GB 24567-2009Sodium monofluorophosphate for tooth-paste industry (English PDF)

5.6 Determination of free fluorine content

5.6.1 Method summary Sample in acid medium to fluoride ion selective electrode as indicator electrode, a saturated calomel electrode as the reference electrode, measurement test solution Liquid fluoride concentration.

5.6.2 Reagents and materials

5.6.2.1 sodium nitrate solution. 30g/L;

5.6.2.2 nitric acid solution. 1 + 150;

5.6.2.3 hexamethylenetetramine solution. 50g/L;

5.6.2.4 fluoro standard solution. 1mL solution containing fluorine (F) 1mg; Refining. two water in a plastic beaker with GB/T 6682-2008 predetermined dissolving sodium fluoride, make a saturated solution. Removed by filtration Insoluble materials, the filtrate was added ethanol to precipitate sodium fluoride. The resulting crystals were filtered and washed with absolute ethanol and crystallized placed 105 °C ~ Electric oven 110 °C, the drying to constant mass. Weigh 0.2210g NaF (refined) (accurate to 0.0002g), dissolved in water, all transferred to 100mL volumetric flask, dilute with water Release to the mark. Store in plastic bottle.

5.6.2.5 fluoro standard solution. 1mL solution containing fluorine (F) 0.1mg; Pipette Pipette 10mL fluoro standard solution (5.6.2.4), placed in 100mL flask, diluted with water to the mark. Storage Plastic bottle.

5.6.2.6 fluoro standard solution. 1mL solution containing fluorine (F) 0.01mg. Pipette Pipette 10mL fluoro standard solution (5.6.2.5) into 100mL volumetric flask, dilute to the mark, shake. Storage In a plastic bottle (the solution is valid for 10d).

5.6.3 Instruments and equipment

5.6.3.1 digital ion meter or pH meter. Accuracy ± 0.5%;

5.6.3.2 fluoride ion selective electrode;

5.6.3.3 calomel electrode;

5.6.3.4 magnetic stirrer.

5.6.4 Analysis of step

5.6.4.1 Preparation of test solution Weigh about 0.2g sample, accurate to 0.0002g, set 50mL volumetric flask, add 5mL dissolved in water, were added with a pipette 5mL diluted sodium nitrate solution and 5mL hexamethylenetetramine solution, plus 5mL nitric acid solution, add water to the mark.

5.6.4.2 Preparation of the calibration standard solution with fluorine Each pipette Pipette 25mL fluoro standard solution (5.6.2.5) and fluorine standard solution (5.6.2.6), were placed in two 50mL capacity Bottle with pipette add 5mL nitrate solution and 5mL hexamethylenetetramine solution, 5mL nitric acid solution was added to adjust the pH of the solution To 5-6, dilute to the mark. They were transferred to two drying plastic bottles.

5.6.4.3 Determination Open digital ion meter, connect the electrode, press the mode key "MODE" until "CONC" mode indication, adjust the instrument temperature Room temperature. According to double standards into law, carried out by the above calibration slope calibration and positioning fluoro standard solution. The test solution was poured into a plastic beaker, under stirring after equilibrium 4min, was measured.

5.6.5 Calculation Results Free fluorine content of fluorine (F) the mass fraction of 3 and its value is expressed in%, according to equation (3) Calculated. 3 = rho × Vp × 10 -3 (3) Where. rho

--- Numerical test solution was measured fluoride ion concentration, in milligrams per milliliter (mg/mL); Numerical volume Vp

--- test solution, in milliliters (mL); Take the arithmetic mean of the parallel determination results of the measurement results, the results of two parallel determination of the absolute difference is not more than 0.01%.

5.7 Determination of total fluorine content

5.7.1 Method summary The test solution was pre-hexamethyldisilazane by perchloric acid saturated ether acidification, the formation of a hydrophobic fluorine-trimethyl silane, diffusion is a basic solution Absorption, hydrolysis of F ions in the absorbing solution to the fluoride ion selective electrode as measuring electrode, a saturated calomel electrode as the reference electrode, measured Test fluoride ion concentration in the solution.

5.7.2 Reagents

5.7.2.1 sodium hydroxide solution. 4g/L;

5.7.2.2 nitric acid solution. 1 + 150;

5.7.2.3 perchlorate hexamethyldisilazane ether saturated solution; The 100mL perchloric acid solution (1 + 3.3) poured into a 175mL separating funnel, add 50mL hexamethyl ether by vigorous shaking After placing stratification, the lower is the perchlorate hexamethyldisilazane saturated ether solution.

5.7.2.4 hexamethylenetetramine solution. 15g/L.

