GB 5009.93-2017_English: PDF (GB5009.93-2017)
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| Standard ID | GB 5009.93-2017 (GB5009.93-2017) | | Description (Translated English) | Food safety national standard -- Determination of selenium in food | | Sector / Industry | National Standard | | Classification of Chinese Standard | X09 | | Word Count Estimation | 11,113 | | Date of Issue | 2017-04-06 | | Date of Implementation | 2017-10-06 | | Older Standard (superseded by this standard) | SN/T 0860-2000; SN/T 0926-2000; GB/T 21729-2008; GB 5009.93-2010 | | Regulation (derived from) | State Health and Family Planning Commission Notice No. 5 of 2017 | | Standard ID | GB 5009.93-2010 (GB5009.93-2010) | | Description (Translated English) | National food safety standard. Determination of selenium in foods | | Sector / Industry | National Standard | | Classification of Chinese Standard | C53 | | Classification of International Standard | 67.040 | | Word Count Estimation | 8,848 | | Date of Issue | 2010-03-26 | | Date of Implementation | 2010-06-01 | | Older Standard (superseded by this standard) | GB/T 5009.93-2003 | | Regulation (derived from) | Circular of the Ministry of Health (2010)7 | | Issuing agency(ies) | Ministry of Health of People's Republic of China | | Summary | This Chinese standard specifies the use hydride generation atomic fluorescence spectrometry and fluorescence method for the determination of selenium in foods approach. This standard applies to the determination of selenium in foods. | | Standard ID | GB/T 5009.93-2003 (GB/T5009.93-2003) | | Description (Translated English) | Determination of selenium in foods | | Sector / Industry | National Standard (Recommended) | | Classification of Chinese Standard | C53 | | Classification of International Standard | 67.040 | | Word Count Estimation | 7,751 | | Date of Issue | 2003-08-11 | | Date of Implementation | 2004-01-01 | | Older Standard (superseded by this standard) | GB/T 12399-1996; GB 13105-1991 | | Adopted Standard | AOAC 3.102-1984; NEQ; AOAC 3.103-1984; NEQ; AOAC 3.104-1984; NEQ; AOAC 3.105-1984; NEQ; AOAC 3.106-1984; NEQ; AOAC 3.107-1984; NEQ | | Drafting Organization | Institute of Nutrition and Food Hygiene, Chinese Academy of Preventive Medicine | | Administrative Organization | Ministry of Health of the People Republic of China | | Regulation (derived from) | Announcement of Newly Approved National Standards No. 5, 2010 (No. 160 overall); Satcom (2010) 7 | | Proposing organization | Ministry of Health of the People Republic of China | | Issuing agency(ies) | The People Republic of China Ministry of Health, China National Standardization Management Committee |
GB 5009.93-2017
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
National food safety standard -
Determination of selenium in foods
ISSUED ON. APRIL 06, 2017
IMPLEMENTED ON. OCTOBER 06, 2017
Issued by. National Health and Family Planning Commission of the
People’s Republic of China;
China Food and Drug Administration.
3. No action is required - Full-copy of this standard will be automatically &
immediately delivered to your EMAIL address in 0~60 minutes.
Table of Contents
Foreword ... 3
1 Scope .. 4
2 Principle ... 4
3 Reagents and materials ... 4
4 Instruments and equipment .. 6
5 Analysis procedure .. 6
6 Expression of analysis results .. 8
7 Precision ... 8
8 Others ... 8
9 Principle ... 9
10 Reagents and materials ... 9
11 Instruments and equipment .. 11
12 Analysis procedure ... 11
13 Expression of analysis results ... 12
14 Precision ... 13
15 Others ... 13
Annex A Microwave digestion temperature rise program reference conditions
... 14
Foreword
This Standard replaces GB 5009.93-2010 “National food safety standard -
Determination of selenium in foods”, GB/T 21729-2008 “Tea - Determination of
selenium content”, SN/T 0860-2000 “Method for the determination of selenium in
canned mushroom for export - Fluorometry” and SN/T 0926-2000 “Method for the
determination of selenium in tea for import and export - Fluorimetry”.
