A gas chromatography-quartz crystal microbalance for speciation of sulfur compounds in landfill gas.
A new method, based on separation with gas chromatography and detection with a quartz crystal microbalance, was used for the quantification of ethane-1-thiol, propane-1-thiol, ethyl methyl sulfide, propane-2-thiol, butane-2-thiol and butane-1-thiol. The analytical error, the analysis time and the general analytical performance are identical for gas chromatography-mass spectrometry (GC-MS) and gas chromatography-quartz crystal microbalance (GC-QCM). However, the GC-QCM method constitutes a low cost alternative to GC-MS for monitoring individual sulfur compounds in landfill gas. It is an easily assembled apparatus made with an injection device, a furnace, a column, a crystal cell and a quartz crystal.
Preparation and application of cryptand-coated piezoelectric crystal gas-chromatographic detector
A re-usable and sensitive cryptand-22-coated quartz-crystal membrane piezoelectric sensor with a homemade computer interface for signal acquisition and data processing was prepared and applied as a gas-chromatographic (GC) detector for various organic molecules. The oscillating frequency of the quartz crystal decreased due to the adsorption of organic molecules on cryptand-22. Effects of functional group, molar mass, steric hindrance and polarity of organic molecules on frequency responses of the cryptand-coated piezoelectric crystal detector were investigated. The cryptand-coated piezoelectric crystal GC detector had demonstrated high sensitivity for various polar organic molecules and good reproducibility when re-used. The frequency responses of the cryptand-coated crystal for various molecules were in the following order: carboxylic acids (RCOOH)≫primary amines (R-NH2)>alcohols (ROH)>secondary amines (R2NH)>tertiary amines (R3N)>ketones. More polar molecules exhibited better frequency responses. The effect of temperature and amount of coating on the frequency responses of cryptand-coated crystal GC detector were also investigated. The cryptand-coated piezoelectric crystal GC detector compared well with the commercial thermal conductivity detector (TCD).
Collection and analysis of trace organic vapour pollutants in ambient atmospheres
Abstract The technique by which organic contaminants in ambient air are analysed by adsorption on porous polymers and subsequent thermal desorption into a gas chromatograph is gaining in popularity. We present here an analysis of the adsorption characteristics of one of the commonly used adsorbents, Tenax-GC. The capacity of this adsorbent to collect a variety of organic vapours has been investigated with respect to changes in sampling flow-rate, temperature, vapour concentration and humidity. Safe sampling volumes are tabulated for 71 organic compounds, and a plot is presented for the interpolation of estimated values for unlisted compounds.