5.7.3 Instruments and equipment

5.7.3.1 digital ion meter or pH meter. Accuracy ± 0.5%;

5.7.3.2 fluoride ion selective electrode;

5.7.3.3 calomel electrode;

5.7.3.4 magnetic stirrer;

5.7.3.5 diffusion chamber. made of teflon or polypropylene round (see Figure 1).

a) Diffusion cover. 110mm × 20mm;

b) diffusion chamber. 110mm × 60mm;

c) absorption cell. L × S × H = 75mm × 50mm × 35mm. 1

--- diffusion cover; 2

--- diffusion chamber; 3

--- absorption cell. Figure 1 diffusion chamber

5.7.4 Analysis of step

5.7.4.1 Preparation of test solution Weigh about 0.2g sample, accurate to 0.0002g, placed in 100mL beaker, dissolved in water, all transferred to 250mL volumetric flask Diluted with water to the mark. Pipette pipette 5mL test solution was placed in the left side of the diffusion chamber (inclined 30o diffuser plate should be placed into three compartments). Pipette Pipette tube 5mL sodium hydroxide solution was placed in the middle chamber diffusion chamber. Take about 13mL of perchloric acid hexamethyl ether saturated solution was placed diffusion Box on the right. The interface diffusion chamber vacuum grease or Vaseline smeared with reclosable lid sealed. The diffusion box placed on the swing meter shaking 2h (again Place 24h).

5.7.4.2 Determination Open digital ion meter, connect the electrode, press the mode key "MODE" until "CONC" mode indication, adjust the instrument temperature Room temperature. According to double standards into law, carry out calibration and positioning slope calibration with fluoride standard solution (5.6.4.2). The diffusion box is opened, the middle chamber with a pipette add 5mL hexamethylenetetramine buffer and 5mL nitric acid solution to adjust the pH of the solution To 5-6, after stirring state balance 4min, were measured.

5.7.5 Calculation Results The total fluorine content of fluorine (F) the mass fraction of 4 and its value is expressed in%, according to equation (4) Calculated. 4 = rho × Vp × 10 -3 × 100 (4) Where. rho

--- Numerical test solution was measured fluoride ion concentration, in milligrams per milliliter (mg/mL); Vp

--- diffusion chamber value of the total volume of liquid in the intermediate chamber, in milliliters (mL); Vp 1

--- numerical diffusion box test solution volume in milliliters (mL); 2

--- value Vp of the total volume of the test solution, in milliliters (mL of); Take the arithmetic mean of the parallel determination results of the measurement results, the results of two parallel determination of the absolute difference is not more than 0.2%.

5.8 Determination of Arsenic

5.8.1 Method summary With GB/T 610-2008 4.1.1.

5.8.2 Reagents With GB/T 610-2008 in Chapter 3. Arsenic standard solution. 1mL solution containing arsenic (As) 0.001mg. Pipette Pipette 1mL arsenic standard solution according to HG/T 3696.2 prepared, placed in 1000mL volumetric flask, dilute to the mark with water Degree, shake.

5.8.3 Instruments With GB/T 610-2008 in 4.1.2.

5.8.4 Analysis of step Weigh accurately 1.0g ± 0.001g sample placed in 100mL beaker, add 50mL water, the following press GB/T 610-2008 in 4.1.3 "plus 6mL hydrochloride" operation. The test solution was the color can not be deeper than the standard. Standard with a pipette of 2mL arsenic standard solution, and treated in the same sample at the same time.

5.9 Determination of Heavy Metal Content

5.9.1 Method summary In acidic medium, heavy metal ions in the sample with sodium sulfide and generated brown by comparison with standard color solution, to determine a sample The content of heavy metals.

5.9.2 Reagents

5.9.2.1 nitrate solution. 1 + 1;

5.9.2.2 ammonia solution. 2 + 3;

5.9.2.3 glacial acetic acid. 2 + 1;

5.9.2.4 sodium sulfide solution;

5.9.2.5 Lead standard solution. 1mL solution containing lead (Pb) 0.01mg. Pipette Pipette 1mL lead standard solution according to HG/T 3696.2 prepared, placed in 100mL volumetric flask, dilute to the mark with water Degree, shake.

5.9.3 Analysis of step

5.9.3.1 Preparation of test solution Weigh accurately 1.0g ± 0.01g sample was placed in 100mL beaker, add 10mL water and 0.5mL nitric acid solution, aqueous ammonia solution Adjusted to pH~5 (precision strip test).

5.9.3.2 Determination The test solution was fully transferred to 50mL colorimetric tube, add 0.5mL acetic acid solution, add water to about 50mL, add 3 drops of vulcanization Soda solution, shake, in the dark place 10min, compared with the lead standard colorimetric solution. Standard colorimetric solution with a pipette of 2mL lead standard solution, and treated in the same sample at the same time.

5.10 Determination of lead content

5.10.1 Method summary After the sample is dissolved in dilute acid, into the atomic absorption spectrophotometer (graphite furnace), and after electrothermal atomic absorption 283.3nm resonance line, In a certain concentration range, the absorption values of lead content in line with Lambert - Beer law, compared with standard series quantitation.

5.10.2 Reagent

5.10.2.1 nitric acid;

5.10.2.2 nitrate solution. 1 + 5;

5.10.2.3 nitric acid solution. 3 + 97;

5.10.2.4 nitric acid - perchloric acid mixture. Vp (HNO3). Vp (HclO4) = 4.1;

5.10.2.5 Lead standard solution. 1mL solution containing lead (Pb) 0.01mg; Pipette Pipette 1mL lead standard solution according to HG/T 3696.2 prepared, placed in 100mL volumetric flask, dilute to the mark with water Degree, shake.