Compare this Standard with GB 5009.93-2010, the main changes are as follows.
- RETAIN the hydride atomic fluorescence spectrometry as Method I, fluorescence
spectrophotometry as Method II;
- ADD the inductively coupled plasma mass spectrometry as Method III.
National food safety standard -
Determination of selenium in foods
1 Scope
This Standard specifies the determination of selenium content in foods by hydride
atomic fluorescence spectrometry, fluorescence spectrometry and inductively coupled
plasma mass spectrometry.
This Standard applies to the determination of selenium in all types of foods.
Method I -- Hydride atomic fluorescence spectrometry
2 Principle
After the sample is acid-heated and digested, in the 6 mol/L hydrochloric acid medium,
the hexavalent selenium in the sample is reduced to tetravalent selenium. Sodium
borohydride or potassium borohydride is used as the reducing agent to reduce the
tetravalent selenium in the hydrochloric acid medium to hydrogen selenide, which is
introduced by carrier gas (argon) into the atomizer for atomization. In the irradiation of
selenium hollow cathode lamp, the ground-state selenium atoms are excited to a high
energy state. When deactivating back to the ground state, the fluorescence of the
characteristic wavelength is emitted, of which the fluorescence intensity is proportional
to the selenium content. Compare with the standard series.
3 Reagents and materials
Unless otherwise indicated, the reagents used in this method are analytical regents,
and the water is the Grade 2 water as specified in GB/T 6682.
3.1 Reagents
3.1.1 Nitric acid (HNO3). excellent regent.
3.1.2 Perchloric acid (HClO4). excellent regent.
3.1.3 Hydrochloric acid (HCl). excellent regent.
3.1.4 Sodium hydroxide (NaOH). excellent regent.
3.1.5 Hydrogen peroxide (H2O2).
3.1.6 Sodium borohydride (NaBH4). excellent regent.
3.1.7 Potassium ferricyanide [K3Fe(CN)6].
3.2 Preparation of reagents
3.2.1 Nitric acid - perchloric acid mixed acid (9 + 1). MIX 900 mL of nitric acid with 100
mL of perchloric acid.
3.2.2 Sodium hydroxide solution (5 g/L). WEIGH 5 g of sodium hydroxide; DISSOLVE
in 1000 mL of water; MIX well.
3.2.3 Sodium borohydride solution (8 g/L). WEIGH 8 g of sodium borohydride;
DISSOLVE in sodium hydroxide solution (5 g/L); MIX well. PREPARE before use.
3.2.4 Hydrochloric acid solution (6 mol/L). WEIGH 50 mL of hydrochloric acid; slowly
ADD to 40 mL of water; COOL; DILUTE with water to 100 mL; MIX well.
3.2.5 Potassium ferricyanide solution (100 g/L). WEIGH 10 g of potassium ferricyanide;
DISSOLVE in 100 mL of water; MIX well.
3.2.6 Hydrochloric acid solution (5 + 95). MEASURE 25 mL of hydrochloric acid; slowly
ADD to 475 mL of water; MIX well.
3.3 Standard
Selenium standard solution. 1000 mg/L, or selenium standard solution at a certain
concentration certified by the state and awarded the standard substance certificate.
3.4 Preparation of standard solutions
3.4.1 Selenium standard intermediate solution (100 mg/L). accurately PIPETTE 1.00
mL of selenium standard solution (1000 mg/L) in a 10 mL volumetric flask; ADD
hydrochloric acid solution (5 + 95) to the mark; MIX well.
3.4.2 Selenium standard use solution (1.00 mg/L). accurately PIPETTE 1.00 mL of
selenium standard intermediate solution (100 mg/L) in a 100 mL volumetric flask; ADD
hydrochloric acid solution (5 + 95) to the mark; MIX well.
