Fluorimetric characterization of single-walled carbon nanotubes

Single-walled carbon nanotubes (SWCNTs) are a family of structurally related artificial nanomaterials with unusual properties and many potential applications. Most SWCNTs can emit spectrally narrow near-IR fluorescence at wavelengths that are characteristic of their precise diameter and chiral angle. Near-IR fluorimetry therefore offers a powerful approach for identifying the structural species present in SWCNT samples. Such characterization is increasingly important for nanotube production, study, separation, and applications. General-purpose and specialized instruments suitable for SWCNT fluorimetric analysis are described, and methods for interpreting fluorimetric data to deduce the presence and relative abundances of different SWCNT species are presented. Fluorescence methods are highly effective for detecting SWCNTs in challenging samples such as complex environmental or biological specimens because of the methods’ high sensitivity and selectivity and the near absence of interfering background emission at near-IR wavelengths. Current limitations and future prospects for fluorimetric characterization of SWCNTs are discussed.     

Application of solid-phase microextraction for determination of organic vapours in gaseous matrices

This paper reviews the practical applications of solid-phase microextraction (SPME) in the analysis of organic vapours which are pollutants of atmospheric air, indoor air and workplace air. Applications to headspace of solids and liquids such as different waters, soils, food, etc., are also included. Problems related to calibration in SPME analysis of gaseous matrices are also dealt with. Calibration procedures and apparatus for generation of standard gaseous mixtures are described. Advantages and limitations of SPME based gas chromatographic methods of air organic pollutants are discussed.     

Preparation and performances of small bore columns packed with reversed-phase materials and their use for the evaluation of air pollutants

Summary The preparation of small bore columns (1 mm i.d.) packed with reversed-phase materials is described. High efficiency (H_min=2 dp), coupled with a small C term (0.005 sec) have been obtained so that high speed can be combined with sufficient resolution for the separation of complex organic mixtures. These columns have been used for the separation of air pollutants dispersed in different matrices (air, particulate matter and rain water). Practical applications include the determination of aldehydes in air and emission samples, PAHs, nitrated and oxygenated PAHs in dust sampled from the stack of an industrial emission or collected in a urban area and the analysis of organic components dissolved in rain water collected at a rural site. Specific detection of these pollutants has been achieved by connecting small bore columns to UV absorbance, voltammetric and fluorimetric detectors. Mass spectra of some specific components have been recorded using the off-line technique.This work has been performed as a part of a Research Doctorate thesis to be discussed at the University of Rome.Dedicated to Prof. Dr. A. Liberti on the occasion of his 70th birthday.     

A fluorescence toolbox: A review of investigation of electrophoretic separations,process, and interfaces

This review focuses on fluorescence spectroscopy techniques for the investigation of electrophoretic separations. Fluorescence has been used as a sensitive detector for capillary, gel, and microchip electrophoresis for decades. However, advanced fluorescence methods can be used to study transport, interfacial phenomena, intermolecular and affinity interactions, and other processes that occur during separation. This so‐called spectroscopic toolkit can be implemented to understand fundamental behavior in electrophoresis and electrokinetic chromatography. Techniques such as fluorescence recovery after photobleaching, fluorescence correlation spectroscopy, and fluorescence anisotropy are discussed in relation to electrophoretic separations. Newer methods such as super‐resolution microscope are also introduced.     

