GB 5009.260-2016Determination of sodium copper chlorophyllin in foods -- Spectrophotometric method (English PDF)

3.1 Reagents and materials

3.1.1 Sodium hydroxide.

3.1.2 Ammonium acetate.

3.1.3 Methanol.

3.1.4 Glacial acetic acid.

3.1.5 Polyamide powder. particle size of 0.150mm ~ 0.180mm.

3.2 Reagent preparation

3.2.1 Sodium hydroxide solution (4 mol/L). weigh 16.0 g of sodium hydroxide,

use water to dissolve and set volume to 100 mL.

3.2.2 Sodium hydroxide solution (0.1 mol/L). weigh 0.40 g of sodium hydroxide,

use water to dissolve and set volume to 100 mL.

3.2.3 Ammonium acetate buffer solution (0.2 mol/L). weigh 7.708 g of

ammonium acetate, use water to dissolve and set volume to 500 mL.

3.2.4 Desorption solution. 0.1 mol/L sodium hydroxide solution + methanol =

1+10 (volume ratio).

3.3 Standard product

Sodium copper chlorophyll, content >=99.0%.

3.4 Preparation of standard solution

3.4.1 Standard stock solution

Accurately weigh 0.0500 g of sodium copper chlorophyll standard product that

has been dried at 105°C ± 1°C to constant weight and is converted to 100%

mass by its purity. Use water to dissolve and set volume to a 100mL brown

volumetric flask. The concentration of this solution is 500 µg/mL. Prepare it at

the same day when use it. Store it from light.

3.4.2 Standard working solution

Accurately pipette 10 mL of 500 µg/mL standard solution to a 100mL beaker.

Add 30 mL of 0.2 mol/L ammonium acetate solution. Use 4 mol/L sodium

hydroxide solution and glacial acetic acid to adjust pH 5 ~ 6. Add into 3.0 g of

polyamide powder. Completely stir 2min. Place it still from light 5min. Use about

4.1 Spectrophotometer.

4.2 Balance. resolution of 0.0001g.

4.3 G3 sand core funnel.

4.4 Suction-filtration device. vacuum pump, suction-filtration bottle.

4.5 Constant temperature drying oven.

4.6 Small sample mincer.

4.7 Porcelain mortar.

5.1 Specimen preparation

5.1.1 Pretreatment of determination specimen of sodium copper

chlorophyll

5.1.1.1 Pretreatment of beverage, alcohol samples

Well shake the sample. Accurately weigh 5mL ~ 10mL (to the nearest of 0.1 mL)

of sample to a 100mL beaker. Heat in 55°C ~ 60°C water bath for 3min ~ 5min.

Remove alcohol.

5.1.1.2 Pretreatment of canned food sample

Place a representative sample in the mincer to fully mash. Accurately weigh 1g

~ 10g of (to the nearest of 0.001g) well-mixed slurry to a 100mL beaker.

5.1.1.3 Pretreatment of candy sample

Place the sample in the porcelain mortar to finely grinded and well mixed.

Accurately weigh 1g ~ 10g of (to the nearest of 0.001g) sample into a 100mL

beaker.

5.1.2 Post-treatment of testing sample solution

Add 30mL of 0.2 mol/L ammonium acetate solution into a 100mL beaker that

contains testing sample powder or sample slurry. Dissolve and well mix the

sample solution. Use 4 mol/L sodium hydroxide solution and glacial acetic acid

to adjust pH 5 ~ 6. Add into 3.0 g of polyamide powder. Completely stir 2min.

Use about 20mL of 60°C ± 2°C distilled water to transfer the sample solution to

G3 sand core funnel for suction-filtration. Discard the filtrate. Then use 75mL of

desorption solution to desorb the pigment in 3 times. Perform suction-filtration.

And use 20 mL of desorption solution to wash the residual liquid clean in the

filter bottle. Collect the filtrate. Use desorption solution to set volume to 100 mL.

5.2 Apparatus conditions

5.2.1 Measuring wavelength. 405nm.

5.2.2 Cuvette. 1cm.

5.3 Production of standard curve

Respectively take 0mL, 5.0mL, 10mL, 20mL, 30mL, 40mL, 50mL of standard

working solutions into 100mL volumetric flasks. Use desorption solution to dilute

to the scale. Prepare into standard series with concentrations of 0 µg/mL, 5

µg/mL, 10 µg/mL, 20 µg/mL, 30 µg/mL, 40 µg/mL, 50 µg/mL. Take 0 µg/mL

solution as blank. Determine its absorbance value. Draw the standard curve of

which the concentration is the abscissa and the absorbance is the ordinate.

5.4 Determination of specimen solution

Take the sample preparation solution that has been pretreated. Take the 0

µg/mL of the standard curve as blank. Determine its absorbance value. Obtain

the concentration of sodium copper chlorophyll in the sample solution based on

the standard curve.

0.005 g/kg.

......