GB 5009.139-2014 English PDF (GB5009.139-2014)

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GB 5009.139-2014: National food safety standard -- Determination of caffeine in beverages
GB 5009.139-2014
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
National food safety standard - Determination of
caffeine in beverages
ISSUED ON: DECEMBER 01, 2014
IMPLEMENTED ON: MAY 01, 2015
Issued by: National Health and Family Planning Commission of the
People's Republic of China
Table of Contents
Foreword ... 3 
1 Scope ... 4 
2 Principle ... 4 
3 Reagents and materials ... 4 
4 Instruments and equipment... 5 
5 Analysis steps ... 5 
6 Expression of analysis results ... 7 
7 Precision ... 7 
8 Other ... 7 
Annex A Caffeine chromatogram ... 9 
National food safety standard - Determination of
caffeine in beverages
1 Scope
This Standard specifies the method for determination of caffeine content in cola
beverages, coffee, tea and solid and liquid beverage products - High
performance liquid chromatography.
This Standard applies to the determination of caffeine content in cola beverages,
coffee, tea and their solid and liquid beverage products.
2 Principle
After the cola-type beverage is degassed, use water to extract, magnesium
oxide to purify. For non-dairy coffee and tea liquid beverage products, use water
to extract, magnesium oxide to purify. Milky coffee and tea liquid beverage
products are precipitated by trichloroacetic acid solution. For coffee, tea and
solid beverage products, use water to extract, magnesium oxide to purify. Then
separate by C18 chromatographic column. Use UV detector to detect. Use
external standard method to quantify.
3 Reagents and materials
NOTE: Unless otherwise specified, the reagents used in this method are all analytically
pure, and the water is grade one water specified in GB/T 6682.
3.1 Reagents
3.1.1 Magnesium oxide (MgO).
3.1.2 Trichloroacetic acid (CCl3COOH).
3.1.3 Methanol (CH3OH): Chromatographically pure.
3.2 Reagent preparation
Trichloroacetic acid solution (10 g/L): Weigh 1g of trichloroacetic acid (3.1.2)
into a 100 mL volumetric flask. Use water to set volume till the scale mark.
3.3 Standard product
through a microporous membrane for use.
5.1.2 Non-dairy coffee and tea liquid products: Weigh 5 g of (to the nearest of
0.001 g) sample. Add water to set volume to 5 mL (make the caffeine content
in the sample solution within the range of the standard curve). Shake well. Add
0.5 g of magnesium oxide. Shake well. Stand still. Take the supernatant and
filter it through a microporous membrane for use.
5.1.3 Milky coffee and tea liquid products: Weigh 1 g of (to the nearest of 0.001g)
sample. Add trichloroacetic acid solution to make the volume up to 10 mL (make
the caffeine content in the sample solution within the range of the standard
curve). Shake well. Stand still. Make protein subside. Take the supernatant and
filter through a microporous membrane for use.
5.1.4 Coffee, tea and solid products: Weigh 1 g of (to the nearest of 0.001g) of
crushed homogeneous sample with less than 30 meshes into a 250 mL
Erlenmeyer flask. Add about 200 mL of water. Put in boiling water bath for 30
min. Shake from time to time. Take out and cool by running water for 1 min. Add
5 g of magnesium oxide. Shake. Put in the boiling water bath for 20 min again.
Take out the Erlenmeyer flask. Cool to room temperature. Transfer to a 250 mL
volumetric flask. Add water to the mark (make the caffeine content in the sample
solution within the range of the standard curve). Shake well. Stand still. Take
the supernatant and filter through a microporous membrane for use.
5.2 Instrument reference conditions
Chromatographic column: C18 column (particle size is 5 μm, column length of
150 mm × diameter of 3.9 mm) or a chromatographic column with equivalent
performance.
Mobile phase: methanol + water=24+76.
Flow rate: 1.0 mL/min.
Detection wavelength: 272 nm.
Column temperature: 25°C.
Injection volume: 10 μL.
5.3 Production of standard curve
Inject the standard series of working fluids into the liquid chromatograph.
Determine the corresponding peak area. Take the concentration of the standard
working fluid as the abscissa and the peak area as the ordinate to draw a
standard curve (the standard chromatogram of caffeine is shown in Figure A.1
in Annex A).