Probing the Association Behavior of Hydrophobic Organic Compounds with Dissolved Humic Materials

The association mechanism between hydrophobic organic compounds (HOC) and dissolved humic materials (DHM) has continued to be one of the interesting areas in environmental applications. The goal of the research reported in this dissertation is to investigate the association behavior of HOC with DHM. The first part of this research involves steady-state fluorescence measurements of these multi-component systems to study the effect of DHM content on the association mechanism of HOC, in particular using pyrene as a model. Results showed that steady-state fluorescence alone may not provide enough information about the quenching mechanism of pyrene with DHM. Lifetime based fluorescence measurements allow for a deeper mechanistic understanding as compared to the traditional steady-state technique. However, photobleaching, dissolved oxygen, and HOC adsorption to cell walls are problems encountered in lifetime measurements. These effects can directly complicate the interpretation of fluorescence lifetime results. Therefore, a new approach to frequency-domain lifetime measurements, based on frequency segmentation and recombination, was developed during the second part of this dissertation research to address these experimental considerations. The frequency segmentation and recombination method was evaluated using a simple two component system consisting of fluorescein and rhodamine B mixture. Comparison of experimental data collected in traditional and segmented fashion with simulated data demonstrated the validity of the technique. The newly developed method was applied to mixtures of pyrene and DHM to further investigate the pyrene quenching mechanism with DHM. Finally, the chemical effect of chiral pesticides (coumachlor, difenacoum, warfarin, and napropamide) in the presence of Leonardite humic acid standard (LHAS) was investigated by use of steady-state fluorescence spectroscopy. In addition, the chiral recognition ability and enantiomeric selectivity of LHAS with pure enantiomers of 1,1\u27-bi-2-naphthol bis (trifluoro - methanesulfonate) and 1-(9-anthryl)-2,2,2-trifluoroethanol, used as probes of the interaction, were investigated using liquid-state 19F NMR spectroscopy. To further study DHM enantioselectivity with chiral compounds, the interaction of R or S-1-(9-anthryl)-2,2,2-trifluoroethanol with LHAS was evaluated for samples monitored in the dark and exposed to light for different time periods by use of high performance liquid chromatography

Study of isotherm and kinetic models of lanthanum adsorption on activated carbon loaded with recently synthesized Schiff’s base

AbstractA new effective adsorbent was developed for a selective extraction and determination of lanthanum from aqueous media by use of inductively coupled plasma-optical emission spectrometry. The new adsorbent was based on activated carbon modified with Schiff’s base derived from diethylenetriamine and 3,4-dihydroxybenzaldehyde (AC-DETADHBA). Isotherm and kinetic models were systematically investigated to evaluate the analytical potential of the AC-DETADHBA phase toward La(III) by employing a batch adsorption technique. Surface properties of AC-DETADHBA were characterized by Fourier transform infrared spectrometry. The maximum static adsorption capacity was determined to be 144.80mgg−1 at pH 6, providing that the adsorption capacity of La(III) was improved by 61.79% with the AC-DETADHBA phase as compared to the carboxylic acid derivative of activated carbon after only 1h contact time. Adsorption isotherm results demonstrated that the adsorption process was mainly monolayer on a homogeneous adsorbent surface, confirming the validity of Langmuir adsorption isotherm model. Data obtained from kinetic models study indicated that the adsorption of La(III) onto the AC-DETADHBA phase obeyed a pseudo second-order kinetic model. In addition, results of thermodynamic investigation also revealed that the adsorption mechanism of AC-DETADHBA toward La(III) is a general spontaneous process and favorable. The effect of several coexisting metal ions displayed that the recovery of La(III) was not affected by the medium composition containing either individual or mixed metals. Finally, the newly proposed method gave satisfactory results for the determination of La(III) in environmental water samples

Chiral Recognition of Amino Acids by Use of a Fluorescent Resorcinarene

The spectroscopic properties of a chiral boronic acid based resorcinarene macrocycle employed for chiral analysis were investigated. Specifically, the emission and excitation characteristics of tetraarylboronate resorcinarene macrocycle (TBRM) and its quantum yield were evaluated. The chiral selector TBRM was investigated as a chiral reagent for the enantiomeric discrimination of amino acids using steady-state fluorescence spectroscopy. Chiral recognition of amino acids in the presence of the macrocycle was based on diastereomeric complexes. Results demonstrated that TBRM had better chiral discrimination ability for lysine as compared to the other amino acids. Partial least squares regression modeling (PLS-1) of spectral data for macrocycle-lysine guest-host complexes was used to correlate the changes in the fluorescence emission for a set of calibration samples consisting of TBRM in the presence of varying enantiomeric compositions of lysine. In addition, validation studies were performed using an independently prepared set of samples with different enantiomeric compositions of lysine. The results of multivariate regression modeling indicated good prediction ability of lysine, which was confirmed by a root mean square percent relative error (RMS%RE) of 5.8%

