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GB 5009.75-2014: National food safety standard - Determination of Lead in Food Additives Delivery: 9 seconds. True-PDF full-copy in English & invoice will be downloaded + auto-delivered via email. See step-by-step procedure Status: Valid GB 5009.75: Historical versions
Similar standardsGB 5009.75-2014: National food safety standard - Determination of Lead in Food Additives---This is an excerpt. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.), auto-downloaded/delivered in 9 seconds, can be purchased online: https://www.ChineseStandard.net/PDF.aspx/GB5009.75-2014GB NATIONAL STANDARD OF THE PEOPLE’S REPUBLIC OF CHINA National Food Safety Standard -- Determination of Lead in Food Additives ISSUED ON: SEPTEMBER 21, 2015 IMPLEMENTED ON: MARCH 21, 2016 Issued by: National Health and Family Planning Commission of the People's Republic of China. Table of ContentsForeword ... 3 1 Scope ... 4 2 Principle ... 4 3 Reagents and materials ... 4 4 Instruments and equipment ... 6 5 Sample processing ... 7 6 Determination ... 8 7 Presentation of analysis results ... 8 8 Precision ... 9 9 Others ... 9 10 Principle ... 9 11 Reagents and materials ... 10 12 Instruments and equipment ... 11 13 Analysis steps ... 11 14 Presentation of analysis results ... 13 15 Precision ... 13 16 Others ... 13 Annex A Reference conditions for microwave digestion ... 14 National Food Safety Standard -- Determination of Lead in Food Additives1 ScopeThis Standard specifies the limit test and quantitative test methods for lead in food additives. This Standard applies to the limit test and quantitative test of lead in food additives. Method One -- Diphenylthiocarbazone (dithizone) colorimetric method2 PrincipleThe specimen is treated by adding diammonium hydrogen citrate, potassium cyanide and hydroxylamine hydrochloride to eliminate the interference of iron, copper, zinc and other ions. At pH 8.5 ~ 9.0, lead ions and diphenylthiocarbazone (dithizone) form a red complex. Extract with chloroform and compare with the standard series to do limit test or quantitative test.3 Reagents and materialsNOTE: Unless otherwise specified, all reagents used in this method are analytically pure and water is grade one water as specified in GB/T 6682. 3.1 Reagents 3.1.1 Nitric acid (HNO3). 3.1.2 Sulfuric acid (H2SO4). 3.1.3 Ammonia (NH3·H2O). 3.1.4 Hydrochloric acid (HCl). 3.1.5 Phenol red (C19H14O5S). 3.1.6 Chloroform (CHCl3). 3.1.7 Diammonium hydrogen citrate (C6H14N2O7). 3.1.8 Hydroxylamine hydrochloride (NH2OH·HCl). 3.1.9 Potassium cyanide (KCN). 3.1.10 Diphenylthiocarbazone (dithizone) (C13H12N4S). 3.1.11 Ethanol (C2H6O). 3.1.12 Perchloric acid (HClO4). 3.2 Reagent preparation 3.2.1 Nitric acid solution (1+1): Take 50 mL of nitric acid and slowly add it into 50 mL of water. 3.2.2 Ammonia solution (1+1): Mix 1 part of ammonia water with 1 part of water. If it contains lead, re-distillate it using an all-glass distiller. 3.2.3 Phenol red indicator solution (1 g/L ethanol solution): Weigh 100 mg of phenol red. Dissolve it in 100 mL of ethanol (filter if necessary). 3.2.4 Diammonium hydrogen citrate solution (500 g/L): Weigh 100 g of diammonium hydrogen citrate and dissolve it in 100 mL of water. Add two drops of phenol red indicator solution. Add ammonia solution (1+1) to adjust the pH to 8.5~9.0 (from yellow to red, add two more drops). Extract with dithizone solution several times. 10 mL~20 mL each time, until the chloroform layer turns green and does not change. Discard the chloroform layer. Wash twice with chloroform, 5 mL each time. Discard the chloroform layer. Add water to dilute to 200 mL. 3.2.5 Ammonia solution (1+99): Mix 1 part chlorine water with 99 parts water. 