Validated spectrophotometric and fluorimetric methods for analysis of clozapine in tablets and urine

Five spectrophotometric methods and one fluorimetric method have been developed and validated for the analysis of clozapine. The spectrophotometric methods were based on the charge-transfer complexation reaction between clozapine as electron donor and each of iodine as sigma-acceptor or 7,7,8,8-tetracyanoquinondimethane (TCNQ), 2,3-dichloro-5,6-dicyano-1,4-benzo-quinone (DDQ), tetracyanoethane (TCNE), and p-chloranilic acid (pCA) as pi-acceptors. The obtained complexes were measured spectrophotometrically at 365, 843, 460, 414, and 520 nm for iodine, TCNQ, DDQ, TCNE, and pCA, respectively. The fluorimetric method was based on the oxidation of clozapine in the presence of perchloric acid by cerium (IV), and subsequent measuring the fluorescence of the produced cerium (III) fluorimetrically at lambda(excitation) 260 and lambda(emission) 355 nm. Under the optimum assay conditions, Beer's law was obeyed at concentrations ranged from 4-200 microg mL(-1) for the spectrophotometric methods and from 24-250 ng mL(-1) for the fluorimetric method. The limits of detection for the spectrophotometric methods were 1.12, 1.76, 2.22, 0.95, and 13.26 microg mL(-1) for iodine, TCNQ, DDQ, TCNE, and pCA, respectively. The limit of detection for the fluorimetric method was 6.69 ng mL(-1). The proposed methods were successfully applied to the analysis of clozapine in tablets with good recoveries. The fluorimetric method could also be applied to the analysis of clozapine in spiked urine samples. The molar ratios and the reaction mechanisms were investigated.     

Direct laser photo-induced fluorescence determination of bisphenol A

Classical photo-induced fluorescence methods are conducted in two steps: a UV irradiation step in order to form a photo-induced compound followed by its fluorimetric determination. Automated flow injection methods are frequently used for these analyses. In this work, we propose a new method of direct laser photo-induced fluorescence analysis. This new method is based on direct irradiation of the analyte in a fluorimetric cell in order to form a photo-induced fluorescent compound and its direct fluorimetric detection during a short irradiation time. Irradiation is performed with a tuneable Nd:YAG laser to select the optimal excitation wavelength and to improve the specificity. It has been applied to the determination of bisphenol A, an endocrine disrupter compound that may be a potential contaminant for food. Irradiation of bisphenol A at 230 nm produces a photo-induced compound with a much higher fluorescence quantum yield and specific excitation/emission wavelengths. In tap water, the fluorescence of bisphenol A increases linearly versus its concentration and, its determination by direct laser photo-induced fluorescence permits to obtain a low limit of detection of 17 μg L⁻¹.     

Passive sampling and/or extraction techniques in environmental analysis: a review

The current state-of-the-art of passive sampling and/or extraction methods for long-term monitoring of pollutants in different environmental compartments is discussed in this review. Passive dosimeters that have been successfully used to monitor organic and inorganic contaminants in air, water, sediments, and soil are presented. The application of new approaches to the determination of pollutants at the sampling stage is discussed. The main milestones in the development of passive techniques for sampling and/or extraction of analytes, and in biomonitors used in environmental analysis, are summarized in this review. Passive samplers and biomonitors are compared.     

Benzyl 2-pyridyl ketone 2-pyridylhydrazone as reagent for the fluorimetric determination of zinc at ng/ml levels

A sensitive fluorimetric method for the determination of zinc, based on the formation of a fluorescent chelate with benzyl 2-pyridyl ketone 2-pyridylhydrazone is described. In darkness, the fluorescence develops rapidly and remains stable for 1 hr. The detection limit is 15 ng/ml. The effect of reaction variables, and methods of removing interferences, are discussed.     

Determination of mycotoxins in human foods

This tutorial review deals with the analytical methods available for the determination of mycotoxins in food commodities. As the secondary metabolites of a range of fungal species, mycotoxins possess diverse chemical structures, presenting analytical chemists with a unique set of challenges in the microg kg(-1) (ppb) range. A number of analytical methods have been applied to mycotoxin analysis. These include widely applicable HPLC methods with UV or fluorimetric detection, which are extensively used both in research and for legal enforcement of food safety legislation and for regulations in international agricultural trade. Other chromatographic methods, such as TLC and GC, are also employed for the determination of mycotoxins, whereas recent advances in analytical instrumentation have highlighted the potential of LC-MS methods, especially for multi-toxin determination and for confirmation purposes. Conventional chromatographic methods are generally time consuming and capital intensive, and hence a range of methods, mostly based on immunological principles, have been developed and commercialised for rapid analysis. These methods include, among others, enzyme-linked immunosorbent analysis (ELISA), direct fluorimetry, fluorescence polarization, and various biosensors and strip methods.     

