Application of the membrane interphase probe (MIP): an evaluation

Abstract

Background, aim, and scope The membrane interphase probe (MIP™) from Geoprobe Systems® has frequently been applied in different countries for the characterization of soil contaminated with volatile organic carbons (VOCs). Experience shows that misinterpretation of the collected data is common. This is mainly due to the lack of understanding and knowledge related to the detectors used, their detection limits, and the sensitivity of the MIP system. It has been noticed that the sensitivity of the system given by the producer and by different users are rather optimistic, e.g., the values given are lower (= better) than those actually experienced in the field. A need for a better understanding of the MIP system sensitivity, combined with a more scientifically based interpretation of the collected data, exists. Materials and method Both laboratory tests (using solutions) as well as field measurements were carried out using different detector configurations to allow a better interpretation of the detector signals/system sensitivity and to collect qualitative information. These configurations were:(1) detectors stand alone; (2) the use of a 2-ml sample loop, and (3) a purge and trap system. The configurations (2) and (3) are used in combination with a capillary column to carry out on-site qualitative and semiquantitative analyses. Results and discussion With respect to the configuration of "detectors stand alone," detection limits for toluene (in aqueous solutions) range between 4 ppm (flame ionization detector-FID) and 10 ppm [photo ionization detector (PID)]. For chlorinated aliphatic hydrocarbons (CAHs), observed limits are 10 ppm (FID), 4-50 ppm (PID), and 3-10 ppm [dry electrolytic conductivity detector (DELCD)]. When using the 2-ml sample loop, relatively high concentrations have to be initially present in the soil. Observed detection limits for mono-aromatic hydrocarbons are 5-100 ppm; for CAHs, 1-50 ppm; for alkanes, 250-400 ppm; and for MTBE, 25 ppm. The application of purge and trap results in a better resolution and the detection of lower concentrations. Consequently, a better identification of the pollution with depth is possible. In this case, the detection limits are a function of the concentrations and the flushing time. In relation to the qualitative analyses, it was found that the configuration of the MIP-system with the built-in capillary column and the 2-ml sample loop or the purge and trap preconcentrator, respectively, are useful to carry out on-site analyses, thus allowing a better identification of the pollution in a vertical profile. Conclusions The measurements carried out using the MIP with detectors stand-alone or in combination with a loop or trap, or connected to a column, confirm that analysis is indeed very useful to characterize VOC source zones when knowing and understanding its performance. This relates mainly to the detection limits of the MIP system. For a selection of parameters, such limits have been obtained. These values seem to be more realistic than those found in the few referen...

Membrane Interface Probe Protocol for Contaminants in Low‐Permeability Zones

“…In areas where concentrations are lower (down to about 0.1 mg/kg), the ECD was more useful because of its greater sensitivity to PCE and TCE and therefore lower detection limits. These detection limits are similar to those cited by Ravella et al () for the MIP ECD (200 µg/L PCE or TCE) but lower than those cited by Bronders et al () for the MIP PID (10 mg/L TCE, 50 mg/L PCE).…”

“…(2) "Standard" is based on standard protocol for MIP use detailed by ASTM (2012) and/or the baseline value used as part of this project (see Tables 1 and 2). PCE or TCE) but lower than those cited by Bronders et al (2009) for the MIP PID (10 mg/L TCE, 50 mg/L PCE). The disparity in ECD response to compounds having two chlorine atoms (i.e., cis-1,2-DCE) vs. compounds having three or more chlorine atoms (i.e., TCE and PCE) likely introduced variability and complicated data interpretation.…”

Delineation of subsurface hydrocarbon contamination at a former hydrogenation plant using spectral induced polarization imaging

“…This method allows the measurement of the distribution of hydrogeological, geotechnical and geophysical properties along a vertical profile by advancing small probes into the subsurface (Lessoff et al, 2010;Schulmeister et al, 2003). It is also applicable for the highly resolved characterization of contamination patterns and for delineation of contaminant source areas and plumes by direct sampling (Rein et al, 2011) or by indirect methods, for example, by screening for volatile organic compounds (Bronders et al, 2009). Though the minimally invasive direct push technology is comparably time and cost efficient, a large number of soundings is often necessary to reliably characterize contaminated sites.…”

Carry‐Over Effects of the Membrane Interface Probe

“…However, experience gathered from field and laboratory testing has indicated that the application of this system (and therefore interpretation and assessment of measured results) is not always straightforward (Bronders et al 2009). Often results are misinterpreted, for example, when attempting to quantify concentrations of contaminants in the soil or groundwater.…”