ВОЛЬТАМПЕРОМЕТРИЧЕСКИЙ СЕНСОР ДЛЯ ОПРЕДЕЛЕНИЯ МАЛАТИОНА И ДИАЗИНОНА

The current article suggests a voltammetric method for the quantitative determination of malathion and diazinon using a modified electrode. The method is based on the adsorption concentrating of pesticides onto a graphite-containing electrode modified by polyaniline and a Co (III) chelate complex with 2,2'-dipyridyl. Analytical signals are determined by the recovery of cobalt (III) from mixed-ligand complexes with malathion and diazinon at the peak potentials of 0.65 and 0.47 respectively. The method allows one to determine pesticides within 0.05-1.50 mg / l with the following detection limits calculated by the 3s-criterion: 0.02 mg / l (malathion) and 0.015 mg / L (diazinon). The sensor functions as the sampler, as the sample preserver, and as the indicator electrode. The method has been approved for determining the presence of phosphorus-containing pesticides in natural waters and in acid extracts from soil and plants. The results obtained by the suggested method were compared with the results of determining malathion and diazinon by chromatography method. The developed technique exhibits high sensitivity, instrumentation simplicity, and quickness. The developed electrode allows one to store information for at least 10 days, while the analytical signal changes by no more than 15%.Keywords: pesticides, malathion, diazinon, adsorption voltammetry, modified electrode, polyaniline, cobalt 2,2'-dipyridyl.DOI: http://dx.doi.org/10.15826/analitika.2019.23.3.014(Russian)V.V. Shelkovnikov, K.Yu. Novolokov National Research Tomsk State University, pr. Lenina, 36, Tomsk, 634050, Russian FederationПредложена вольтамперометрическая методика количественного определения малатиона и диазинона с использованием модифицированного электрода. Методика основана на адсорбционном концентрировании пестицидов на графитосодержащем электроде, модифицированном полианилином и хелатным комплексом Co(III) с 2,2'-дипиридилом. Аналитические сигналы обусловлены восстановлением кобальта (III) из разнолигандных комплексов с малатионом и диазиноном при потенциалах 0.65 и 0.47 В соответственно. Разработанная методика позволяет проводить определение пестицидов в диапазоне концентраций 0.05 – 1.50 мг/л с пределом обнаружения, рассчитанным по 3s-критерию: 0.02 мг/л (малатион) и 0.015 мг/л (диазинон). Сенсор совмещает в себе функции пробоотбора, консервации образца и индикаторного электрода. Методика апробирована для определения фосфорсодержащих пестицидов в природных водах и кислотных вытяжках из почвы и растений. Проведено сравнение результатов, полученных по предлагаемой методике, с результатами определения малатиона и диазинона методом хроматографии. Преимуществом разработанной методики является высокая чувствительность, простота аппаратурного оформления, экспрессность анализа. Разработанный электрод позволяет сохранять информацию об анализируемом объекте не менее 10 суток, при этом аналитический сигнал меняется не более чем на 15 %.Ключевые слова: пестициды, малатион, диазинон, адсорбционная вольтамперометрия, модифицированный электрод, полианилин, 2,2'-дипиридил кобальтаDOI: http://dx.doi.org/10.15826/analitika.2019.23.3.01

«Quadrupole» mode DR filter for C-band applications

The possibility of reducing the radiation loss of dielectric resonator (DR) to the external environment has been investigated for the first time by applying higher order mode of DR, namely “quadrupole” type, with higher Q factor. The “quadrupole” mode for constructing narrow band-pass filter (<1%) has been studied. The resonant frequencies of dielectric resonator have been calculated on grounds of approximate analytical method as well as finite element method. The coupling coefficients of the rectangular DR with coplanar line have been scrutinized both as a function of the glass substrate’s height, namely bs, on which the DR is situated, and as a function of the DR’s displacement toward the center line, namely y₀. The synthesized two-resonator band-pass filter has the improved gain slope. The minimum value of insertion loss at the central frequency of 5.9 GHz is - 2.4dB, the shape factor is equal to 3.45

Isolation of Mn(II), Fe(III), Cu(II) and Ni(II) ions on strongly acidic cation-exchange resins followed by determination of inorganic arsenic by anodic stripping voltammetry