3.4.3 Selenium standard series solutions. respectively PIPETTE 0 mL, 0.500 mL, 1.00
mL, 2.00 mL and 3.00 mL of selenium standard use solution (1.00 mg/L) in 100 mL
volumetric flasks; ADD 10 mL of potassium ferricyanide solution (100 g/L); ADD
hydrochloric acid solution (5 + 95) to the mark; MIX well for test. The mass
concentrations of the selenium standard series solutions are 0 μg/L, 5.00 μg/L, 10.0
μg/L, 20.0 μg/L and 30.0 μg/L, respectively.
NOTE. The mass concentration of selenium in the standard series solutions may be determined
according to the sensitivity of the instrument and the actual content of selenium in the sample.
potassium ferricyanide solution (100 g/L); ADD water to constant volume; MIX well for
test. At the same time carry out the reagent blank test.
5.2.2 Microwave digestion
WEIGH 0.2 g ~ 0.8 g (to the nearest 0.001 g) of solid sample or accurately PIPETTE
1.00 mL ~ 3.00 mL of liquid sample; PLACE in the digestive tube; ADD 10 mL of nitric
acid and 2 mL of hydrogen peroxide; SHAKE to mix well. DIGEST in the microwave
digestion instrument, and the recommended microwave digestion conditions are
shown in Annex A (set digestion conditions according to different instruments). After
the digestion is completed and cool, TRANSFER the digestion solution into the conical
flask; ADD a few grains of glass beads; continue to HEAT on the electric hot plate to
near dry, it must not be evaporated to dry. ADD 5 mL of hydrochloric acid solution (6
mol/L); continue to HEAT until the solution becomes clear and colorless accompanied
by white smoke; COOL; TRANSFER to a 10 mL volumetric flask. ADD 2.5 mL of
potassium ferricyanide solution (100 g/L); ADD water to constant volume; MIX well for
test. At the same time carry out the reagent blank test.
5.3 Determination
5.3.1 Instrument reference conditions
Adjust the instruments to the best condition according to their performance. Reference
conditions. negative high voltage 340 V; lamp current 100 mA; atomization
temperature 800 °C; furnace height 8 mm; carrier gas flow rate 500 mL/min; shielding
gas flow rate 1000 mL/min; standard curve method of measurement method; peak
area of reading method; delay time 1 s; reading time 15 s; solution adding time 8 s;
sample injection volume 2 mL.
5.3.2 Plotting of standard curve
TAKE hydrochloric acid solution (5 + 95) as the carrier, sodium borohydride solution (8
g/L) as the reducing agent. INJECT sample continuously with the zero tube of the
standard series. After the reading is stable, introduce the selenium standard series
solutions into the instrument according to the order of the mass concentration from low
to high, to measure their fluorescence intensity. The standard curve is plotted by taking
the mass concentration as the abscissa and the fluorescence intensity as the ordinate.
5.3.3 Sample determination
Under the same test conditions as the determination of standard series solutions, the
blank solution and the sample solution are respectively introduced into the instrument,
and the corresponding fluorescence intensity is measured, to compare with the
standard series.
NOTE. This reagent has a certain toxicity, personnel who use this reagent shall pay attention
to protection.
10.2.3 Nitric acid - perchloric acid mixed acid (9 + 1). MIX 900 mL of nitric acid with
100 mL of perchloric acid.
10.2.4 Hydrochloric acid solution (6 mol/L). MEASURE 50 mL of hydrochloric acid;
slowly ADD to 40 mL of water; COOL; ADD water to 100 mL; MIX well.
