GB 31604.33-2016National food safety standard - Food contact materials and products Determination of nickel migration (English PDF)

3.1 Reagents

3.1.1 Nitric acid (HNO3).

3.1.2 Ammonium dihydrogen phosphate (NH4H2PO4).

3.1.3 Reagents for preparing food simulants. According to specifications of GB

31604.1.

4.1 Atomic absorption spectrometer. equipped with graphite furnace atomizer,

nickel hollow cathode lamp.

4.2 Analytical balance. with a division of 0.1 mg.

5.1 Pretreatment of samples

According to the expected use and the use conditions of the sample to be tested,

carry out the migration test in accordance with the migration test methods and

test conditions specified in GB 5009.156 and GB 31604.1. After the soaking

solution is thoroughly mixed, take part of the soaking solution for analysis. If the

soaking solution is neutral or alkaline, add an appropriate amount of nitric acid

so that the concentration of nitric acid in the test solution is about 5 % (volume

fraction). At the same time carry out the sample blank test.

5.2 Determination

5.2.1 Instrument test conditions

Instrument reference conditions are shown in Table A.1.

5.2.2 Plotting of standard curves

PIPETTE 10 µL of nickel standard solution and 5 µL of ammonium dihydrogen

phosphate solution (20 g/L) (the optimal injection volume may be determined

in accordance with the instrument used) in the order of concentration from low

to high, INJECT them into the graphite furnace at the same time. After

atomization, MEASURE the absorbance value. Take the concentrations of the

standard series as the abscissa and take the corresponding absorbance values

as the ordinate to plot the standard curve.

5.2.3 Determination of samples

Under the same test conditions as those for the determination of standard

solution, PIPETTE 10 µL of sample solution and 5 µL of ammonium dihydrogen

phosphate solution (20 g/L) (the optimal injection volume may be determined

in accordance with the instrument used), INJECT them into the graphite furnace

at the same time. After atomization, MEASURE the absorbance value.

ammonia to decolorize, then reacts with basic dimethylglyoxime to form red

complexes, which are compared with the standard series to quantify.

10.1 Reagents

10.1.1 Diammonium hydrogen nitrite [(NH4)2HC6H5O7].

10.1.2 Dimethylglyoxime [(CH3)2C2(NOH)2].

10.1.3 Ethanol (C2H5OH).

10.1.4 Chloroform (CHCl3).

10.1.5 Bromine Water (Br2).

10.1.6 Sodium hydroxide (NaOH).

10.1.7 Hydrochloric acid (HCl).

10.1.8 Ammonia (NH3 · H2O).

10.1.9 Nitric acid (HNO3). excellent regent.

10.1.10 Reagents for preparing food simulants. according to the specifications

of GB 31604.1.

10.2 Preparation of reagents

10.2.1 Diammonium hydrogen nitrite solution (100 g/L). WEIGH 10 g of

diammonium hydrogen nitrite and DISSOLVE in water to 100 mL.

10.2.2 Ethanol solution (95 + 5). ADD 5 mL of water to 95 mL of ethanol, MIX

well.

10.2.3 Dimethylglyoxime ethanol solution (10 g/L). DISSOLVE 1 g of

dimethylglyoxime and DISSOLVE in 100 mL of ethanol solution (95 + 5), MIX

well. If there is any insoluble material, filter and the filtrate is for later use.

10.2.4 Sodium hydroxide solution (0.2 mol/L). DISSOLVE 1.0 g of sodium

hydroxide in 125 mL of water.

10.2.5 Basic dimethylglyoxime solution (10 g/L). WEIGH 1 g of

11.1 Spectrophotometer. with 1 cm cuvette.

11.2 Analytical balance. with a division of 0.1 mg.

12.1 Pretreatment of samples

The same as subclause 5.1.

12.2 Determination

12.2.1 Plotting of standard curves

Respectively PIPETTE 0 mL, 0.250 mL, 0.500 mL, 1.00 mL, 2.00 mL, 3.00 mL,

4.00 mL, 5.00 mL of nickel standard use solution (10.0 mg/L) to 100-mL

volumetric flasks, ADD food simulants to the mark, the corresponding

concentration series are 0 µg/L, 25.0 µg/L, 50.0 µg/L, 100 µg/L, 200 µg/L, 300

µg/L, 400 µg/L and 500 µg/L. ADD sodium hydroxide solution (20 %) to adjust

to neutral or weak alkaline, LET STAND for 2 h, FILTER, TRANSFER the filtrate

into a 250-mL separatory funnel, ADD 2 mL of diammonium hydrogen nitrite

solution (100 g/L), ADD a few drops of ammonia solution (2 mol/L) to adjust the

solution pH to 8 ~ 9. ADD 2 mL of dimethylglyoxime ethanol solution (10 g/L),

ADD 10 mL of chloroform, vigorously SHAKE for 1 min, LET STAND,

SEPARATE chloroform into a 60-mL separatory funnel. ADD 5 mL of chloroform

to the aqueous layer and REPEAT the above operations twice, COMBINE

chloroform solution, DISCARD the aqueous layer. USE 10 mL of ammonia

solution (0.3 mol/L) to wash the chloroform layer, vigorously SHAKE for 30 s,

LET STAND, SEPARATE the chloroform layer into another 60-mL separatory

funnel; ADD 10 mL of hydrochloric acid solution (0.5 mol/L) to the funnel,

vigorously SHAKE for 1 min, LET STAND, SEPARATE the chloroform layer into

another separatory funnel. ADD 5 mL of hydrochloric acid solution (0.5 mol/L)

and operate as above, COMBINE the hydrochloric acid solution, TRANSFER

to a 25-mL colorimetric tube with stopper, ADD 2 mL of bromine water, SHAKE.

LET STAND for 1 min, ADD ammonia solution (5 mol/L) until colorless, ADD 2

mL of ammonia solution (5 mol/L), COOL to room temperature in running water.

ADD 2 mL of basic dimethylglyoxime solution (10 g/L), ADD water to 25 mL and

MIX thoroughly, LET STAND for 20 min. DETERMINE the absorbance at 540

nm. TAKE the absorbance as the ordinate and the standard concentration as

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