Recent Advances in Analytical Techniques

Remarkable techniques for the separation and detection of small quantities of analytes have been developed in recent years. However, it is still difficult to directly analyze species of interest in complex matrices. Although some methods have been reported for direct injection into an analytical instrument, removal of interfering substances during sample preparation is an important step in the analytical process. This procedure is usually tedious and time consuming. To reduce the tedium of this task and the time required for sample preparation, many unique extraction techniques have been introduced and applied to the analysis of substances in environmental, food, and biological samples. This chapter describes useful sample preparation techniques, including conventional and newly developed ones, for determining analytes of interest in biological, environmental, and food sources.

Electrochemical sensors have been widely used in recent decades because they have many advantages such as high sensitivity, selectivity, stability, with the use of simple instrumentation low cost and can be successfully applied in the samples of clinical, environmental interest, and industry in general. Due to the versatility of these devices, they can be prepared from materials that provide higher reactivity and selectivity. The carbon based carbon materials are widely employed because of the ability to form a wide variety of composite materials. The composites based on graphene and carbon nanotubes have attracted great interest because they have important features, such as high speed in transferring electrons, high surface area, good chemical and mechanical stability, and therefore, they are used in the development of electrochemical sensors. Other promising materials used in the electrodes modification to electroanalytical applications are the Molecularly Imprinted Polymers and / or Ionically (MIP) and (IIP) that have become an important analytical tool due to the biomimetic recognition systems such as the specific antigen-antibody. These materials have many advantages when compared to organic systems such as ease of synthesis, stability in storage for long periods of time and cost. Some inorganic compounds have also been applied as modifiers of electrodes to enhance their electrochemical properties. Among these inorganic compounds, there are the nanoparticles of noble metals, which provide an increased surface area due to the nanoscale and nanostructured metal oxides that present numerous electronic properties and different applications. Thus this study aims to explore the use of new materials used in the development of electrochemical sensors.

The in vivo flow cytometry is an emerging tool to monitor circulating tumor cells (CTCs) in vivo. As a non-invasive method, the in vivo flow cytometry allows long-term monitoring of CTCs without changing their native biological environment. It has been applied for monitoring CTC dynamics in extensive biomedical researches on cancer therapy. In this chapter, the principles of fluorescence based and photoacoustic based in vivo flow cytometry are introduced. A number of studies concerning basic research in cancer therapy with in vivo flow cytometry are reviewed. Potential applications and disadvantages of in vivo flow cytometry in cancer therapy are also discussed.

Glow discharges (GDs), either coupled to optical emission or to mass spectrometry, have been widely investigated during the last three decades for a high variety of direct solid analytical applications. The intrinsic characteristics of these techniques, e.g. low matrix effects, multi-elemental capabilities, analytical sensitivity and good depth resolution, explain the continuous effort towards new developments aiming at further broadening their applications field and, so, the interesting applications reported so far. In this chapter, a brief description of the basics of the GDs is given first. Most recent instrumental advances will be then described in detail, both for optical emission and mass spectrometry, together with the analytical improvements that these instrumental progresses have allowed. Particular interest is paid to GD time-of-flight mass spectrometry, as this instrumentation (commercially launched in 2014) has proved to be promising in terms of high depth resolution, fast acquisition rates and time-gated detection, showing also interesting capabilities to obtain both elemental and molecular information. Finally, recent applications of GD techniques are described (focusing on the last five years). Special attention is given to the characterization of advanced materials such as multilayers, thin film solar cells and polymers.

Beer is one of the most popular alcoholic beverages worldwide, taste and flavor being the main factors which contribute for consumers’ acceptance, and its volatile components represent the major contributors for beer global and peculiar aroma properties. Also, beer volatile components may be used to monitor the impact of raw materials composition, yeast metabolism, beer aging, beer distinction and screening of off-flavors, among others. The analysis of beer volatile fraction is very challenging due to the presence of CO2, and also a diversity of chemical structures, namely with different polarities, volatilities, and a wide concentration range. Thus, beer volatile analysis requires an effective extraction technique to recover representative information, minimizing modifications or/and loss of components. The different extraction and gas chromatographic techniques that have been used for beer volatile composition will be critically presented, exploring their advantages and drawbacks; wherein solid phase microextraction combined with gas chromatography is the methodology most frequently used, and a special attention will be given to these techniques. Furthermore, over the last decades, significant improvements have occurred on the chromatographs (namely the multidimensional ones), detection systems, columns technology and algorithms that contribute to the reduction of analysis time, making the methods more expeditious and user-friendly. Taking into account the information available in the literature, a comprehensive outline about the volatile components previously determined in beers is included, considering, when existing, data about their detection and quantification limits. This review presents the state-ofthe- art for researches who want to study beer volatile characterization.

Nanomaterials are being investigated for a vast variety of biomedical applications such as drug delivery, biosensors, tissue engineering, bioimaging etc. Most of the approaches utilize nano-scale biomaterials for developing unique functionalities required by fabricating biomedical devices. During the past few decades, photodynamic therapy (PDT) has been developed as an upcoming therapy for the treatment of various life threatening diseases such as cancer and some common bacterial infections. It is based on the photochemical reactions between light and tumour tissue generated using photosensitizing agents. The present chapter focuses on the various materials developed as photodynamic therapeutic agents and their future prospects.