Determination of 37 Volatile Organic Compounds/35 Volatile Halogenated Hydrocarbons in Solid Waste Headspace/Gas Chromatography-Mass Spectrometry (1)

1.

This method is suitable for the determination of the content of volatile organic compounds in solid waste and solid waste leachate.

Second, the principle of the method

Under certain temperature conditions, the volatile components in the sample in the headspace bottle volatilize to the headspace, generating vapor pressure, and the gas-liquid (solid) three-phase reaches the thermodynamic dynamic equilibrium

3.

(1) Methanol: pesticide residue level

(2) Quartz sand: 40-100 mesh, burned in a muffle furnace at 400°C for 4 hours, placed in a desiccator to cool to room temperature, and transferred to a ground glass bottle for storage

(3) Sodium chloride : pure superior grade, the pretreatment is the same as quartz sand

(4) Phosphoric acid ; superior grade or above

(5) Extractant: ultrapure water; no VOCs interference, can be purchased or prepared in the laboratory

(6) Matrix modifier: Measure 500 mL of ultrapure water, add a few drops of premium grade phosphoric acid to adjust to pH ≤ 2, add 180 g of sodium chloride , dissolve and mix

(7) Mixed standard solution of volatile organic compounds: p=1000ug/mL, and the solvent is methanol

(8) Internal standard: fluorobenzene , 1,4-dichlorobenzene-d4, chlorobenzene-d5, mixed standard solution, p=1000ug/mL, solvent is methanol , and other materials with similar properties can also be used

(9) Substitute: Toluene-d ₈ , p-bromofluorobenzene mixed standard solution, p=1000ug/mL, the solvent is methanol , and other materials with similar properties can also be used

(10) p-bromofluorobenzene: p=10ug/mL, the solvent is methanol

Four, instruments and equipment

(1) Solution delivery pump

(2) Zero headspace device (with 0.

(3) Flip the oscillator
.

(4) Reciprocating oscillator
.

(5) Headspace instrument
.

(6) EI source single quadrupole gas-mass spectrometer
.

Five, pre-treatment

(1) Solid waste leachate (refer to HJ299-2007)

Take two samples, one for determination of moisture content, and the other for toxicity leaching experiment
.

(1) Determining the moisture content: Weigh 50-100g of sample in a container with a lid, and dry it at 105°C until the relative deviation of the two weighing values ​​is less than ±1% when the weight is constant
.

(2) Seal the sample and place it in the refrigerator to cool to 4°C, weigh the sample with a dry mass of 40-50g (the sample diameter should be less than 9.
5mm, otherwise it will be crushed first), and quickly transferred to zero headspace extraction Device (ZHE)
.
After installing the ZHE, use an air pump or compressed gas to slowly pressurize and discharge the air
.

(3) According to the moisture content of the sample, calculate the volume of the required extract according to the liquid-solid ratio of 10:1 (L/kg), transfer the extract to the ZHE with a solution transfer pump, install the ZHE, and add slowly Press to exhaust the air and close the ZHE valve
.

(4) Fix the ZHE on the flip-type oscillating device, adjust the speed to 30±2r/min, and oscillate at 23℃±2℃ for 18h±2h
.
After the shaking stops, remove the ZHE, check whether the device is leaking (if leaks, sample and leaching again), collect the leaching solution with the same leaching solution collection device (Tedlar air bag can be used) that collects the initial liquid phase, and store it in refrigerator for analysis
.

Note: If the sample contains the initial liquid phase, it should be filtered
.
If the percentage of dry solids is less than or equal to 9% of the total sample volume, the initial liquid phase obtained is the leaching solution, which can be analyzed directly; if the percentage of dry solids is greater than 9% of the total sample volume, continue with the above leaching step, and the obtained diffusion The effluent is mixed with the initial liquid phase and analyzed
.

(5) Filtration: Use compressed air or pressure pump to filter the leaching liquid in ZHE under pressure, and store it in a cold storage at 4°C for processing
.

(6) Headspace analysis preparation:

Pipette 10mL extract, add a certain amount of internal standard and substitute solution (the on-board mass concentration is recommended to be consistent with the mass concentration of substitute and internal standard in the standard series), put it into the headspace instrument for automatic sample injection, and then connect to the GC -MS for analysis
.

(2) Solid waste samples

1.
Low-content solid waste samples (samples with predicted content lower than 100jg/kg)

Take the sample out of the refrigerated environment at 4°C and return to room temperature.
Weigh 2g of the sample and place it in a headspace bottle.
Quickly add 10 mL of matrix modifier, internal standard solution and substitute solution.
The mass concentration of the surrogate and the internal standard is the same), immediately sealed, on a shaker at a frequency of 150 times/min for 10 minutes, and wait for the headspace-GC/MS detection
.

2.
High-volume samples of solid waste (samples with predicted content higher than 100ug/kg)

Take out the sample bottle used for the high-content sample test and allow it to return to room temperature
.

Weigh 2g of sample into a headspace bottle, quickly add 10mL of methanol , seal, and oscillate on a shaker at a frequency of 150 times/min for 10 minutes
.
After standing and settling, use a disposable Pasteur glass pipette to pipette about 1 mL of the extract into a 2 mL brown glass bottle
.
After returning the extract to room temperature before analysis, add 2.
0 g of quartz sand, 10 mL of matrix modifier and 10 to 100 uL of methanol extract to the empty headspace bottle
.
Add the internal standard solution and the substitute solution (same as the low-content sample step), immediately seal, and oscillate on a shaker at a frequency of 150 times/min for 10 minutes, and wait for the headspace-CC/MS detection
.

Related Links: Solid Waste-Determination of Dioxins-Isotope Dilution High Resolution-Gas Chromatography-High Resolution Mass Spectrometry (4)