QB/T 5015-2016 English PDF (QBT5015-2016)

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QB/T 5015-2016: The determination of a- amino nitrogen in sugar beet
QB/T 5015-2016
QB
LIGHT INDUSTRY STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 67.180
Classification No.: X30
Filing No.: 55590-2016
The determination of α-amino nitrogen in sugar beet
ISSUED ON: JULY 11, 2016
IMPLEMENTED ON: JANUARY 01, 2017
Issued by: Ministry of Industry and Information Technology of PRC
Table of Contents
Foreword ... 3 
1 Scope ... 4 
2 Normative references ... 4 
3 Principle ... 4 
4 Reagent ... 4 
5 Instruments ... 5 
6 Sample preparation ... 5 
7 Determination ... 6 
8 Calculation ... 6 
9 Precision ... 7 
The determination of α-amino nitrogen in sugar beet
1 Scope
This standard specifies the determination method for α-amino nitrogen in sugar
beet.
This standard applies to the determination of α-amino nitrogen in sugar beet.
2 Normative references
The following documents are essential to the application of this document. For
the dated documents, only the versions with the dates indicated are applicable
to this document; for the undated documents, only the latest version (including
all the amendments) are applicable to this standard.
GB/T 6682 Water for analytical laboratory use - Specification and test
methods
3 Principle
In a slightly acidic (pH 6.0) copper salt solution, α-amino nitrogen forms a blue
complex with copper ions; the depth of the blue color is proportional to the
content of α-amino nitrogen. It is subject to colorimetric quantitation at a
wavelength of 580 nm, to determine the content of α-amino nitrogen.
4 Reagent
Unless otherwise specified, all reagents used are of analytical pure.
4.1 Water
It shall meet the requirements of grade-3 water in GB/T 6682.
4.2 Alkaline lead acetate solution
Basic lead acetate solution: The density is (1.24 ± 0.01) g/mL; each 100 mL
contains 9.5 g ~ 10.5 g of alkaline lead salt (calculated as PbO).
4.3 Diluted basic lead acetate solution
balance which has a balance of 0.01 g. Transfer the mixture of the beet paste
and the paste paper to the high-speed tissue masher. Add (177.0 ± 0.35) mL of
basic lead acetate dilute solution (4.3). Cover the masher. Turn on the stirring
motor. Dip it at 12000 r/min ~ 15000 r/min for 3 min (temperature 20 °C). Filter
it. Take a clear solution to prepare for use.
7 Determination
Accurately pipette 50 mL of the sample extract into a 100 mL volumetric flask.
Use distilled water to dissolve it and make the volume reach to the mark. Then
pipette 25 mL of the solution into a 250 mL beaker.
Pipette 0 mL, 5 mL, 10 mL, 20 mL, 30 mL, 40 mL, 50 mL, respectively, of
standard amino nitrogen solution in a 100 mL volumetric flask. Use distilled
water to dissolve and make its volume reach to the mark. These solutions
respectively contain α-amino nitrogen of 0 mg/100 mL, 1.3 mg/100 mL, 2.6
mg/100 mL, 5.2 mg/100 mL, 7.8 mg/100 mL, 10.4 mg/100 mL, 13 mg/100 mL,
respectively. Pipette 25 mL of the standard solution into a 250 mL beaker.
Add 25 mL sodium acetate solution and 10 mL copper reagent to the test
solution and standard solution, respectively. After mixing, use a 5 cm cuvette to
adjust the zero point with distilled water. At a wavelength of 580 nm, measure
the absorbance and draw a standard curve for comparison .
8 Calculation
The formula for calculating the content of α-amino nitrogen in the specimen:
Where:
X - The content of α-amino nitrogen in the specimen, in milligrams per
hundred grams (mg/100 g)
A - The mass of α-amino nitrogen in the sample solution for determination,
in milligrams (mg);
m - The mass of the specimen, in grams (g).
It is expressed as the arithmetic mean of two independent determination
results obtained under repeatability conditions, retaining 3 significant digits.