Applications

Sublimation is applicable to a wide range of organic and inorganic compounds in an equally wide range Figure 4 Apparatus for sublimation at reduced pressure. Coolant is circulated through the cold finger, CF, whilst a vacuum is applied to the sample chamber. Figure 4 Apparatus for sublimation at reduced pressure. Coolant is circulated through the cold finger, CF, whilst a vacuum is applied to the sample chamber. Figure 5 Improved sublimation apparatus proposed by Eisenbraun et al. (1978)....

Commercial Membrane Separation Processes

The current status of membrane separation technology is summarized in Table 1. There are seven commercial membrane separation processes. Of these, the first five - microfiltration, ultrafiltration, reverse osmosis, electrodialysis and dialysis - are all well-established technologies with a market served by several experienced companies. Although incremental improvements in membranes and membrane systems for these technologies are expected, no major breakthroughs appear imminent. The remaining...

Classification of Distillation Processes

There are many criteria under which one can classify distillation type of accessories, operating mode, design calculation assumptions, etc. Distillation can either be binary or multicomponent. According to the type of accessories used to increase the mass transfer in the separation process, a distillation column can be packed (use of packing) or staged (use of plates). It can be batch or continuous. Also, according to the assumptions made and accuracy expected in a distillation design...

Magnetic Separations in Microbiology Cell Biology Medicine and Parasitology

IMS and, in some cases, lectin-magnetic separations are often used in the above-mentioned disciplines. In microbiology they are especially used for the detection of pathogenic microorganisms. IMS enables the time necessary for detection of the target pathogen to be shortened. Target cells are magnetically separated directly from the sample or the pre-enrichment medium. Isolated cells can than be identified by standard, specific microbiological procedures. IMS is not only faster but also usually...

Behaviour of Electronic Absorption Spectra in Supercritical CO2

When using UV-Vis detection for SFC of carotenoids, attention must be paid to spectral shifts that occur in supercritical fluids, in comparison to those measured in liquid solvents. This is particularly relevant as the effect can influence qualitative and quantitative results. The shape of the absorption spectra of all-trans- -carotene, 15-cis- -carotene and the xanthophylls, zeaxanthin, cathaxanthin and astaxanthin, which are nonacidic oxygen derivatives of the carotenes, are similar in both...

Video Densitometry

Video densitometry has been developed in the last few years and is now being deployed throughout industry and research. Such instruments use an imag Figure 4 (See Colour Plate 27). Separation of pesticides in tap water on an HPTLC silica gel plate by AMD. Multi-wavelength (six wavelengths) evaluation permits resolution by optical means of fractions insufficiently separated. Reprinted from Camag literature, CAMAG, Muttenz, Switzerland. Figure 4 (See Colour Plate 27). Separation of pesticides in...

Limitations of Diffusion Dialysis

A necessary condition of dialysis is that the solute concentration in the recovery stream must be lower than in the feed stream in order to provide a driving force for diffusion. This is not a real limitation in applications where the diffusing solute is a waste that can be easily discarded. But this condition can be a limitation when the diffusing solute is the desired product, because the product is often recovered at a low concentration. Fortunately, the acid from steel pickling solution can...

HV gYGV Y dY

Where Tmax xmax w, is the dimensionless coordinate of the maximal concentration of the focused zone. R can be experimentally determined as the ratio of the retention volume (or the retention time) of an unretained sample component (equal to the volume of the channel) divided by the retention volume (retention time) of the retained sample component. The simple and known relationship between the X and the particle size make it possible to calculate the PSD from the experimental retention data....

Gas Separation

The process The study of gas permeation through membranes has a long history dating back to the work of Thomas Graham in the mid-nineteenth century. However, the first systematic studies with polymers of the type used today did not begin until 100 years later. The mechanism of gas permeation developed in the 1950s and 1960s was the solution-diffusion model. In this model, the rate of diffusion through the polymer membrane is governed by Fick's law of diffusion. For simple gases, it can be shown...

Overpressured Layer Chromatography

In addition to capillary action, the force driving solvent migration in OPLC is the external pressure. Depending on the desired mobile-phase velocity, operating pressures up to 50 bar can currently be used. In OPLC (Figure 2) the vapour phase is completely eliminated the chromatographic plate is covered with an elastic membrane under external pressure, thus the separation can be performed under controlled conditions. The absence of any vapour space must Figure 2 Schematic diagram of online...

