Recommended isolated-line profile for representing high-resolution spectroscopic transitions (IUPAC Technical Report)

The report of an IUPAC Task Group, formed in 2011 on "Intensities and line shapes in high-resolution spectra of water isotopologues from experiment and theory" (Project No. 2011-022-2-100), on line profiles of isolated high-resolution rotational-vibrational transitions perturbed by neutral gas-phase molecules is presented. The well-documented inadequacies of the Voigt profile (VP), used almost universally by databases and radiative-transfer codes, to represent pressure effects and Doppler broadening in isolated vibrational-rotational and pure rotational transitions of the water molecule have resulted in the development of a variety of alternative line-profile models. These models capture more of the physics of the influence of pressure on line shapes but, in general, at the price of greater complexity. The Task Group recommends that the partially Correlated quadratic-Speed-Dependent Hard-Collision profile should be adopted as the appropriate model for high-resolution spectroscopy. For simplicity this should be called the Hartmann--Tran profile (HTP). The HTP is sophisticated enough to capture the various collisional contributions to the isolated line shape, can be computed in a straightforward and rapid manner, and reduces to simpler profiles, including the Voigt profile, under certain simplifying assumptions.Comment: Accepted for publication in Pure and Applied Chemistr

Recommended Isolated-Line Profile for Representing High-Resolution Spectroscopic Transitions (IUPAC Technical Report)

The report of an IUPAC Task Group, formed in 2011 on Intensities and line shapes in high-resolution spectra of water isotopologues from experiment and theory (Project No. 2011-022-2-100), on line profiles of isolated high-resolution rotational-vibrational transitions perturbed by neutral gas-phase molecules is presented. The well-documented inadequacies of the Voigt profile (VP), used almost universally by databases and radiative-transfer codes, to represent pressure effects and Doppler broadening in isolated vibrational-rotational and pure rotational transitions of the water molecule have resulted in the development of a variety alternative line-profile models. These models capture more of the physics of the influence of pressure on line shapes but, in general, at the price of greater complexity. The Task Group recommends that the partially Correlated quadratic-Speed-Dependent Hard-Collision profile (pCqSD-HCP) should be adopted as the appropriate model for high-resolution spectroscopy. For simplicity this should be called the Hartmann-Tran profile (HTP). The HTP is sophisticated enough to capture the various collisional contributions to the isolated line shape, can be computed in a straightforward and rapid manner, and reduces to simpler profiles, including the Voigt profile, under certain simplifying assumptions. © 2014 IUPAC & De Gruyte

New methods for the speciated detection of peroxy radicals

Organic peroxy radicals, RO2, are a key component of the reaction cycles that control the chemical composition of the troposphere and how efficiently pollutants like greenhouse gases are removed. They are formed through the oxidation of any biogenic or anthropogenic volatile organic compound (VOC) in the troposphere and lead to the production of ozone, secondary organic aerosols, organic nitrates and more. Despite the significance of RO2 radicals in tropospheric chemistry, there are currently no methods in regular use that can perform speciated measurements of the radicals in the field, instead only the sum of all RO2 can be measured routinely. In this thesis a new method is developed to specifically detect the methyl-peroxy radical, CH3O2, which is the simplest and most abundant RO2 radical in the troposphere. The method is based on Fluorescence Assay by Gas Expansion (FAGE) and detects CH3O2 by converting it to CH¬3O by titration with NO, which is then detected by Laser Induced Fluorescence (LIF) using ~298 nm light to excite the A2A1 (’3 = 3) X2E (”3 = 0) electronic transition. With a limit of detection of ~2 × 108 molecule cm 3 for a 5-minute averaging time the method could be a viable technique in low NOx environments where CH3O2 levels are estimated to be ~2 - 6 × 108 molecule cm 3. The method was tested using the Highly Instrumented Reaction for Atmospheric Chemistry (HIRAC), an atmospheric simulation chamber that can operate at temperatures between ~250 – 350 K. Using the new FAGE method in conjunction with HIRAC, the temperature dependent kinetics of the CH3O2 self-reaction were measured between 268 – 344 K, giving a temperature dependent rate coefficient of k6.1 = (4.2±3.8) × 10 14 exp[(516±284)/T] cm3 molecule 1 s 1 and a value at 298 K of k6.1 = (2.37 ± 1.09) × 10 13 cm3 molecule 1 s 1. No significant temperature dependence was found, but the rate coefficients are approximately 30 % lower than current literature. A ROxLIF instrument, newly developed for HIRAC, was also used to make preliminary measurements of the CH3O2 self-reaction at 295 K, finding a value that was similarly ~30 % lower than literature. The temperature dependence of the CH3O2 + HO2 reaction was also measured using the new FAGE method, giving a temperature dependent rate coefficient of k6.3 = (1.26 ± 0.38) × 10 13 exp[(1119 ± 89)/T] cm3 molecule 1 s 1 and a value at 298 K of k6.3 = (5.38 ± 0.18) × 10 12 cm3 molecule 1 s 1, agreeing well with literature values