Efficient synthesis and characterization of Polyaniline@Aluminium–succinate metal-organic frameworks nanocomposite and its application for Zn(II) ion sensing

A new class of conductive metal-organic framework (MOF), polyaniline- aluminum succinate (PANI@Al-SA) nanocomposite was prepared by oxidative polymerization of aniline monomer using potassium persulfate as an oxidant. Several analytical techniques such as FTIR, FE-SEM, EDX, XRD, XPS and TGA-DTA were utilized to characterize the obtained MOFs nanocomposite. DC electrical conductivity of polymer-MOFs was determined by four probe method. A bare glassy carbon electrode (GCE) was modified by nafion/PANI@Al-SA, and examined for Zn (II) ion detection. Modified electrode showed improved efficiency by 91.9%. The modified electrode (PANI@Al-SA/nafion/GCE) exhibited good catalytic property and highly selectivity towards Zn(II) ion. A linear dynamic range of 2.8–228.6 µM was obtained with detection limit of LOD 0.59 µM and excellent sensitivity of 7.14 µA µM−1 cm−2. The designed procedure for Zn (II) ion detection in real sample exhibited good stability in terms of repeatability, reproducibility and not affected by likely interferents. Therefore, the developed procedure is promising for quantification of Zn(II) ion in real samples

Development of Polymer Based Nanocomposites as a Marker of Cadmium in Complex Matrices

Poly(propylene carbonate)/β-cyclodextrin (PPC-BCD) nanocomposites were developed as effective extractor for a specific extraction and separation of cadmium(II) by use of inductively coupled plasma-optical emission spectrometry. The selectivity of nanocomposites with different wt% of BCD (PPC-BCD 0.5, PPC-BCD 1, PPC-BCD 3, PPC-BCD 5, or PPC-BCD 10) was investigated toward Cd(II). Based on selectivity and pH studies, Cd(II) was the most quantitatively adsorbed on PPC-BCD 5 phase at pH 6, indicating that PPC-BCD 5 was the most selective toward Cd(II) among other nanocomposites. On the basis of adsorption isotherm study, the superior adsorption capacity of PPC-BCD 5 phase for Cd(II) was found to be 149.25 mg·g−1, following the Langmuir adsorption isotherm model. The kinetic of adsorption for Cd(II) has been examined by pseudo-first- and second-order models. The kinetic exploration suggested a pseudo-second-order kinetic model for the adsorption of Cd(II) on the PPC-BCD 5. Additionally, results of thermodynamic investigation demonstrated favorable spontaneous process for the adsorption mechanism of PPC-BCD 5 toward Cd(II)

Efficient synthesis and characterization of Polyaniline@Aluminium–succinate metal-organic frameworks nanocomposite and its application for Zn(II) ion sensing

A new class of conductive metal-organic framework (MOF), polyaniline- aluminum succinate (PANI@Al-SA) nanocomposite was prepared by oxidative polymerization of aniline monomer using potassium persulfate as an oxidant. Several analytical techniques such as FTIR, FE-SEM, EDX, XRD, XPS and TGA-DTA were utilized to characterize the obtained MOFs nanocomposite. DC electrical conductivity of polymer-MOFs was determined by four probe method. A bare glassy carbon electrode (GCE) was modified by nafion/PANI@Al-SA, and examined for Zn (II) ion detection. Modified electrode showed improved efficiency by 91.9%. The modified electrode (PANI@Al-SA/nafion/GCE) exhibited good catalytic property and highly selectivity towards Zn(II) ion. A linear dynamic range of 2.8–228.6 µM was obtained with detection limit of LOD 0.59 µM and excellent sensitivity of 7.14 µA µM−1 cm−2. The designed procedure for Zn (II) ion detection in real sample exhibited good stability in terms of repeatability, reproducibility and not affected by likely interferents. Therefore, the developed procedure is promising for quantification of Zn(II) ion in real samples

Efficient synthesis and characterization of Polyaniline@Aluminium–succinate metal-organic frameworks nanocomposite and its application for Zn(II) ion sensing

