УМЕНЬШЕНИЕ СЛУЧАЙНОЙ СОСТАВЛЯЮЩЕЙ ПОГРЕШНОСТИ КОЛИЧЕСТВЕННЫХ ГАЗОХРОМАТОГРАФИЧЕСКИХ ОПРЕДЕЛЕНИЙ СПОСОБОМ ВНЕШНЕГО СТАНДАРТА ЗА СЧЕТ ИСПОЛЬЗОВАНИЯ СИГНАЛА РАСТВОРИТЕЛЯ

Uncertainties of the results of quantitative determinations in gas chromatography using the methods based on the absolute peak areas (including the external standard method) are rather “sensitive” to the reproducibility of injections. The effective way to compensate for such errors is to introduce the additional standards into the samples, followed by replacing the absolute peak areas by their ratios to peak areas of the standards. It is important to underline that any constituents of the samples can be used as additional standards, including the solvents. Solvents can be used for these purposes even if the heights of their peaks are restric­ted when the analytical signals exceed the amplifier limits. Using the relative peak areas does not require any extra sample processing besides the registration of peak areas for solvents. Comparing the commonly known and modified methods of external stan­dard demonstrates that using the relative peak areas instead of the absolute ones does not influence the overall precision of determinations (according to the criterion “intro­duced-determined”) but improve the reproducibility by 2-3 times. The problem of increasing the reliability of such statistical evaluations of results is discussed and to solve it, it is proposed to change the “design” of the experiments. Instead of series of successive analyses of similar origin samples, the use of parallel determinations is preferable. This can be realized, for example, during the fulfillment of student’s practical works.Keywords: quantitative chromatographic analysis, external standard, solvent as an additional standard, decreasing the uncertainty of quantificationDOI: http://dx.doi.org/10.15826/analitika.2022.26.2.005Igor G. Zenkevich, Sofia V. Byvsheva, Artur I, Gerasimov, Sergei V. Gladnev, Michael V. Grigoriev, Nina V. Gubina, Egor A. Didenko, Alexander S. Kazantsev, Tatiana D. Kalutskaia, Elena V. Katernuk, Alla A. Koblova, Danil V. Krutin, Kseniya P. Malkova, Svetlana A, Metliaeva, Valeria S. Odegova, Daria S. Smirnova, Valeri A. Spivakovskyi, Pavel V. Terno St. Petersburg State University, Institute for Chemistry,Universitetskii prosp., 26, St. Petersburg 198504, Russian FederationПогрешности результатов количественных газохроматографических опре­де­лений способами, предполагающими использование абсолютных площадей хроматографических пиков, в том числе внешнего стандарта, «чувстви­тельны» к воспроизводимости дозирования проб. Эф­фек­тивным приемом ком­пен­сации таких погрешностей является введение в анализируемые образцы до­полнитель­ных стандартов и замена абсолютных площадей пиков их отношени­ями к пло­щадям пиков стандартов. Важно, что в качестве дополнительных ста­н­дартов мо­ж­но использовать любые компоненты образцов, в том числе входя­щие в их со­с­тав растворители.  В модифицированном варианте количе­ст­вен­ного анализа спо­собом внеш­не­го стандарта растворитель можно использовать, даже если его пи­ки регистри­ру­ются в «усеченном» виде в результате ограничения выходных сиг­на­лов усили­те­ля. Использование относительных площадей пиков не требует никаких до­по­л­нительных операций с образцами, кроме регистрации площадей пиков раст­во­рителя. Сравнение обычного и модифицированного вариантов способа внешне­го стандарта показывает, что за­ме­на абсолютных значений площадей пиков от­но­шениями площадей пиков целе­во­го аналита и растворителя не влияет на ха­рактеристики точности опреде­лений по критерию «введено-найдено», но уме­ньшает случайную соста­в­­ля­ю­щую погрешности оп­ре­делений в 2–3 раза. Обсуждается проблема повышения достоверности подобных статисти­чес­ких оценок, для чего представляется це­ле­со­образным изменение «дизайна» экс­пе­риментальных операций. Вместо последова­те­льных анализов однотипных об­разцов предпочтительнее использовать параллель­ные определения, что мож­но достичь, например, при выполнении практических ра­бот сту­дентами.Ключевые слова: количественный газохроматографический анализ, способ внеш­него стандарта, растворитель как дополнительный стандарт, уменьшение случайной составляющей погрешностей определенийDOI: http://dx.doi.org/10.15826/analitika.2022.26.2.00

Verdazyl radical building blocks: synthesis, structure, and sonogashira cross-coupling reactions

