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This standard replaces GB/T 5009.178-2003 Determination of Formaldehyde for Food Packaging Material, "8 Formaldehyde" in GB/T 5009.61-2003 Method for Analysis of Hygienic Standard of Products of Tripolycyanamide for Food Packaging, "7.2 Free formaldehyde" in GB/T 5009.69-2008 Method for Analysis of Hygienic Standard of Epoxy Phenolic Coatings for Inner Wall of Food Cans and determination of formaldehyde in water-based simulants in GB/T 23296.26-2009 Food Contact Materials - Polymer - Determination of Formaldehyde and Hexamethylenetetramine in Food Simulants - Spectrophotometry.
The following main changes have been made with respect to GB/T 5009.178-2003:
——The standard name is revised as National Food Safety Standard - Food Contact Materials and Articles - Determination of Formaldehyde Migration;
——Oscillographic polarography is deleted, acetylacetone spectrophotometry and chromotropic acid spectrophotometry are added.
National Food Safety Standard
Food Contact Materials and Articles - Determination of Formaldehyde Migration
1 Scope
This standard specifies the spectrophotometry for determining formaldehyde migration in food contact materials and their products.
This standard is applicable to the determination of formaldehyde migration in food contact materials and their products.
Method I Acetylacetone Spectrophotometry
2 Theory
When food simulants contact with specimen, formaldehyde in the specimen is migrated to food simulants. At the existence of ammonium acetate, formaldehyde reacts with acetylacetone and generates yellow 3,5-diacetyl-1,4-dihydrolutidine, then the absorbance of test solution is determined at 410nm with spectrophotometer, and the content of formaldehyde in food simulants is obtained by comparing with standard series, so as to obtain the migration of formaldehyde in the specimen.
3 Reagents and Materials
Unless otherwise specified, analytically pure reagents and Grade 3 water (specified in GB/T 6682-2008) are used for the purposes of this method.
3.1 Reagents
3.1.1 Absolute alcohol (CH3CH2OH).
3.1.2 Anhydrous ammonium acetate (CH3COONH4).
3.1.3 Acetylacetone (C5H8O2).
3.1.4 Glacial acetic acid (CH3COOH): guaranteed reagent.
3.1.5 Sodium hydroxide (NaOH).
3.2 Preparation of reagents
3.2.1 Water-based food simulants: they are prepared according to GB 5009.156.
3.2.2 Acetylacetone solution: dissolve 15.0g of anhydrous ammonium acetate in a proper amount of water, transfer the solution in a 100mL volumetric flask, add 40μL of acetylacetone and 0.5mL of glacial acetic acid, dilute them to the scale with water, mix well. Prepare the solution immediately before use.
3.3 Preparation of standard solutions
3.3.1 Formaldehyde solution (37%~40%, mass fraction): preserve it at 0℃~4℃.
3.3.2 Formaldehyde standard stock solution: pipet 5.0mL of formaldehyde solution into a 1 000mL volumetric flask, dilute it to the scale with water, preserve the solution at 0℃~4℃ for a valid period of 12 months, make calibration before use (see Annex A), or prepare by using formaldehyde solution standards directly.
3.3.3 Formaldehyde standard working solution: accurately transfer certain volumes of formaldehyde standard stock solution according to calibrated formaldehyde concentration, dilute them with corresponding simulants respectively until each liter is equivalent to 10mg of formaldehyde. Prepare the working solution immediately before use.
4 Apparatuses
4.1 Ultraviolet-visible spectrophotometer.
4.2 Thermostat water bath: with the accuracy controlled at ±1℃.
4.3 Colorimetric tube with stopper: 10mL (with division).
5 Analytical Procedures
5.1 Migration test
Subject sample to migration test according to the intended use and service conditions of to-be-tested sample and the requirements of GB 5009.156 and GB 31604.1. Pay attention to the tightness from the migration test to the determination to avoid the volatilization loss of formaldehyde. Conduct blank test at the same time.
5.2 Color reaction
Pipet 5.0mL of simulant specimen solution and blank solution into 10mL colorimetric tubes respectively, add 5.0mL of acetylacetone solution, cover the bottle stoppers, then shake well. Put colorimetric tubes in 40℃ water bath for 30min, then take them out and place under room temperature for cooling.
5.3 Plotting of standard curve
Take seven 10mL colorimetric tubes, add into corresponding formaldehyde standard working solutions according to the type of used simulants in migration test in accordance with Table 1, supplement with corresponding simulants to 5.0mL, then add 5.0mL of acetylacetone solution, cover the bottle stoppers and shake well. Put colorimetric tubes in 40℃ water bath for 30min, then take them out and place under room temperature for cooling.
Table 1 Preparation of Standard Working Solution Series
Adding amount of formaldehyde standard working solution/mL 0 0.5 1.0 1.5 2.0 2.5 3.0
Concentration of formaldehyde standard working series/(mg/L) 0 1.0 2.0 3.0 4.0 5.0 6.0
Transfer the standard working solution series after color reaction into 10mm cuvettes, take the blank solution after color reaction as reference, and determine the absorbance of standard solutions at 410nm. Plot the standard curve by taking the concentration of standard solutions as horizontal coordinate and the absorbance as longitudinal coordinate.
5.4 Determination of specimen solution and blank solution
Transfer the specimen solution and blank solution after color reaction into 10mm cuvettes, take the blank solution after color reaction as reference, and determine the absorbance of specimen solution at 410nm. Calculate the concentration (mg/L) of formaldehyde in specimen solution according to the standard curve.
Contents
Foreword i
1 Scope
2 Theory
3 Reagents and Materials
4 Apparatuses
5 Analytical Procedures
6 Expression of Analysis Results
7 Precision
8 Others
9 Theory
10 Reagent and Materials
11 Analytical Procedures
12 Expression of Analysis Results
13 Precision
14 Others
Annex A Calibration of Formaldehyde Standard Stock Solution