A new class of conductive metal-organic framework (MOF), polyaniline- aluminum succinate (PANI@Al-SA) nanocomposite was prepared by oxidative polymerization of aniline monomer using potassium persulfate as an oxidant. Several analytical techniques such as FTIR, FE-SEM, EDX, XRD, XPS and TGA-DTA were utilized to characterize the obtained MOFs nanocomposite. DC electrical conductivity of polymer-MOFs was determined by four probe method. A bare glassy carbon electrode (GCE) was modified by nafion/PANI@Al-SA, and examined for Zn (II) ion detection. Modified electrode showed improved efficiency by 91.9%. The modified electrode (PANI@Al-SA/nafion/GCE) exhibited good catalytic property and highly selectivity towards Zn(II) ion. A linear dynamic range of 2.8–228.6 µM was obtained with detection limit of LOD 0.59 µM and excellent sensitivity of 7.14 µA µM−1 cm−2. The designed procedure for Zn (II) ion detection in real sample exhibited good stability in terms of repeatability, reproducibility and not affected by likely interferents. Therefore, the developed procedure is promising for quantification of Zn(II) ion in real samples

Efficient synthesis and characterization of Polyaniline@Aluminium–succinate metal-organic frameworks nanocomposite and its application for Zn(II) ion sensing

A new class of conductive metal-organic framework (MOF), polyaniline- aluminum succinate (PANI@Al-SA) nanocomposite was prepared by oxidative polymerization of aniline monomer using potassium persulfate as an oxidant. Several analytical techniques such as FTIR, FE-SEM, EDX, XRD, XPS and TGA-DTA were utilized to characterize the obtained MOFs nanocomposite. DC electrical conductivity of polymer-MOFs was determined by four probe method. A bare glassy carbon electrode (GCE) was modified by nafion/PANI@Al-SA, and examined for Zn (II) ion detection. Modified electrode showed improved efficiency by 91.9%. The modified electrode (PANI@Al-SA/nafion/GCE) exhibited good catalytic property and highly selectivity towards Zn(II) ion. A linear dynamic range of 2.8–228.6 µM was obtained with detection limit of LOD 0.59 µM and excellent sensitivity of 7.14 µA µM−1 cm−2. The designed procedure for Zn (II) ion detection in real sample exhibited good stability in terms of repeatability, reproducibility and not affected by likely interferents. Therefore, the developed procedure is promising for quantification of Zn(II) ion in real samples

Use of nanomaterials in the pretreatment of water samples for environmental analysis

The challenge of providing clean drinking water is of enormous relevance in today’s human civilization, being essential for human consumption, but also for agriculture, livestock and several industrial applications. In addition to remediation strategies, the accurate monitoring of pollutants in water sup-plies, which most of the times are present at low concentrations, is a critical challenge. The usual low concentration of target analytes, the presence of in-terferents and the incompatibility of the sample matrix with instrumental techniques and detectors are the main reasons that renders sample preparation a relevant part of environmental monitoring strategies. The discovery and ap-plication of new nanomaterials allowed improvements on the pretreatment of water samples, with benefits in terms of speed, reliability and sensitivity in analysis. In this chapter, the use of nanomaterials in solid-phase extraction (SPE) protocols for water samples pretreatment for environmental monitoring is addressed. The most used nanomaterials, including metallic nanoparticles, metal organic frameworks, molecularly imprinted polymers, carbon-based nanomaterials, silica-based nanoparticles and nanocomposites are described, and their applications and advantages overviewed. Main gaps are identified and new directions on the field are suggested.publishe

Global burden of 288 causes of death and life expectancy decomposition in 204 countries and territories and 811 subnational locations, 1990–2021: a systematic analysis for the Global Burden of Disease Study 2021

