The trace volatile organic compounds (VOCs) in landfill gas were examined at seven U.K. waste disposal facilities. Over 140 compounds were identified, of which more than 90 were common to all seven sites. The groups of compounds and concentrations observed were alkanes, 302−1543 mg m-3; aromatic compounds, 94−1906 mg m-3; cycloalkanes, 80−487 mg m-3; terpenes, 35−652 mg m-3; alcohols and ketones, 2−2069 mg m-3; and halogenated compounds, 327−1239 mg m-3. The observed variations in landfill gas composition were largely attributed to differ ences in the waste composition and the stage reached in the decomposition processes at each of the sites. Three sites were found to have total chlorine concentrations, derived from the organochlorine compounds in the gas, of above 250 mg m-3. Chlorine contents of this level were considered to be potentially damaging to landfill gas fueled engines used for electricity generation. Chloroethene (>0.1−87 mg m-3) was identified as the most abundant toxic component. Chloroethene levels in the landfill gases from two of the sites studied were found in excess of the U.K. maximum exposure limit by a factor of 5 and 3. Total VOCs emissions from four of the seven sites studied were estimated to be of the order of 104 kg/yr.

A piezoelectric sensor coated with an artificial biomimetic recognition element has been developed for the determination of L-menthol in the liquid phase. A highly specific noncovalently imprinted polymer (MIP) was cast in situ on to the surface of a gold-coated quartz crystal microbalance (QCM) electrode as a thin permeable film. Selective rebinding of the target analyte was observed as a frequency shift quantified by piezoelectric microgravimetry with the QCM. The detectability of L-menthol was 200 ppb with a response range of 0-1.0 ppm. The response of the MIP-QCM to a range of monoterpenes was investigated with the sensor binding menthol in favor of analogous compounds. The sensor was able to distinguish between the D- and L-enantiomers of menthol owing to the enantioselectivity of the imprinted sites. To our knowledge, this is the first report describing enantiomeric resolution within an MIP utilizing a single monomer-functional moiety interaction. It is envisaged that this technique could be employed to determine the concentration of terpenes in the atmosphere.

An acoustic wave sensor coated with an artificial biomimetic recognition element has been developed to selectively screen for nandrolone in the liquid phase. A highly specific covalently imprinted polymer (MIP) was spin coated on to one electrode of a quartz crystal microbalance (QCM) as a thin permeable film. Selective rebinding of the nandralone was observed as a frequency shift in the QCM for concentrations up to 0.2 ppm with the sensor binding shown to favour nandrolone over analogous compounds.

A chemically coated piezoelectric sensor has been developed for the determination of PAHs in the liquid phase. An organic monolayer attached to the surface of a gold electrode of a quartz crystal microbalance (QCM) via a covalent thiol-gold link complete with an ionically bound recognition element has been produced. This study has employed the PAH derivative 9-anthracene carboxylic acid which, once bound to the alkane thiol, functions as the recognition element. Binding of anthracene via pi-pi interaction has been observed as a frequency shift in the QCM with a detectability of the target analyte of 2 ppb and a response range of 0-50 ppb. The relative response of the sensor altered for different PAHs despite pi-pi interaction being the sole communication between recognition element and analyte. It is envisaged that such a sensor could be employed in the identification of key marker compounds and, as such, give an indication of total PAH flux in the environment.