Selective detection of nitrogen and oxygen containing volatile organic compounds: use of metal-modified polysiloxanes as sensor coatings

Determination of carbon monoxide using a coated quartz crystal sensor

Carbon monoxide was detected and determined by a piezoelectric quartz crystal sensor coated with nickel(II)-phthalocyanine 50 % (v/v) solution in glycerine. Studies on the effect of temperature, flow rate, and some possible interferents were carried out. Calibration curves, sensor stability (lifetime) and the precision of measurements were also verified. The resulting selectivity is probably due to the coordinative binding between the electronically unsatured metal complexes and the analyte. The analytical curve is linear in the concentration range 0.10 to 1.0 % (v/v).

Practice and theory of enantioselective complexation gas chromatography

The practice and theory of enantioselective complexation GC is comprehensively reviewed for the first time. A multitude of racemic oxygen-, nitrogen- and sulfur-containing selectands can be separated without prior derivatization into enantiomers by complexation GC on optically active metal(II) bis[3-(perfluoroacyl)-(1R)-camphorate] selectors. Peak inversion is obtained when the selectors with opposite configuration are employed. Applications pertain to chiral analysis in asymmetric synthesis, enzymatic reactions, pheromone and flavour chemistry. Although the use of enantioselective complexation GC has diminished recently with the advent of modified cyclodextrins in enantioselective GC, the inherent principles of enantiorecognition together with other enantioselective phenomena can be elucidated easily by complexation GC. Using the concept of the retention-increment R' which allows the distinction between non-enantioselective and enantioselective contributions to retention, concise thermodynamic parameters of enantioselectivity - deltaD,L(deltaG) are accessible. The enantiomerization of configurationally labile enantiomers can be investigated and quantified by complexation GC. Four distinct enantioselective processes and four different coalescence phenomena have been discerned in complexation GC.

Effective use of molecular recognition in gas sensing: results from acoustic wave and in situ FT-IR measurements

To probe directly the analyte/film interactions that characterize molecular recognition in gas sensors, we recorded changes to the in situ surface vibrational spectra of specifically functionalized surface acoustic wave (SAW) devices concurrently with analyte exposure and SAW measurement of the extent of sorption. Fourier transform infrared external-reflectance spectra (FT-IR-ERS) were collected from operating 97-MHz SAW delay lines during exposure to a range of analytes as they interacted with thin-film coatings previously shown to be selective: cyclodextrins for chiral recognition, nickel camphorates for Lewis bases such as pyridine or organophosphonates, and phthalocyanines for aromatic compounds. In most cases where specific chemical interactions--metal coordination, "cage" compound inclusion, or pi-stacking--were expected, analyte dosing caused distinctive changes in the IR spectra, together with anomalously large SAW sensor responses. In contrast, control experiments involving the physisorption of the same analytes by conventional organic polymers did not cause similar changes in the IR spectra, and the SAW responses were smaller. For a given conventional polymer, the partition coefficients (or SAW sensor signals) roughly followed the analyte fraction of saturation vapor pressure. These SAW/FT-IR results support earlier conclusions derived from thickness-shear mode resonator data.