HJ 642-2013Soil and sediment. Determination of volatile organic compounds-Headspace-gas chromatography/mass method (English PDF)

5.3 Sodium chloride (NaCl). excellent grade pure

After burning at 400 ° C for 4 h in a muffle furnace, it was placed in a desiccator and cooled to room temperature, and transferred to a ground glass bottle for storage.

5.4 Phosphoric acid (H3PO4)). excellent grade pure.

5.5 Matrix modifier

Measure 500ml of experimental water (5.1), add a few drops of phosphoric acid (5.4) to adjust pH <= 2, add 180g of sodium chloride (5.3), Dissolve and mix. Store at 4 ° C for 6 months.

5.6 Standard stock solution. rho=1000 mg/L~5000 mg/L

Standard certified solutions can be purchased directly or in standard materials.

5.7 Standard use solution. rho=10 mg/L~100 mg/L.

Volatile targets such as dichloromethane, trans-1,2-dichloroethylene, 1,2-dichloroethane, cis-1,2-dichloroethylene and chloroacetate Standard intermediates such as olefins must be prepared separately, and the storage period is usually one week. The standard use solution of other targets is stored in compact.

The shelf life is one month or prepared according to the manufacturer's instructions.

5.8 Internal standard solution. rho=250 mg/L

Fluorobenzene, chlorobenzene-d5 and 1,4-dichlorobenzene-d4 were selected as internal standards. A certified standard solution can be purchased directly.

5.9 Alternative standard solution. rho=250 mg/L

Toluene-d8 and 4-bromofluorobenzene were used as substitutes. A certified standard solution can be purchased directly.

5.10 4-bromofluorobenzene (BFB) solution. rho=25 mg/L the certified standard solution can be purchased directly or can be prepared with a high concentration standard solution.

5.11 Quartz sand. 20~50 mesh. Before use, it is necessary to pass the test to confirm that the concentration of the target compound or target compound is lower than the method.

The detection limit.

5.12 Carrier gas. high purity helium, >=99.999%, deoxidized by deoxidizer, dehydrated by molecular sieve.

Note 1. All the above standard solutions are treated with methanol as the solvent. The standard solution after preparation or unsealing should be placed in a compact bottle, and protected from light under 4 °C.

Save, the shelf life is generally 30d. Recover to room temperature and mix before use.

7.1 Sample collection and preservation

7.1.1 Sample Collection

Soil samples were collected and stored in accordance with the relevant regulations of HJ/T 166. In accordance with the relevant provisions of GB 17378.3 Collection and storage of sediment samples. The tool for collecting samples should be applied to metal products and should be purified before use. Can be taken Samples were screened at a high concentration and low concentration using a portable instrument for the determination of volatile organic compounds. All samples should be Collect at least 3 parallel samples.

Use a shovel or a medicine spoon to collect the sample into the vial (6.12) as soon as possible and fill it as much as possible. Quickly remove sample vial the sample adhered to the grain and the outer surface, and the sample bottle is sealed. Put it in a portable freezer and bring it back to the lab.

Note 2. When the concentration of volatile organic compounds in the sample is greater than 1000 µg/kg, the sample is regarded as a high content sample.

Note 3. Do not stir the soil and sediment during sample collection to avoid evaporation of organic matter in soil and sediment.

7.1.2 Sample storage

Samples should be analyzed as soon as they are sent to the laboratory. If it cannot be analyzed immediately, it should be sealed and stored below 4 °C, and the shelf life is not exceeded.

After 7 days. The sample storage area should be free of organic interference.

7.2 Preparation of samples

7.2.1 Low content sample

Remove the sample vial from the laboratory. After returning to room temperature, weigh 2g of the sample into the headspace bottle and quickly move it into the top empty bottle.

Add 10ml matrix modifier (5.5), 1.0µl substitute (5.9) and 2.0µl internal standard (5.8), immediately seal and oscillate the oscillation on the device was oscillated at a frequency of 150 times/min for 10 min, to be tested.