3.2.6 Hydroxylamine hydrochloride solution (200 g/L): Weigh 20 g of hydroxylamine hydrochloride. Dissolve in 40 mL of water. Add two drops of phenol red indicator solution. Add ammonia solution (1+1) to adjust the pH to 8.5~9.0 (add two more drops when the color changes from yellow to red). Extract with dithizone chloroform solution several times, 10 mL~20 mL each time until the chloroform layer remains green. Wash twice with chloroform, 5 mL each time. Discard the chloroform layer. Add hydrochloric acid (1+1) to the water layer to make it acidic. Add water to 100 mL. 3.2.7 Potassium cyanide solution (100 g/L): Weigh 10 g of potassium cyanide. Dissolve it in water and make up to 100 mL. WARNING: Potassium cyanide (KCN) is a hazardous chemical and appropriate protective measures shall be taken. 3.2.8 Dithizone stock solution (0.05% chloroform solution): Weigh 0.5 g of finely ground dithizone and dissolve it in 50 mL of chloroform. If there is any residue, filter it with filter paper into a 250 mL separatory funnel. Extract it with ammonia solution (1+99) three times, 100 mL each time. Filter the extract with absorbent cotton into a 500 mL separatory funnel. Adjust it to acidity with hydrochloric acid solution (1+1). 4.2 125 mL separatory funnel. 4.3 250 mL Kjeldahl flask or 250 mL conical flask. 4.4 Electronic balance: with a sensitivity of 0.1 mg and 1 mg.5 Sample processing5.1 Preparation of inorganic specimens The "specimen processing" of inorganic samples is measured according to the corresponding standard methods. 5.2 Preparation of organic specimens In addition to the corresponding standard methods for organic specimens, the "specimen processing" is generally carried out according to the following methods: a) Wet digestion: Weigh 5.000 g of the specimen and place it in a 250 mL conical flask. Add 10 mL of nitric acid. After leaving it for a while (or overnight), heat it. After the reaction has subsided, remove it and cool it. Add 5 mL of sulfuric acid along the wall of the flask. Continue heating until the solution in the flask begins to turn brown. Keep adding nitric acid (if necessary, add some perchloric acid) until the organic matter is completely decomposed. Continue heating until a large amount of white sulfur dioxide smoke is generated. The solution shall be colorless or slightly yellow in the end. After cooling, add 20 mL of water and boil it. Remove the remaining nitric acid until white smoke is generated. Do this twice. Let it cool. Transfer the solution to a 50 mL volumetric flask. Wash the conical flask 2~3 times with a small amount of water. Transfer the washing solution to the volumetric flask. Add water to the mark. Mix well and set aside. Take the same amount of nitric acid and sulfuric acid. At the same time, do a reagent blank test. b) Dry ashing method: This method is used for specimens that are not suitable for wet digestion. Weigh 5.000 g of specimen into a porcelain crucible. Add an appropriate amount of sulfuric acid to wet the specimen. After careful carbonization, add 2 mL of nitric acid and 5 drops of sulfuric acid. Carefully heat until the white smoke evaporates. Transfer to a high-temperature furnace. Ash completely at 500°C. Take out after cooling. Add 1 mL of nitric acid solution (1+1). Heat to dissolve the ash. Transfer the specimen solution to a 50 mL volumetric flask (filter if necessary). Wash the crucible with a small amount of water. Transfer the washing solution to the volumetric flask. Add water to the mark. Mix well and set aside. Take a crucible and do a reagent blank test at the same time.6 Determination6.1 Limit test Take appropriate amount of specimen solution and standard lead solution (lead content not less than 5 μg) and place them in 125 mL separatory funnels respectively. Add nitric acid solution (1%) to 20 mL. Add 1 mL of diammonium hydrogen citrate solution (500 g/L), 1 mL of hydroxylamine hydrochloride solution (200 g/L) and