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This standard replaces GB/T 23243-2009 Determination of Perfluorooctane Sulfonates (PFOS) in the Food Packaging Material - High Performance Liquid Chromatography-Tandem Mass Spectrometry.
The following changes have been made with respect to GB/T 23243-2009 (the previous edition):
——This standard is renamed as "National Food Safety Standard - Food Contact Materials and Articles - Determination of Perfluorooctane Sulfonate (PFOS) and Perfluorooctanoate (PFOA)";
——The application scope of the standard is extended;
——The determination object (perfluorooctanoate (PFOA)) is added;
——The sample preparation method is added;
——The purification step is added, and weak anion-exchange solid-phase extraction column is adopted for purification;
——The sensitivity of detection method is improved.
National Food Safety Standard
Food Contact Materials and Articles
Determination of Perfluorooctane Sulfonate (PFOS) and Perfluorooctanoate (PFOA)
1 Scope
This standard specifies the determination method for perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) in food contact materials and articles through liquid chromatography-tandem mass spectrometry.
This standard is applicable to determination of PFOS and PFOA in such food contact materials and articles as carton, rubber, polyethylene, plastic, resin, non-stick pan coating, etc.
2 Principle
PFOS and PFOA in food contact materials and articles are extracted through accelerated solvent extraction method by taking methanol as extraction solvent, purified by weak anion-exchange solid-phase extraction column, separated by liquid chromatography, ionized by electrospray ionization source (ESI), detected in multiple reaction monitoring mode (MRM) and quantatively determined by isotope internal standard method.
3 Reagents and Materials
Unless otherwise specified, analytically-pure reagents and Class-I water (defined in GB/T 6682) are adopted for the purpose of this method.
Note: all organic solvents and materials used in this standard shall be subjected to blank test prior to use; if the background value is higher than the quantitation limit, the organic solvent shall be redistilled or the test material shall be changed until the background value is lower than the quantitation limit.
3.1 Reagents
3.1.1 Methanol (CH3OH): chromatographically pure.
3.1.2 Acetonitrile (CH3CN): chromatographically pure.
3.1.3 Ammonium acetate (CH3COONH4): guaranteed reagent.
3.1.4 Glacial acetic acid (CH3COOH).
3.1.5 Aqua ammonia (NH3·H2O).
3.2 Preparation of reagents
3.2.1 5 mmol/L ammonium acetate
Weigh 0.385g of ammonium acetate, dissolve it with water and scale the volume to 1,000mL, shake well, and filter it with 0.22 μm filter membrane.
3.2.2 0.1 % amonium methanol
Take 200mL of methanol, pour it into a 250mL volumetric flask, accurately transfer 250 μL of aqua ammonia and pour it into the methanol, scale the volume with methanol and mix uniformly through ultrasound.
3.2.3 25 mmol/L ammonium acetate buffer solution (pH=4.0±0.5)
Take 0.385 g of ammonium acetate, dissolve it with 180 mL of water, add glacial acetic acid to adjust the pH value to 4± 0.5, and scale the volume with water to 200mL.
3.3 Standard products
3.3.1 Perfluorooctane sulfonate (PFOS) (C8HF17O3S; CAS No.: 1763-23-1): with purity ≥99%, or reference material approved and awarded with reference material certificate by the State.
3.3.2 Perfluorooctanoate (PFOA) [CF3(CF2)6COOH; CAS No.: 335-67-1]: with purity ≥98%, or reference material approved and awarded with reference material certificate by the State.
3.3.3 1,2,3,4-13C4-PFOS (MPFOS) and 13C4-PFOA (MPFOA) standard product solutions: with concentration of 50 μg/mL.
3.4 Preparation of standard solutions
3.4.1 PFOS and PFOA mixed standard stock solution
Accurately weigh 5 mg (accurate to 0.00001 g) of PFOS and PFOA respectively, dilute and scale the volume with methanol in a 100mL volumetric flask to prepare it into PFOS and PFOA standard solution with the concentration of both PFOS and PFOA of 50 μg/mL, and preserve it at -4℃.
3.4.2 PFOS and PFOA mixed standard working solution
Pipet PFOS and PFOA standard solution and dilute it with methanol to prepare into mixed standard working solution with the concentration of both PFOS and PFOA of 100ng/mL, and preserve it at -4℃.
3.4.3 Isotope internal standard mixed working solution
Pipet MPFOS and MPFOA mixed standard stock solution and dilute it with methanol to prepare it into isotope internal standard mixed working solution with the concentration of both MPFOS and MPFOA of 100ng/mL, and preserve it at -4℃.
3.4.4 Mixed standard working solutions of PFOS, PFOA and isotope internal standard
Dilute PFOS and PFOA mixed standard working solution and isotope internal standard mixed working solution with methanol to prepare a series of mixed working solutions with concentration of PFOS and PFOA of 2 ng /mL, 5 ng/mL, 10 ng/mL, 20 ng/mL and 40 ng/mL respectively and isotope internal standard concentration of 2ng/mL, and preserve them at -4℃.
3.5 Materials
3.5.1 Microporous filter membrane membrane: organic system; with pore diameter of 0.22 μm.
3.5.2 Weak anion exchanger (WAX) solid-phase extraction column: 150 mg/6 mL.
3.5.3 Liquid nitrogen.
4 Instruments and Apparatus
Note: in order to reduce the pollution of PFOS and PFOA introduced into the high performance liquid chromatography pipe, it is necessary to replace the pipeline made of Teflon with that made of PEEK or stainless steel.
4.1 Liquid chromatography tandem mass spectrometer: equipped with electrospray ionization source (ESI).
4.2 Balance: with sensibility of 0.01 mg.
4.3 Accelerated solvent extractor.
4.4 Vortex oscillator.
4.5 Nitrogen blowing instrument.
4.6 Freezer mixer.
5 Analysis Steps
5.1 Specimen preparation
Plastic or silica gel specimen: scissor it so that it’s smaller than 5 mm× 5 mm in size, grind it into powder with liquefrozen grinder; resin specimen: smash it and grind it into powder with liquefrozen grinder; coating specimen: scrape off the coating with penknife and grind it into powder with liquefrozen grinder; carton or polyethylene specimen: scissor it so that it’s smaller than 1 cm× 1 cm in size.
Foreword i
1 Scope
2 Principle
3 Reagents and Materials
4 Instruments and Apparatus
5 Analysis Steps
6 Expression of Analysis Results
7 Accuracy
8 Others
Annex A Chromatogram
