Membrane Interface Probe (MIP)

Membrane Interface Probe (MIP) testing is a fast, highly repeatable and cost effective means of mapping out contaminant plumes. It is a means of continuous gaseous sampling, with depth, which can repeatedly build a profile of contamination on site. The results are viewed real-time allowing for scope flexibility and ongoing evaluation of the investigation. A discrete soil samples – MOSTAP, Shelby or water – can be deployed for verification. Lankelma have a Geoprobe Heated Trunk Line system which increases both reliability and productivity.

Principles

Using hydraulic push, a 46 mm probe is advanced into the ground and paused every 33 cm to allow a raised heater block to act on the soil and vaporise any Volatile Organic compounds (VOCs) present. The probe consists of a gas permeable membrane connected via a trunk line to a Gas Chromatograph (GC) on the CPT rig. The GC has three detectors and Electrical Conductivity (EC) is also measured from 2 x EC dipoles on the probe.

Results are compared to pre-response tests carried out prior to testing to semi-quantify the findings.

  1. Photo Ionisation Detector (PID)– For detection of <10.6 eV compounds. – (>1 part per million)
  2. Flame Ionisation Detector (FID) – For detection of all hydrocarbons. – (>10 parts per million)
  3. Dry Electrolytic Conductivity Detector (DELCD) – For detection of chlorinated/brominated species. – (>1 part per million)

Deliverables and R&D

Lankelma offer a detailed MIP report including compound pre-response test graphical comparison. MIP plots provide a dual-scale representation of VOC contamination, to compensate for the large range in contaminant concentration, as well as a log scale depiction of basic soil type for granular and cohesive materials from the probe’s electrical conductivity detector. Profiles are built of VOCs and their detector responses.

With the recent advances in MIP reporting, we are committed to continuing our environmental R&D. As part of our ongoing research we are detailing the capability of the MIP overall. We have identified FID/PID detector response to carbon chain length of C2-C14 compounds, PID response to C6 compounds across differing functional groups (Alkanes/Alkenes/Alkynes) & different halogenated C2 compounds to DELCD response.