Electrochemical Analysis of Some Toxic Metals by Ion-Selective Electrodes.

An overview of potentiometric sensors that are capable of detecting toxic heavy metal ions in environmental samples is presented and discussed. Notwithstanding the tremendous work performed so far, it is obvious that still several limitations do exist in terms of selectivity, limits of detection, dynamic ranges, applicability to specific problems, and reversibility. A survey on important advances in potentiometric sensors with regard to high selectivity, lower detection limit, fast response time, and on-line environmental analysis is presented in this review article.

Electrochemical spectroscopic investigations on the interaction of an ytterbium complex with DNA and their analytical applications such as biosensor.

Metal ion-DNA interactions are important in nature, often changing the genetic material's structure and function. A new Yb complex of YbCl(3) (tris(8-hydroxyquinoline-5-sulfonic acid) ytterbium) was synthesized and utilized as an electrochemical indicator for the detection of DNA oligonucleotide based on its interaction with Yb(QS)(3). Cyclic voltammetry (CV) and fluorescence spectroscopy were used to investigate the interaction of Yb(QS)(3) with ds-DNA.

Fluorescence "Turn-On" chemosensor for the selective detection of beryllium.

A new fluorogenic method for selective and sensitive determination of beryllium using 2,6-diphenyl-4-benzo-9-crown-3-pyrane (DBCP) was developed. The proposed fluorescent probe undergoes fluorescent emission intensity enhancement upon binding to beryllium ions in MeOH/H(2)O (70:30, v/v) solution. The fluorescence enhancement of DBCP is attributed to a 1:1 complex formation between DBCP and Be(2+) ion, which has been utilized as the basis for selective detection of Be(2+) ion.

A highly selective fluorescent probe for pyrophosphate detection in aqueous solutions.

A novel and simple fluorescence enhancement method is introduced for selective pyrophosphate (PPi) sensing in an aqueous solution. The method is based on a 1:1 metal complex formation between tris(8-hydroxyquinoline-5-sulphonate) thulium(III) [Tm(QS)(3)] and PPi ion. The linear response covers a concentration range of 1.

Sample preparation method for the analysis of some organophosphorus pesticides residues in tomato by ultrasound-assisted solvent extraction followed by dispersive liquid-liquid microextraction.

A very simple and economic method for organophosphorus pesticides (OPPs) residues analysis in tomato by means of gas chromatography-flame photometric detection (GC-FPD) has been developed. The method involves a rapid and small-scale extraction. The sample was homogenised and extraction of the OPPs with acetone was carried out assisted by sonication.

Concentration and Temperature Effects on the Electronic Absorption Spectra of 1-pyridinyl-2-methylene-benzenecarbohydrazonic Acid Following Solvatochromic Studies.

In this work, UV-Vis. electronic spectra of 1-pyridinyl-2-methylene-benzene carbohydrazonic acid (L) have been studied. The different bands observed have been assigned to the proper electronic transitions.

A new technique for spectrophotometric determination of pseudoephedrine and guaifenesin in syrup and synthetic mixture.

The accuracy in predicting different chemometric methods was compared when applied on ordinary UV spectra and first order derivative spectra. Principal component regression (PCR) and partial least squares with one dependent variable (PLS1) and two dependent variables (PLS2) were applied on spectral data of pharmaceutical formula containing pseudoephedrine (PDP) and guaifenesin (GFN). The ability to derivative in resolved overlapping spectra chloropheniramine maleate was evaluated when multivariate methods are adopted for analysis of two component mixtures without using any chemical pretreatment.

A novel methodology based on solvents less dense than through dispersive liquid-liquid microextraction: application in quantitation of in fruit juices and soft drinks by fiber optic-linear array detection spectrophotometry.

In this study a novel methodology is proposed for utilizing solvents less dense than water by using a dispersive liquid-liquid microextraction (DLLME) technique. Conventional microextraction vessels and facile strategy have been used. We have avoided using routine microextraction solvents in the DLLME procedure that are mostly chlorinated, dense, environmentally hazardous and expensive which limits the application of this method to some extent.

Application of an Hg2+ selective imprinted polymer as a new modifying agent for the preparation of a novel highly selective and sensitive electrochemical sensor for the determination of ultratrace mercury ions.

A simple and very selective electrode, based on a mercury ion imprinted polymer (IIP), and its application for the determination of Hg(2+) ions in the real samples is introduced. Mercury ion selective cavities were created in the vinyl pyridine based cross-linked polymer. In order to fabricate the sensor carbon particles and polymer powder were mixed with melted n-eicosane.

