Acid effects in ICP-AES

Summary The influence of concentration and nature of the acid, type and tuning of RF-generator, method of solution introduction (flow injection or two-nebulizer method) are investigated to understand the nature of acid matrix interferences in ICP-AES. Sixteen elements and nine different spectrometers wer used to study the matrix interferences caused by HCl, HNO₃, HClO₄, H₂SO₄, H₃PO₄. There are two effects connected with acid: depression of the analyte emission signals and irregular signal changes for different elements. The values of these effects depend on the RF-generator type. The obvious results of introducing acid in the plasma are a decrease in plasma temperature and departures from LTE.

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Einfluß von Säuren in der ICP-AES

     

Raman spectra and structural features of ClOF2 + cation in a solution of anhydrous HF

The Raman spectra of ClOF₂ ⁺ cation in solutions of anhydrous HF were studied. In the ClOF₂ ⁺HF₂ ⁻ and ClOF₂ ⁺BF₄ ⁻−HF systems, this cation exists as a pyramidal structure (C _s symmetry), while in the ClOF₂ ⁺AuF₆ ⁻−HF system, it exists as a planar structure (C _2v symmetry). Based on nonempirical calculations by the Hartree-Fock-Roothaan method, an explanation for the dependence of the structure of the ClOF₂ ⁺ cation on the nature of the anion was proposed. For the Cl−O bond vibrations, the correlation functions of vibrational and rotational relaxations were calculated, and the characteristic times of these processes were determined. The main contribution to the formation of the band contours corresponding to the above-mentioned modes is made by the vibrational dephasing. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 3, pp. 432–437, March, 1998.     

Base-pressure pulsations behind a cylinder and disk in a subsonic stream flow

Base-pressure fluctuations behind a long cylinder (l/d 5–10) and the disk (l/ d 0.0) is investigated experimentally in this paper. The spectral and correlation characteristics of the base-pressure fluctuations behind axisymmetric bodies at a Mach number M 1.0 are generalized on the basis of the data obtained and the results of other authors.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 181–183, January–February, 1977.     

Pressure fluctuations and heating of a gas by the inflow of a supersonic jet into a cylindrical cavity

The formation of pressure fluctuations at the inflow of a jet into a cavity (or the so-called resonance tube) was first observed by Hartmann. Further investigations showed that at the same time there is a heating of the gas in the cavity [1, 2]. It was established in [1, 2] that at subsonic and slightly supersonic velocities (M < 2.0) the cavity air can be heated up to 500–700 °K. Further investigations [4, 6] showed that by using monatomic gases inside the cavity one can reach even higher temperatures (T 800–900 °K). The resonance tubes find an application as powerful sound sources. There is also a possibility of their use in thermochemistry, and for the plasma production [6], In the literature, there is an absence of data on the resonance tube characteristics for large Mach numbers. In the present work we investigate the resonance tubes for M = 3.2–4.0. These investigations have shown that pressure oscillations can occur at these Mach numbers with the peak-to-peak amplitude of P 0.4·P_o, where P_o is the total pressure in the inflowing jet. Depending on the clearance between the nozzle and the cavity, both low- and high-frequency oscillations can be set up. It is established that the most intense shock-wave heating of the gas takes place at high-frequency fluctuations, although their amplitude is smaller in comparison with the low-frequency ones. It is shown that the cold air inside the cavity can be heated by means of the fluctuations up to T 1600 °K or more.Translated from Izvestiya Akamemii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 104–111, September–October, 1977.     

Optimum Analytical Parameters for the Chromatographic Characterization of Pesticides

Correlation coefficients were considered for various combinations of analytical parameters for a series of 20 most widely used pesticides. These parameters included gas-chromatographic retention indices (RIs) on standard nonpolar polydimethylsiloxane stationary phases, RIs in reversed-phase HPLC, data on out-of-column phase equilibria (distribution constants K _pin heterophase solvent systems), UV-spectroscopic characteristics, and the most important mass-spectrometric characteristics. A combination of RIs with the relative absorbance A _rel= A(254)/A(220) and distribution constants in the hexane–acetonitrile system was found to be most informative for the HPLC identification of compounds from this class.     

Vegetable phenols as effective inhibitors of thermal polymerization for petrochemical plants

A new source of effective polymerization inhibitors for petrochemical industry was suggested: polyphenols recovered from wood and other vegetable raw materials.     

Third harmonic generation in the field of a backward pump wave

Third harmonic generation in a nonlinear medium the refractive index of which is negative at the pump frequency and positive at the harmonic frequency with allowance for self-action effects is considered theoretically. An exact solution of equations that describe the parametric interaction of continuous waves has been obtained analytically. The behavior of the solution is analyzed depending on the degree of violation of the phase matching condition. It is shown that, in a definite domain of values of nonlinear susceptibilities of the third order, there exists a critical value of the phase detuning at which the monotonic transform of the pump into the harmonic is changed by a periodical one. This phenomenon does not occur when the third harmonic is generated in ordinary media with a positive refractive index.     

Specific Features of Reversed-Phase High-Performance Liquid Chromatography as Applied to Determining the Distribution Coefficients of Pesticides in the Hexane-Acetonitrile System

The suitability of reversed-phase high-performance liquid chromatography for determining the distribution coefficients of organic compounds in the hexane-acetonitrile system was considered. A version of the necessary additional step in the sample preparation procedure was proposed, namely, changing from nonpolar hexane to a solvent unlimitedly miscible with the eluent. The distribution coefficients were determined for 20 pesticides by the proposed method and compared with those determined by gas chromatography.