http://lovely-physics.persiangig.com/document/DLLME.pdf

Determination of organic compounds in water using dispersive liquid-liquid microextraction

Evolution of dispersive liquid-liquid microextraction method.

Molecular imaging is the visualization, characterization and measurement of biological processes at the molecular and cellular levels in humans and other living systems. Molecular imaging agents are probes used to visualize, characterize and measure biological processes in living systems. These two definitions were put forth by the Sociey of Nuclear Medicine (SNM) in 2007 as a way to capture the interdisciplinary nature of this relatively new field. The emergence of molecular imaging as a scientific discipline is a result of advances in chemistry, biology, physics and engineering, and the application of imaging probes and technologies has reshaped the philosophy of drug discovery in the pharmaceutical sciences by providing more cost effective ways to evaluate the efficacy of a drug candidate and allowing pharmaceutical companies to reduce the time it takes to introduce new therapeutics to the marketplace. Finally the impact of molecular imaging on clinical medicine has been extensive since it allows a physician to diagnose a patient’s illness, prescribe treatment and monitor the efficacy of that treatment non-invasively.

Single Photon Emission Computed Tomography (SPECT) and Positron Emission Tomography (PET) were the first molecular imaging modalities used clinically. SPECT requires the use of a contrast agent labeled with a gamma emitting radionuclide, which should have an ideal gamma energy of 100-250 keV. These gamma rays are recorded by the detectors of a dedicated gamma camera or SPECT instrument and after signal processing can be converted into an image indentifying the localization of the radiotracer. PET requires the injected radiopharmaceutical to be labeled with a positron emitting radionuclide. As the radionuclide decays it ejects a positron from its nucleus which travels a short distance before being annihilated with an electron to release two 511 keV gamma rays 180° apart that are detected by the PET scanner (Figure 1). After sufficient acquisition time the data are reconstructed using computer based algorithms to yield images of the radiotracer’s location within the organism. When compared to SPECT, PET has greater advantages with respect to sensitivity and resolution and has been gaining in clinical popularity, with the number of PET-based studies expected to reach 3.2 million by 2010.1 While SPECT and PET technology has been around for decades, its use remained limited because of the limited availability of relevant isotopes which had to be produced in nuclear reactors or particle accelerators. However, the introduction of the small biomedical cyclotron, the self-contained radionuclide generator and the dedicated small animal or clinical SPECT and PET scanners to hospitals and research facilities has increased the demand for SPECT and PET isotopes.



Figure 1

Cartoon depicting the fundamental principle of Positron Emission Tomography (PET). As the targeting group interacts with the cell surface receptor, the positron emitting radio-metal decays by ejecting β+ particles from its nucleus. After traveling ...



Traditional PET isotopes such as 18F, 15O, 13N and 11C have been developed for incorporation into small molecules, but due to their often lengthy radio-syntheses, short half-lives and rapid clearance, only early time points were available for imaging, leaving the investigation of biological processes, which occur over the duration of hours or days, difficult to explore. With the continuing development of biological targeting agents such as proteins, peptides, antibodies and nanoparticles, which demonstrate a range of biological half-lives, a need arose to produce new radionuclides with half-lives complementary with their biological properties. As a result, the production and radiochemistry of radiometals such as Zr, Y, In, Ga and Cu have been investigated as radionuclide labels for biomolecules since they have the potential to combine their favorable decay characteristics with the biological characteristics of the targeting molecule to become a useful radiopharmaceutical (Tables ​(Tables11 and ​and22).2



Table 1

Gamma- and Beta-Emitting Radiometals





Table 2

Positron-Emitting Radiometals



The number of papers published describing the production or use of these radiometals continues to expand rapidly, and in recognition of this fact, the authors have attempted to present a comprehensive review of this literature as it relates to the production, ligand development and radiopharmaceutical applications of radiometals (excluding 99mTc) since 1999. While numerous reviews have appeared describing certain aspects of the production, coordination chemistry or application of these radiometals,2-18 very few exhaustive reviews have been published.10,12 Additionally, this review has been written to be used as an individual resource or as a companion resource to the review written by Anderson and Welch in 1999.12 Together, they provide a literature survey spanning 50 years of scientific discovery. To accomplish this goal, this review has been organized into three sections: the first section discusses the coordination chemistry of the metal ions Zr, Y, In, Ga and Cu and their chelators in the context of radiopharmaceutical development; the second section describes the methods used to produce Zr, Y, In, Ga and Cu radioisotopes; and the final section describes the application of these radiometals in diagnostic imaging and radiotherapy.

