FOCUS
NEW MICROWAVE BOMBS
PAT. PENDING
Now in two sizes, 23 ml and 45 ml. The speed and convenience of microwave heating can now be applied to the digestion of inorganic, organic, or biological materials in a Teflon Lined Bomb. The new Parr Microwave Digestion Bombs have been designed to combine the advantages of closed high-pressure and high temperature digestion with the requirements of microwave heating. Many samples can be dissolved or digested with less than one minute heating times. As with all Parr Digestion Vessels, careful design and testing effort have gone into the safety and sealing aspects of this unique vessel and operating environment. Call or write for Bulletin 4781 with complete technical details.
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Nel Velthorst from the Free University of The Netherlands discussed recent advances in laser applications, especially for fluorescence in microcolumn chromatography and capillary electrophoresis (CE). According to Velthorst, low-temperature fluorescence line narrowing has very high selectivity for identification purposes. It can be used with thin-layer chromatography or as an off-line detection method in micro LC. A different type of detection scheme was discussed by Douglas Westerlund from Sweden's University of Uppsala. He reviewed methods for the indirect detection (photometric) of organic and inorganic analytes in reversed-phase HPLC. Indirect detection requires a probe compound with a large UV-absorbance or fluorescence, or strong electrochemical response as a mobilephase component. An injected sample produces migrating zones where the local mobile phase deviates from the bulk. Analytes will thus coelute where deficiencies or excesses of the probe—depending on charge and hydrophobicity—result in respectively negative or positive peaks (1,2). Velthorst also discussed indirect methods, describing results from Frei's laboratory on indirect UV-vis and fluorescence detection. Analyte ions affect the concentration of absorbing/ emitting compounds in the mobile phase or in a postcolumn addition, resulting in a negative peak. Luminescence-quenching techniques were also presented, wherein an added detector species with a long luminescence lifetime is efficiently quenched by the analyte. In addition, work was presented from C. Gooijer's laboratory at the Free University of The Netherlands on novel luminescence detection approaches, especially luminescence quenching of a Tb-acetylacetonate complex to determine inorganic ions under ion-pair, reversed-phase HPLC conditions. An overview of conventional, on-line HPLC electrochemical (EC) and fastscanning EC detection for normal and microcolumn modes was given by L. J. Nagels from the Rijksuniversitair Centrum Antwerpen in Belgium. He emphasized using very slow flow rates for microcolumn LC-EC interfacing and characterized a disposable copolymer EC detector for analyses at flow rates of < 10 /ig/min. Several symposium speakers described EC detection schemes. L. Huber from Hewlett-Packard presented a flow-through solid electrode for EC detection in reversed-phase HPLC. This particular commercial unit combines a disposable, glassy carbon thinlayer electrode with optional pulsed
456 A · ANALYTICAL CHEMISTRY, VOL. 62, NO. 7, APRIL 1, 1990
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