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On-site soil VOCs monitoring by Membrane Inlet Probe plus MS200 TOF MS ( work by Green River)

Photo
Geoprobe soil sampling on-site

Introduction

Schematic of probe

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.

Photo mounted on crawler

Experiment

Objectives

Use the MIP+MS200 TOF MASS to monitor the following chlorinated compounds in underground soil:

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).

Calibration graph for ChloroformCalibration graph for ChlorobenzeneCalibration graph for TrichloroethyleneCalibration graph for DichloromethaneCalibration graph for 1,2-chloroethaneCalibration graph for 1,1,2-trichloroethane

On-site test

Photo of MS200 on-site
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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