10.2.5 Ammonia solution (1 + 1). MIX 5 mL of water with 5 mL of ammonia.
10.2.6 EDTA mixture.
a) EDTA solution (0.2 mol/L). WEIGH 37 g of EDTA-2Na; ADD water and HEAT until
completely dissolved; COOL and DILUTE to 500 mL with water;
b) Hydroxylamine hydrochloride solution (100 g/L). WEIGH 10 g of hydroxylamine
hydrochloride to dissolve in water; DILUTE to 100 mL; MIX well;
c) Cresol red indicator (0.2 g/L). WEIGH 50 mg of cresol red to dissolve in a small
amount of water; ADD 1 drop of ammonia solution (1 + 1); after completely
dissolved, DILUTE with water to 250 mL; MIX well;
d) Respectively TAKE 50 mL of EDTA solution (0.2 mol/L) and hydroxylamine
hydrochloride solution (100 g/L); ADD 5 mL of cresol red indicator (0.2 g/L);
DILUTE to 1 L with water; MIX well.
10.2.7 Hydrochloric acid solution (1 + 9). MEASURE 100 mL of hydrochloric acid;
slowly ADD to 900 mL of water; MIX well.
10.3 Standard
Selenium standard solution. 1000 mg/L, or selenium standard solution at a certain
concentration certified by the state and awarded the standard substance certificate.
10.4 Preparation of standard solutions
10.4.1 Selenium standard intermediate solution (100 mg/L). accurately PIPETTE 1.00
mL of selenium standard solution (1000 mg/L) in a 10 mL volumetric flask; DILUTE
with hydrochloric acid solution (1 %) to the mark; MIX well.
10.4.2 Selenium standard use solution (50.0 μg/L). accurately PIPETTE 0.50 mL of
selenium standard intermediate solution (100 mg/L); DILUTE with hydrochloric acid
solution (1 %) to 1000 mL; MIX well.
10.4.3 Selenium standard series solutions. accurately PIPETTE 0 mL, 0.200 mL, 1.00
mL, 2.00 mL and 4.00 mL of standard selenium use solution (50.0 μg/L), which are
equivalent to containing 0 μg, 0.010 0 μg, 0.050 0 μg, 0.100 μg and 0.200 μg of
12.3.1 Instrument reference conditions
Adjust the instruments to the best condition according to their performance. The
reference conditions. excitation light wavelength 376 nm, emission light wavelength
520 nm.
12.3.2 Plotting of standard curve
Measure the fluorescence intensity of 4,5-Benzo piaselenol in selenium standard
series solution on the instrument, respectively, according to the order of mass from low
to high. The standard curve is plotted by taking the mass as the abscissa and the
fluorescence intensity as the ordinate.
12.3.3 Determination of sample solution
After the digested sample solution of 12.2 and the blank solution are added with
hydrochloric acid solution (1 + 9) to 5 mL, ADD 20 mL of EDTA mixture, USE ammonia
solution (1 + 1) and hydrochloric acid solution (1 + 9) to adjust it to pale red-orange
(pH 1.5 ~ 2.0). The following steps are operated in the darkroom. ADD 3 mL of DAN
reagent (1 g/L); MIX well; HEAT in the boiling water bath for 5 min; REMOVE and
COOL; ADD 3 mL of cyclohexane; SHAKE for 4 min; TRANSFER all the solution into
the separatory funnel; after it is layered, DISCARD the water layer, and carefully POUR
the cyclohexane layer from the top of the separatory funnel into the test tube with a lid.
Do not make cyclohexane mixed with water droplets, for test.
13 Expression of analysis results
The content of selenium in the sample is calculated according to equation (2).
where.
X - the content of selenium in the sample, in milligram...
......
GB 5009.93-2010
National food safety standard.Determination of selenium in foods
National Standards of People's Republic of China
National Food Safety Standard
Determination of Selenium in Food
National food safety standard
Determination of selenium in foods
People's Republic of China Ministry of Health issued
Issued on. 2010-03-26
2010-06-01 implementation
Foreword
This standard replaces GB/T 5009.93-2003 "Determination of selenium in foods."
