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Sample digestion methods commonly used in Nanjing binglab graphite digestion system

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Sample digestion methods commonly used in Nanjing binglab graphite digestion system

Graphite digester is one of the direct, effective and economical sample pretreatment methods for elemental analysis


Nanjing Binglab (https://www.njbinglab.com/) is a professional manufacturer of laboratory products, engaged in the production, development and sales of high-tech trace analytical laboratory containers, to fill the gap in China.


Common Sample Digestion Methods for Graphite Digestion Instruments
1. Environmental field
2. Food field
3. Plant field

1. Environmental field

graphite digester

Soil digestion
Instrument: graphite digestion instrument + PTFE digestion tube / PFA digestion tube
Reagent:
1. Hydrochloric acid (HCI): p=1.19g/mL, Premium Pure
2. Nitric acid (HNO3): p=1.42g/mL, Premium Pure
3. Hydrofluoric acid (HF): p=1.49g/mL
4. Perchloric acid (HCIO4): p=1.68g/mL, Premium Pure


steps:
1. Weigh 0.2-0.5g of soil sample into a polytetrafluoroethylene digestion tube, add 10mL hydrochloric acid HCI, and insert it into the digestion well.
2. Set the temperature of the digestion instrument to 100°C, heat until there is a small amount of sample left, then remove it and cool it down.
3. Add 5mL nitric acid HNO3, 5mL hydrofluoric acid HF, 3mL perchloric acid HCIO4, and cover.
4. Set the temperature of the digestion instrument to 170°C, heat up for about 1 hour, and open the cover after cooling.
5. Continue to heat the volatilized silicon until the temperature rises to 200°C. After a small amount of thick white smoke evaporates, take it off and cool it, and the liquid becomes transparent.


Digestion of sewage
Instrument: Graphite digester + PTFE digestion tube / PFA digestion tube
Reagent:
1. Nitric acid (HNO3): p=1.42g/mL, Premium Pure
2. Sulfuric acid (H2SO4): ρ=1.84g/mL, Premium Pure
3. Potassium permanganate (KMnO4): 5%.


step:
1. Take 20mL sample (or appropriate amount) into the PTFE digestion tube.
2. Add 0.5mL nitric acid HNO3, 1mL sulfuric acid H2SO4, and mix the sample evenly.
3. Add 3mL .5% potassium permanganate KMnO4 solution and let it stand for 15 minutes. If the sample fades from purple or brown, add 2 ml potassium permanganate KMnO4 solution.
4. Place the lid on the digestion tube leaving a gap to allow a little pressure, but not to let too much smoke escape.
5. Heat to reflux at 95°C for 2 hours without boiling.
6. After cooling, the sample is digested.


2. Food field

graphite digester with PFA tube

Rice digestion
Instrument: graphite digester + PTFE digestion tube / PFA digestion tube
Reagent:
1. Nitric acid (HNO3): p=1.42g/mL, Premium Pure
2. Perchloric acid (HCIO4): p=1.68g/mL, Premium Pure


step:
1. Weigh 1.0g of the rice sample that has been crushed and passed through a 100-mesh sieve into a digestion tube, plug it with a plug with a hole, add 10mL of mixed acid HNO3+HCIO4 (4+1), leave overnight.
2. Plug the stopper with a hole, insert it into the digestion hole of the digestion instrument, set the temperature of the digestion instrument to 65°C, heat slowly to mix the sample and acid completely, and keep at 65°C for 15 minutes.
3. Raise the temperature to 100°C. At this time, the digestion tube is filled with reddish-brown dense smoke, keep for 30min, the sample is digested, and the sample solution is transparent and pale yellow.
4. Open the tube stopper, raise the temperature to 180-190°C, drive off excess acid, the solution is colorless and clear, about 2ml.


Fish Digestion
Instrument: Graphite digester + PTFE digestion tube / PFA digestion tube
Reagent:
1. Nitric acid (HNO3): ρ=1.42g/mL, Premium Pure
2. Perchloric acid (HCIO4): p=1.68g/mL, Premium Pure


steps:
1. Dry the fish meat at 120°C, grind it with an agate mortar, weigh 0.5g of the ground sample into a digestion tube, and add 8mL of HNO3 nitric acid.
2. Plug the stopper with a hole, insert it into the digestion hole of the digestion instrument, set the temperature of the digestion instrument to 130°C, and rise from room temperature to 130°C in about 15 minutes.
3. After heating up to 130°C, let the acid reflux to clean the inner wall of the test tube, and keep it for 20 minutes, and the solution is basically clear.
4. Remove to cool and add about 2 mL of perchloric acid HCIO4.
5. Set the temperature to 190-200°C, insert it into the digestion hole of the digestion instrument, and continue to heat until the white smoke is almost exhausted, and the solution remains 1-2 mL. The solution is clear and transparent, basically colorless.


