Newer Developments

Natural colourants often played an important role as pharmaceuticals. Thus, complex mixtures containing indigo powder have a firm place in traditional Chinese medicine. [43] That halogenated derivatives of indigo are still of biological interest, is demonstrated by the following example  

Recently, in the terrestrial Streptomycetes strain GW48/1497, there were discovered for the first time derivatives of 5,5 -dichloroindigo, a previously unknown natural product these derivatives were named akashin A, B and C (Nepalese, akash = heaven). [44] In these, 5,5 -dichloroindigo is unsymmetrically bonded to various sugars (Fig. 2.16). 

---

Projection radiography has long been used for pipe inspection and corrosion monitoring. In this traditional tangential wall thickness estimation the distance of border lines of the projected wall shadows of a pipe onto the film is a direct measure for the wall thickness. This method is not considered here, newer developments can be found in / /. 

More recendy, advanced generation gasifiers have been under development, and commercialisation of some of the systems has become a reaUty (36,41). In these newer developments, the emphasis has shifted to a greater throughput, relevant to the older gasifiers, and also to high carbon conversion levels and, thus, higher efficiency units. 

Newer developments involve poly(4-methyl-l-pentene) (TPX), PS or PPE blends, and block copolymers. 

The disk refiner, a newer development used for fine paper grades, includes one or two rotary disks and two or four working surfaces. The surfaces are pressed together uniformly by hydraulic pressure and guided by high precision, heavy-duty bearing systems. Stock usuaUy is fed through the center of one plate and leaves between the plates at their circumferences. 

A significant step towards commercial success came with a discovery in the late 1950s by E. Ulrich at 3M when he found that copolymerization of hydrogen bonding monomers, like acrylic acid with alkyl acrylates resulted in cohesively strong, yet tacky materials [63]. Since then, newer developments in such areas as polymer crosslinking, and the synthesis and copolymerization of new monomers, have led to a rapid penetration of acrylics throughout the PSA industry. 

In conclusion, the Hofmann-Loffler-Freytag reaction tends to give moderate and sometimes poor yields for the preparation pyrrolidines under the classic conditions. Nonetheless, the utility of this reaction to functionalize molecules via the aminyl radical mechanism plays an unique role in the tool box for the organic chemist, enabling transformations not easily achievable using other means. Furthermore, milder conditions and better yields can be achieved by taking advantages of the newer developments such as the Suarez modification. 

The earliest attempts to obtain optically active sulfoxides by the oxidation of sulfides using oxidants such as chiral peracids did not fare well. The enantiomeric purities obtained were very low. Biological oxidants offered great improvement in a few cases, but not in others. Lately, some very encouraging progress has been made using chiral oxaziridines and peroxometal complexes as oxidants. Newer developments in the use of both chemical oxidants and biological oxidants are described below. 

When data of a single type accumulate, new forms of statistical analysis become possible. In the following, conventional control and Cusum charts will be presented. In the authors opinion, newer developments in the form of tight (multiple) specifications and the proliferation of PCs have increased the value of control charts especially in the case of on-line in-process controlling, monitors depicting several stacked charts allow floor supervi-... 

In 1976, Radiometer61 presented for the first time a microprocessor-controlled titration system. Since then, the microprocessor has been used preferentially and as a fully integrated part (in line) in electroanalytical instruments as a replacement for the on-line microcomputer used before. Bos62 gave a comprehensive description of the set-up and newer developments with microprocessors in relation to microcomputers and indicated what they can do in laboratory automation. Many manufacturers are now offering versatile microprocessor-controlled titrators such as the Mettler DL 40 and DL 40 RC MemoTitrators, the Metrohm E 636 Titroprocessor and the Radiometer MTS 800 multi-titration system. Since Mettler were the first to introduce microprocessor-controlled titrators with their Model DK 25, which could be extended to a fully automated series analysis via the ST 80/ST 801 sample transport and lift together with the CT 21/CT211 identification system, we shall pay most attention to the new Mettler MemoTitrators, followed by additional remarks on the Metrohm and Radiometer apparatus. 

It is appropriate to identify our approach to developing the present review in the context of the Co chapter in CCC(1987). The first-edition chapter on Co featured a focused discussion and tabulation of synthetic methods, and many of these basic methods are still employed in synthesis today. Consequently, to avoid repetition, there will be diminished description here where prior appropriate methods have been provided, and only newer developments featured. The last two decades feature the development of many mixed-donor and sophisticated multidentate and macrocyclic ligands, which found limited coverage in the previous edition, and these will be discussed in more detail herein. Reaction kinetics and mechanism were also described thoroughly in the previous edition. We shall not reiterate this material, since the core mechanisms of many reactions involving Co compounds are now adequately defined. 