This standard replaces the standards previously issued as follows.
--GB/T 5009.93-2003;
--GB/T 12399-1996;
--GB 13105-1991.
National Food Safety Standard
Determination of Selenium in Food
1 Scope
This standard specifies the method for the determination of selenium in foods by hydride generation atomic fluorescence spectroscopy and fluorescence.
This standard applies to the determination of selenium in food.
2 Normative references
The standard file referenced in the application of this standard is essential. For dated references, only the edition date of the note
Apply to this standard. For undated references, the latest edition (including any amendments) applies to this standard.
The first method hydride generation atomic fluorescence spectrometry
Principle 3
After heating the sample by acid digestion, at 6 mo1/L HCl medium, the reduction of hexavalent selenium in the sample into tetravalent selenium, sodium boron hydride or boron
Potassium hydride as the reducing agent, the reduction of tetravalent selenium in the medium of hydrochloric acid into hydrogen selenide (H2Se), by a carrier gas (argon) into the atomizer into
Line atomization in selenium hollow cathode lamp illumination, the ground state of selenium atoms are excited to high energy state, the deactivation to the ground state, emitting a characteristic wave
Long fluorescence, and fluorescence intensity is proportional to the selenium content. Quantitative comparison with the standard series.
4 Reagents and materials
Unless otherwise specified, the reagents used in this method are analytically pure water GB/T 6682 provisions tertiary water.
4.1 Nitric acid. pure class distinctions.
4.2 perchloric acid. pure class distinctions.
4.3 hydrochloride. pure class distinctions.
4.4 mixed acid. nitric acid and perchloric acid of 9. 1 volume mix.
4.5 Sodium hydroxide. pure class distinctions.
4.6 a solution of sodium borohydride (8 g/L). Weigh 8.0 g of sodium borohydride (of NaBH4), was dissolved in sodium hydroxide solution (5 g/L), and then
The volume to 1000 mL, and mix.
4.7 ferricyanide (100 g/L). Weigh 10.0 g potassium ferricyanide [(K3Fe (CN) 6)], was dissolved in 100 mL of water, and mix.
4.8 selenium standard stock solution. Weigh 100.0 mg selenium (spectroscopically pure), was dissolved in a small amount of nitric acid, add 2 mL perchloric acid, boiling water bath
Heated 3 h ~ 4 h, after cooling plus 8.4 mL of hydrochloric acid, then cook in boiling water bath for 2 min, accurately diluted to 1000 mL, the concentration of hydrochloric acid
Of 0.1 mo1/L, the concentration of the stock solution is equivalent to 100 μg of selenium per milliliter.
4.9 selenium standard application solution. take 100μg/mL stock selenium standard solution 1.0 mL, the volume to 100 mL, this application concentration of 1μg/mL.
Note. You can also purchase the certified national standard element solution.
4.10 hydrochloric acid (6 mol/L). Measure 50 mL of hydrochloric acid (4.3) slowly added 40 mL of water, cool and dilute to 100 mL.
4.11 Hydrogen peroxide (30%).
5. Apparatus
5.1 atomic fluorescence spectrometer with selenium hollow cathode lamp.
5.2 Electric hot plate.
5.3 microwave digestion system.
5.4 Balance. a sense of the amount of 1 mg.
5.5 mill.
5.6 oven.
Step 6 Analysis
6.1 Sample Preparation
6.1.1 Food. The specimen was washed with water three times, at 60 ℃ drying, grinding, store in a plastic bottle and set aside.
6.1.2 vegetables and other plant foods. Take the edible portion washed with water with gauze to absorb water droplets, homogenised reserve.