5.10.2.6 Lead standard solution. Pipette 1.00mL, 2.00mL, 4.00mL lead standard solution (5.10.2.5) were placed in 100mL flask, add nitric acid solution (5.10.2.3) diluted to the mark. Per ml solution of lead (Pb) were 0.0001mg, 0.0002mg, 0.0004mg.

5.10.2.7 water; meet GB/T 6682-2008 the provisions of secondary water.

5.10.3 Instruments and equipment

5.10.3.1 The glassware is required to nitric acid solution (5.10.2.2) soaked overnight with water repeatedly washed with deionized water will Xian clean;

5.10.3.2 atomic absorption spectrophotometer (with furnace and lead hollow cathode lamp).

5.10.4 Analysis step

5.10.4.1 Preparation of test solution Weigh the sample 1.0g, set 10mL volumetric flask, add water and 0.2mL nitric acid - perchloric acid mixture, diluted with water to the mark, Shake well. Preparation

5.10.4.2 blank test solution But without addition of the sample, the preparation of the test solution and other operations at the same time in the same manner.

5.10.4.3 Determination According to their instrument performance to an optimal state. Draw standard curve. Pipette formulated above lead standard solution injected into the furnace, measured obtaining absorbance values obtained absorbance and concentration Relationship linear regression equation. Sample assay. Pipette test solution and the blank test solution injected into the graphite furnace, obtaining the measured absorbance values, substituting one yuan line standard series Regression equation obtained sample solution of lead content.

5.10.5 Calculation Results Lead in lead (Pb) mass fraction 5 and its value is expressed in%, according to equation (5) Calculated. 5 = (Ba Ba 1- 0) × Vp × 10-6 (5) Where. Numerical test solution Ba 1

--- lead concentration in micrograms per milliliter (µg/mL); Ba 0

--- numerical test blank solution lead concentration in micrograms per milliliter (µg/mL); Numerical volume Vp

--- test solution, in milliliters (mL); Take the arithmetic mean of the parallel determination results of the measurement results, the results of two parallel determination of the absolute difference is not more than 0.0001%.

5.11 Determination of Water-insoluble content

5.11.1 Method summary Samples were dissolved in water, sintered glass crucible by the insolubles were filtered off, residue was washed with water, dried and the mass balance that can be used insolubles.

5.11.2 instruments and equipment

5.11.2.1 sintered glass crucible. filter plate pore size of 5µm ~ 15µm;

5.11.2.2 electric oven. temperature can be controlled at 105 °C ± 2 °C.

5.11.3 analysis step It weighs about 10g sample, accurate to 0.0002g, placed in 100mL beaker, add 30mL water 60 °C ~ 70 °C dissolved with stirring. Has been used in 105 °C ± 2 °C electric oven drying to constant quality glass crucible sand filtration, washed with hot water insolubles, each with 20mL Water, washed five times, placed in 105 °C ± 2 °C in electric oven, and dried to a constant mass.

5.11.4 Calculation Results Water-insoluble mass fraction 6 and its value is expressed in%, according to equation (6) Calculated. (6) Where. Take the arithmetic mean of the parallel determination results of the measurement results, the results of two parallel determination of the absolute difference is not more than 0.01%.

5.12.1 Method summary The glass electrode and a reference electrode immersed in the test solution, constitute a galvanic cell potential and pH of the solution is related by measuring the original The potential of the battery can be derived pH of the solution.

5.12.2 instruments and equipment .( PH meter with a glass electrode, calomel electrode or composite electrode) accuracy 0.1pH units.

5.12.3 analysis step Weigh accurately 2.0g ± 0.01g sample was placed in 150mL beaker, add 100mL water dissolved, it has been corrected acidimeter pH value of the solution. Determination of loss on drying of 5.13

5.13.1 Method summary Drying the sample at a certain temperature in order to reduce the quality of the sample to calculate the drying loss.

5.13.2 Instruments Electric oven. temperature can be controlled at 105 °C ± 2 °C.

5.13.3 analysis step Use has been dried to a constant mass of 105 °C ± 2 °C weighing bottle Weigh about 5g samples, accurate to 0.0002g, placed in 105 °C ± 2 °C electric oven, and dried to a constant mass.

5.13.4 Calculation Results Drying loss mass fraction 7 and its value is expressed in%, according to equation (7) Calculated. (7) Where. Take the arithmetic mean of the parallel determination results of the measurement results, the results of two parallel determination of the absolute difference is not more than 0.01%.

12.54 Free fluorine (as F), /% <=

0.68 Total Fluoride (as F), /% >=

13.0 Arsenic (As), /% <= 0.0002 Heavy metals (Pb), /% <=

0.002 Lead (Pb), /% <= 0.0002 Water-insoluble, /% <=

0.15 pH value (20g/L solution) 6.5-