СЕЛЕКТИВНОЕ ОПРЕДЕЛЕНИЕ МАССОВОЙ КОНЦЕНТРАЦИИ ДИОКСИДА ХЛОРА В ПРОМЫШЛЕННЫХ ВЫБРОСАХ МЕТОДОМ КАПИЛЛЯРНОГО ЭЛЕКТРОФОРЕЗА

The task of the selective determination of chlorine dioxide in gas environments, including the emissions from the pulp and paper mills, is relevant and in demand. Current article presents a brief review of the existing methods and procedures for measuring the chlorine dioxide in liquid and gas environments, and identifies the problems in controlling the chlorine dioxide in industrial emissions from the pulp and paper production due to the influence of the related substances: molecular chlorine, hydrochloride, hydrochlorate and sulfur dioxide. As a result, to achieve the required selectivity of the chlorine dioxide determination, the procedure for its preliminary oxidation with the hydrogen peroxide to the chlorite-ion was developed, followed by the measuring of its mass concentration by the capillary electrophoresis. The conditions of sampling, all stages of sample preparation and measurements on the instrument were optimized. Based on the experimental studies, a method for measuring the chlorine dioxide in the industrial emissions in the form of chlorite ion in the range from 0.025 to 0.3 mg/m3 with an expanded uncertainty of 25% has been developed. The contributions of the components of uncertainties affecting the measurement result were summarized in the budget of the uncertainties prepared during the metrological certification of the measurement procedure. The developed method is more selective and reliable in comparison to the traditional methods (“wet chemistry”) used for the measuring of the chlorine dioxide in industrial emissions.Key words: chlorine dioxide, chlorite-ion, capillary electrophoresis, measurement techniques, industrial emissionsDOI: http://dx.doi.org/10.15826/analitika.2019.23.2.006(Russian)Irina B. Maksakova, Lydmila V. Eliseeva, Marina M. Bezruchko, Anatoliy I. Krylov D.I. Mendeleyev Institute for Metrology (VNIIM), Moskovskii pr., 19,Saint-Petersburg, 190005, Russian FederationЗадача селективного определения диоксида хлора в газовых средах, включая выбросы целлюлозно-бумажных производств (ЦБП), актуальна и востребована. В статье представлен краткий обзор существующих методов и методик измерений диоксида хлора в жидких и газовых средах, выявлены проблемы контроля диоксида хлора в промышленных выбросах ЦБП, обусловленные влиянием сопутствующих веществ: молекулярный хлор, гидрохлорид, гидрохлорат и диоксид серы. В результате для достижения необходимой селективности определения диоксида хлора отработана процедура его предварительного окисления пероксидом водорода до хлорит-иона с последующим измерением его массовой концентрации методом капиллярного электрофореза. Оптимизированы условия пробоотбора, всех стадий пробоподготовки и выполнения измерений на приборе. На основе проведенных экспериментальных исследований разработана методика измерений диоксида хлора в промышленных выбросах в виде хлорит-иона в диапазоне от 0.025 до 0.3 мг/м3 при расширенной неопределенности 25 %. Вклады составляющих неопределенностей, оказывающих влияние на результат измерений суммированы в бюджете неопределенностей, подготовленном при метрологической аттестации методики измерений. Разработанная методика является более селективной и достоверной в сравнении с используемыми традиционными методами («мокрой химии») измерений диоксида хлора в промышленных выбросах.Ключевые слова: диоксид хлора, хлорит-ион, капиллярный электрофорез, методики измерений, промышленные выбросыDOI: http://dx.doi.org/10.15826/analitika.2019.23.2.00

Fission of Entangled Spins: An Electronic Structure Perspective

Electronic structure aspects of singlet fission process are discussed. Correlated adiabatic wave functions of the bright singlet and dark multiexciton states of tetracene and pentacene dimers are analyzed in terms of their character (excitonic, charge-resonance, multiexciton). At short interfragment separation (3.5–4 Å), both multiexcitonic and singly excited singlet states have noticeable charge-resonance contributions that fall off quickly at longer distances. Nonadiabatic couplings between the states are discussed. The limitations of diabatic framework in the context of singlet fission are explained. Based on the Cauchy–Schwarz inequality, we propose using the norm of one-particle transition density matrix, ∥γ∥, as a proxy for couplings. The analysis of ∥γ∥ and state characters reveals that the couplings between the multiexciton and singly excited states depend strongly on the weights of charge-resonance configurations in these states. To characterize energetics relevant to triplets separation step, we consider multiexciton binding energy (<i>E</i>_b) defined as the difference between the quintet and singlet multiexciton states. The effect of fragment orientation on the couplings and <i>E</i>_b is analyzed

CCQM-K131 Low-polarity analytes in a multicomponent organic solution: polycyclic aromatic hydrocarbons (PAHs) in acetonitrile

Solutions of organic analytes of known mass fraction are typically used to calibrate the measurement processes used to determine these compounds in matrix samples. Appropriate value assignments and uncertainty calculations for calibration solutions are critical for accurate measurements. Evidence of successful participation in formal, relevant international comparisons is needed to document measurement capability claims (CMCs) made by national metrology institutes (NMIs) and designated institutes (DIs). To enable NMIs and DIs to update or establish their claims, in 2015 the Organic Analysis Working Group (OAWG) sponsored CCQM-K131 "Low-Polarity Analytes in a Multicomponent Organic Solution: Polycyclic Aromatic Hydrocarbons (PAHs) in Acetonitrile". Polycyclic aromatic hydrocarbons (PAHs) result from combustion sources and are ubiquitous in environmental samples. The PAH congeners, benz[a]anthracene (BaA), benzo[a]pyrene (BaP), and naphthalene (Nap) were selected as the target analytes for CCQM-K131. These targets span the volatility range of PAHs found in environmental samples and include potentially problematic chromatographic separations. Nineteen NMIs participated in CCQM-K131. The consensus summary mass fractions for the three PAHs are in the range of (5 to 25) μg/g with relative standard deviations of (2.5 to 3.5) %. Successful participation in CCQM-K131 demonstrates the following measurement capabilities in determining mass fraction of organic compounds of moderate to insignificant volatility, molar mass of 100 g/mol up to 500 g/mol, and polarity pKow < −2 in a multicomponent organic solution ranging in mass fraction from 100 ng/g to 100 μg/g: (1) value assignment of primary reference standards (if in-house purity assessment carried out), (2) value assignment of single and/or multi-component organic solutions, and (3) separation and quantification using gas chromatography or liquid chromatography