6.1.3 Other solid samples. crushing, mixing spare.
6.1.4 Liquid Sample. Mix and set aside.
6.1.5 Sample Digestion
6.1.5.1 Electric heating digestion board. Weigh 0.5 g ~ 2 g (accurate to 0.001g) sample, the liquid sample drawn 1.00mL ~ 10.00 mL,
Placed digestion flask, add 10.0 mL of mixed acid and a few grains of glass beads, cover the surface of the dish cold digestion overnight. The next day on a hot plate heated and and
When supplemented with nitric acid. When the solution becomes clear and colorless with white smoke, and heating was continued to a residual volume of about 2 mL, must not be evaporated to dryness. cold
But, along with 5.0 mL of hydrochloric acid (4.10), and heating was continued until the solution becomes clear and colorless with white smoke appears, restore the hexavalent selenium to tetravalent
selenium. Cooled, transferred to a 50 mL volumetric flask to volume and mix aside. While doing the blank test.
6.1.5.2 Microwave Digestion. Weigh 0.5 g ~ 2 g (accurate to 0.001g) in the digestive tract sample, add 10 mL of nitric acid, 2 mL peroxide
Hydrogen, shaking mixing, digestion in microwave digestion instrument, which digest the recommended conditions are shown in Table 1 (self-digestion can be set according to different instruments
condition).
Table 1 Recommended conditions of microwave digestion
After cooling into the flask, add a few grains of glass beads, hot plate heating was continued until nearly dry, must not evaporated. Plus 5.0 mL salt
Acid (4.10), and heating was continued until the solution becomes clear and colorless with white smoke appears, hexavalent selenium reduced to tetravalent selenium. Cool, and transferred the sample
STAGE POWER RAMP ℃ HOLD
1 1600 W 100% 6.00 120 ℃ 1.00
2 1600 W 100% 3.00 150 ℃ 5.00
3 1600 W 100% 5.00 200 ℃ 10.00
Digestion in 25 mL volumetric flask to volume and mix aside. While doing the blank test.
Absorb 10.0 mL sample digestion in 15 mL centrifuge tube, add hydrochloric acid (4.3) 2.0 mL, iron potassium cyanide solution (4.7) 1.0 mL,
Mix tested.
6.2 preparation of standard curve
Were taken 0.00 mL, 0.10 mL, 0.20 mL, 0.30 mL, 0.40 mL, 0.50 mL standard application solution in 15 mL centrifuge tube with
Deionized water volume to 10 mL, respectively, and then add hydrochloric acid (4.3) 2 mL, iron potassium cyanide solution (4.7) 1.0 mL, mix, made of standard workers
For the curve.
6.3 Determination
6.3.1 Instrument Reference conditions. negative high voltage. 340 V; lamp current. 100 mA; atomization temperature. 800 ℃; furnace height. 8 mm; carrier gas
Flow rate. 500 mL/min; shielding gas flow rate. 1000 mL/min; measurement method. standard curve method; reading mode. peak area; delay
Room. 1 s; reading time. 15 s; dosing time. 8 s; injection volume. 2 mL.
6.3.2 Determination of. setting the optimal conditions for the instrument, the furnace temperature was raised gradually to the desired temperature, start measuring stable after 10 min ~ 20 min.
Continuous series of zero standard tube injection until after the reading has stabilized, the standard series of measurements into the standard curve. Into the sample measurement points
Do not blank and sample measurement sample digestion, before each test different samples should be cleaned injector. The measurement results calculated according to the sample 7.
7 expression analysis
According to equation (1) calculate the content of selenium in the sample.
1000) (0
××
×× - =
VCCX. (1)
Where.
X - sample selenium content in milligrams per kilogram or milligrams per liter (mg/kg or mg/L);
C - determining the concentration of sample digestion, in units of nanograms per milliliter (ng/mL);
0C - blank samples to determine the concentration of digestive juice, unit nanograms per milliliter (ng/mL);
m - mass of the sample (by volume) in grams or milliliters (g or mL);
V - sample digestion total volume in milliliters (mL).
The arithmetic mean of two under the same condition of independent determination results indicated that the results to three significant figures.
