摘要:

The design, development and calibration of a novel analytical reaction microcalorimeter is described. The instrument uses a modified Teflon stopcock as the reaction chamber, an aluminum block with built-in syringes as the equilibrium chamber and a thermistor bead as the detector. Operational amplifiers are used for signal amplification. The reaction of two thermally equilibrated reagents occurs inside the reaction chamber. Using microliter quantities of reagents, the microcalorimeter is sensitive to energy changes in the order of millicalories per mole.

ISSN:1073-9149    

DOI:10.1080/10739148908543699

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A dedicated portable fluorometer has been used with a capillary-well fiber-optic chemical sensor (FOCS) to develop a calibration method for this sensor for gaseous chloroform. The FOCS has been modified so that its operational reliability has been greatly improved. The complete remote fiber fluorimetry (RFF) device was used to characterize the chloroform contamination of a shallow water-well field. The lowest detected gaseous chloroform concentration was 1.2 ng/mL over an aqueous chloroform concentration of 12 ng/mL.

ISSN:1073-9149    

DOI:10.1080/10739148908543700

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A thermal desorption modulator is a short length of the analytical column (or a piece of tubing containing an adsorbent) placed at the head of the column in a GC. A carrier gas containing sample may be continuously introduced into a chromatographic column through a modulator. Analytes transfer from the carrier gas onto a stationary phase within the modulator and can be released from the modulator by rapid heating. A concentrated pulse of analytes generated in this fashion serves the same purpose as an injection. Thus, chromatography using modulators does not need any injection device because the equivalent of an injection is generated internally within the flow stream. In addition to serving as an alternative to an injection valve, a modulator also preconcentrates the sample.

ISSN:1073-9149    

DOI:10.1080/10739148908543701

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Techniques and instrumentation have been developed for the electrosorptive detection of selected anions at mercury and silver in ion chromatography and of surface-active organic substances at mercury. Detection based on differential double-layer capacitance has proven most generally useful, although pulse-based methods are also beneficial, especially at silver where they have special utility in countering adsorption effects. An ancillary, and more specialized technique developed for the determination of ions senses adsorption indirectly, relying on the kinetic facilitation imparted the rate of electroreduction of a transition-metal reactant by an adsorbed species. A less generally useful, but nevertheless complementary scheme based on the “tensammetric” peak may also be employed for the determination of organic species. A novel approach investigated for application to both ionic and neutral species is based on changes in the drop time of mercury caused by adsorption-induced changes in surface tension at the mercury/aqueous interface. Finally, more elaborate, “hyphenated” techniques - capacitive/capacitive and capacitive/amperometric detection - have also been developed for application to selected ions.

ISSN:1073-9149    

DOI:10.1080/10739148908543702

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

ISSN:1073-9149    

DOI:10.1080/10739148908543703

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

ISSN:1073-9149    

DOI:10.1080/10739148908543704

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

ISSN:1073-9149    

DOI:10.1080/10739148908543705

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor