Examples of Analytical Applications

As previously mentioned, this section describes two examples of analytical applications involving the use of the unique spectroscopic properties of gold nanoparticles. The use of changes in the plasmon resonance absorption of gold nanoparticles as a basis for the development of improved aggregation-based immunoassays is then discussed. 

Perturbation mechanisms for the various acoustic devices were discussed in general terms in Chapter 3. In this chapter, these mechanisms are reviewed specifically in the context of chemical and biochemical analysis. Performance criteria are discussed, and the fundamental coating-analyte interactions giving rise to sensor responses are presented as a basis for classification. Relevant physical and chemical models of these interactions are described, and examples of analytical applications employing each type of interaction are given to illustrate their advantages and limitations. While references have been included to illustrate specific points, this chapter is not intended to comprise an exhaustive review of the literature, particularly for TSM resonators, for which the number of references is far too great to be fully reviewed here. For more detailed information on the diversity of sensor applications, the reader is referred to the many review articles that have been published on these topics [2-8,13-15]. 

An example of analytical application was the determination of LMW aliphatic amines, a group of important compounds widely found in environmental samples, usually in aqueous solution. Detection of these amines at trace level is difficult due to their high basicity and strong adsorption on solid surfaces (Figure 11.19). 

In this section, some representative examples of analytical applications are presented. It is not intended to give a complete overview. 

Typical examples of analytical applications of conventional MECA include the determination of saccharin (sulfur-containing sweetener) in soft drinks, total sulfur and sulfate in detergents, phosphate in detergents and rocks, sulfur dioxide in air, inorganic sulfate in urine, and halides in pesticides. 

Typical examples of analytical applications of gas generation MECA detection include the determination of ammonium in fertiHzers, fluorine in toothpaste, boron in steel samples, and thiamine and cephalosporins in pharmaceutical preparations. 

TLC is generally less sensitive and gives worse separation than HPLC. However, it predominates over HPLC in at least two aspects It allows for the analysis of many samples at the same time, and it requires limited sample pretreatment. These features are very important in the analysis of antibiotics, which usually concerns controlling their level in many complicated matrices such as blood, urine, dietary products, and pharmaceuticals. Thus, TLC can be a very useful screening method preceding HPLC analysis. Nevertheless, there are also many examples of analytical applications of TLC, which can achieve selectivity and sensitivity comparable with those characteristic of HPLC. The future of the analytical option in antibiotic analysis is connected with progress in detection and the development of FFPC methods. 

Table 6.6 A few selected examples of analytical applications of nanomaterials...

Other types of reactions can be used to chemically separate an analyte and interferent, including precipitation, electrodeposition, and ion exchange. Two important examples of the application of precipitation are the... 

Blanco and co-workers" reported several examples of the application of multiwavelength linear regression analysis for the simultaneous determination of mixtures containing two components with overlapping spectra. For each of the following, determine the molar concentration of each analyte in the mixture. 

The earliest examples of analytical methods based on chemical kinetics, which date from the late nineteenth century, took advantage of the catalytic activity of enzymes. Typically, the enzyme was added to a solution containing a suitable substrate, and the reaction between the two was monitored for a fixed time. The enzyme s activity was determined by measuring the amount of substrate that had reacted. Enzymes also were used in procedures for the quantitative analysis of hydrogen peroxide and carbohydrates. The application of catalytic reactions continued in the first half of the twentieth century, and developments included the use of nonenzymatic catalysts, noncatalytic reactions, and differences in reaction rates when analyzing samples with several analytes. 

Laser based mass spectrometric methods, such as laser ionization (LIMS) and laser ablation in combination with inductively coupled plasma mass spectrometry (LA-ICP-MS) are powerful analytical techniques for survey analysis of solid substances. To realize the analytical performances methods for the direct trace analysis of synthetic and natural crystals modification of a traditional analytical technique was necessary and suitable standard reference materials (SRM) were required. Recent developments allowed extending the range of analytical applications of LIMS and LA-ICP-MS will be presented and discussed. For example ... 