The possibility of ion exchange technique with of IC-H Hypersep cartridge (Metrohm, Switzerland), sulfonated cation-exchange resins KU-2-8 (Russia) and Purolite C100 (UK) has been shown for ion separation of Mn (II), Fe(III), Cu(II) and Ni(II) ions from arsenite and arsenate ions. The conditions for ion-exchange removal of interfering cations in water when determining different arsenic(III, V) by stripping voltammetry have been optimized. The KU-2-8 cation-exchange resin based cartridge was found to be appropriate for use in the proposed sample preparation for water. The developed technique of analysis has been applied for the separated determination of inorganic arsenic forms in waters of different origin by anodic stripping voltammetry. The correctness of experimental results has been confirmed by the standard addition method

Holographic recording in a photopolymer by optically induced detachment of chromophores

We demonstrate holographic recording in a new photopolymer system. The recording material is created by copolymerization of an optically inert monomer, methyl methacrylate, and a second monomer that is optically sensitive. On exposure of the recording material to light, a portion of the optically sensitive component detaches from the polymer matrix and causes hologram amplification through diffusion of the free molecules. We measured postrecording grating amplifications as high as 170% by this process. The recorded holograms are persistent at room temperature under continuous illumination at the recording wavelength. (C) 2000 Optical Society of America

Моделирование радиосистемы на частоте 130 ГГц с использованием QPSK модуляции

Досліджена радіосистема на частоті 130 Ггц з модуляцією QPSK із застосуванням програмного пакету AWR, проаналізований вплив нелінійності на спектр сигналу. На основі отриманих результатів визначені вимоги до окремих функціональних вузлів.130 GHz radio system with QPSK modulation using AWR software is studied; influence of nonlinearity on signal spectrum is analyzed. Based on obtained results requirements for some functional units are defined.Исследована радиосистема на частоте 130 ГГц с модуляцией QPSK с применением программного пакета AWR, проанализировано влияние нелинейности на спектр сигнала. На основе полученных результатов определены требования к отдельным функциональным узлам

Электрохимическое поведение триптофана и 5-гидрокситриптофана на модифицированном многостенными углеродными нанотрубками и полифолиевой кислотой электроде

A possible mechanism for the concentration and oxidation of tryptophan and 5-hydroxytryptophan on an electrode modified with carbon nanotubes and polyfolic acid has been proposed. The influence of the pH of the solution, the accumulation potential, and the potential sweep speed on the analytical signals of amino acids has been investigated. When the pH increases, the potentials of the anode peaks shift to the region of negative values; the I – pH dependence passes through the maximum with the pH of 6.8. Based on the processing of the dependences of the peak current and the peak potential on the potential sweep speed, it has been found that tryptophan and 5-hydroxytryptophan oxidize with the participation of two electrons and two protons. The transfer process of the first electron limits the electrochemical reaction. The process is controlled by diffusion and adsorption. The diffusion coefficients are equal to 9.7.10–6 cm2/s and 7.4.10–6 cm2/s for tryptophan and 5-hydroxytryptophan, the maximum adsorption value for tryptophan has been 1.63.10–10 mol/cm2 and for 5-hydroxytryptophan it has been 6.41.10–1 mol/cm2. The optimal parameters of concentration and oxidation of tryptophan and 5-hydroxytryptophan in the compresence have been established: the pH of 6.8; the accumulation potential of 0.1 V, the electrolysis time of up to 120 s, the optimal scanning velocity of 120 mV/s. The limit of quantification has been 5.10–8 MВ работе предложен возможный механизм концентрирования и окисления триптофана и 5-гидрокситриптофана на электроде, модифицированном углеродными нанотрубками и полифолиевой кислотой. Исследовано влияние рН раствора, потенциала накопления, скорости развертки потенциала на аналитические сигналы аминокислот. При повышении рН потенциалы анодных пиков смещаются в область отрицательных значений, зависимость I – pH проходит через максимум при рН 6,8. На основании обработки зависимостей тока пика и потенциала пика от скорости развертки потенциала установлено, что окисление триптофана и 5-гидрокситриптофана происходит при участии двух электронов и двух протонов. Лимитирует электрохимическую реакцию процесс переноса первого электрона. Процесс контролируется диффузией и адсорбцией. Коэффициенты диффузии равны 9,7.10–6 см2/с и 7,4.10–6 см2/с для триптофана и 5-гидрокситриптофана, величина предельной адсорбции для триптофана составила 1,63.10–10 моль/см2, а для 5-гидрокситриптофана – 6,41.10–11 моль/см2. Установлены оптимальные параметры концентрирования и окисления триптофана и 5-гидрокситриптофана при совместном присутствии: рН 6,8; потенциал накопления –0,1 В, время электролиза до 120 с, оптимальная скорость развертки 120 мв/с. Нижняя граница определяемых концентраций составила 5.10–8

