Preconcentration and detection of chlorinated organic compounds and benzene Stephen T. Hobson, * Sabina Cemalovic and Sanjay V. Patel Received 3rd November 2011, Accepted 26th December 2011 DOI: 10.1039/c2an16053f Remote and automated detection of organic compounds in subsurface aquifers is crucial to superfund monitoring and environmental remediation. Current monitoring techniques use expensive laboratory instruments and trained personnel. The use of a filled tubular preconcentrator combined with a chemicapacitive detector array presents an attractive option for the unattended monitoring of these compounds. Five preconcentrator materials were exposed to common target compounds of subsurface remediation projects (1,1,2-trichloroethane, trichloroethylene, t-1,2-dichloroethylene, benzene, and perchloroethylene). Rapid heating of the tube caused the collected, concentrated effluent to pass over the surface of a chemicapacitive detector array coated with four different sorbent polymers. A system containing a porous ladder polymer and the sensor array was subsequently used to sample the analytes injected onto sand in a laboratory test, simulating a subsurface environment. With extended collection times, effective detection limits of 5  3 ppbV for 1,1,2-trichloroethane and 145  60 ppbV for benzene were achieved. Effects of the preconcentrator material structure, the collection time, and sensor material on the system performance were observed. The resultant system presents a solution for remote, periodic monitoring of chlorinated organic compounds and other volatile organic compounds in a soil matrix. Introduction As the dangers of exposure to organic compounds are becoming better understood, the regulations for the safe levels and moni- toring these compounds have also become more stringent. 1 Sensor systems to find and monitor contaminants in the subsurface are of interest to regulatory agencies and industrial concerns. Monitoring is particularly vital in residential areas near industrial or government sites where degreasing compounds were improperly used and disposed. These solvents can migrate into groundwater and residences (i.e. vapor intrusion) as they permeate the ground. 2 A recent study of wells reported that trichloroethylene (TCE) and perchloroethylene (PCE) occurred with a higher frequency in concentrations approaching the Maximum Concentration Level (MCL) for drinking water. 3 Current ‘‘direct push’’ or ‘‘push-probe’’ techniques typically analyze thermally desorbed vapors from subsurface contaminants. Analytical techniques include high performance liquid chroma- tography (HPLC) or gas chromatography (GC) in tandem with a mass spectroscopy. 4 Current ground and drinking water measurement and analyses are performed in accordance with the U.S. EPA’s specifications under method 502.2 and 551.1 utilizing trap and purge or liquid extraction followed by GC analysis. Site characterization and analysis penetrometer systems (SCAPS) have been used with different sensors/technologies to provide depth profiles and plume maps from contaminated sites. The ‘‘unit cost per sample’’ associated with the analyses of volatile organic compounds (VOCs) were: SCAPS Head Space VOC sensors ($564); direct push and offsite analysis ($1358); and conventional monitoring water well installation with offsite analysis ($2792). 5 SCAPS with laser induced fluorescence (LIF) has also been used to analyze fuels in situ underground. 6 Tech- nologies involved in these processes include membrane interface probes, fiber-optics for lasers, heaters for vaporizing contami- nates, or hydrosparge tubes and pumps to forcibly draw liquid or vapor samples to the surface for analysis. 7 A one-time measurement event may include up to 10 sampling locations and consume one tube per contaminant per sampling location, plus 1–2 additional tubes for quality control/quality assurance. This type of measurement is repeated monthly (or as needed) for the duration of the remediation process. Collection and transportation of samples introduces irreproducibility, contam- ination, and long time delays. Replacing the conventional methods with an inexpensive, automated, and reproducible process will enable wide spread deployments, fast action on possible alarms, and periodic process monitoring in remediation operations. In response to this need, Zellers and coworkers have reported on the development of instruments for the detection and quantification of chlorinated organic compounds. 8 Seacoast Science, Inc., 2151 Las Palmas Drive, Suite C., Carlsbad, CA, 92011, USA. E-mail: sthobson@seacoastscience.com; Fax: +760-268- 0662; Tel: +760-268-0083 1284 | Analyst, 2012, 137, 1284–1289 This journal is ª The Royal Society of Chemistry 2012 Dynamic Article Links C < Analyst Cite this: Analyst, 2012, 137, 1284 www.rsc.org/analyst PAPER Downloaded by RSC Internal on 04 January 2013 Published on 23 January 2012 on http://pubs.rsc.org | doi:10.1039/C2AN16053F View Article Online / Journal Homepage / Table of Contents for this issue