Carcinoembryonic antigen admittance biosensor based on Au and ZnO nanoparticles using FFT admittance voltammetry.

In this work, a highly sensitive carcinoembryonic antigen fast Fourier transform admittance biosensor is introduced. The proposed biosensor is based on bilayer films of ZnO/Au nanoparticles as an immobilization matrix. These layers are prepared by self-assembly and deposition method on a gold electrode surface, respectively.

Pyrophosphate selective recognition in aqueous solution based on fluorescence enhancement of a new aluminium complex.

A novel and simple fluorescence enhancement method for selective pyrophosphate(PPi) sensing was proposed based on a 1:1 metal complex formation between bis(8-hydroxy quinoline-5-solphonat) chloride aluminum(III) (Al(QS)(2)Cl), (L) and PPi in aqueous solution. The linear response range covers a concentration range of 1.6 × 10(-7) to 1.

Separation and preconcentration system based on microextraction with ionic liquid for determination of copper in water and food samples by stopped-flow injection spectrofluorimetry.

In this work, an efficient in situ solvent formation microextraction (ISFME) was combined with stopped-flow injection spectrofluorimetry (SFIS) for the determination of copper. In the proposed approach, thiamine was oxidized with copper(II) to form hydrophobic and highly fluorescent thiochrome (TC), which was subsequently extracted into ionic liquid as an extractant phase. A small amount of an ion-pairing agent (NaPF(6)) was added to the sample solution containing a water-miscible ionic liquid ([Hmim][BF(4)]) to obtain a hydrophobic ionic liquid ([Hmim][PF(6)]), which acted as the extraction phase.

A new Schiff's base ligand immobilized agarose membrane optical sensor for selective monitoring of mercury ion.

A highly selective optical sensor was developed for the Hg(2+) determination by chemical immobilization of 2-[(2-sulfanylphenyl)ethanimidoyl]phenol (L), on an agarose membrane. Spectrophotometric studies of complex formation between the Schiff's base ligand L and Hg(2+), Sr(2+), Mn(2+), Cu(2+), Al(3+), Cd(2+), Zn(2+), Co(2+) and Ag(+) metal ions in methanol solution indicated a substantially larger stability constant for the mercury ion complex. Consequently, the Schiff's base L was used as an appropriate ionophore for the preparation of a selective Hg(2+) optical sensor, by its immobilization on a transparent agarose film.

Modified ionic liquid cold-induced aggregation dispersive liquid-liquid microextraction combined with spectrofluorimetry for trace determination of ofloxacin in pharmaceutical and biological samples.

Background And The Purpose Of The Study: Ofloxacin is a quinolone synthetic antibiotic, which acts against resistant mutants of bacteria by inhibiting DNA gyrase. This antibacterial agent is widely used in the treatment of respiratory tract, urinary tract and tissue-based infections, which are caused by Gram-positive and Gram-negative bacteria. In this work, an efficient modified ionic liquid cold-induced aggregation dispersive liquid-liquid microextraction (M-IL-CIA-DLLME) was combined with spectrofluorimetry for trace determination of ofloxacin in real samples.

QSAR study of C allosteric binding site of HCV NS5B polymerase inhibitors by support vector machine.

Multiple linear regressions (MLR) and support vector machine (SVM) were used to develop quantitative structure-activity relationship (QSAR) models of novel Hepatitis C virus (HCV) NS5B polymerase inhibitors. Various kinds of molecular descriptors were calculated to represent the molecular structures of compounds, such as chemical, topological, geometrical, and quantum descriptors. Principal component analysis (PCA) was used to select the training set.

Computational studies on effects of MDMA as an anticancer drug on DNA.

This research is designed to further understand the effects of the novel drug MDMA on biologic receptor of DNA. The ultimate goal is to design drugs that have higher affinity with DNA. Understanding the physicochemical properties of the drug as well as the mechanism by which it interacts with DNA should ultimately enable the rational design of novel anticancer or antiviral drugs.

An index of local sensitivity to non-ignorability for multivariate longitudinal mixed data with potential non-random dropout.