two drops of phenol red indicator solution to the specimen solution and the standard working solution of lead (1 mg/mL). Adjust to red with ammonia solution (1+1). Add 2 mL of potassium cyanide solution (100 g/L) to each. After mixing, add 5.0 mL of dithizone working solution. Shake vigorously for 1 min. After standing and stratification, filter the chloroform layer through absorbent cotton into a 1 cm colorimetric cup. At a wavelength of 510 nm, adjust the zero point with chloroform and measure the absorbance or perform visual colorimetry. The absorbance or chromaticity of the sample solution shall not be greater than that of the standard lead solution. If the specimen is processed, the lead limit standard shall also be treated in the same way. 6.2 Quantitative determination Pipette 10.0mL (or appropriate amount) of specimen solution and the same amount of reagent blank solution into 125 mL separatory funnels, respectively. Add 1% nitric acid solution to each until 20 mL. Pipette 0.0 mL, 0.1 mL, 0.3 mL, 0.5 mL, 0.7 mL, 1.0 mL (equivalent to 0 μg, 1 μg, 3 μg, 5 μg, 7 μg, 10 μg of lead, respectively) of the lead standard working solution and place them in 125 mL separatory funnels. Add nitric acid solution (1%) to 20 mL each. Add 1 mL of diammonium hydrogen citrate solution (500 g/L), 1 mL of hydroxylamine hydrochloride solution (200 g/L) and two drops of phenol red indicator solution to the sample solution, reagent blank solution and lead standard solution. Adjust to red with ammonia solution (1+1). Add 2 mL of potassium cyanide solution (100 g/L) to each. Mix well. Add 5.0 mL of dithizone working solution to each. Shake vigorously for 1 min. After standing for stratification, filter chloroform through absorbent cotton into a 1 cm colorimetric cup. Adjust the zero point with a zero tube at a wavelength of 510 nm and measure the absorbance. Draw a standard curve.7 Presentation of analysis resultsThe lead content in the specimen is calculated according to formula (2):12 Instruments and equipmentNOTE: All glassware used must be soaked in nitric acid solution (1+4) for more than 24 h, rinsed repeatedly with water, and finally rinsed with deionized water. 12.1 Atomic absorption spectrophotometer (with graphite furnace and lead hollow cathode lamp). 12.2 Muffle furnace. 12.3 Drying thermostat. 12.4 Porcelain crucible. 12.5 Pressure digester, pressure digestion tank or pressure bomb. 12.6 Adjustable electric heating plate, adjustable electric furnace. 12.7 Electronic balance: with a sensitivity of 0.1 mg and 1 mg. 12.8 Microwave digester, microwave digestion tank.13 Analysis steps13.1 Specimen preparation 13.1.1 Digestion method using pressure digestion tank: Weigh 1.000 g~2.000 g of specimen (weigh the specimen according to the instructions for use of the pressure digestion tank) into a polytetrafluoroethylene inner tank. Add 2 mL~4 mL of nitric acid and soak overnight. Add 2 mL~3 mL of 30% hydrogen peroxide (the total amount cannot exceed 1/3 of the tank volume). Cover the inner cover. Tighten the stainless- steel jacket. Put it into a constant temperature drying oven. Keep it at 120℃~140℃ for 3 h~4 h. Cool it naturally to room temperature in the oven. Wash or filter the digestion solution into a 10 mL or 25 mL volumetric flask (depending on the salt content of the sample after digestion). Wash the tank with water in small amounts several times. Combine the washing solution in a volumetric flask and dilute to the mark. Mix well for later use. Perform a reagent blank test at the same time. 13.1.2 Microwave digestion: Weigh 0.500 g~2.000 g of specimen into a digestion tank. Add 10.0 mL of nitric acid and 2.0 mL of hydrogen peroxide (30%). Mix well. Digest in a microwave digestion instrument. Recommended digestion conditions are shown in Annex A. After digestion is completed, cool naturally