Determination of 13 semi-volatile organic compounds in solid waste leachate-gas chromatography-mass spectrometry (1)

1.

This method is suitable for the determination of semi-volatile organic content in solid waste leachate

Second, the principle of the method

By means of liquid-liquid extraction , the semi-volatile organic compounds in the leachate are extracted with dichloromethane , and after treatments such as concentration and purification, they enter the gas chromatography-mass spectrometer for detection

3.

(1) Dichloromethane : pesticide residue level

(2) Concentrated sulfuric acid: pure superior grade

(3) Concentrated nitric acid: pure superior grade

(4) Ultra-pure water: No interference from the target, it can be purchased or prepared in the laboratory

(5) Sodium chloride : pure superior grade

(6) Anhydrous sodium sulfate: pure top grade

(7) Extractant: Add a mixture of concentrated sulfuric acid and concentrated nitric acid with a mass ratio of 2:1 to ultrapure water (about 2 drops of 1L water) to make the pH 3.

(8) Semi-volatile organic compound standard solution: ρ=1000ug/mL, the solvent is n-hexane

(9) Internal standard: mixed standard solution of naphthalene-d8, acenaphthene-d10, qi-d12, perylene-d12, phenanthrene-d10, ρ=1000ug/mL, solvent is n-hexane

(10) decafluoro triphenylphosphonium : ρ = 10ug / mL, the solvent is n-hexane

Four, instruments and equipment

(1) High pressure filter

(2) Flip the oscillator

(3) Separation funnel: 250mL
.

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

(5) Chromatographic column: DB-35MS (30m×0.
32mm×0.
25um), or other equivalent capillary columns
.

(6) Concentration device: equipment with equivalent performance such as nitrogen blowing concentrator and rotary evaporator
.

Five, pre-treatment

(1) Preparation of solid waste leachate (refer to HJ/T299)

"Semi-Volatile Organic Compound Analysis Technology-Preparation of Sulfuric Acid and Nitric Acid from Leachate"

(2) Extraction

Take 200 mL of the extract in a separatory funnel, adjust the pH to slightly less than 2 with a 1:1 (volume ratio) sulfuric acid aqueous solution, add an appropriate amount of sodium chloride according to the sample , and dissolve; then add dichloromethane and acetone , and shake vigorously 10min (pay attention to outgassing), stand to separate layers; repeat the extraction two more times, combine the extracts, the volume of the three extracts are 30mL dichloromethane+10mL acetone , 20mL dichloromethane+10mL acetone, 20mL dichloromethane+ After 10mL of acetone, the extract is dehydrated by anhydrous sodium sulfate, concentrated by rotary evaporation to about 1mL, and a certain amount of internal standard solution is added (the on-board mass concentration is recommended to be consistent with the internal standard in the standard series), and it is ready to be tested on the machine
.

Note: When the sampling volume of the extract is 100mL, it is recommended to change the amount of dichloromethane to 15mL each time and acetone to 8mL each time
.

(3) Purification

Flori silica, silica gel, alumina, etc.
can be used for purification.
For the compounds in Table 3-7, concentrated sulfuric acid is not suitable for purification
.

Six, analysis and testing

(1) Instrument conditions (for reference only, can be adjusted appropriately according to the actual instrument)

(1) Gas chromatographic conditions: the temperature of the injection port is 280°C, the column flow rate is 1.
2mL/min, the splitless injection time is 1min, and the temperature of the transmission line (interface) is 280°C
.

(2) Mass spectrometry conditions: EI ion source, temperature 250℃, ionization energy 70eV
.
The SIM scan parameters are shown in Table 3-6
.

Table 3-6 SIM scan parameter table

According to the performance of the instrument and the relevant standard limit requirements, the data can also be collected in a full scan mode.
The full scan parameter is 50～550amu
.
The grouping situation can be adjusted according to the separation of each peak and the number of description points of each peak (usually more than 10)
.

(2) Retention time and standard curve

Using dichloromethane as the dilution solvent, prepare a standard series of more than 5 points (such as 0.
04ug/mL, 0.
10ug/mL, 0.
40ug/mL, 0.
60ug/mL, 0.
80 ug/mL, the mass concentration of the internal standard is 0.
6ug/mL), and the internal standard method is used for quantification
.
The retention time and qualitative and quantitative ions under the reference instrument conditions are shown in Table 3-7
.

Table 3-7 Retention time and qualitative and quantitative reference ions

Related Links: Solid Waste Leachate-Determination of Polychlorinated Biphenyls-Gas Chromatography (2)