Multivariate longitudinal data with mixed continuous and discrete responses with the possibility of non-ignorable missingness are often common in follow-up medical studies and their analysis needs to be developed. Standard methods of analysis based on the strong and the unverifiable assumption of missing at random (MAR) mechanism could be highly misleading. A way out of this problem is to start with methods that simultaneously allow modelling non-ignorable mechanism, which includes somehow troubling computations that are often time consuming, then we can use a sensitivity analysis, in which one estimates models under a range of assumptions about non-ignorability parameters to study the impact of these parameters on key inferences.

Simultaneous spectrophotometric determination of 2-thiouracil and 2-mercaptobenzimidazole in animal tissue using multivariate calibration methods: concerns and rapid methods for detection.

Two multivariate calibration methods, partial least squares (PLS) and principal component regression (PCR), were applied to the spectrophotometric simultaneous determination of 2-mercaptobenzimidazole (MB) and 2-thiouracil (TU). A genetic algorithm (GA) using partial least squares was successfully utilized as a variable selection method. The concentration model was based on the absorption spectra in the range of 200 to 350 nm for 25 different mixtures of MB and TU.

Quantitative structure-activity relationship (QSAR) study of interleukin-1 receptor associated kinase 4 (IRAK-4) inhibitor activity by the genetic algorithm and multiple linear regression (GA-MLR) method.

A linear quantitative structure-activity relationship (QSAR) model is presented for the modelling and prediction for the interleukin-1 receptor associated kinase 4 (IRAK-4) inhibition activity of amides and imidazo[1,2-α] pyridines. The model was produced using the multiple linear regression (MLR) technique on a database that consisted of 65 recently discovered amides and imidazo[1,2- α] pyridines. Among the different constitutional, topological, geometrical, electrostatic and quantum-chemical descriptors that were considered as inputs to the model, seven variables were selected using the genetic algorithm subset selection method (GA).

Complexes of 2-hydroxyacetophenone semicarbazones: A novel series of superoxide dismutase mimetics.

A series of copper(II) and zinc complexes of 2-hydroxyacetophenone semicarbazones have been prepared and evaluated as superoxide dismutase (SOD) mimetics. The SOD-like activity of parent ligands and complexes were determined by the inhibition of nitroblue tetrazolium (NBT) reduction method, using xanthine/xanthine oxidase as the superoxide radical generator. The obtained results indicate that Cu(II) complexes exhibited the most potent SOD-like activities with the IC(50) values ranging from ca.

Determination of terbium in phosphate rock by Tb3+-selective fluorimetric optode based on dansyl derivative as a neutral fluorogenic ionophore.

For the first time a highly sensitive and selective fluorimetric optode membrane was prepared for determination of trace amounts of Tb(III) ions in phosphate rock samples. The Tb(III) sensing system was constructed by incorporating 5-(dimethylamino)-N'-(2-hydroxy-1-naphthoyl) naphthalene-1-sulfonohydrazine (L) as a neutral Tb(III)-selective fluoroionophore, in the plasticized PVC membrane containing sodium tetraphenyl borate as a liphophilic anionic additive. The response of the optode is based on the strong fluorescence quenching of L by Tb(3+) ions.

A transition model for ordinal response data with random dropout: an application to the fluvoxamine data.

Many methods are available to analyze incomplete longitudinal ordinal responses. In this paper a general transition model is proposed for longitudinal ordinal responses with random dropout. Maximum likelihood estimates are obtained for the transition probabilities when there are repeated observations.

Fluorescence "turn-on" chemosensor for the selective detection of zinc ion based on Schiff-base derivative.

N,N'-phenylenebis(salicylideaminato) (L) has been used to detect trace amounts of zinc ion in acetonitrile-water solution by fluorescence spectroscopy. The fluorescent probe undergoes fluorescent emission intensity enhancement upon binding to zinc ions in MeCN/H(2)O (1:1, v/v) solution. The fluorescence enhancement of L is attributed to the 1:1 complex formation between L and Zn(II), which has been utilized as the basis for selective detection of Zn(II).

QSAR study on melanocortin-4 receptors by support vector machine.

Quantitative structure activity relationship (QSAR) of the melanocortin-4 receptor (MC4R) binding affinities (K(i)) of trans-4-(4-chlorophenyl) pyrrolidine-3-carboxamides of piperazinecyclohexanes was studied. A suitable set of molecular descriptors was calculated and the genetic algorithm (GA) was employed to select those descriptors that resulted in the best-fit models. The multiple linear regression (MLR), and the support vector machine (SVM) were utilized to construct the linear and nonlinear QSAR models.