Current Analytical Chemistry - Volume 2, Issue 3, 2006

The possibility of determining the content of various active pharmaceutical principles (Carbamazepine, Diclofenac, Ofloxacin, Sulfamethoxazol, Clofibric acid and Propranolol) in water and in commercial formulation by Voltammetric- Polarographic methods has been investigated. The considered pharmaceutical principles are the ones selected by the Rempharmawater European Union Program, as belonging to the class of the most used in Europe and six commercial drugs have been considered. The obtained data were compared with the results by UV spectrophotometry.

Several alternative methods of conducting affinity electrophoresis are described, including countercurrent affinity electrophoresis, antibody affinity electrophoresis, functional affinity electrophoresis, and avidin functional affinity electrophoresis. The basis of these new techniques is to catch the prey molecules while they migrate electrophoretically through the immobilized bait molecules region of the polyacrylamide gel. Potential applications of these techniques will be indicated.

A new flow injection method for the determination of levofloxacin based on the enhancement of the intensity of chemiluminescence (CL) from the luminol-KIO4 system was described in this paper. The enhanced chemiluminescence intensity was linear with the concentration of levofloxacin over the range from 7 ng mL-1 to 1000 ng mL-1 (r2ε0.9991) with a detection limit (3s) of 2 ng mL-1. At a flow rate of 2.0 mL min-1, a complete analytical process could be performed within 0.5 minute, with a relative standard deviation of less than 3.0% (nε5). The recovery for the levofloxacin samples was from 91.0% to 109.4%. The proposed method was applied successfully in the determination of levofloxacin in tablets, eyedrop, human serum and urine samples.

The study of telomeric DNA has acquired importance through the discovery of the relationship between telomerase activity in most cancer cells and telomere folding into tetraplex structure (guanine-quadruplex). G-quadruplexes exhibit four-stranded structure containing one or more nucleic acid strands with a central channel able to accommodate metal cations. Coordination of certain metal cations stabilizes G-quadruplex as do some promising small organic molecules. Among many techniques employed to explore properties of G-quadruplexes, fluorescence spectroscopy has been recognized as a powerful tool due to high sensitivity and multidimensionality. Information about concentration, molecular structure, binding events, and motion can be obtained using fluorescence methods, e.g., the fluorescence resonance energy transfer (FRET) technique. This review will show how fluorescence spectroscopy contributes to G-quadruplex research and will focuse on the FRET application, describing briefly also the underlying principles. Review will summarize the current developments in the field of the various applications of fluorescent measurements for both the fundamental structural investigations of Gquadruplexes and their complexes with organic ligands as well as some practical applications. Applications include fluorescence and FRET-based selection of efficient quadruplex-binding ligands and metal cations, design of molecular probes for protein recognition and development of sensors for detection of potassium ions in aqueous solution.

This paper reviews the use of X-ray fluorescence spectrometry (XRFS) for non-destructive studies of valuable metallic objects in the fields of jewelry, archaeology and art, as well as its application in the analysis of coatings and solutions, due to the interest of these issues in jewelry manufacture. The general features of the technique as well as the most outstanding results obtained in the commented fields are described, taking into account the most important sources of error, mainly in the case of samples that have suffered corrosion processes.

The layer-by-layer assembly technique is a rich, versatile, and significantly inexpensive approach to the formation of thin films via alternating adsorption of positively and negatively charged species from aqueous solutions. Polymer organic and organic/inorganic thin films formed using this technique may contain a number of different functional groups, including electro-optic, electrochromics, conducting, dielectric layers with or without redox pairs, and functional organic and inorganic nanoparticles. Ease of preparation, accurate control over film thickness as well as flexibility in the choice of constituents makes this technique very promising for electroanalytical chemistry. Many applications have been founded for the LBL assembled films, such as electrocatalysis, direct electrochemistry, biosensor, electrochromics, selective permeation, biofuel cell, and other analysis. Newly development based on the alternating layer methods in electroanalytical chemistry should be addressed.

The analytical community continues to search for cost-effective, reliable, and even portable analytical techniques that can give reliable and fast-response results for a variety of biochemicals. Advances in the field of microelectro- mechanical systems (MEMS) and their uses now offer unique opportunities in the design of ultrasensitive analytical devices. Microcantilevers (MCLs) have been emerged as a novel unique platform for label-free biosensor or bioassay. This short review summarizes the biosensors using microcantilever (MCL) technology. DNA-based, antibody-based, enzyme- based, and membrane-based MCL sensors are discussed. The review is intended to provide an experts in this field an overview of MCL biosensors and to help the non-experts in the field to acquire a good understanding of the development of MCL biosensors and the main issues to be considered for further development of this biosensor technique.

The methylation of DNA is an epigenetic modification that can play an important role in the control of gene expression in mammalian cells. The aberrant or accidental methylation of CpG islands in the promoter region has been observed for many cancer-related genes resulting in the silencing of their expression. Hence, it has become a focus of scientific attraction currently. Many of the early procedures developed gave only somewhat limited information about methylation patterns, for example, the overall levels of 5-methycytosine in the genome or the frequency of methylation of cytosines within certain restriction sites. However, in the last few years, there has been an explosion of interest in DNA methylation, and with it, many new and powerful techniques have been developed to facilitate methylation analysis, especially the advent of many high-throughput methods (e.g., restriction landmark genome scanning, differential methylation hybridization, and DNA microarray). In this paper, the key techniques currently available are reviewed and the advantages and disadvantages are discussed. This review will be valuable in selecting the best techniques to address particular questions concerning methylation status of genome DNA.

DNA mutation is the major cause of gene evolution. The variation of DNA sequence may result in genetic diseases, genotypes, single nucleotide polymorphism, and drug resistance of pathogens. Using biochip technologies, detection of mutations can be performed in parallel under identical conditions, hereby providing a solution to continuously increasing demands for large-scale genetic analysis. This article reviews the development of the biochips for mutation analysis. Features, limitations and applications of various principles are discussed.

The mathematical models are established for conventional atomic spectrometric signals by simulating experimental results with computer. The laboratory-made derivative measurement system is described. The mathematical models of derivative signals are developed for flame atomic absorption spectrometry (FAAS), cold vapour atomic absorption spectrometry (CVAAS), hydride generation atomic absorption spectrometry(HGAAS) and flow injection flame atomic absorption spectrometry (FIFAAS) and gas chromatography atomic absorption spectrometry (GCAAS). The intensity of derivative signal is in direct relation to concentration of analyte with a good linearity. A theoretical principle is developed for derivative-FAAS, derivative-FAES, derivative-CVAAS, derivative-HGAAS derivative-FIFAAS, and derivative- GCAAS. The performance and application of the derivative atomic absorption spectrometry in trace element analysis are reviewed.