Acid-base equilibria of dipyridylethylenes studied by absorption and fluorescence spectrometry

In connection with photochemical and fluorimetric studies and with previous pK measurements on styrylpyridines, the acid-base equilibria of the trans-1,2-dipyridylethylenes have been studied by absorption and fluorescence spectrometry. The results obtained by the two methods are compared and the pK's of first and second protonation discussed in dependence with the nitrogen positional isomerism. The measurements of the dissociation constant of the trans-3-styrylpyridinium ion is also reported as a particularly convenient application of fluorescence spectrometry.     

Assay for 9-acridanone in urban atmosphere by thin-layer chromatography fluorimetric procedures

9-Acridanone has been found in urban atmospheres. Four two-dimensional thin-layer Chromatographic methods have been described for the assay of this compound in urban atmospheres and in air pollution source effluents. Fluorimetric assay was done either directly on the plate or after elution. The best method involved two-dimensional separation on alumina-cellulose followed by elution and fluorimetric analysis of the acidic methanol solution. Urban atmospheres contain approximately 0.4 ng of 9-acridanone/m(3) of air.     

Analysis of agrochemicals by capillary electrophoresis

An increasing amount of articles using capillary electrophoresis as an investigation tool for pesticides and environmental pollutants were found over the last few years in analytical chemistry oriented journals. This review covers a wide literature range of the 1990s and concentrates on the analysis of organic agrochemicals (herbicides, fungicides, insecticides, acaricides, etc.) with capillary electrophoresis (capillary zone electrophoresis, micellar electrokinetic chromatography with CE-UV-visible or laser-induced fluorescence detection) as well as with the on-coming hyphenated techniques like capillary electrophoresis-electrospray ionization mass spectrometry. The principal preconcentration methods that allowed real sample analysis with CE are also briefly discussed. The pesticides, the separation methods, the used electrolytes, the detection types, the detection limits and the preconcentration methods were classified and presented in tabulated form as a rapid information tool.     

Working principle and application of photocatalytic optical fibers for the degradation and conversion of gaseous pollutants

Photocatalytic optical fibers are promising for the degradation of gaseous and volatile pollutants in air due to their high specific surface area, high light utilization efficiency, easy regeneration, and sustainability. In particular, photocatalytic optical fibers have proven highly useful for the removal and conversion of different kinds of air pollutants in air. However, these fibers suffer from low photocatalytic degradation efficiencies. In this review, we have focused on introducing photocatalytic quartz optical fibers and photocatalytic plastic optical fibers for the degradation and transformation of gas-phase air pollutants. The principle of photocatalytic optical fibers and main methods for improving their photocatalytic and light utilization efficiencies based on semiconductor photocatalytic coatings are summarized. Moreover, the Langmuir-Hinshelwood kinetic rate equation was summarized to analyze the photocatalytic reduction of gaseous pollutants. Finally, an outlook on the future of photocatalytic optical fibers toward the removal and conversion of gaseous air pollutants is discussed.     

Organic analysis by luminescence methods

This review presents the major features of luminescence methods relating to the estimation of organic compounds in solution. A notation for reporting fluorimetric determinations is proposed. The outstanding factors affecting the fluorescence of solutions are briefly reviewed, and determinations of compounds offering a native fluorescence are illustrated by selected examples. Special attention is paid to functional fluorimetry and to the determination of non-fluorescent compounds by means of chemical reactions giving rise to fluorescent species. Some enzymatic reactions are described, as far as they allow the estimation of definite chemicals. Phosphorimetry and chemiluminescence are exemplified. An appendix presents some new functional fluorimetric determinations developed by the authors.     

