SN/T 3927-2014 PDF English
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Determination of sodium thiocyanate in dairy products for export
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SN/T 3927-2014: Determination of sodium thiocyanate in dairy products for export---This is an excerpt. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.), auto-downloaded/delivered in 9 seconds, can be purchased online: https://www.ChineseStandard.net/PDF.aspx/SNT3927-2014
Determination of sodium thiocyanate in dairy products for export
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Foreword
The standard are compiled according as the GB/T 1.1-2009.
The standard was proposed by and is under the charge of the Certification and Accreditation Admin-
istration of the People's Republic of China.
The standard was drafted by Shandong Entry-Exit Inspection and Quarantine Bureau of the People's
Republic of China, Shanxi Entry-Exit Inspection and Quarantine Bureau of the People's Republic of
China, Hunan Academy of Inspection and Quarantine.
The standard was mainly drafted by Hu Qiaoru, Yang Lijun, Wang Jing, Dulijun, Cui Fengj ie,
Song Xiaohua,Cong Weihong,Liu Yumin,Fu Yingwen,Cui He,Zhai Jinyi,Zhao Youyou,Liu Hongyan,
Yao Yating, Huang zhiqiang.
Determination of sodium thiocyanate in
dairy products for export
1 Scope
This standard specifies the ion chromatographic method and gas chromatographic method for the de-
termination of sodium thiocyanate in dairy products of export.
This standard is applicable to the determination of sodium thiocyanate in sterilized milk, pasteurized
milk, yoghurt, formula milk, milk beverage,milk powder, formula milk powder, cheese and condensed
milk of export.
2 Normative references
The following referenced documents are indispensable for the application of this document. For
dated references,only the edition cited applies. For undated references, the latest edition of the ref-
erenced document (including any amendments) applies.
GB/T 6682 Water for analytical laboratory use-Specification and test method
Ion chromatography
3 Principle
The sample was extracted and precipitated protein with acetonitrile, then the extract was cleaned,
separated by anion exchange column, potassium hydroxide solution as eluent. The determination was
aceieved by ion chromatography equipped with conductance detector,qualitatified with the retention
time and quantified by external standard method.
4 Reagents and materials
Unless otherwise specified, the reagents used should be analytical pure. And the water should comply
with the requirement of GB/T 6682 (first class water).
4.1 Sodium thiocyanate standard CNaSCN,CAS No..540-72-7) .purity;?..99.99%.
tate protein at room temperature and then centrifuge at 6 OOO r/min for 10 min. Accurately pipette
1.0 ml (V2 ) of the supernatant into a color comparison tube with cap,dillute to 10 ml (V3 ) with
water, shake it on the vortex mixer and take the extract to filter through a 0.22 µm membrane, then
cleaned by SPE column(for example Guard II RP column) ,discard the first 3 ml of solution and take
the middle section of the filtrate for Ion chromatography determination. If the sodium thiocyanate
exceeds the range of the standard curve, the sample amount should be reduced or the multiple should
be increased.
7 .1.2 Solid sample
Accurately weigh 1.0 g test sample (accurate to 0.01 g) into a color comparison tube with cap, add
4 g water and shake it on the vortex mixer for 2 min, then dillute to 10 ml( V1 )with acetonitrile. Mix
it well on the vortex, then stand for 20 min to precipitate prettied at room temperature and then cen-
trifuge at 6 OOO r/min for 10 min. Accurately pipette 1.0 ml ( V2 ) of the supernatant into a color
comparison tube with cap,dillute to 10 ml ( V3) with water,shake it on the vortex mixer and take
the extract to filter through a 0.22 µm membrane, then cleaned by SPE column(for example Guard II
RP column) ,discard the first 3 ml of solution and take the middle section of the filtrate for Ion chro-
matography determination. If the sodium thiocyanate exceeds the range of the standard curve, the
sample amount should be reduced or the multiple should be increased.
7 .2 Chromatography operating conditions
7.2.1 Chromatography column. hydroxide selective, high-capacity anion exchange column compatible with
gradient elution,for example Ion Pac® AS 16,4 mm x 250 mm (with Ion Pac® AG 16,4 mm x 50 mm
guard column).
7 .2.2 The temperature of column. 30 °C.
7.2.3 Eluent. potassium hydroxide solution, the concentration of 45 mmol/l-60 mmol/l,utilizing a
gradient elution program (0.00 min-13.00 min,45.0 mmol/l;13.00 min-18.00 min,60.0 mmol/l;
18.00 min-23.00 min,45.0 mmol/l).
7 .2.4 Suppressor. ASRS-300 4 mm anion suppressor; external water suppression mode (flow rate.
1.5 ml/min) ,suppression current is 112 mA-149 mA.
7.2.5 Flow rate. 1.0 ml/min.
7 .2.6 Injection volume. 100 µL.
7 .2. 7 Detector. conductance detector.
7 .3 Standard curve
According to need, dilute sodium thiocyanate (SCN-) standard work solution with water step by
step,and prepare serial standard work sol1Jtion of applicable concentrations (referred linear range.
a) Chromatographic column. capillary column, BP10 25 m x 0.32 mm (id) x 0.50 µm(film thickness);
b) Temperature programme.40 °C (keep 5 min) ,50 °C /min to 200 °C (keep 2 min);
c) Carrier gas. Nitrogen (purity~99.999%);
d) Injection port temperature. 150 °C;
e) Detector temperature.260 °C;
f) Split ratio.100. 1;
g) Flow rate.1.0 ml/min.
15.3 Standard Curve
Accurately pipette 10 ml of the sodium thiocyanate standard work solution (12.8) into headspace
bottle,add 0.1 ml Chloramine T solution and mix for test. The standard solution are determined ac-
cording to chromatography operating conditions (15.2). Based on the chromatogram,draw the stand-
ard curve with the concentration of sulfur dioxide as abscissa and the response of the peak area (or
peak high) as ordinate, and calculate the linear regression equation condition, the retention time of
sodium thiocyanate ion derivative is about 2.50 min, For chromatogram of the standard see Figure
A.2 in Annex A.
15.4 Sample analysis
The standard solution and the sample are determined according to chromatography operating condi-
tions (15.2) ,and the quantitative analysis is conducted on the basis of peak area of sodium thiocya-
nate ion derivative with external standard method. The responses of the standard solution and the
sample should be in the linearity of the instrument.
15.5 Blank test
The operation of the blank test is the same as the described in the method of determination, but with
the omission of sample addition.
15.6 Calculation and result presentation
The content of sodium thiocyanate in the test sample is calculated by Formula (2) .
X =Cc - c 0 ) x V x 1 OOO ...( 2 )
mx1000
......
Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al.
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