Second-order nonlinear optical properties of composite material of an azo-chromophore with a tricyanodiphenyl acceptor in a poly(styrene-co-methyl methacrylate) matrix

© 2017 Elsevier B.V.The composite material of new synthesized 4-((4-(N,N-n-dibutylamino) phenyl)diazenyl)-biphenyl-2,3,4-tricarbonitrile (GAS dye) in commercial poly(styrene-co-methyl methacrylate) (PSMMA) was prepared, poled and its nonlinear optical properties compared with DR1 dye were studied. High thermal stability of the composite material was revealed, and the maximal concentration of the chromophore was found to reach ∼20 wt%. The dipole moment, polarizability tensor, and first hyperpolarizability tensor of the investigated dyes were calculated by within the framework of the coupled perturbed density functional theory. A nanosecond second-harmonic generation Maker fringes technique was used which is capable of providing the magnitude of the second-order nonlinearity of optical materials at a wavelength of 1064 nm. For the tested GAS–PSMMA composite material, maximal coefficient d33 was found to be 50 pm/V. The nonlinear optical response, which was achieved here, shows possible usefulness of the GAS dye as a component for molecular design of nonlinear-optical materials with advanced characteristics

Searching for chameleon-like scalar fields with the ammonia method

(Abridged) The ammonia method, which has been proposed to explore the electron-to-proton mass ratio, mu = m_e/m_p, is applied to nearby dark clouds in the Milky Way. This ratio, which is measured in different physical environments of high (terrestrial) and low (interstellar) densities of baryonic matter is supposed to vary in chameleon-like scalar field models, which predict strong dependence of both masses and coupling constant on the local matter density. High resolution spectral observations of molecular cores in lines of NH3 (J,K) = (1,1), HC3N J = 2-1, and N2H+ J = 1-0 were performed at three radio telescopes to measure the radial velocity offsets, DeltaV = V_rot - V_inv, between the inversion transition of NH3 (1,1) and the rotational transitions of other molecules with different sensitivities to the parameter dmm = (mu_obs - mu_lab)/mu_lab. The measured values of DeltaV exhibit a statistically significant velocity offset of 23 +/- 4_stat +/- 3_sys m/s. When interpreted in terms of the electron-to-proton mass ratio variation, this infers that dmm = (2.2 +/- 0.4_stat +/- 0.3_sys)x10^{-8}. If only a conservative upper bound is considered, then the maximum offset between ammonia and the other molecules is |DeltaV| <= 30 m/s. This gives the most accurate reference point at z = 0 for dmm: |dmm| <= 3x10^{-8}.Comment: 23 pages, 11 figures, 6 tables. Accepted for publication in A&A. Title and text corrected, references update

Quantum cascade laser frequency stabilisation at the sub-Hz level

Quantum Cascade Lasers (QCL) are increasingly being used to probe the mid-infrared "molecular fingerprint" region. This prompted efforts towards improving their spectral performance, in order to reach ever-higher resolution and precision. Here, we report the stabilisation of a QCL onto an optical frequency comb. We demonstrate a relative stability and accuracy of 2x10-15 and 10-14, respectively. The comb is stabilised to a remote near-infrared ultra-stable laser referenced to frequency primary standards, whose signal is transferred via an optical fibre link. The stability and frequency traceability of our QCL exceed those demonstrated so far by two orders of magnitude. As a demonstration of its capability, we then use it to perform high-resolution molecular spectroscopy. We measure absorption frequencies with an 8x10-13 relative uncertainty. This confirms the potential of this setup for ultra-high precision measurements with molecules, such as our ongoing effort towards testing the parity symmetry by probing chiral species