CE detection of chlorophenols Chlorophenols have been widely used as herbicides, pesticides, and wood preservatives. HPLC and GC are the standard methods for analyzing chlorophenols, but CE with UV-vis detection has also been used for analysis. John H. T. Luong and colleagues at the National Research Council Canada described the use of an amperometric detector instead for monitoring chlorophenols by CE. The amperometric cell consists of an Ag/AgCl reference electrode, a platinum counter electrode, and a gold working Amperometric detection cell and working electrode. electrode. Because the working electrode was large relative to the capillary inner diameter, good oxidaCE with amperometric detection suction efficiency without precise alignment cessfully measured pentachlorophenol in was possible. To maintain proper potensoil at 35 mg/kg, monitored the oxidation tials, they used a simple ungrounded volof chlorophenols by eerie sulfate, and foltammograph; they observed no disturlowed the photodegradation of pentachlobance in the electrophoretic potential or rophenol in the presence of titanium dioxcurrent. The detecting electrode also ide. (Environ. Sci. Technol. o997,31, maintained a steady baseline current. 1794-1800)
copy and imaging into a single system. They have built a high-speed imaging spectrometer system that analyzes micrometer-sized features in transmitted For analytical chemists, what the eye light with wavelengths that range from can't see is often valuable information. UV to near-IR (250-975 nm). Thomas Johansson and Anders Pettersson with the Swedish Pulp and Paper The instrument uses xenon and haloResearch Institute combined spectrosgen lamps, a motorized sample stage, microscope optics with slitdetermined field of view, three parallel optical recording channels, and a dispersive optical recording system with holographic gratings and charge-coupled device cameras. Objects can be visualized in different wavelengths, and a spectrum can be generated for each location. The system can measure objects UD to 900 urn x 27 mm with a SDectral resolution of better than 5 nm and a spatial resolution of better than 5 um The authors presented examples of wood fibers measured with the instrument bchematic diagram tor the imaging spectrometer (Rev Sci In%trum 1997 system. (Adapted with permission from Rev. Sci Instrum. 68 1962-711 Copyright 1997 American Institute of Physics.)
Images in many wavelengths
Analyzing PAH products Many polycyclic aromatic hydrocarbons (PAHs) are known to be potent mutagens and carcinogens. Interestingly, some environmental samples contaminated with PAHs have been found to be more carcinogenic than can be accounted for on the basis of total PAH content. One potential source of this increased carcinogenicity are PAH oxidation products such as polyaromatic quinones. However, measuring these trace oxidation products in complex environmental matrixes is difficult and will require new analytical methods. Guenter K. Eigendorf and colleagues from the University of British Columbia and the Royal Military College (both in Canada) described using GC/MS/MS in a quadrupole ion trap to detect polyaromatic quinones from a settling pond used by an aluminum smelter. Many of these same quinones were undetectable by standard GC/MS analysis because of interferences in the matrix. The researchers fragmented the molecular ion via collision-induced dissociation (CID), using resonant and nonresonant waveforms. This process yielded product ions corresponding to the loss of CO or, for alkylated compounds, CO plus CH3. CID conditions were optimized using anthroquinone and 2-methylanthraquinone. Nonresident CID provided the best characteristic spectra for confirmation, generating spectra with intense fragment ions, and molecular ion information. (Talanta 1 9 9 7 44 985-1001)
Background-subtracted mass spectrum from a nonresident GC/ MS/MS analysis of sediment extract. (Adapted with permission from Talanta. Copyright 1997 Elsevier Science.)
Analytical Chemistry News & Features, August 1, 1997 453 A
