 6286Thiourea solution (10g/L): Dissolve 5g of thiourea in 500mL of oxalic acid solution (9.5). 9.7Thiourea solution (20g/L): Dissolve 10g of thiourea in 500mL of oxalic acid solution (9.5). 9.81mol/L hydrochloric acid: Take 100mL of hydrochloric acid, add it to water, and dilute to 1200mL. 9.9Ascorbic acid standard solution: Weigh 100mg of pure ascorbic acid and dissolve it in 100mL of oxalic acid solution (9.4). Each milliliter of this solution is equivalent to 1mg of ascorbic acid.
9.10Activated carbon: Add 100g of activated carbon to 750mL of 1mol/L hydrochloric acid, reflux for 1h2h, filter, wash with water several times until there is no iron ion (Fe+) in the filtrate, and then place it in a 110℃ oven to dry. Method for testing iron ions: Use Prussian blue reaction. Mix 20g/L potassium ferrous nitride and 1% hydrochloric acid in equal amounts, and drip the filtrate above. If there are iron ions, a blue precipitate will be produced. 10 Instruments
10.1 Constant temperature box: 37℃±0.5℃.
10.2 Visible-ultraviolet spectrophotometer.
10.3 Masher.
11 Analysis steps
11.1 Preparation of samples
The whole experimental process should be protected from light.
11.1.1 Preparation of fresh samples: Weigh 100g of fresh sample and absorb 100mL of 20g/L oxalic acid solution, pour into the masher to make a slurry, take 10g~40g of the slurry (containing 1mg~2mg ascorbic acid) and pour into a 100mL volumetric flask, dilute to the scale with 10g/L oxalic acid solution, and mix well. 11.1.2 Sample preparation: weigh 1g~4g of dry sample (containing 1mg~2mg ascorbic acid) and put it into a mortar, add 10g/L oxalic acid solution and grind it into a homogenate, pour it into a 100mL volumetric flask, dilute it to the mark with 10g/L oxalic acid solution, and mix it. 11.1.3 Filter the solutions in 11.1.1 and 11.1.2, and set aside the filtrate. Samples that are difficult to filter can be centrifuged, and the supernatant can be poured out, filtered, and set aside.
11.2 Oxidation treatment
Take 25mL of the above filtrate, add 2g of activated carbon, shake for 1min, filter, and discard the first few milliliters of filtrate. Take 10mL of this oxidation extract, add 10mL of 20g/L sulfur gland solution, mix, and this sample is the dilution. 627
GB/T5009.86—2003
11.3 Color reaction
11.3.1 Add 4 mL of diluent (11.2) to each of the three test tubes. One test tube is used as a blank. Add 1.0 mL of 20 g/L 2,4-dinitrophenylhydrazine solution to the remaining test tubes. Place all test tubes in a 37°C ± 0.5°C constant temperature box or water bath and keep warm for 3 hours. 11.3.23 hours later, take out the test tubes and place all test tubes except the blank tube in ice water. After taking out the blank tube, cool it to room temperature, then add 1.0 mL of 20 g/L 2,4-dinitrophenylhydrazine solution, place it at room temperature for 10 minutes to 15 minutes, and then place it in ice water. The rest of the steps are the same as the test sample. 11.485% sulfuric acid treatment
After the test tubes are placed in ice water, add 5mL of 85% sulfuric acid to each test tube. The dripping time should be at least 1min, and the test tubes should be shaken while adding. Take the test tubes out of the ice water and place them at room temperature for 30min before colorimetry. 11.5 Colorimetry
Use a 1cm colorimetric cup, adjust the zero point with blank solution, and measure the absorbance at a wavelength of 500nm. 11.6 Drawing of standard curve
11.6.1 Add 2g of activated carbon to 50mL of standard solution, shake for 1min, and filter. 11.6.2 Take 10mL of filtrate and place it in a 500mL volumetric flask, add 5.0g of sulfur gland, and dilute to the scale with 10g/L oxalic acid solution. The ascorbic acid concentration is 20μg/mL.
11.6.3 Take 5, 10, 20, 25, 40, 50, 60 mL of the dilution solution and place them in 7 100 mL volumetric flasks respectively. Dilute to the mark with 10 g/L sulfur gland solution so that the concentration of ascorbic acid in the final dilution is 1, 2, 4, 5, 8, 10, 12 g/mL respectively. 11.6.4 Form a knee and compare colors according to the sample determination steps. 11.6.5 Draw a standard curve with the absorbance value as the ordinate and the ascorbic acid concentration (μg/mL) as the abscissa. 12 Calculation of results
See formula (2).
Wherein?
X—total ascorbic acid content in the sample, in milligrams per 100 grams (mg/100g); (2)
—the concentration of total ascorbic acid in the "sample oxidation solution" obtained from the standard curve or calculated by the regression equation, in micrograms per milliliter (μg/mL);
the volume of the sample fixed with 10g/L oxalic acid solution, in milliliters (mL). F—the dilution factor during the sample oxidation process; m—the mass of the sample, in grams (g). The calculated result is expressed to two decimal places. 13 Precision
The absolute difference between two independent determination results obtained under repeatability conditions shall not exceed 10% of the arithmetic mean. 6283 Take 5, 10, 20, 25, 40, 50, 60 mL of the dilution solution and place them in 7 100 mL volumetric flasks respectively. Dilute to the mark with 10 g/L sulfur gland solution so that the concentration of ascorbic acid in the final dilution solution is 1, 2, 4, 5, 8, 10, 12 g/mL respectively. 11.6.4 Form a knee and compare colors according to the sample determination steps. 11.6.5 Draw a standard curve with the absorbance value as the ordinate and the ascorbic acid concentration (μg/mL) as the abscissa. 12 Calculation of results
See formula (2).
Wherein?
X—total ascorbic acid content in the sample, in milligrams per 100 grams (mg/100g); (2)
—the concentration of total ascorbic acid in the "sample oxidation solution" obtained from the standard curve or calculated by the regression equation, in micrograms per milliliter (μg/mL);
the volume of the sample fixed with 10g/L oxalic acid solution, in milliliters (mL). F—the dilution factor during the sample oxidation process; m—the mass of the sample, in grams (g). The calculated result is expressed to two decimal places. 13 Precision
The absolute difference between two independent determination results obtained under repeatability conditions shall not exceed 10% of the arithmetic mean. 6283 Take 5, 10, 20, 25, 40, 50, 60 mL of the dilution solution and place them in 7 100 mL volumetric flasks respectively. Dilute to the mark with 10 g/L sulfur gland solution so that the concentration of ascorbic acid in the final dilution solution is 1, 2, 4, 5, 8, 10, 12 g/mL respectively. 11.6.4 Form a knee and compare colors according to the sample determination steps. 11.6.5 Draw a standard curve with the absorbance value as the ordinate and the ascorbic acid concentration (μg/mL) as the abscissa. 12 Calculation of results
See formula (2).
Wherein?
X—total ascorbic acid content in the sample, in milligrams per 100 grams (mg/100g); (2)
—the concentration of total ascorbic acid in the "sample oxidation solution" obtained from the standard curve or calculated by the regression equation, in micrograms per milliliter (μg/mL);
the volume of the sample fixed with 10g/L oxalic acid solution, in milliliters (mL). F—the dilution factor during the sample oxidation process; m—the mass of the sample, in grams (g). The calculated result is expressed to two decimal places. 13 Precision
The absolute difference between two independent determination results obtained under repeatability conditions shall not exceed 10% of the arithmetic mean. 628
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