This article summarizes the chemistry of alkali metals with group 14, 15, and 16 ligands with specific emphasis on structure and bonding. With several excellent, recent review articles in the area, we focus specifically on newer developments, with already reviewed material only mentioned briefly to show trends and connections. 

In conventional synthetic transformations, enzymes are normally used in aqueous or organic solvent at moderate temperatures to preserve the activity of enzymes. Consequently, some of these reactions require longer reaction times. In view of the newer developments wherein enzymes can be immobilized on solid supports [183], they are amenable to relatively higher temperature reaction with adequate pH control. The application of MW irradiation has been explored with two enzyme systems namely Pseudomonas lipase dispersed in Hyflo Super Cell and commercially available SP 435 Novozym (Candida antarctica lipase grafted on an acrylic resin). 

The technically relevant fuel cell types are shown in Fig. 13.5 a newer development of the PEM fuel cell is the direct-methanol fuel cell (DMFC), which uses a diluted... 

For pertinent reviews on HMF, see (a) Lewkowski, J. Synthesis, chemistry and applications of 5-hydroxymethylfurfural and its derivatives, ARKIVOC, 2001, 17-54 (b) B. F. M. Kuster, Manufacture of 5-hydroxymethylfurfural, Starch/Starke, 1990, 42, 314-321. Newer developments (c) Bicker, M. Hirth, J. Vogel, H. Dehydration of fructose to 5-hydroxymethylfurfural in sub- and supercritical acetone. Green Chem.,... 

This chapter deals with the properties of high-pressure liquid chromatography columns. It is divided into two sections column physics and column chemistry. In the section on column physics, we discuss the properties that influence column performance, such as particle size, column length and column diameter, together with the effect of instrumentation on the quality of a separation. In the section on column chemistry, we examine in depth the surfaces of modern packings, as well as the newer developments such as zirconia-hased packings, hybrid packings or monoliths. We have also included a short section on... 

SP refers to a family of solid/liquid handling techniques to extract or to enrich analytes from sample matrices into an analyzable format, namely, the final analyte solution. While SP techniques are well documented, " few publications address the specific requirements for drug product preparations, most of which tend to employ the simple dilute and shoot approach. A more elaborate SP is often needed for complex sample matrices (e.g., lotions and creams). Many newer SP technologies such as solid-phase extraction (SPE), " supercritical fluid extraction (SFE), "i° pressurized fluid extraction or accelerated solvent extraction (ASE)ii"i and robotics " " are topics of numerous research papers, symposia and commercial promotion. However, for reasons discussed later, these newer developments have had little impact on the way pharmaceutical laboratories conduct their SP for drug products today. 

The second part deals with applications of solvent extraction in industry, and begins with a general chapter (Chapter 7) that involves both equipment, flowsheet development, economic factors, and environmental aspects. Chapter 8 is concerned with fundamental engineering concepts for multistage extraction. Chapter 9 describes contactor design. It is followed by the industrial extraction of organic and biochemical compounds for purification and pharmaceutical uses (Chapter 10), recovery of metals for industrial production (Chapter 11), applications in the nuclear fuel cycle (Chapter 12), and recycling or waste treatment (Chapter 14). Analytical applications are briefly summarized in Chapter 13. The last chapters, Chapters 15 and 16, describe some newer developments in which the principle of solvent extraction has or may come into use, and theoretical developments. 

Newer developments are astemizole, cetirizine, loratadine, mequitazine and terfenadine which are basically devoid of central side effects and effects on the autonomic transmission. This is not due to an inability of the drugs to pass the blood brain barrier, since these drugs are quite lipophilic but probably to their selectivity towards Hi-receptors. These drugs can be used in the chronic treatment of allergic disorders. 

As well as typical sample preparation methods such as filtration and liquid-liquid extraction, newer developments are now extensively used. The first of these is solid-phase extraction (SPE). This is a rapid, economical, and sensitive technique that uses several different types of cartridges and disks, with a variety of sorbents. Sample preparation and concentration can be achieved in a single step. Interfering sugars can be eluted with aqueous methanol on reversed-phase columns prior to elution of flavonoids with methanol. 

One of the newer developments in the production of alcohols is the direct catalytic hydration of ethylene to ethyl alcohol. Temperature and pressure must be higher than in the conventional process, but the use and reconcentration of large amounts of sulfuric acid are avoided. 

---