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Coordinating Radiometals of Copper, Gallium, Indium, Yttrium and Zirconium for PET and SPECT Imaging of Disease

Preconcentration techniques for uranium(VI) and thorium(IV) prior to analytical determination-an overview.

Determination of cadmium, copper, lead and zinc in water samples by flame atomic absorption spectrometry after cloud point extraction

Homogeneous liquid–liquid extraction of uranium(VI) from acetate aqueous solution

Homogeneous liquid–liquid extraction with 
perfluorooctanate ion (PFOA–) was utilized for the 
preconcentration of certain types of metal chelates, such as 
diethyldithiocarbamate, 1,10-phenanthroline and desferrioxamine B. Under 
the experimental conditions {i.e., 
[PFOA−]T = 6.0 × 10−3 
mol l−1, [acetone]T = 2.0 vol%, 
[HCl]T=0.72 mol l−1, room temperature}, 
the maximum concentration factor was 500-fold. A method was then developed 
to determine those metal chelates deposited in a microdroplet on 
filter-paper using X-ray fluorescence spectrometry. As a result, when three 
types of chelating agent were used together in the process, 15 metal ions 
[Ti(IV), Zr(IV), V(V), Nb(V), 
Ta(V), W(VI), Fe(II), Co(II), 
Ni(II), Pd(II), Cu(II), 
Au(III), Hg(II), Bi(III) and 
Se(IV)] were simultaneously determined. The recovery of each 
metal was ca. 83–100%, except for W(VI) which was 
60.2%. The calibration curves for each metal ion were linear over the range 
from 5.0 × 10−7 to 1.0 × 10−5 
mol l−1. The detection limits were at the 
10−8 mol l−1 level and the relative 
standard deviations were below 5%.

Homogeneous liquid-liquid extraction followed by X-ray fluorescence spectrometry of a microdroplet on filter-paper for the simultaneous determination of small amounts of metals

A homogeneous liquid-liquid extraction method for 36 metal ions with diethyldithiocarbamate was studied. As a result, 11 metal ions were extracted as metal-chelates. Under the experimental conditions, the maximum concentration factor was 500 (i.e., 0.1 mL of sedimented liquid phase was produced from 50 mL of aqueous phase). Moreover, the proposed method was utilized as a preconcentration method for X-ray fluorescence analysis of these metals. The recovery of each metal was ca. 97–100%. All calibration curves were linear over the range of 5.0 × 10–7 mol L–1 to 1.0 × 10–5 mol L–1. The detection limits were at the ¶10–8 mol L–1 levels and the relative standard deviations were below 5% (5 determinations). When the proposed method was used for the determination of contaminants in a synthetic sample (Al-based alloy model) and of components in an Au-Pd alloy, the results were satisfactory.

X-ray fluorescence analysis of trace metal ions following a preconcentration of metal-diethyldithiocarbamate complexes by homogeneous liquid-liquid extraction.

The adsorption and desorption properties of trans-Resveratrol (Res) on the cellulose cotton were investigated under various conditions, such as the pH, alcohol percentage, temperature and equilibrium times. Moreover, the acidic-dissociation constants were determined to be pKa1 = 8.01, pKa2 = 9.86 and pKa3 = 10.5 by a curve-fitting method. Also, it was found that the adsorption depended on the temperature and salting effect. On the other hand, the desorptions from cellulose were examined using several kinds of water-miscible organic solvents (methanol, ethanol, acetone and THF).

Atsushi Takahashi

Papers

Homogeneous liquid–liquid extraction of uranium(VI) from acetate aqueous solution

Homogeneous liquid-liquid extraction followed by X-ray fluorescence spectrometry of a microdroplet on filter-paper for the simultaneous determination of small amounts of metals

X-ray fluorescence analysis of trace metal ions following a preconcentration of metal-diethyldithiocarbamate complexes by homogeneous liquid-liquid extraction.

Adsorption and desorption properties of trans-resveratrol on cellulose cotton.

Adsorption behaviors of high-valence metal ions on desferrioxamine B immobilization nylon 6,6 chelate fiber under highly acidic conditions.