Background: Regular, detailed reporting on population health by underlying cause of death is fundamental for public health decision making. Cause-specific estimates of mortality and the subsequent effects on life expectancy worldwide are valuable metrics to gauge progress in reducing mortality rates. These estimates are particularly important following large-scale mortality spikes, such as the COVID-19 pandemic. When systematically analysed, mortality rates and life expectancy allow comparisons of the consequences of causes of death globally and over time, providing a nuanced understanding of the effect of these causes on global populations. Methods: The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2021 cause-of-death analysis estimated mortality and years of life lost (YLLs) from 288 causes of death by age-sex-location-year in 204 countries and territories and 811 subnational locations for each year from 1990 until 2021. The analysis used 56 604 data sources, including data from vital registration and verbal autopsy as well as surveys, censuses, surveillance systems, and cancer registries, among others. As with previous GBD rounds, cause-specific death rates for most causes were estimated using the Cause of Death Ensemble model—a modelling tool developed for GBD to assess the out-of-sample predictive validity of different statistical models and covariate permutations and combine those results to produce cause-specific mortality estimates—with alternative strategies adapted to model causes with insufficient data, substantial changes in reporting over the study period, or unusual epidemiology. YLLs were computed as the product of the number of deaths for each cause-age-sex-location-year and the standard life expectancy at each age. As part of the modelling process, uncertainty intervals (UIs) were generated using the 2·5th and 97·5th percentiles from a 1000-draw distribution for each metric. We decomposed life expectancy by cause of death, location, and year to show cause-specific effects on life expectancy from 1990 to 2021. We also used the coefficient of variation and the fraction of population affected by 90% of deaths to highlight concentrations of mortality. Findings are reported in counts and age-standardised rates. Methodological improvements for cause-of-death estimates in GBD 2021 include the expansion of under-5-years age group to include four new age groups, enhanced methods to account for stochastic variation of sparse data, and the inclusion of COVID-19 and other pandemic-related mortality—which includes excess mortality associated with the pandemic, excluding COVID-19, lower respiratory infections, measles, malaria, and pertussis. For this analysis, 199 new country-years of vital registration cause-of-death data, 5 country-years of surveillance data, 21 country-years of verbal autopsy data, and 94 country-years of other data types were added to those used in previous GBD rounds. Findings: The leading causes of age-standardised deaths globally were the same in 2019 as they were in 1990; in descending order, these were, ischaemic heart disease, stroke, chronic obstructive pulmonary disease, and lower respiratory infections. In 2021, however, COVID-19 replaced stroke as the second-leading age-standardised cause of death, with 94·0 deaths (95% UI 89·2–100·0) per 100 000 population. The COVID-19 pandemic shifted the rankings of the leading five causes, lowering stroke to the third-leading and chronic obstructive pulmonary disease to the fourth-leading position. In 2021, the highest age-standardised death rates from COVID-19 occurred in sub-Saharan Africa (271·0 deaths [250·1–290·7] per 100 000 population) and Latin America and the Caribbean (195·4 deaths [182·1–211·4] per 100 000 population). The lowest age-standardised death rates from COVID-19 were in the high-income super-region (48·1 deaths [47·4–48·8] per 100 000 population) and southeast Asia, east Asia, and Oceania (23·2 deaths [16·3–37·2] per 100 000 population). Globally, life expectancy steadily improved between 1990 and 2019 for 18 of the 22 investigated causes. Decomposition of global and regional life expectancy showed the positive effect that reductions in deaths from enteric infections, lower respiratory infections, stroke, and neonatal deaths, among others have contributed to improved survival over the study period. However, a net reduction of 1·6 years occurred in global life expectancy between 2019 and 2021, primarily due to increased death rates from COVID-19 and other pandemic-related mortality. Life expectancy was highly variable between super-regions over the study period, with southeast Asia, east Asia, and Oceania gaining 8·3 years (6·7–9·9) overall, while having the smallest reduction in life expectancy due to COVID-19 (0·4 years). The largest reduction in life expectancy due to COVID-19 occurred in Latin America and the Caribbean (3·6 years). Additionally, 53 of the 288 causes of death were highly concentrated in locations with less than 50% of the global population as of 2021, and these causes of death became progressively more concentrated since 1990, when only 44 causes showed this pattern. The concentration phenomenon is discussed heuristically with respect to enteric and lower respiratory infections, malaria, HIV/AIDS, neonatal disorders, tuberculosis, and measles. Interpretation: Long-standing gains in life expectancy and reductions in many of the leading causes of death have been disrupted by the COVID-19 pandemic, the adverse effects of which were spread unevenly among populations. Despite the pandemic, there has been continued progress in combatting several notable causes of death, leading to improved global life expectancy over the study period. Each of the seven GBD super-regions showed an overall improvement from 1990 and 2021, obscuring the negative effect in the years of the pandemic. Additionally, our findings regarding regional variation in causes of death driving increases in life expectancy hold clear policy utility. Analyses of shifting mortality trends reveal that several causes, once widespread globally, are now increasingly concentrated geographically. These changes in mortality concentration, alongside further investigation of changing risks, interventions, and relevant policy, present an important opportunity to deepen our understanding of mortality-reduction strategies. Examining patterns in mortality concentration might reveal areas where successful public health interventions have been implemented. Translating these successes to locations where certain causes of death remain entrenched can inform policies that work to improve life expectancy for people everywhere. Funding: Bill & Melinda Gates Foundation