A large yield of nitrogen atoms can be achieved at atmospheric pressure, from an Ar-N2 surface-wave-induced microwave discharge with half the microwave power needed with a pure N2 discharge. The dissociation of N2 molecules into atomic nitrogen in this Ar-N2 discharge is close to 22% at 0.3% N2 concentration and decreases with increasing nitrogen concentration. The maximum nitrogen atom yield per watt is reached at 3% of N2. Such a low power and simple nitrogen atom source, with a typical flow rate of 10 l min-1, is of interest for achieving metal nitriding at atmospheric pressure.

This analytical method offers a new way of measuring pentachlorophenol (PCP) in soil, wood, and water samples by gas chromatography and its hydrocarbon solvent by FT-IR spectroscopy. The distinctive feature of this method is that both the PCP and the oil are extracted from a single 1-g sample. They are first extracted from the wood or soil samples with a 1:1 mixture of Freon 113 and methanol using ultrasonication. An aliquot of the resulting organic phase is then added to an aqueous phase buffered at pH 9.2 with Na2HPC>4. The oil remaining in the organic phase is analyzed by FT-IR, whereas the PCP in the aqueous phase is acetylated by reaction with acetic anhydride, back-extracted in Freon 113, and injected into the gas chromatograph. Low-PCP-content water samples (<5 //g/L) are acidified and extracted in Freon 113, which is then added to the aqueous phase. High-PCP-content water samples (>5 µ g/L) are buffered and treated as the buffered aqueous phase. Extraction recoveries for the different matrices range from 94 to 115%. The absolute detection limits (3 ) for PCP and the hydrocarbon solvent are respectively 28 ng and 0.1 mg for a 1-g solid sample or a 100-mL volume of water sample. The PCP content of wood samples was compared with that obtained by neutron activation analysis and correlated with a 0.97 coefficient. The precision of the analytical method is better than 10% for both analytes. This analytical approach was successfully applied to the radial characterization of freshly treated poles for their PCP and oil contents.Pentachlorophenol (PCP) is widely used as a biocide in the wood preservation industry.* 1 It is dissolved in a hydrocarbon solvent such as oil and pressure-injected in the wood. The biocide-oil solution is present in the wood but also in the soil or water in the vicinity of wood-treatment plants. Also, it migrates out of the wood poles used by telephone companies and electrical utilities. In response to the environmental problems this creates, predictive software for evaluating the behavior of PCP and oil migrating from wood poles to the environment is under development at Hydro-Québec.

Radial density distributions of excited atoms in plasma columns of helium, neon, and argon, sustained by a travelling electromagnetic surface wave, are examined as a function of frequency over the range 200 kHz – 2450 MHz. This investigation is conducted using an end-on measurement method. At low frequencies (<50 MHz), these radial distributions show a maximum at the axis (J0 Bessel-like behavior), whereas as frequency is increased beyond 50 MHz up to 2450 MHz, the radial distributions flatten and finally exhibit a minimum at the axis with a maximum close to the tube wall. Comparison with a DC positive column plasma, working under the same gas-pressure and tube-diameter conditions, is made as a function of cross-section average electron density. The surface-wave discharge operated in the microwave frequency range (>300 MHz) yields larger cross-section average densities for atoms in a metastable or resonant state, typically a factor of 2–3 at 1011 electrons∙cm−3. This result arises because the two types of discharges have different radial-density distributions for excited atoms.

Argon surface-wave plasmas produced at power ranging from 0.5 to 1.2 kW are sustained at atmospheric pressure for the study of direct aqueous solution introduction. The plasmas are generally operated at 2450 MHz, but some results are also obtained for a 400 W 27 MHz surface-wave plasma. The emission spectra have been studied between 220 and 940 nm with a medium-resolution spectrometer and with an intensified photodiode array as detector. The effect of the operating parameters (gas flow rate, power) on intensity and signal-to-background noise ratio has been investigated for selected analytes. The detection limits were determined for several analytes (Ba, Ca, Cu, Cr, and Zn) and were found to be comparable to the detection limits obtained with other microwave-induced plasmas.

Some fundamental properties of radiofrequency and microwave surface-wave induced plasmas were determined in the frequency domain from 200 to 2450MHz. Argon and helium plasmas at atmospheric pressure were sustained under various experimental conditions (absorbed power, flow-rate and enclosed or open-air discharges). Excitation temperatures were found to be approximately 2400 K for argon and 3000 K for helium, whereas rotational temperatures (N2 and N2+) were lower (2000 K). Electron densities were in the range 3-4 x lO'4ecm-3 for argon and were a factor of three lower for the helium plasma. Under these operating conditions, frequency proved to have little or no effect on the fundamental parameters measured.