A general and effective method for the synthesis of 3-phenylveradzyl radicals bearing a variety of iodophenyl substituents has been developed. The synthesized radicals have been characterized by ESR, UV/Vis spectroscopy, and cyclic voltammetry. Structures of biphenyl-substituted radicals have been solved by X-ray crystal structure analysis. The synthesized iodoverdazyls are applicable in the Sonogashira coupling reaction for the preparation of a wide range of ethynyl derivatives. Both N-2 and C-6 substituents were functionalized through Sonogashira coupling

Remote beam output audits: A global assessment of results out of tolerance

Background and purpose: Remote beam output audits, which independently measure an institution’s machine calibration, are a common component of independent radiotherapy peer review. This work reviews the results and trends of these audit results across several organisations and geographical regions. Materials and methods: Beam output audit results from the Australian Clinical Dosimetry Services, International Atomic Energy Agency, Imaging and Radiation Oncology Core, and Radiation Dosimetry Services were evaluated from 2010 to the present. The rate of audit results outside a ±5% tolerance was evaluated for photon and electron beams as a function of the year of irradiation and nominal beam energy. Additionally, examples of confirmed calibration errors were examined to provide guidance to clinical physicists and auditing bodies. Results: Of the 210,167 audit results, 1323 (0.63%) were outside of tolerance. There was a clear trend of improved audit performance for more recent dates, and while all photon energies generally showed uniform rates of results out of tolerance, low (6 MeV) and high (≥18 MeV) energy electron beams showed significantly elevated rates. Twenty nine confirmed calibration errors were explored and attributed to a range of issues, such as equipment failures, errors in setup, and errors in performing the clinical reference calibration. Forty-two percent of these confirmed errors were detected during ongoing periodic monitoring, and not at the time of the first audit of the machine. Conclusions: Remote beam output audits have identified, and continue to identify, numerous and often substantial beam calibration errors. Keywords: Global harmonization group, Remote beam output audit, Dosimetry audit, Calibration, Q

Direct observation of the dead-cone effect in quantum chromodynamics

The direct measurement of the QCD dead cone in charm quark fragmentation is reported, using iterative declustering of jets tagged with a fully reconstructed charmed hadron

Direct observation of the dead-cone effect in quantum chromodynamics

At particle collider experiments, elementary particle interactions with large momentum transfer produce quarks and gluons (known as partons) whose evolution is governed by the strong force, as described by the theory of quantum chromodynamics (QCD) [1]. The vacuum is not transparent to the partons and induces gluon radiation and quark pair production in a process that can be described as a parton shower [2]. Studying the pattern of the parton shower is one of the key experimental tools in understanding the properties of QCD. This pattern is expected to depend on the mass of the initiating parton, through a phenomenon known as the dead-cone effect, which predicts a suppression of the gluon spectrum emitted by a heavy quark of mass m and energy E, within a cone of angular size m/E around the emitter [3]. A direct observation of the dead-cone effect in QCD has not been possible until now, due to the challenge of reconstructing the cascading quarks and gluons from the experimentally accessible bound hadronic states. Here we show the first direct observation of the QCD dead-cone by using new iterative declustering techniques [4, 5] to reconstruct the parton shower of charm quarks. This result confirms a fundamental feature of QCD, which is derived more generally from its origin as a gauge quantum field theory. Furthermore, the measurement of a dead-cone angle constitutes the first direct experimental observation of the non-zero mass of the charm quark, which is a fundamental constant in the standard model of particle physics.The direct measurement of the QCD dead cone in charm quark fragmentation is reported, using iterative declustering of jets tagged with a fully reconstructed charmed hadron.In particle collider experiments, elementary particle interactions with large momentum transfer produce quarks and gluons (known as partons) whose evolution is governed by the strong force, as described by the theory of quantum chromodynamics (QCD). These partons subsequently emit further partons in a process that can be described as a parton shower which culminates in the formation of detectable hadrons. Studying the pattern of the parton shower is one of the key experimental tools for testing QCD. This pattern is expected to depend on the mass of the initiating parton, through a phenomenon known as the dead-cone effect, which predicts a suppression of the gluon spectrum emitted by a heavy quark of mass $m_{\rm{Q}}$ and energy $E$, within a cone of angular size $m_{\rm{Q}}$/$E$ around the emitter. Previously, a direct observation of the dead-cone effect in QCD had not been possible, owing to the challenge of reconstructing the cascading quarks and gluons from the experimentally accessible hadrons. We report the direct observation of the QCD dead cone by using new iterative declustering techniques to reconstruct the parton shower of charm quarks. This result confirms a fundamental feature of QCD. Furthermore, the measurement of a dead-cone angle constitutes a direct experimental observation of the non-zero mass of the charm quark, which is a fundamental constant in the standard model of particle physics