Digestion of raisins
Instrument: Graphite digester + PTFE digestion tube / PFA digestion tube


Reagent:
1. Nitric acid (HNO3): p=1.42g/mL, superior grade


step:
1. Weigh 0.5 g of raisin sample into a digestion tube, and add 8 mL of HNO3.
2. Plug the stopper with a hole, insert it into the digestion hole of the digestion instrument, set the temperature of the digestion instrument to 130°C, and rise from room temperature to 130°C in about 15 minutes.
3. After the temperature was raised to 130°C, the acid was refluxed and cleaned the inner wall of the test tube, and kept for 30 minutes, and the solution was clarified. Sample weighing amount, acid addition amount, digestion temperature, and heating time are only for reference. In actual operation, each parameter can be adjusted according to different types of samples to achieve the best digestion effect.


3. Plant field

graphite digester

Vegetables digestion
Instrument: Graphite digester + PTFE digestion tube / PFA digestion tube


Reagent:
1. Nitric acid (HNO3): p=1.42g/mL, superior grade
2. Perchloric acid (HCIO4): p=1.68g/mL, superior grade


step:
1. Take the edible part of fresh vegetables, wash them with tap water and double distilled water in turn, dry the surface water, dry them in an oven at a constant temperature of 100-105°C, take them out, grind them finely, and place them in a desiccator.
2. Weigh 0.5g of the crushed and ground vegetable sample into the digestion tube, plug the tube with a hole, add 15mL of mixed acid HNO3+HCIO4 (4+1), and let it stand overnight.
3. Set the temperature of the digestion instrument to 65C, insert the digestion tube into the digestion hole, let the acid reflux to clean the inner wall of the test tube, completely mix the sample with the acid, and keep it for 10 minutes.
4. Raise the temperature to 100°C. At this time, the digestion tube is filled with reddish-brown smoke, and keep for 30 minutes to digest the sample. If the sample is not completely digested, add 5mL of mixed acid HNO3+ HCIO4 (4+1) after cooling, reset the temperature, and continue Digest until the sample solution is transparent and pale yellow.


Digestion of Ginkgo Biloba Extract
Instrument: Graphite digestion instrument + PTFE digestion tube / PFA digestion tube
Reagent:
1. Nitric acid (HNO3): p=1.42g/mL, superior grade
step:
1. Weigh 0.5g of the sample into the digestion tube, add 8.0mL of HNO3 nitric acid, and insert it into the digestion well.
2. Put on the stopper and set the thermodigester to 120°C.
3. After the temperature was raised to 130°C, the acid was refluxed to clean the inner wall of the test tube and kept for 20 minutes, the solution was basically clear.
4. After rising to 130°C, continue to digest for 1.5-2 hours until it reaches a light yellow clear liquid, then remove it.
5. Heat up to 160°C and continue heating for an appropriate time.


Digestion of tea
Instrument: GS-36 PTFE digestion tube/PFA digestion tube
Reagent:
1. Nitric acid (HNO3): p=1.42g/mL, superior grade
2. Perchloric acid (HCIO4): p=1.68g/mL, superior grade
3. Hydrogen peroxide (H2O2): 30%, analytically pure


step:
1. Weigh 0.5g of the tea sample that has been pulverized and passed through a 120-mesh sieve into a digestion tube (hard glass tube), add 10mL of nitric acid HNO3, plug the tube with a hole, and let it stand overnight.
2. Insert into the digestion hole of the digestion instrument, set the temperature of the digestion instrument to 65 “C, heat slowly to make the sample bubble and mix, and keep the constant temperature at 65 °C for 15 minutes.
3. Raise the temperature to 135°C, keep it for 1h, and digest the sample.
4. If the digestion is not complete, add 5mL mixed acid HNO3+ HCIO4 (4+1) after cooling, or add hydrogen peroxide H2O2 dropwise, raise the temperature and keep the temperature until the solution is transparent.
5. Raise the temperature to 160°C, and flush the acid to about 2mL.

PTFE digestion tube

PTFE digestion tube


Material: high-purity polytetrafluoroethylene, the product does not add any recycled materials, and has no defects such as black spots, yellow spots, cracks, etc. Strong corrosion resistance, aqua regia, hydrofluoric acid, sulfuric acid, hydrochloric acid, nitric acid, acetone, alcohols and other inorganic and organic samples; the tube body has no adsorption, non-stick, convenient for experimental cleaning
Applicable brands: supporting Labtech Auto DigiBlock S60, Gedanner DS series, Polytech automatic graphite digestion instrument DigestLinc ST60D, DEENA sample automatic graphite digestion and pretreatment system.

graphite digestion apparatus

PFA digestion tube

                                                                                                                PFA digestion tube with graduation
Specifications: 50ml/60ml (customizable)
Transparency: transparent, with a scale to fix the volume, when used as a digestion bottle or tube, you can observe the reaction of the sample in the tube
Material: PFA soluble polytetrafluoroethylene, the raw material is imported Teflon, low dissolution and precipitation, chemical resistance, can withstand strong acid, strong alkali, aqua regia, magic acid, hydrofluoric acid, nitric acid, sulfuric acid, etc. and organic and inorganic solvents.


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