8 Precision
Two independent determination results under the absolute difference in repeatability condition must not exceed 10% of the arithmetic mean.
The second method Fluorescence
Principle 9
The sample was digested with a mixed acid, selenium compound oxidation of inorganic selenium Se4, under acidic conditions Se4 with 2,3-diaminonaphthalene
(2,3-Diaminonaphthalene, abbreviated as DAN) reacts 4,5 Benzopiaselenol selenium brain (4,5-Benzo piaselenol), then
Cyclohexane extraction. Fluorescence intensity was measured at an excitation wavelength of 376 nm, emission wavelength of 520 nm condition to calculate the sample
Selenium.
10 Reagents and materials
Unless otherwise specified, the reagents used in this method are analytically pure water GB/T 6682 provisions tertiary water.
10.1 selenium standard solution. Weigh accurately element selenium (spectroscopically pure) 100.0 mg, dissolved in a small amount of concentrated nitric acid, perchloric acid was added 2 mL (70% to 72
%), Boiling water bath to 3 h ~ 4 h, added 8.4 mL HCl (hydrochloric acid concentration of 0.1 mol/L) after cooling. Then cook in boiling water bath
2min. Accurately diluted to 1000 mL, this is the stock solution (Se content. 100 μg/mL). With 0.1 mol/L hydrochloric acid stock solution using
Diluted to 0.05 μg per ml selenium. In the refrigerator, valid for two years.
10.2 DAN reagent (1.0g/L). This reagent formulated in a dark room. Weigh DAN (purity 95% ~ 98%) 200 mg in the vicinity of the cone cover
Shaped flask, 0.1 mol/L hydrochloric acid, 200 mL, was shaken for about 15 min it has completely dissolved. Add about 40 mL cyclohexane, continue to oscillate 5
min. This solution was poured stuffed with glass wool (or cotton) in a separatory funnel, to be layered cyclohexane layer was filtered, collected DAN solution layer,
Purification by repeated with cyclohexane until the cyclohexane until minimize fluorescence (about 5 to 6 times purification). The DAN storage solution purified in brown
Color bottle, add about 1 cm thick cover surface cyclohexane, into the refrigerator. If necessary, prior to use purified once again with cyclohexane.
Warning. This reagent has some toxicity, the use of this reagent should be regular staff laboratory work experience. The user's responsibility to take appropriate safety and health measures,
And to ensure compliance with the relevant provisions of the State regulations.
10.3 mixed acid. nitric acid and perchloric acid are mixed in 91 volumes.
Sulfuric acid to 10.4 Selenium. Take 200 mL of concentrated sulfuric acid was slowly poured into 200 mL of water, was added 48% hydrobromic acid 30 mL, mix, sand bath to
On heating to appear white smoke, then the volume should be 200 mL.
10.5 EDTA mixture
10.5.1 EDTA solution (0.2 mol/L). Weigh disodium EDTA 37 g, add water and heated until completely dissolved, cooled and diluted to
500 mL;
10.5.2 hydroxylamine hydrochloride solution (100 g/L). Weigh 10 g of hydroxylamine hydrochloride dissolved in water and dilute to 100 mL;
10.5.3 cresol red indicator (0.2 g/L). Weigh 50 mg of cresol red dissolved in a little water, add ammonia (11) 1 drop until completely dissolved
After the solution diluted with water to 250 mL.
10.5.4 take EDTA solution (10.5.1) and hydroxylamine hydrochloride solution (10.5.2) for each 50 mL, plus cresol red indicator (10.5.3) 5 mL,
Diluted with water to 1 L, and mix.
Ammonia 10.6 (11).
10.7 hydrochloric acid.
10.8 Cyclohexane. the need to test whether the fluorescent impurities, distilled otherwise after use, used recycled cyclohexane, redistilled before use.
10.9 hydrochloric acid (19).
11 instruments and equipment
11.1 fluorescence spectrophotometer.
11.2 balance. a sense of the amount of 1mg.
