-
Categories
-
Pharmaceutical Intermediates
-
Active Pharmaceutical Ingredients
-
Food Additives
- Industrial Coatings
- Agrochemicals
- Dyes and Pigments
- Surfactant
- Flavors and Fragrances
- Chemical Reagents
- Catalyst and Auxiliary
- Natural Products
- Inorganic Chemistry
-
Organic Chemistry
-
Biochemical Engineering
- Analytical Chemistry
- Cosmetic Ingredient
-
Pharmaceutical Intermediates
Promotion
ECHEMI Mall
Wholesale
Weekly Price
Exhibition
News
-
Trade Service
Instant noodles have become a fast food choice of many consumers because of their convenience, time-saving and economic characteristics
.
But research shows that instant noodles contain harmful substances, lead is one of them
For the determination of lead in food, five methods are given in "GB5009.
12-2010 National Food Safety Standard for the Determination of Lead in Food", namely graphite furnace atomic absorption spectrometry, hydride atomic fluorescence spectrometry, flame atomic absorption spectrometry Method, dithizone colorimetry and single-scan polarography
.
This training uses graphite furnace atomic absorption spectrometry (according to the first method in GB5009.
12-2010)
.
1.
Purpose requirements
(1) Understand the determination method of lead in food
.
(2) Master the principle, method and operation process of graphite furnace atomic absorption spectrometry for determination of lead
.
(3) Master the principle and operation process of wet ashing
.
2.
Principles of training
After ashing or acid digestion, the sample is injected into the graphite furnace of the atomic absorption spectrophotometer, and after electrothermal atomization, the lead at a wavelength of 283.
3nm has a specific absorption for the spectrum emitted by the lead hollow cathode lamp
.
Within a certain range, its absorption value is proportional to the lead content
3.
Training supplies
(1) Atomic absorption spectrophotometer (with graphite furnace and lead hollow cathode lamp)
.
(2) Muffle furnace
.
(3) Balance: Sensitivity is 1mg
.
(4) Dry thermostat
.
(5) Porcelain crucible
.
(6) Pressure digestion device, pressure digestion tank or pressure melting bomb
.
(7) Adjustable electric heating plate, adjustable electric furnace
.
(8) Nitric acid : pure superior grade
.
(9) Ammonium persulfate
.
(10) Hydrogen peroxide (30%)
.
(11) Perchloric acid : pure superior grade
.
(12) Nitric acid solution (1+1): Measure 50 mL of nitric acid and slowly pour into 50 mL of water
.
(13) Nitric acid solution (0.
5mol/L): Take 3.
2ml of nitric acid, add 50ml of water, dilute with water and dilute to 100ml
.
(14) Nitric acid solution (1.
0mol/L): Measure 6.
4mL of nitric acid, add 50mL of water, and dilute to 100mL
.
(15) Ammonium dihydrogen phosphate solution (20g/L): Take 2.
0 g of ammonium dihydrogen phosphate , dissolve it with deionized water and dilute to 100 mL
.
(16) Mixed acid: nitric acid + perchloric acid (9+1)
.
Mix 9 parts of nitric acid with 1 part of perchloric acid
(17) Lead standard stock solution: accurately weigh 1.
000g metallic lead (99.
99%) or 1.
598g lead nitrate (excellent grade pure), add in nitric acid (1+1) not more than 37mL in batches , heat to dissolve, transfer into 1000mL Volumetric flask, use 0.
5mol/L nitric acid solution to make the volume to the mark
.
Store in a polyethylene bottle and store in the refrigerator
(18) Lead standard liquid: Pipette 1.
0 mL of lead standard stock solution into a 100 mL volumetric flask each time, and add nitric acid (0.
5 mol/L) to the mark
.
After multiple dilutions in this way, each 1mL contains 10.
4.
Safety reminder
The reagents used in this training, such as nitric acid and perchloric acid , are all strong oxidants and are highly corrosive.
Take care to avoid skin contact and inhalation of vapor
.
A large amount of acid mist and smoke will be generated during the digestion process, so it must be carried out in a fume hood
Related Links: Determination of Heavy Metals and Other Trace Elements in Food
