On-site soil VOCs monitoring by Membrane Inlet Probe plus MS200 TOF MS ( work by Green River)
Geoprobe soil sampling on-site
Introduction
The Geoprobe MIP system is a modern technique for soil VOCs sampling and monitoring. The system combines a Membrane Inlet Probe (MIP) and a GC-ECD/FID. The Geoprobe MIP is a driller equipped with a heated membrane inlet. When the probe is pushed underground, VOCs in the soil permeate through the membrane, leaving the water behind. A Nitrogen stream is delivered to the probe to bring the VOCs back to the GC-ECD/FID. In conventional operation, when the GC-ECD/FID signal rises, the nitrogen carrier gas is collected in a tedlar bag and sent to a GCMS laboratory for analysis of hazardous compounds.
When Geoprobe MIP is connected to an MS200, it becomes an on-site soil contaminant sampling and analysis system. MS200 is a high performance TOF mass spectrometer; it can do the qualification and quantification of VOCs in seconds. When the driller is pushing down, we can easily obtain the compound and concentration information as a function of the soil depth.
Experiment
Objectives
Use the MIP+MS200 TOF MASS to monitor the following chlorinated compounds in underground soil:
- Chloroform
- Chlorobenzene
- Trichloroethylene
- Tetrachloroethene
- Dichloromethane
- 1.2-chloroethane
- 1.1.2-trichloroethane
MS200 configuration
- Sampling time:
- 20sec
- Mass Range:
- 1-300amu
Sample preparation for calibration
Prepare 4 different concentrations of chlorinated compounds in 50L water tank. Immerse the MIP into the water tank then obtain the calibration curve of each compound.
| Chloroform | |||||
|---|---|---|---|---|---|
| con.(ppm) | Avg.(ppb) | ms200_1 | ms200_2 | ms200_3 | ms200_4 |
| 20 | 23.93 | 21.7 | 29.3 | 22.8 | 21.9 |
| 40 | 42.25 | 41.8 | 42.7 | 40.1 | 41.8 |
| 60 | 54.43 | 52.3 | 54.6 | 54.6 | 56.2 |
| 100 | 92.35 | 92.2 | 92.5 | 97.6 | 99.3 |
| Chlorobenzene | |||||
|---|---|---|---|---|---|
| con.(ppm) | Avg.(ppb) | ms200_1 | ms200_2 | ms200_3 | ms200_4 |
| 20 | 21.33 | 21.3 | 22.7 | 21.9 | 19.4 |
| 40 | 42.55 | 42.8 | 42.3 | 41.8 | 40.5 |
| 60 | 57.45 | 55.3 | 59.6 | 63.4 | 61.2 |
| 100 | 105.10 | 100.6 | 104.5 | 107.7 | 107.6 |
| Trichloroethylene | |||||
|---|---|---|---|---|---|
| con.(ppm) | Avg.(ppb) | ms200_1 | ms200_2 | ms200_3 | ms200_4 |
| 20 | 22.63 | 23.3 | 24.8 | 20.2 | 22.2 |
| 40 | 44.35 | 41.4 | 44.3 | 45.3 | 46.4 |
| 60 | 61.30 | 60.5 | 61.6 | 61.8 | 61.3 |
| 100 | 104.10 | 109.5 | 101.6 | 101.7 | 103.6 |
| Dichloromethane | |||||
|---|---|---|---|---|---|
| con.(ppm) | Avg.(ppb) | ms200_1 | ms200_2 | ms200_3 | ms200_4 |
| 20 | 24.00 | 21.3 | 21.3 | 25.3 | 28.1 |
| 40 | 37.675 | 37.3 | 38.5 | 36.2 | 38.7 |
| 60 | 63.725 | 63.7 | 61.2 | 63.9 | 66.1 |
| 100 | 106.1 | 102.3 | 109.6 | 105.1 | 107.4 |
| 1,2-chloroethane | |||||
|---|---|---|---|---|---|
| con.(ppm) | Avg.(ppb) | ms200_1 | ms200_2 | ms200_3 | ms200_4 |
| 20 | 22.85 | 20.9 | 23.8 | 24.3 | 22.4 |
| 40 | 44.50 | 44.2 | 44.6 | 44.8 | 44.4 |
| 60 | 63.00 | 65.9 | 60.2 | 64.3 | 61.6 |
| 100 | 132.33 | 130.1 | 137.2 | 141.6 | 120.4 |
| 1,1,2-trichloroethane | |||||
|---|---|---|---|---|---|
| con.(ppm) | Avg.(ppb) | ms200_1 | ms200_2 | ms200_3 | ms200_4 |
| 20 | 26.68 | 24.2 | 26.6 | 27 | 28.9 |
| 40 | 49.40 | 48.8 | 50.2 | 49.3 | 49.3 |
| 60 | 60.75 | 59.6 | 60.6 | 62.1 | 60.7 |
| 100 | 101.80 | 101.6 | 101.3 | 102.6 | 101.7 |
We find that there is roughly a ratio of 1000 between the concentration in water (ppm) and the vapour concentration measured by the MS200 (ppb).
On-site test
| Component name | Coefficient ( counts) | Calibrated concentration (ppm) |
|---|---|---|
| Trichloroethylene | 77042 | 1052 |
| Chlorobenzene | 31.09 | 0.1038 |
| Chloroform | 421.9 | 3.518 |
| Dichloromethane | 920.4 | 189.1 |
Conclusion
The MIP + MS200 TOF-MS system provides a fast and accurate on-site soil VOCs detection solution. You don't need to collect lots of sample and don't need to wait a long time to get the result. When use this system in soil remediation, it reduces the time to find the contaminated area significantly.
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Last updated: 10:52 24/06/2016
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