Membrane Interface Probe - MIP
ZEBRA is a Geoprobe Certified MIP Service Specialist
How It Works
The Membrane Interface Probe (MIP) is a percussion tolerant VOC sensor that can continuously log volatile organics that diffuse through a semi-permeable membrane.
Using a carrier gas, the VOCs are brought to the surface through tubing which is connected to a laboratory grade ECD, PID & FID for immediate analysis. ZEBRA is currently using an 0.I. Analytical Model 4410 Flame Ionization Detector and an 0.I. Analytical Model 4430 Photo ionization Detector. In response to our client's requests to use the MIP on sites where chlorinated solvents were present, ZEBRA has added an Electron Capture Device (ECD) to the MIP system. To enhance the system ZEBRA is currently using custom made PEEK trunklines to reduce the carry over effect produced by logging in areas of highly concentrated contamination. Peek allows the detectors to return to baseline level quicker then teflon, reducing the down time between high concentration points.
ZEBRA has completed the installation of two MIP systems on a 4x4 Diesel Mule and a 4X4 John Deere Gator. These "data acquisition vehicles" will work with any of our Direct Push units at any location on the East Coast. One of the significant advantages of 
ZEBRA’s MIP data acquisition vehicles is that they are completely self contained (including a full set of Direct Push 1.5" probe rods pre-strung with the data trunkline) in order to allow the on site ZEBRA Direct Push unit to quickly change from driving the MIP rods to collecting soil and groundwater samples, installing monitoring points or injecting Bio-Remediation compunds. ZEBRA can provide you with a wide variety of options in the field that will allow you to respond to the data you receive from the MIP/Conductivity system. ZEBRA data acquisition vehicles have the smallest footprint in the industry allowing them to move from point to point, in the woods, inside buildings, and other areas of limited access.
ZEBRA is one of the few probing contractors in the country that has experience working with the system and we are one of few companies on the East Coast that owns two MIP systems. ZEBRA completed an extensive subsurface investigation project at a former industrial facility located in New York. As part of the project, ZEBRA mobilized two MIP units to the site. Both MIP units worked on site for twenty eight (28) days and performed extremely well by identifying the presence and relative concentrations of volatile organic contaminants.
Read the Probing Times Article
The data collected with the membrane probe compared favorably to the existing, laboratory grade analytical data already available. Recently, ZEBRA has successfully completed several large projects utilizing the MIP system.
Probe Animation
An integral part of the MIP system is the direct sensing soil conductivity system. This system utilizes a specially designed probe that will withstand the rigors of percussion probing while taking continuous measurements of soil conductivity as it is being driven into the ground. The sensing probe is linked to a control box where the signal is received by a field computer. The signal from the probe is matched with precise depth measurements and logged on the screen. The consultant is able to read real time data showing changes in soil conductivity/resistivity. These changes can be used to identify lithology, contaminant plumes, salt water intrusion, or any other subsurface condition that displays a change in conductivity/resistivity.
MIP Detectors
Detector |
Contaminates |
Limit |
Carrier Gas |
PID |
BTEX | 1 ppm | Nitrogen, Helium, Compressed Air |
FID |
Methane, Butane | N/A | Nitrogen, Helium, Compressed Air |
ECD |
Chlorinateds (TCE, PCE) | 250 ppb | Nitrogen, 95% Argon, 5% Methane |
XSD |
Chlorinateds (TCE, PCE) | 1 ppm | Nitrogen, Helium, Compressed Air |
DELCD |
Chlorinateds (TCE, PCE) | 1 ppm | Nitrogen, Helium, Compressed Air |
*Limiting factors: signal to noise ratio, length of trunkline, membrane wear
Flow and Pressure
Controller |
100 ft Trunkline |
150 ft Trunkline |
| Primary Gauge | 20 psi (136 kPa) | 20 psi (136 kPa) |
| Mass Flow Controller | 7-12 psi (47,6-81,6 kPa) | 9-15 psi (61,2-102 kPa) |
| Probe Flow | 20-60 mL/min* | 20-60 mL/min* |
| Dryer Flow | 2 × Probe Flow | 2 × Probe Flow |
Testing
Test Type |
Response |
Sanity |
Geoprobe Recommendation |
yes |
no |
Known Concentrations |
yes |
no |
Most Reliable/Consistent |
yes |
no |
Trip Time Testing Only |
no |
yes |
Membrane/System Testing |
yes |
no |