Signal transfer with excitation-emission matrices between a portable fluorimeter based on light-emitting diodes and a master fluorimeter

In this work, the transfer of the excitation-emission matrices between a portable fluorimeter based on LEDs and a master fluorimeter based on a xenon source was carried out. Enrofloxacin was the analyte of interest and it was measured alone or in binary mixtures with flumequine (partially overlapped signals) or with ciprofloxacin (fully overlapped signals). The maintenance and transfer of the unequivocal identification of the fluorophores between both instruments are shown. The precision in the determination performed with the portable fluorimeter approximated to that made with the master fluorimeter using this transfer and it did not introduce bias. The correlation coefficients of the calibrations based on PARAFAC using EEM signals were higher than 0.999, whereas the values of the capability of detection ranged from 14.8 to 26.9 μg L−1 for probabilities of false positive and false negative fixed at 0.05. These results contribute to the effort to perform the fluorimetric detection outside the laboratory and to promote the use of databases of fluorescence spectra for the unequivocal identification in remote of fluorophores of interest and/or regulated.Spanish MINECO (AEI/FEDER, UE) through projects CTQ2014-53157-R and CTQ2017‐88894‐R and by Junta de Castilla y León through project BU012P17 (all co‐financed with European FEDER funds

Gold nanoparticle to antibody conjugates for diagnosis applications: molecular interactions and immunoassay development

Thesis for the Master degree in Structural and Functional BiochemistryBionanotechnology is an area of rapidly increasing research interest, whose development can potentially improve many fields of our society by providing several advances in biomedical, energy and environment research fields. The present work includes both applied and basic research on bionanoconjugates of gold nanoparticles (AuNP) with antibodies (Ab) referred to as AuNP@Ab. The two main themes of research are: i) development of a fluorescence immunoassay for malaria diagnosis, using a sensing methodology involving the competitive binding between a fluorophore-labeled antigen (CyAg) and the unlabeled antigen (Ag) to the AuNP@Ab conjugates. The Ag is a new biomarker of malaria infection, the heat shock protein 70 from Plasmodium falciparum (PfHsp70). ii) physico-chemical characterization of the interaction between the Ag and the AuNP@Ab using Fluorescence, Differential Centrifugal Sedimentation (DCS), and Agarose Gel Electrophoresis(AGE), intended at understanding the nature of the binding, particularly its specificity and the influence of nonspecific protein competitors. The immunoassay for malaria diagnosis was successfully established using fluorescence detection for AuNPs of different diameters (15 and 30 nm) and using AGE detection for 30 nm-AuNPs. The AuNP@Ab bionanoconjugates exhibited a specific response to the target Ag, with little, or none, non-specific binding when purified transferrin (Trf) is used. Non-specific binding of proteins from plasma was nevertheless detected. Ag binding to AuNP@Ab was assessed in competitive conditions both with plasma and with Trf. Trf inhibited the Ag binding, while plasma inhibited the Ag binding as accessed by DCS but the same conclusion could not be made for fluorescence due to the large background signal caused by plasma unspecific binding

Procedure to build a signal transfer set, independent of the target analytes, between a portable fluorimeter based on light-emitting diodes and a master fluorimeter