to room temperature. Open the lid to remove acid. Wash or filter the digestion solution into a 10 mL~25 mL volumetric flask (depending on the salt content of the sample after digestion). Wash the tank with water in small amounts several times. Combine the washing solution in a volumetric flask and dilute to the mark. Mix well and set aside. Perform a reagent blank test at the same time. 13.1.3 Dry ashing: Weigh 1.000 g~5.000 g of the specimen (depending on the lead content) into a porcelain crucible. First, carbonize on an adjustable electric hot plate with low heat until smokeless. Transfer to a muffle furnace and ash for 6 h~8 h at 500℃. Cool. If the individual samples are not completely ashed, add 1 mL of mixed acid and heat on an adjustable electric furnace with low heat. Repeat several times until digestion is complete. Remove and cool. Dissolve the ash with nitric acid solution (0.5 mol/L). Wash or filter the specimen digestion solution into a 10 mL or 25 mL volumetric flask (depending on the salt content of the sample after digestion). Wash the porcelain crucible with water in small amounts several times. Combine the washing solution in a volumetric flask and dilute to the mark. Mix well for later use. Perform a reagent blank test at the same time. 13.1.4 Wet digestion: Weigh 1.000 g~5.000 g of the specimen into a conical flask or a tall beaker. Put a few glass beads. Add 10 mL of mixed acid (or add 1 mL~2 mL of nitric acid). Cover and soak overnight. Add a small funnel and digest on an electric stove. If it turns brown-black, add more mixed acid until white smoke comes out. The digestion liquid is colorless and transparent or slightly yellow. Remove and cool. Wash or filter the digestion liquid into (depending on the salt content of the specimen after digestion) a 10 mL or 25 mL volumetric flask. Wash with water in small amounts several times. Combine the washing liquid in the volumetric flask. Make up to the mark. Mix well and set aside. Perform a reagent blank test at the same time. 13.2 Determination 13.2.1 Instrument conditions: Adjust to the best state according to the performance of each instrument. Reference conditions: Wavelength is 283.3 nm; Slit is 0.7nm; Lamp current is 8 mA; Drying temperature is 120℃, 20 s; Ashing temperature is 800℃, lasting 15 s~20 s; Atomization temperature is 1600℃~1800℃, lasting 4s~5s; Background correction is deuterium lamp or Zeeman effect. 13.2.2 Draw the standard curve: Take 10 μL of each of the lead standard solutions prepared in 11.4.2 (10.0 ng/mL, 20.0 ng/mL, 40.0 ng/mL, 60.0 ng/mL, 80.0 ng/mL (or μg/L)). Inject into the graphite furnace. Measure the absorbance and obtain the linear regression equation of the relationship between the absorbance and concentration. 13.2.3 Specimen determination: Take 10 μL of specimen solution and reagent blank solution, respectively. Inject into graphite furnace. Measure its absorbance. Substitute into the linear regression equation of the standard series to obtain the lead content in the specimen solution. 13.2.4 Use of matrix modifier: In order to reduce background interference, an appropriate amount of matrix modifier ammonium dihydrogen phosphate solution (20 g/L) shall be injected. Generally, it is 5 μL or the same amount as the specimen. When ......Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al. Tips & Frequently Asked Questions:Question 1: How long will the true-PDF of English version of GB 5009.75-2014 be delivered?Answer: The full copy PDF of English version of GB 5009.75-2014 can be downloaded in 9 seconds, and it will also be emailed to you in 9 seconds (double mechanisms to ensure the delivery reliably), with PDF-invoice.Question 2: Can I share the purchased PDF of GB 5009.75-2014_English with my colleagues?Answer: Yes. 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