Soil and sediment Determination of petroleum hydrocarbons (C10-C40) by gas chromatography.
Reagents & Materials.
1.Reference Materials.
Petroleum hydrocarbons (C10-C40) mixed standard solution: 31000 mg L, solvent is n-hexane, 2Reagent.
2.1 n-hexane: chromatographically pure, 4L bottle;
2.2 Dichloromethane: chromatographic pure, 500ml bottle;
2.3 quartz sand: analytically pure, 500g bottle;
2.4. Diatomaceous earth: chromatographic pure, 1kg bottle;
3 consumables. 3.1 Flory silica purification cartridge: 1 g 6 ml
The standard solution is validated with a blank reagent and has no spurious peaks.
4. Standard text and original records.
1.Standard text.
The laboratory has issued a controlled version of the standard text of "Determination of Petroleum Hydrocarbons (C10-C40) in Soil and Sediment - Gas Chromatography" to the relevant testing personnel.
3.Monitoring reports.
The monitoring report has a fixed format and is also included in the quality management system.
5. Environment. Organic solvents are used in the pretreatment of petroleum hydrocarbons (C10-C40) projects, and ventilation equipment is provided in the pretreatment laboratory, and extraction, concentration and extraction purification can be carried out in a desktop fume hood, and the laboratory is equipped with air conditioning to maintain a temperature of 25, which can meet the needs of the pretreatment process, testing process and equipment of petroleum hydrocarbons (C10-C40) project.
The pre-treatment and testing laboratories of the petroleum hydrocarbon (C10-C40) project are organic pretreatment room and large instrument room 2, respectively, and there is no cross-infection of other projects in the adjacent area.
The staff of the project are equipped with gas masks, 3M activated carbon masks, rubber gloves, lab coats and other protective equipment.
Sixth, the experimental part.
1.Collection and storage of samples.
Samples were collected from brown grinding bottles with glass stoppers, and after sample collection, they were sealed and stored in the dark and refrigerated below 4 days, and the extraction was completed within 14 days. The extract 4 or less was sealed and stored in the dark, and the analysis was completed within 40 days.
2.Sample preparation.
Remove foreign matter from the sample and weigh about 10 g (accurate to 0.).01g) The sample was added to the mortar, an appropriate amount of diatomaceous earth was added, and ground into quicksand.
3.Preparation of specimens.
3.1 Extraction.
Using a high-throughput pressurized fluid extractor, the process is to take the washed extraction cell and tighten the bottom cap and place it vertically on a horizontal surface. Place a dedicated fiberglass membrane at the bottom and a dedicated funnel at the top. Weigh an appropriate amount of sample with a small beaker, carefully transfer the sample to the extraction pool through a special funnel according to the number, remove the funnel, tighten the cap, pick up the extraction cell vertically and steadily, tighten the caps at both ends, and put it vertically and smoothly into the sample tray of the pressurized fluid extraction device. Each cell corresponds to a clean receiving bottle, and the number of the cell and the receiving bottle corresponding to each sample is recorded. Once the conditions are set, the program is started and the instrument completes the extraction automatically.
Extractor conditions:
Carrier pressure: 07mpa
Heating temperature: 120
Extraction cell pressure: 10MPa
Nitrogen purge time: 60s
Number of extractions: 2 times.
3.2. Concentrate.
Place the receiving flask in a high-flux vacuum parallel concentrator and concentrate to 10ml。
3.3. Purification.
In turn, 10ml of n-hexane-dichloromethane mixed solvent and 10ml of n-hexane activated Flori silica were used to purify the cartridges. When the n-hexane on the column is nearly dry, all the concentrate is transferred to the purification column, and the effluent is collected, the concentrate collection device is washed with about 2ml of n-hexane, transferred to the purification column, and then the purification column is washed with 12ml of n-hexane, combined with the effluent, and concentrated to 10ml, to be tested.
4.Instrument conditions.
Injection port: temperature 320, splitless injection (splitless ratio 60:1), splitless time 075min, purging flow 50ml/min；
Program Heating:
Detector: 330, air flow 350ml min, tail blowing flow 30ml min, hydrogen flow 40ml min.
Column flow: 20ml/min；
5.Calibration curve drawing and sample determination.
5.1. Use a microsyringe to pipette an appropriate amount of the standard solution of petroleum hydrocarbons (C10-C40), dilute it with n-hexane, and mix well. Formulated into a standard series of petroleum hydrocarbons (C10-C40) with mass concentrations of 0 mg L, 248 mg L, 775 mg L, 1550 mg L, 3100 mg L, 9300 mg L.
4.2. Sample determination.
The specimen is measured according to the same instrument conditions as the calibration curve.
4.3. Blank test.
The same volume of quartz sand was taken, a blank sample was prepared according to the sample, and the measurement was carried out according to the same instrument conditions as the calibration curve.
5.Calculation and presentation of results.
5.1. Qualitative and quantitative analysis: qualitative according to the retention time of the reference material chromatogram, and the total peak area is quantified.
5.2 Result calculation.
The content of petroleum hydrocarbons (C10-C40) in the soil, calculated according to the formula:
Where: the content of petroleum hydrocarbons (C10-C40) in soil, mg kg;
Petroleum hydrocarbons (C10-C40 concentration, mg L;
Volume of extract after concentration and volume, ml;
m—sample volume (wet weight), g;
Soil dry matter content, %.
6. The detection limit and the lower limit of determination of the method.
When the sample size is 10When 0g, the volume is 10 ml, injection volume 1At 0ul, the detection limit of the method for extracting petroleum hydrocarbons in soil samples was 60 mg kg, the lower limit of determination is 24 mg kg.
Detection limit of 2 to 5 times the method. (The detection limit of the method was obtained by measuring 7 times with blank spiked 155ug ml).
7.Precision.
Relative standard deviation within the laboratory: standard curve point determination. (The standard curve points of 3100 mg l (310 mg kgmg l (496 mg kgmg l (697 mg kg) were measured 6 times in each of the three groups, and the results of the three groups were obtained).
8.Accuracy.
Sample spike method. (The standard solutions of 3100 mg L and 4960 mg L were added to the soil samples with a microsyringe and measured 6 times each, and two sets of results were obtained.) ）
Appendix: Table 1 Standard curve.
Table 2: Test data table of method detection limit and lower limit of determination.
Table 3 Data table of method precision test.
Table 4 Data sheet of method accuracy test.
Actual sample spike test data).
VII. Conclusions. 1.The ability and training of personnel, instruments and equipment, reagents and materials, standard texts, original records, and laboratory environment can all meet the conditions for the development of "Determination of Petroleum Hydrocarbons in Soil and Sediment (C10-C40) Gas Chromatography";
2.The linear range is r9996, to meet the requirements of "Determination of Petroleum Hydrocarbons in Soil and Sediment (C10-C40) Gas Chromatography".999 requirements;
3.The detection limit is 4mg kg, which meets the requirements of 6mg kg in the "Determination of Petroleum Hydrocarbons in Soil and Sediment (C10-C40) Gas Chromatography".
4.The precision is: 9%, which meets the precision range in the "Determination of Petroleum Hydrocarbons in Soil and Sediment (C10-C40) Gas Chromatography". 8%-4.5% requirement.
5.The accuracy is: 5%, which meets the accuracy range in the "Determination of Petroleum Hydrocarbons in Soil and Sediment (C10-C40) Gas Chromatography". 3%-109% requirement.