Other example of the application of described method may give analysis of copper in brass. It is well known that for the analytical line of copper CuKa the strong absorption takes place in Fe, Mn, Sn, Pb. These elements have the similar effect on ZnKa. It is possible to suppose that the ratio IcuKb IznKa less effected by the named elements. The analysis that was realized has confirmed that the variation of the named above ratio is about 25 less then variation of L. ... 

The coupling of supercritical fluid extraction (SEE) with gas chromatography (SEE-GC) provides an excellent example of the application of multidimensional chromatography principles to a sample preparation method. In SEE, the analytical matrix is packed into an extraction vessel and a supercritical fluid, usually carbon dioxide, is passed through it. The analyte matrix may be viewed as the stationary phase, while the supercritical fluid can be viewed as the mobile phase. In order to obtain an effective extraction, the solubility of the analyte in the supercritical fluid mobile phase must be considered, along with its affinity to the matrix stationary phase. The effluent from the extraction is then collected and transferred to a gas chromatograph. In his comprehensive text, Taylor provides an excellent description of the principles and applications of SEE (44), while Pawliszyn presents a description of the supercritical fluid as the mobile phase in his development of a kinetic model for the extraction process (45). 

Coulometry. Even in water, controlled potential or potentiostatic coulometry is a difficult and often time-consuming technique, as the analyte must participate in a direct electrode reaction. Therefore, in non-aqueous media there are only a few examples of its application, e.g., the potentiostatic coulometry of nitro and halogen compounds in methanol (99%) with graphical end-point prediction, as described by Ehlers and Sease153. 

Several examples of the application of quantum mechanics to relatively simple problems have been presented in earlier chapters. In these cases it was possible to find solutions to the Schrtidinger wave equation. Unfortunately, there are few others. In virtually all problems of interest in physics and chemistry, there is no hope of finding analytical solutions, so it is essential to develop approximate methods. The two most important of them are certainly perturbation theory and the variation method. The basic mathematics of these two approaches will be presented here, along with some simple applications. 

Typical systems. A considerable number of immobilized polyether systems have been synthesized both for phase transfer catalysis as just discussed and for use in a number of analytical applications. Such immobilized systems are generally synthesized by either copolymerization of suitably functionalized macrocycles in the presence of cross-linking agents or by appending functionalized macrocycles to existing polymeric substrates. Structures (184)-(186) give examples of different... 

The analytical usefulness of this reaction, stems mainly from that fact that the electrochemically generated Ru(bpy)33+ species can be reduced by a large number of potential analyte compounds, or their electrochemical derivatives, via high-energy electron transfer reactions, to produce the Ru(bpy)32+ excited species, without the need for an electrochemical reduction step. The converse is also true. The reduction of peroxodisulfate (S2082-) for example, in the presence of Ru(bpy)32+, produces the Ru(bpy)32+ excited species and an ECL emission, from the reaction of Ru(bpy)3+ and S04 [20], Although this latter system has been used for the determination of both Ru(bpy)32+ [21] and S2082- [22], the vast majority of analytical applications use the co-oxidation route. 

Electron probe and X-ray fluorescence methods of analysis are used for rather different but complementary purposes. The ability to provide an elemental spot analysis is the important characteristic of electron probe methods, which thus find use in analytical problems where the composition of the specimen changes over short distances. The examination of the distribution of heavy metals within the cellular structure of biological specimens, the distribution of metal crystallites on the surface of heterogeneous catalysts, or the differences in composition in the region of surface irregularities and faults in alloys, are all important examples of this application. Figure 8.45 illustrates the analysis of parts of a biological cell just 1 pm apart. Combination of electron probe analysis with electron microscopy enables visual examination to be used to identify the areas of interest prior to the analytical measurement. 

We have only found one example of the application of an immunoassay kit to the analysis of fluoroquinolones in environmental samples [84]. The assay is able to detect enrofloxcin as standard analyte with sensitivity levels of 5 pg L1. 

Polyaza macrocycle derivatives have been employed in a number of analytical applications." " For example, polymer-immobilized cyclam has been employed for the preconcentration of manganese in seawater prior to analysis." ... 

---