Analysis of heavy organic pollutants of confined atmospheres

Summary An improved procedure for the determination of the less volatile air pollutants of recycled closed atmospheres by activated carbon-Soxhlet extraction is proposed. After total treatment of desorbate, PAH determination is then accomplished by RP-HPLC using both adsorptiometric and fluorimetric UV detection; phenolic compounds are determined by GC-MS.This technique is suitable for very low levels of PAH and phenolic compounds.     

Molecularly imprinted polymers (MIPs) combined with nanomaterials as electrochemical sensing applications for environmental pollutants

It is known that environmental pollution, which is the result of human-induced industrial, domestic, and agricultural practices, poses a threat to our planet. The increasing human population caused several problems such as water and air pollution, which have reached levels threatening human health. There are many different hazardous chemical and biological environmental pollutants in soil, air, and wastewater. It is extremely important to evaluate these health risks and detect these pollutants. The use of electrochemical methods for the detection of environmental pollutants comes to the forefront recently with advantages such as sensitivity, fast response, low cost, and practical use by miniaturization. The molecular imprinting technique is a popular method used for substance analysis by creating a cavity specific to the substance to be analyzed with the polymer used. The use of molecularly imprinted polymer in electrochemical methods and its modification with various nanomaterials bring advantages such as high selectivity, robustness, and sensitivity to electrochemical sensors. Here, the sensitive determination of environmental pollutants with different nanomaterial-modified molecularly imprinted polymer-based electrochemical sensors, the use of different polymerization techniques, and nano-sized modification agents in sensors are evaluated by reviewing recent studies in the literature.     

Fluorimetric determination of iron(III) by quenching the luminescence of the zinc-morin-Triton X-100 system

Summary Simple and highly sensitive fluorimetric methods for iron determination are described. The methods are based on quenching the fluorescence of an aqueous morin solution or zinc-morin-Triton X-100 ternary system. The fluorescence emission is measured at 500 and 503 nm (wavelength of excitation 420 and 433 nm) for morin and the ternary system, respectively. The quenching calibration graphs are linear over the range 0–250 and 0–55 ng Fe/ml and the iron detection limits are 20 and 5 ng/ml using morin and zinc-morin-Triton X-100 system, respectively. The influence of experimental variables such as pH, reagent and surfactant concentrations, temperature, standing time and diverse ions are studied to obtain the optimum conditions. The method has been applied to the determination of iron in aluminium metal.

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Fluorimetrische Eisen(III)-bestimmung durch Luminescenzlöschung des Systems Zink-Morin-Triton X-100

     

Luminescence Technique in the Environmental Control

Luminescence analysis due to its high sensitivity and rather simple equipment is widely used in the environmental control. The most interesting are some methods for the determination of organic pollutants such as oil products, phenols, anionic and cationic surfactants, formaldehyde in waters of different origin, soils, ambient air.     

Analysis of industrial contaminants in indoor air. Part 2. Emergent contaminants and pesticides

This article reviews recent literature on the analysis of several contaminants related to the industrial development in indoor air in the framework of the REACH project. In this second part, the attention is focused on emergent contaminants and biocides. Among these chemicals, phthalates, polybrominated and phosphate flame retardants, fragrances, pesticides, as well as other emerging pollutants, are increasing their environmental and health concern and are extensively found in indoor air. Some of them are suspected to behave as priority organic pollutants (POPs) and/or endocrine disrupting compounds (EDC), and can be found both in air and associated to the suspended particulate matter (PM) and settled dust. Main literature considered for this review is from the last ten years, reporting analytical developments and applications regarding the considered contaminants in the indoor environment. Sample collection and pretreatment, analyte extraction or desorption, clean-up procedures, determination techniques, and performance results are summarized and discussed.