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Sensors for determining humidity in air have been described and investigated. Sensing film of the devices was prepared from polyvinylalcohol and graphitized carbon black disperse phase. The composition, thermal treatment and design of sensing films were investigated and optimized. An optimized humidity sensor has better metrological parameters as compared with its prototype (response time ∼ 45...
A simple technique has been developed for preconcentration of gaseous trace organic compounds on solid sorbents, followed by gas chromatography. The sorbent is packed in a cartridge prepared from a syringe needle placed in the gas chromatographic injector and the analytes previously adsorbed are thermally desorbed at the injector temperature and then directly swept by the carrier gas into the column...
A chemiluminescence (CL) detection for the determination of sulfite using the reaction of Ru(bipy) 32+ (bipy=2,2′-bipyridyl) -SO 32− -KMnO 4 is described. The concentration of sulfite is proportional to the CL intensity from 5.0×10 −8 to 1.25×10 −4 mol l −1 . The limit of detection is 2.5×10 −8 mol l −1 and the relative standard...
A new method for determining ultra-trace levels of hexavalent chromium in ambient air has been developed. The method involves a 24-h sampling of air into potassium hydroxide solution, followed by silica gel column separation of chromium (VI), then preconcentration by complexation and solvent extraction. The chromium (VI) complex was dissolved in nitric acid. The resultant chromium ions were determined...
This work describes a new approach for the determination of trimethylamine (TMA) in water and air by liquid chromatography (LC). The assay is based on the employment of a solid-phase microextraction (SPME) fiber for sampling and for derivatization of the analyte with the fluorogenic reagent 9-fluorenylmethyl chloroformate (FMOC). The fiber, with a Carbowax-templated resin −50μm coating, was first...
Nowadays, environmetrics based on the principles of fuzzy logic has become an important and sophisticated statistical instrument in modern science, being an adequate tool to investigation the principles of interaction of elements/variables and their integration into a system. This paper is intended mainly for a wide community of ecologist, which are interested in principles of using fuzzy logic in...
This review shows the state of the art, from 2000 to nowadays, of the use of semipermeable membrane devices (SPMDs) for monitoring persistent organic pollutants in both, air and aquatic environments. Since their first use in 1990, SPMDs have been employed for many environmental purposes, like air and water pollution monitoring. We have focussed the study in three subjects: (i) novel compounds accumulated...
The reaction between formaldehyde and ammonium ion to produce hexamethylenetetramine is well known. The reaction conditions are very easily controlled in situ and the experiment operation is very simple. However, such derivatization reaction for trace formaldehyde determination using capillary electrophoresis (CE) electrochemiluminescence (ECL) has not been reported before. In this study, the application...
There is presently no instrumentation that can provide (near) real time information on elemental composition of atmospheric aerosols. We describe an arrangement where air is sampled through a cyclone @30L/min with a 50% cutoff @ ~250nm. The particles deposit into a cup through which deionized water is continuously flowing. High purity HNO3 is added downstream and the mixed stream optionally flows...
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