Solid Waste-Determination of Dioxins-Isotope Dilution High Resolution-Gas Chromatography-High Resolution Mass Spectrometry (1)

1.

This method is suitable for the determination of the total amount of dioxin in solid waste

Second, the principle of the method

This method adopts isotope dilution high-resolution gas chromatography-high-resolution mass spectrometry to determine dioxins in solid waste, and stipulates standard operating procedures for solid waste sample processing and instrument analysis, and quality management measures for the entire analysis process

3.

(1) 100/200ng/mL EPA-1613LCS

(2) 200ng/mL EPA-1613ISS

(3) Calibration curve standard: 0.

(4) Toluene : pesticide residue level

(5) Acetone : pesticide residue level

(6) Dichloromethane : pesticide residue level

(7) N-hexane : pesticide residue level

(8) Methanol : pesticide residue level

(9) Cyclohexane: pesticide residue level

(10) Nonane : chromatographically pure

(11) Concentrated sulfuric acid: pure superior grade

(12) Anhydrous sodium sulfate : pure top grade

(13) Neutral silica gel: Ultra-pure neutral silica gel with 120-200 mesh, extracted with pesticide residue methylene chloride for 24 hours before use , and sealed in a clean glass bottle for use after vacuum drying
.

(14) Acidic activated alumina : imported acidic alumina, activated in an oven at 170℃ for 24h before use, and used after natural cooling to room temperature
.

(15)Carbopack C activated carbon: 120～400um imported graphite carbon
.

(16) Celite 545 diatomaceous earth: imported diatomaceous earth, baked at 450℃ for 5h before use, and placed in a clean glass bottle for use after cooling
.

Four, instruments and equipment

(1) Su's extractor
.

(2) Rotary evaporator
.

(3) Nitrogen blowing instrument
.

(4) Glass packed column
.

(5) High resolution gas chromatography-high resolution mass spectrometer
.

Five, pre-treatment

(1) Preparation of solid samples

The sample preparation method of solid waste shall be implemented with reference to HJ/T20-1998
.
The ash and fly ash after the incineration of industrial solid waste and hazardous waste are air-dried and mechanically crushed to reduce the particle size of the sample
.
Use mechanical or manual methods to crush, grind, and screen to make 95% of the sample reach a particle size below 2mm
.
The samples are mixed and reduced into samples for analysis
.

(2) Half body sample

When preparing a semi-solid sample, the sample is naturally air-dried, then crushed, ground, and sieved by mechanical or manual methods, so that 95% of the sample reaches a particle size of less than 2mm
.
The samples are mixed and reduced into samples for analysis
.
For semi-solid samples, the moisture content should be measured at the same time as the sample preparation
.

(3) Liquid samples

When preparing liquid samples, mix them thoroughly and divide them
.
The mixing of samples is carried out manually or mechanically
.
After the samples are mixed, the dichotomy method is used to reduce the amount by half each time, and the final sample amount is about 10 times the amount of the sample for detection and analysis
.

(4) Determination of moisture content

Determine the moisture content for surface and semi-solid samples
.
Weigh more than 5g of the corresponding sample, bake at 105-110°C for 4 hours, cool it to room temperature in a desiccator, and weigh
.
Use formula (1) to calculate the water content wH ₂ o(%)
.

wH ₂ o=(sample weight before drying-sample weight after drying)/sample weight before drying×100% (1)

(5) Sample extraction

1.
Environmental conditions and special equipment in the pretreatment room

The sample extraction and pre-treatment are carried out in the dioxin superclean laboratory
.

Special equipment: heating jacket, rotary evaporator, oven, ultrasonic cleaner, nitrogen blowing instrument, reagent cabinet
.

Supporting facilities: special container for ultra-pure water, bottle washing lye tank, full set of pre-treatment glassware, dryer, bottle drying rack, injection needle
.

2.
Sample extraction

(1) Extraction of solid samples and semi-solid samples:

Weigh a certain amount of sample (freeze-dried, 10g) into a Soxhlet extractor, add 20uL 100/200ng/mL EPA-1613LCS to extract the internal standard, and extract with toluene for more than 18 hours
.

(2) Liquid sample extraction:

Take a certain amount of sample (1L) into the separatory funnel, add an appropriate amount of cleaned NaCl, shake well to dissolve all the NaCl, add 20uL 100/200ng/mL EPA-1613LCS to extract the internal standard, and extract with 100mL dichloromethane .
Place it on the liquid-liquid extractor and oscillate for 10 min (280 times/min), repeat 3 times.
The 3 times the extracts are dehydrated by anhydrous sodium sulfate and combined as the sample extracts
.

(6) Purification

1.
Concentrate

After the extracted solution is near room temperature (otherwise it is easy to suck), use a rotary evaporator to concentrate to near dryness (the sample extracted by dichloromethane can be concentrated to about 2mL), and rinse the concentrated bottle with 16mL dichloromethane several times.
Transfer to a sample bottle and blow dry with a nitrogen blower
.

2.
Concentrated sulfuric acid purification

Add 7 mL of n-hexane to the above sample bottle, ultrasonically shake, then add 8 mL of concentrated sulfuric acid to mix, shake, centrifuge, and take the supernatant
.

Note: If the upper liquid has a darker color, it can be pickled multiple times
.

3.
Silica gel alumina column purification

Packing: Both the acidic silica gel column and the acidic alumina column use dry packing (filling weight is 3.
5g and 4.
5g), the silica gel column and the alumina column are connected in series, and the silica gel column is on top
.

Wash the column: Wet and clean the column with 15-20 mL of n-hexane
.

Passing the column: Add the upper layer purified by concentrated sulfuric acid to the silica gel column, and then wash the concentrated sulfuric acid layer twice with 7mL n-hexane.
The upper cleaning solution is also applied to the column, and the silica gel wall is washed 3 times with 2mL n-hexane, and the silica gel column is removed.
, Use 8mL of dichloromethane-n-hexane solvent with a volume ratio of 6:94 to clean the alumina column several times, and the above eluate can be collected as a waste liquid
.
Then use 16 mL of dichloromethane-n-hexane solvent with a volume ratio of 6:4 to clean the alumina column several times, collect the eluent into a sample bottle, and blow the eluent to nearly dry with nitrogen
.

4.
Carbon column purification

Wash the column: first wash the charcoal column with 10 mL of toluene (fill with 2 g), then wash with 6 mL of n-hexane , and then turn the column upside down
.

Passing the column: Rinse the above sample bottles several times with 6mL cyclohexane-dichloromethane equal volume mixed solvent, and apply the cleaning solution to the column, then use 2mL cyclohexane-dichloromethane equal volume mixed solvent to clean the column wall, then 2mL Wash the column with a dichloromethane/methanol/toluene solvent with a volume ratio of 75:20:5 (the eluent is a waste liquid)
.
The column was inverted, eluted with 30 mL of toluene solvent, and collected the eluate with a 100 mL flat-bottomed flask
.

5.
Concentrate

The eluent was concentrated to near dryness with a rotary evaporator, and the concentration bottle was rinsed several times with 16 mL of dichloromethane .
The rinse was transferred to another sample bottle and dried with a nitrogen blower
.
Rinse the sample bottle several times with 1.
2mL dichloromethane, transfer the rinse solution to a 1.
5mL sharp-bottomed bottle, let the sample dry naturally, use a 25uL injection needle to transfer 20uL 100ng/mL EPA-1613ISS internal sample injection standard (200ng/mLEPA-1613ISS was diluted twice with nonane) into a sharp-bottomed sample bottle and analyzed on the machine
.

Related Links: Solid Waste—Determination of Phenylurea Compounds—Liquid Chromatography (2)