The need of performing “in situ” analytical determinations together with the availability of high-power deep UV-LEDs have led to the use of fluorescence spectroscopy. However, it is necessary to register excitation-emission matrices (EEM) to obtain three-way data which can be decomposed using parallel factor analysis for enabling the unequivocal identification of the analytes. In this context, the feasibility of transferring EEM between a portable fluorimeter based on LEDs and a master fluorimeter based on a xenon source has been recently reported without losing analytical quality. To build the transfer function, the signals of the same N samples must be recorded in the portable and in the master fluorimeter. In literature, these samples always contained the target analytes so the EEM signal transfer methodology is very limited in practice. Therefore, the challenge is to search for a set of samples whose EEM enable to perform the signal transfer without previously knowing the target analytes. The aim of this work is the design of a procedure to build N mixtures of P fluorophores so the N EEM would be optimal for the signal transfer. Five criteria have been defined a priori to identify the quality of a transfer set made up of N EEM. Then, a procedure has been designed to obtain the n mixtures of the P fluorophores “in silico” using the Pareto front of the optimal solutions and a desirability function to choose the desired N EEM. The procedure has been used to find five mixtures of the three chosen fluorophores for the signal transfer (coumarin 120, DL-Tyrosine and DL-Tryptophan) which are chemically different from the analytes of interest (enrofloxacin and flumequine) and are contained in a different matrix. These two analytes are antibiotics which have maximum residue limits set in the EU legislation in force. The correlation coefficients between the experimental reference spectra and the PARAFAC spectral loadings of the data registered with the master fluorimeter were greater than or equal to 0.999 in all cases. On the other hand, the correlation coefficients obtained with the portable fluorimeter ranged from 0.900 to 0.950 once the procedure was applied to the two antibiotics. Therefore, the unequivocal identification of the analytes was ensured.Spanish MINECO (AEI/FEDER, UE) through project CTQ2017‐88894‐R and by Junta de Castilla y León through project BU012P17 (all co‐financed with European FEDER funds)

Pressure-dependent calibration of the OH and HO2 channels of a FAGE HOx instrument using the Highly Instrumented Reactor for Atmospheric Chemistry (HIRAC)

The calibration of field instruments used to measure concentrations of OH and HO2 worldwide has traditionally relied on a single method utilising the photolysis of water vapour in air in a flow tube at atmospheric pressure. Here the calibration of two FAGE (fluorescence assay by gaseous expansion) apparatuses designed for HOx (OH and HO2) measurements have been investigated as a function of external pressure using two different laser systems. The conventional method of generating known concentrations of HOx from H2O vapour photolysis in a turbulent flow tube impinging just outside the FAGE sample inlet has been used to study instrument sensitivity as a function of internal fluorescence cell pressure (1.8-3.8 mbar). An increase in the calibration constants CHO and CHO2 with pressure was observed, and an empirical linear regression of the data was used to describe the trends, with ΔCHO Combining double low line (17 ± 11) % and ΔCHO2 Combining double low line (31.6 ± 4.4)% increase per millibar air (uncertainties quoted to 2σ). Presented here are the first direct measurements of the FAGE calibration constants as a function of external pressure (440-1000 mbar) in a controlled environment using the University of Leeds HIRAC chamber (Highly Instrumented Reactor for Atmospheric Chemistry). Two methods were used: the temporal decay of hydrocarbons for calibration of OH, and the kinetics of the second-order recombination of HO2 for HO2 calibrations. Over comparable conditions for the FAGE cell, the two alternative methods are in good agreement with the conventional method, with the average ratio of calibration factors (conventional : alternative) across the entire pressure range, COH(conv)/COH(alt) Combining double low line 1.19 ± 0.26 and CHO2(conv)/CHO2(alt) Combining double low line 0.96 ± 0.18 (2σ). These alternative calibration methods currently have comparable systematic uncertainties to the conventional method: ∼ 28% and ∼ 41% for the alternative OH and HO2 calibration methods respectively compared to 35% for the H2O vapour photolysis method; ways in which these can be reduced in the future are discussed. The good agreement between the very different methods of calibration leads to increased confidence in HOx field measurements and particularly in aircraft-based HOx measurements, where there are substantial variations in external pressure, and assumptions are made regarding loss rates on inlets as a function of pressure

A Review Focusing on Aspects of Environmental Chemistry

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