B. K. Zuev

Discharge on boiling in a channel: Effect of channel geometry on the performance characteristics of determining metals in a liquid flow by atomic emission spectrometry

Discharge on boiling in a channel was studied as a new atomization and excitation source for spectrochemical analysis in a flow of electrolyte solutions. The discharge arises between the liquid walls of a vapor lock formed in the channel of a dielectric membrane because of the rapid Joule heating of the liquid in the channel. The effect of channel geometry on the reproducibility of the integrated light intensity was studied. The background radiation spectrum was measured over the range 220–900 nm, and the possibility of determining alkali and alkaline earth metals in a flow was studied. The parameters of linear calibration equations and the detection limits for these metals are given.

Adsorption preconcentration of pyrene by silver nanoparticles and its determination in aqueous solutions

The reduction of silver nitrate with sodium borohydrate in an aqueous medium in the presence of cetyl trimethylammonium bromide gives a stable sol of silver, which can adsorb nonpolar organic compounds, e.g., polycyclic aromatic hydrocarbons, on the surface of metal nanoparticles. The subsequent luminescent determination demonstrated the effect of sensitized luminescence of silver nanoparticles, which could provide a basis for the determination of traces of polycyclic aromatic compounds in water.

Discharge on Boiling in a Channel as a New Atomization and Excitation Source for the Flow Determination of Metals by Atomic Emission Spectrometry

A new atomization and excitation source for the spectrochemical analysis of electrolyte solutions was described. This is a discharge on boiling in a channel, which arises in a vapor gap formed in the channel of a dielectric membrane because of Joule heating. Based on the synchronous kinetic measurements of current and light intensities, a qualitative model was proposed for processes occurring in a pulsed discharge on boiling in a channel. The background emission spectrum of the discharge on boiling in a channel was measured. The possibility of exciting lines of alkali and alkaline-earth metals was studied. Calibration graphs for the determination of 0.01–5 mM Na, Mg, and Ca are presented.

Criteria for Assessing the Effect of the Composition of Mixed Media on Analytical Sensitivity in Thermal Lens Spectrometry

The effect of the main parameters of solvent mixtures (water-acetone, water-ethanol, water-acetonitrile, water-ethylene glycol, and chloroform-acetone) of various compositions on the detection limit and analytical range was studied, and the selection criteria for the composition of mixed media were discussed in the context of trace determination by thermal lens spectrometry. It is shown that the strength of the thermal lens effect in the medium cannot serve the measure of its effect on the sensitivity and reproducibility of the determination. The lowest detection limits were reached in the water-ethanol (8 times lower in comparison to water), water-acetone (3 times), and water-ethylene glycol (2.5 times) mixtures with a volume ratio of components of 1: 4, while in water-acetonitrile mixtures (22 times), with a component ratio of 3 : 1.

Rapid Determination of the Chemical Oxygen Demand in Water with the Use of High-Temperature Solid-Electrolyte Cells

A new procedure is proposed for the determination of the oxidazibility of organic and inorganic matter in water (an analogue of the chemical oxygen demand (COD)). The procedure is based on high-temperature oxidation in a controlled binary oxygen–inert gas mixture and the determination of the amount of oxygen consumed for oxidation in a solid-electrolyte cell. A new design for the setup is presented as a monoblock with a vertical sample introduction into the reactor. A sampler of the immersion type is proposed. It has been found that the detection limit obtained with the use of this setup is 5 mg O2/L.

A microplasma analyzer for the determination of alkali and alkaline-earth metals in small volumes of samples of complex phase composition

A microplasma analyzer is developed for the determination of potassium, lithium, calcium, and magnesium in small volumes of samples of complex phase composition on an example of putrefactive lymphocytic wound exudates and articular and amniotic fluids. The operation of the device is based on a drop spark discharge between liquid electrodes, one of which is a drop of a studied solution applied onto the cathode. This scheme allows the reduction of sample volume for a single determination to 15 µL.

Spectrophotometric and thermal lens determination of aluminum with 3-sulfo-5-nitro-4′-diethylamino-2,2′-dihydroxyazobenzene

The conditions of the spectrophotometric and thermal lens determination of aluminum with sulfo-5-nitro-4′-diethylamino-2,2′-dihydroxyazobenzene have been compared. The limit of spectrophotometric detection of aluminum in aqueous solutions has been found to be 8 ng/mL. On the basis of the conditions of spectrophotometric determination, the conditions for thermal lens determination have been proposed (532.0 nm, exciting radiation power of 42 mW); they provide a decrease of the detection limit down to 0.6 ng/mL and an increase of the sensitivity coefficient by an order of magnitude. It has been shown that, in the case of the thermal lens determination of aluminum in water-organic mixtures (50 vol % of dimethyl sulfoxide or 30 vol % acetonitrile), the sensitivity coefficient is respectively 9.1 and 6.3-fold higher as compared with the thermal lens determination in water. As a result, the detection limits are reduced 2.5 and 10-fold, respectively. Aluminum has been determined by thermal lens spectrophotometry in Moscow’s tap water using the standard addition method, its concentration being 0.79 ± 0.07 mg/L, which is above the threshold limit value of the aluminum content of drinking water.

Effect of the Composition of Aqueous-Organic Mixtures on the Sensitivity of Thermal Lens Measurements

Thermooptical properties of aqueous solutions of methanol, acetonitrile, dimethyl sulfoxide, ethylene glycol, glycerol, 1,4-dioxane, and sucrose were studied, and it was found that the analytical thermal lens signal depends on the nature of the organic component, most of all, on the polarity and molecular size. The sensitivity coefficient of thermal lens measurements is increased to a maximum extent in methanol solutions (by 7.3 times at the concentration 50 vol %) and acetonitrile (by 8.8 times at 26 vol %). It was found that a small concentration of water slightly affects the thermooptical properties of polar organic solvents.

New nanomaterials for control of the luminescence of polycyclic aromatic hydrocarbons

New nanomaterials (ordered structures) have been proposed for control of the luminescence of polycyclic aromatic hydrocarbons by solubilization of the latter into ordered structures. These structures are formed by hydrophilic silver nanoparticles adsorbed on a cellulose matrix—filter paper—through their self organization and by molecules of a cationic surfactant—cetyltrimethylammonium bromide—in concentrations exceeding the critical micelle concentration. The observed enhancement of luminescence of solubilized pyrene molecules in the violet spectral range is due to the resonance of the electronic transitions of monomeric pyrene molecules in this range with a plasmon vibrations in silver nanoparticles.

Quantification of boron in water by of spectrophotometry and thermal lens spectrometry using reaction with beryllon III

The conditions for the thermal lens quantification of boron in aqueous solutions with a detection limit of 0.3 ng/mL are found (λ = 532 nm, laser power 40 mW); this value of the detection limit is an order of magnitude lower than that attainable in conventional spectrophotometry. A 1: 1 composition of an aqueous ethylene glycol mixture is proposed, using which as a medium the detection limit for boron was reduced to 0.1 ng/mL. Using spectrophotometry and thermal lens spectrometry, boron was quantified in mineral water; the results agree with the data acquired by the reference method of inductively coupled plasma atomic emission spectrometry.