Semiconductor sensors for the detection of fluorocarbons, fluorine and hydrogen fluoride

Visualisation and identification of peak exposure events in aluminium smelter pot rooms using hydrogen fluoride and aerosol real-time portable spectrometers

A recently developed novel portable real-time hydrogen fluoride spectrometer was used with an aerosol PM10 spectrometer under a PIMEX telemetric measurement strategy to visualize and identify simultaneous occupational air peak exposure events to hydrogen fluoride and PM10 aerosol sub-fractions in aluminium smelter pot rooms using Søderberg or Prebake anode technologies. The hydrogen fluoride and the aerosol concentration data measured during different work operations are plotted and evaluated applying the synchronised videos and air concentrations measured by the spectrometers. The main point-emission sources of HF and PM10 were identified and assessed. The major finding in the study was that the main source of PM10 and HF was partly open cells in a Søderberg pot room, whereas in a Prebake pot room, the point emissions of the two contaminants were associated with hot bath residues and hot replaced anodes. In order to prevent the simultaneous exposure to HF and PM10 among pot room workers it is important to prevent workers from being close to these point-sources under unfavourable ventilation. Storage of hot residues outside electrolytic cells without any point source ventilation should not occur.

Detection of Chemicals by a Reporter Immunoassay: Application to Fluoride

This report describes a concept in which an immunoassay is used indirectly to quantify a nonantigenic very low molecular weight compound participating in a chemical reaction with a haptenic reporter. The detection limit of each reagent is, therefore, governed only by the affinity of the antibodies toward the reporter. Fluoride was used as a model, and silylated estradiol was used as a reporter. Upon silylation with N-O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) or N-O-bis(dimethylterbutylsilyl) trifluoroacetamide (MTBSTFA), estradiol is no longer recognized by antibodies specific to estradiol. After reaction with hydrofluoric acid (HF) or fluoride salts (KF, CsF, NaF), its immunoreactivity is restored, and native estradiol is formed and is detected by immunoassay. The level of synthesized estradiol is dependent on the concentration of fluoride. A fluoride detection limit of 0.3 microg/L (15 nM) is obtained. Potential interference with other acids has been eliminated by choosing the silyl group (trimethylsilyl vs tert-butyldimethylsilyl) and by selecting optimal reaction conditions for the desilylation. The method has been applied to the detection of fluoride salts in natural waters (range 0.28-9.0 mg/L) and in an atmosphere artificially contaminated with HF between 8 and 160 microg/m(3) in the parts-per-billion range. This indirect immunoassay combines simplicity and high sensitivity and, therefore, can be used in field monitoring. Finally, the extension of the concept to other chemicals is discussed.