7.2.2 High content sample

If the preliminary screening of volatile organic compounds at the site is high or low, the determination result is greater than 1000µg/kg.

High content sample. High-content samples were prepared as follows, and the vials for high-content sample testing were removed and allowed to return to room temperature.

Weigh 2g of sample into the headspace bottle, quickly add 10 ml of methanol (5.2), seal, and shake on the shaker at 150 times/min the frequency oscillates for 10 min. After standing to settle, remove about 1 ml of extract with a disposable Pasteur glass pipette to 2 ml.

In a brown glass bottle, the extract can be centrifuged if necessary. The extract can be stored in a refrigerator at 4 ° C, guaranteed the deposit period is 14 days.

After returning the extract to room temperature before analysis, add 2 g of quartz sand (5.11), 10 ml of matrix to an empty headspace vial.

Modifier (5.5) and 10 to 100 µl methanol extract. Add 2.0 µl of internal standard (5.8) and substitute (5.9) and seal immediately.

Oscillation on the oscillator was oscillated at a frequency of 150 times/min for 10 min, to be tested.

Note 4. If the concentration of the target compound in the methanol extract is high, it can be appropriately diluted by adding methanol.

Note 5. If the concentration value is too low or not detected by the high content method, the sample should be re-analyzed using the low content method.

7.3 Preparation of blank samples

7.3.1 Low content blank sample

Replace the sample with 2g quartz sand and prepare a low content blank sample according to the procedure of 7.2.1.

7.3.2 High content blank sample

Replace the high-content sample with 2g quartz sand (5.11) and prepare a high-content blank sample according to the procedure in 7.2.2.

7.4 Determination of moisture

The moisture content of the soil sample is determined according to HJ 613, and the moisture content of the sediment sample is determined according to GB 17378.5.

Row.

8.1 Instrument Reference Conditions

Different working conditions of different models of headspace sampler, gas chromatograph and mass spectrometer should be different according to the instructions of the instrument.

The book is operated. The recommended reference conditions for this standard are as follows.

8.1.1 Headspace Sampler Reference Conditions

Heating equilibrium temperature 60~85 °C; heating equilibrium time 50 min; sampling needle temperature 100 ° C; transmission line temperature 110 ° C;

The transfer line is deactivated and has a quartz capillary column with an inner diameter of 0.32 mm; the pressure equalization time is 1 min; when injecting 0.2 min; needle setting time 0.4 min; headspace bottle pressure 23 psi.

8.1.2 Gas Chromatograph Reference Conditions

Temperature programmed. 40 ° C (for 2 min) 8 ° C/min 90 ° C (for 4 min) 6 ° C/min.200 ° C (guarantee Hold 15 min).

Inlet temperature. 250 °C. Interface temperature. 230 °C. Carrier gas. helium; inlet pressure. 18 psi. Injection method.

Split injection, split ratio. 5.1.

8.1.3 Mass Spectrometer Reference Conditions

Scanning range. 35 amu~300 amu. Scan speed. 1 sec/scan. Ionization energy. 70 eV. Ion source temperature.

230 °C. Quadrupole temperature. 150 °C. Scan mode. full scan (SCAN) or selective ion (SIM) scan.

8.2 Calibration

8.2.1 Instrument performance check

The GC/MS system must perform an instrument performance check before daily analysis. Pipette 2µl of BFB solution (5.10) Direct injection through the GC inlet and analysis by GC/MS. The critical ion abundance of BFB obtained by GC/MS system should be Meet the criteria specified in Table 1, otherwise some parameters of the mass spectrometer need to be adjusted or the ion source cleaned.

Table 1 4-bromofluorobenzene ion abundance standard

Mass-to-charge ratio ion abundance standard mass-to-charge ratio abundance standard 95 base peak, 100% relative abundance 175 mass 174 5% to 9% 96% 95% 5% to 9% 176 Quality 95% to 105% 174 173 is less than 25% of mass 174 177 is 5% to 10% of mass 176 174 is greater than 50% of mass 95

8.2.2 Drawing of the calibration curve

Add 2 g of quartz sand (5.11), 10 ml of matrix modifier (5.5) to the 5 top empty bottles, and then divide into each bottle.

Do not add a certain amount of standard use solution (5.7), the target compound concentration is 5, 10, 20, 50, 100µg/L;

Add a certain amount of substitute (5.9) to each headspace bottle, and add 2.0µl of internal standard solution (5.8), immediately seal. The concentration of the calibration series is shown in Table 2. The configured standard series sample is oscillated on the oscillator at a frequency of 150 times/min Oscillate for 10 min, analyze the samples from low to high concentrations, draw a calibration curve or calculate the average response factor. In this standard the standard total ion chromatogram of 36 volatile organic compounds was determined by standard conditions, as shown in Figure 1.

Table 2 Calibration Series Concentration

Calibration series concentration (µg/L) Substitute concentration (µg/L) Internal standard concentration (µg/L) 1-chloroethylene; 2-1,1-dichloroethylene; 3-dichloromethane; 4-trans-1,2-dichloroethylene; 5-1,2-dichloroethane; 6-cis-1, 2-dichloroethylene; 7-Chloroform; 8-1,1,1-trichloroethane; 9-carbon tetrachloride; 10-1,2-dichloroethanebenzene; 11-fluorobenzene (internal standard 1); 12-trichloroethylene; 13-1,2-Dichloropropane; 14-bromodichloromethane; 15-toluene-d8 (alternative 1); 16-toluene; 17-1,1,2-trichloroethane; 18-tetrachloroethylene; 19-two Bromochloromethane; 20-1,2-dibromoethane; 21-chlorobenzene-d5 (internal standard 2); 22-chlorobenzene; 23-1,1,1,2-tetrachloroethane; 24- Ethylbenzene; 25-room-Xylene p-xylene; 26-o-xylene styrene; 27-bromoform; 28-4-bromofluorobenzene (substitute 2); 29-1,1,2,2-tetrachloroethane;

30-1,2,3-trichloropropane; 31-1,3,5-trimethylbenzene; 32-1,2,4-trimethylbenzene;

33-1,3-dichlorobenzene; 34-1,4-dichlorobenzene-d4 (internal standard 3); 35-1,4-dichlorobenzene; 36-1,2-dichlorobenzene; 37-1 , 2,4-trichlorobenzene; 38-six Chloroprene.

Figure 1 36 kinds of volatile organic compounds standard total ion flow diagram

8.2.2.1 Establishing a calibration curve with an average relative response factor

The relative response factor (RRFi) of the target (or surrogate) in point i of the standard series, calculated according to formula (1) Count.

ISi

ISi

ARRF rho

rho×= (1)

In the formula.

The relative response factor of the i-th target (or surrogate) in the RRFi-standard series;

The response value of the quantified ion of the i-th target (or substitute) in the Ai-standard series;

The i-th point in the AISi-standard series corresponds to the target (or substitute) corresponding to the internal standard quantitation ion response value;

The concentration of the internal standard in the rhoIS-standard series, 50 µg/L;

The mass concentration of the i-th target (or substitute) in the rhoi-standard series, µg/L.

The average relative response factor RRF of the target (or substitute) is calculated according to formula (2).

RRF

RRF

Isum

In the formula.

RRF - the average relative response factor of the target (or substitute);

RRFi--the relative response factor of the i-th target (or substitute) in the standard series;

n--Standard series points, 5.

The standard deviation of RRF is calculated according to formula (3).

RRFRRF

The relative standard deviation of RRF is calculated according to formula (4).

RRF

SDRSD (4)

The relative standard deviation (RSD) of the relative response factor (RRF) of the standard series of targets (or substitutes) should be less than at 20%.

8.2.2.2 Drawing a calibration curve using least squares

The ratio of the response of the target compound to the corresponding internal standard is plotted on the ordinate, and the concentration ratio is plotted on the abscissa, which is established by least squares method.

