GB 5009.248-2016National food safety standard - Determination of lutein in foods (English PDF)

Foreword

This Standard replaces GB/T 23209-2008 "Determination of lutein in milk

powder - HPLC-UV method".

As compared with GB/T 23209-2008, the main changes of this Standard are as

follows.

- CHANGE the standard's name to "National Food Safety Standard -

Determination of lutein in foods";

- EXPAND the scope of application; ADD the liquid chromatography for the

determination of lutein in frozen drinks, rice and flour products, bakery

products, jams, jellies, and beverages;

- MODIFY the "Principles" of the former standard. The former "USE acetone

as a solvent to extract" is changed to "USE diethyl ether-n-hexane-

cyclohexane solvent system to extract";

- ADD the points worthy of notice for the operation process;

- ADD a saponification step for samples with high fat content including milk

powder; and PROVIDE different pretreatment methods to accommodate

various sample matrix analysis needs;

- ADD the correction requirement for the concentration of lutein standard

solution;

- For the phenomenon that lutein may be isomerized during the test operation,

ADD the qualitative and quantitative requirements for cis-lutein produced

due to isomerization.

National Food Safety Standard -

Determination of lutein in foods

1 Scope

This Standard specifies the liquid chromatography for the determination of

lutein in foods.

This Standard applies to liquid chromatography determination of lutein in infant

formula, dairy products, frozen drinks, rice and flour products, bakery products,

jams, jellies, and beverages.

2 Principles

After foods with high fat content (fat content of not less than 3% on a dry basis)

are saponified with potassium hydroxide solution at room temperature to free

lutein, then USE diethyl ether-n-hexane-cyclohexane (40+40+20, volume ratio)

to extract; USE liquid chromatography to separate; USE UV-detector or diode

array detector to detect; and USE external standard method for quantification.

Lutein in the samples of the other foods is directly extracted by diethyl ether-n-

hexane-cyclohexane (40+40+20, volume ratio). After the extract is purified by a

neutral alumina solid phase extraction cartridge, USE liquid chromatography to

separate; USE UV-detector or diode array detector to detect; and USE external

standard method for quantification.

3 Reagents and materials

Unless otherwise stated, the reagents used in this method are of analytically

pure; the water is Grade I water specified in GB/T 6682.

25 mL brown volumetric flasks; USE 0.1% BHT ethanol solution (3.2.4) to dilute

to volume; and OBTAIN a series of standard working solutions having

concentrations of 0.100 µg/mL, 0.200 µg/mL, 0.400 µg/mL, 0.800 µg/mL, and

4 Instruments and equipment

5 Analytical procedures

Note. Because lutein is sensitive to light, unless otherwise stated, all test operations shall

be performed in a yellow or red light source environment with no UV light below 500

nm.

6 Analysis results expression

The content of lutein in the sample shall be calculated according to formula (1).

7 Precision

The absolute difference between the two independent determination results,

obtained under repeated conditions, shall not exceed 15% of the arithmetic

mean.

8 Other

The detection limit of this method. For infant formula, milk powder, ice cream,

bakery nuts, and other foods, when the sampling amount is 2 g and the constant

volume is 5 mL, the detection limit is 3 µg/100 g. For liquid milk, etc., when the

sampling amount is 10 g and the constant volume is 25 mL, the detection limit

is 3 µg/100 g. For rice and flour products, jams, and other foods, when the

sampling amount is 5 g and the constant volume is 10 mL, the detection limit is

3 µg/100 g.

Appendix A

Method for correction of standard solution concentration

The lutein standard solution, after preparation, needs to be calibrated. TAKE 1

mL of standard stock solution; USE ethanol to dilute to 25 mL. PIPETTE this

solution into a 1 cm quartz cuvette. USE ethanol as a blank; USE a

spectrophotometer, under a wavelength of 445 nm, to determine the

absorbance A. According to formula (A.1), calculate the standard solution

concentration.

Appendix B

Liquid chromatogram of standard solution

B.1 Liquid chromatogram of lutein (trans) standard solution

The liquid chromatogram of lutein (trans) standard solution is shown in Figure

B.1.

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