11.3 oven.
11.4 mill.
11.5 heating plate.
11.6 water bath.
12 analysis steps
12.1 sample processing
12.1.1 Food
The sample was washed with water three times, to 60 ℃ oven drying to the surface water, ground with a grinder, store in a plastic bottle, put a packet of camphor fine,
Cork tightly and stored for use.
12.1.2 vegetables and other plant foods
Take the edible portion, after rinsed with distilled water three times, with gauze to absorb water droplets, stainless steel knife chopped, take a certain amount of the sample in an oven at 60 ℃
Dried, weighed and calculated moisture. Smash and set aside.
The calculation should be converted into the fresh weight.
12.1.3 other solid samples
Crushing, mixing the sample and set aside.
12.1.4 liquid sample
Mixing the sample and set aside.
12.2 digested sample
Se said about 0.01 μg ~ 0.5 μg of grain or vegetable and animal specimens 0.5 g ~ 2 g (accurate to 0.001g), a liquid sample
After the draw 1.00mL ~ 10.00 mL in grinding mouth Erlenmeyer flask, add 10 mL 5% sulfuric acid to the selenium, the sample to be moist, plus 20 mL of mixed acid
It was allowed to stand overnight and the next day was gradually heated on a hot plate set. When the violent reaction, the solution was colorless, continue heating until white fumes are generated at this time
Solution gradually turned yellow, reached the end. Some vegetables turbid samples after digestion, making it difficult to determine the end point, then you can pay attention to the bottle
Billowing white smoke appears, at the moment immediately removed, and the solution was cooled and then became colorless. Some higher selenium vegetables contain more Se6, need
After digestion plus 10 mL 10% hydrochloric acid, and heating was continued, so that the end point come back to fully restore Se6 as Se4, otherwise the result will be low.
12.3 Determination
Said digested sample solution was added 20.0 mL EDTA mixture with aqueous ammonia (10.6) and hydrochloric acid (10.9) adjusted to reddish orange
(PH 1.5 ~ 2.0). The following steps in the darkroom operations. add DAN reagent (10.2) 3.0 mL, after mixing, boiling water bath for 5 min,
After removing the cooling, cyclohexane, 3.0 mL, shaken for 4 min, the entire solution into a separating funnel, to be layered aqueous layer was discarded, carefully ring
Hexane layer is made of a separating funnel catchy poured into a lidded test tube, rendering cyclohexane mixed with water droplets, on a fluorescence spectrophotometer with excitation wavelength
376 nm, emission wavelength 520 nm fluorescence intensity 4,5 Benzopiaselenol selenium brain.
12.4 selenium standard curve drawing
Accurately taken selenium standard solution (0.05 μg/mL) 0.00 mL, 0.20 mL, 1.00 mL, 2.00 mL and 4.00 mL, 0.00 equivalent
μg, 0.01 μg, 0.05 μg, 0.10 μg and 0.20 μg selenium, add water to 5.0 mL, press sample measurement step is measured simultaneously.
When the selenium content in the 0.5 μg or less fluorescence intensity and a linear relationship between selenium content in the conventional measurement sample each time just to do a reagent blank
White and selenium content similar to standard sample tube (in duplicate) can be.
12.5 Analysis of the results presentation
Selenium content in the sample according to equation (2).
FF
FF
mX 02
1 - × - = (2)
Where.
X-- sample selenium content in micrograms per gram or microgram per milliliter (μg/g or μg/mL);
m1-- tube selenium mass, in micrograms (μg);
F1-- selenium standard fluorescence readings;
F2-- sample fluorescence readings;
F0-- blank tube fluorescence readings;
Quality m-- sample in grams or milliliters (g or mL).
The arithmetic mean of two under the same condition of independent determination results indicated that the results to three significant figures.
13 Precision
Two independent determination results under the absolute difference in repeatability condition must not exceed 10% of the arithmetic mean.
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