Calibration curve. If the correlation coefficient of the established linear calibration curve is less than 0.990, a nonlinear fitting curve can also be used.

For line calibration, the curve correlation coefficient needs to be greater than or equal to 0.990. When using a non-linear calibration curve, at least 6 concentration points should be used Perform calibration.

8.3 Determination

The prepared sample (7.2) was placed on a headspace sampler and measured according to the instrument reference conditions (8.1).

8.4 Blank test

The prepared blank sample (7.3) was placed on a headspace sampler and measured according to the instrument reference conditions (8.1).

9.1 Qualitative analysis of target compounds

The target is characterized by relative retention time (or retention time) and by comparison to a standard material mass spectrum.

9.2 Quantitative analysis of targets

The calculation is based on the response value of the first characteristic ion of the target and the internal standard. When the first characteristic ion of the target in the sample has for interference, the second characteristic ion quantification can be used, see Appendix B for details.

9.2.1 Calculation of the mass concentration rhoex of the target (or substitute) in the sample

9.2.1.1 Calculated using the average relative response factor

When the target (or substitute) is calibrated using the average relative response factor, the mass concentration of the target in the sample is rhoex Calculate according to formula (5).

RRFA

ISx

×= rhorho (5)

In the formula.

rhoex - the mass concentration of the target (or substitute) in the sample, µg/L;

Ax -- the target (or substitute) quantified ion response value;

AIS - the response value of the internal standard quantitative ion corresponding to the target (or substitute);

rhoIS - concentration of internal standard, µg/L;

RRF - The average relative response factor of the target (or surrogate).

9.2.1.2 Calculation with linear or nonlinear calibration curves

When the target is calibrated using a linear or non-linear calibration curve, the target mass concentration rhoex in the sample passes the corresponding the calibration curve is calculated.

9.2.2 The content of volatile organic compounds (µg/kg) in low-content samples is calculated according to formula (6).

) 100 (

××= rhoomega (6)

In the formula.

ohm-content of the target compound in the sample, µg/kg;

Exrho - calculate the concentration of the target compound (or substitute) based on the response factor or calibration curve, µg/L;

10-base modifier volume, ml;

W-water content of the sample, %;

M-sample amount (wet weight), g.

9.2.3 The content of volatile organic compounds (µg/kg) in high-content samples is calculated according to formula (7).

Cex

Vwm

) 100 (

ohmomega (7)

In the formula.

omega - the content of the target compound in the sample, µg/kg;

Exrho -- calculate the concentration of the target compound based on the response factor or calibration curve, µg/L;

10 - matrix modifier volume, ml;

Vc - extract volume, ml;

m -- sample amount (wet weight), g;

Vs - volume of methanol extract used for headspace determination, ml;

w -- the moisture content of the sample, %;

K - dilution ratio of the extract.

Note 6. If the sample moisture content is greater than 10%, the extract volume Vc should be the sum of the volume of methanol and water in the sample; if the sample moisture content is less than Equal to 10% and Vc is 10 ml.

9.3 Result representation

9.3.1 When the measurement result is less than 100 µg/kg, one digit after the decimal point is retained; when the measurement result is greater than or equal to 100 µg/kg Keep 3 significant digits.

9.3.2 When using the capillary column specified in this standard, the two peaks of meta-xylene and para-xylene are inseparable, and their content is the sum of the two.

10.1 Precision

Six laboratories measured the uniform samples of soil and sediment at two different levels.

When the concentration of volatile organic compounds in the soil is about 100µg/kg and.200µg/kg, the relative standard deviation range in the laboratory is divided.

Not 1.1% to 13% and 1.4% to 15%; the relative standard deviation between laboratories is 1.8% to 14% and 6.7%, respectively.

17%; the repeatability limits ranged from 8.8 to 19.4 µg/kg and 32.5 to 116 µg/kg, respectively; the reproducibility limits rang...