Membrane Electrolysis

A typical example of this kind of application is the membrane electrolysis of sodium chloride to produce chlorine, hydrogen and sodium hydroxide (membrane chlor-alkali process). A schematic diagram for this process is presented in Figure 7. Perfluorocarbon cation exchange membranes for chlor-alkali processes should have an anisotropic structure in their cross-section. The cathode side of the membrane has a thin layer of carboxylic acid groups of a given ion exchange capacity, and the anode side...

Principle of Long Distance Oplc Ldoplc

Long-distance OPLC is a multi-layer development technique with specially prepared plates. Similar to the preparation of layers for linear OPLC development, all four edges of the chromatographic plates must be impregnated with a polymer suspension. The movement of the eluent with a linear solvent front can be ensured by placing a narrow plastic sheet on the layer or scraping a narrow channel in the sorbent for the solvent inlet. Several plates are placed on top of each other to ensure the long...

Terminology Nomenclature

Figure 1(A)-(C) are schematic illustrations of different polymorphs of a compound. In (A) and (B), the molecular conformation is retained but the crystal structures are different. The occurrence of a form such as (C), in which the molecule crystallizes with a significantly different conformation gives rise to the term 'conformational polymorphism'. In addition to the possibility of forming different (but chemically identical) polymorphs, the molecules of a given substance may upon...

Problems in Practical Applications of Bipolar Membranes

Electrodialytic dissociation of water with bipolar membranes is economically very attractive for creating acids and bases. There are, however, several severe problems in practical applications, such as the contamination of the products by salts and low current efficiency at high acid and base concentrations. Salt contamination of the products is related to the properties of the bipolar membrane. The poor current efficiency is the consequence of the proton and hydroxide ion transport in...

Experimental Considerations

If higher concentrations of buffer are used, particularly with high concentrations of organic solvent, then bubble formation can become a problem. This can be overcome by operating the whole capillary under pressure. Figure 4 is a schematic diagram showing such a pressurized apparatus. The packing of small-diameter particles into narrow capillaries represents an enormous challenge. The initial stage is the formation of a suitable retaining frit, which must be capable of retaining particles of...

Basic Instrumental Requirements and Considerations

The main concern in implementing a multidimensional separation solution will be how to design the instrumental set-up. The greater the difference between the two dimensions, the greater the potential difficulty in their coupling, since there will be greater dissimilarity in the mechanisms of separation. The wide choice of column chromatography separation methods explains why the coupling or interfacing may present a challenge. If the two dimensions are of the same chromatographic type - GC-GC,...

Diffusion in Liquids

In liquid systems, with small or medium-sized molecules in dilute solution, diffusion is highly dependent on viscosity, y, and consequently on temperature, T. Assuming a spherical particle, diffusion in liquids can be expressed by the Stokes-Einstein equation, D (10 7T yVm,l). Figure 4 Schematic diagram of the role of interfacial diffusion in liquid-liquid extraction. Each stagnant layer is about 10 2-10 4cm. In this depiction, the molecules diffusing through the liquid-liquid interface contain...

Gas Dispersion

One of the most important hydrodynamic conditions in a mechanical flotation cell is dispersion of gas into fine bubbles. The bubble generation mechanism in Figure 3 Schematic diagram of formation of bubbles in mechanical cells (after Grainger Allen, 1970 courtesy of Transactions of the Institute of Metallurgy, UK). Figure 3 Schematic diagram of formation of bubbles in mechanical cells (after Grainger Allen, 1970 courtesy of Transactions of the Institute of Metallurgy, UK). a mechanical cell is...

Dorr Oliver Cells

The Door-Oliver cell is marketed by Dorr-Oliver, a global corporation and member of the Krauss-Maffei Group. The Dorr-Oliver Company Limited manufacturers flotation cells in a wide range of sizes. Cells with a volume of 0.03 m3 (DO 1) to 2.8 m3 (DO-100) have a flat-bottom tank design. Cells with volumes from 4.2 to 44 m3 come with a U-shaped tank bottom. Cells with volumes from 50 to 150 m3 are available with a round tank with a conical bottom. Details of tank dimensions for the Dorr-Oliver...

Implementation

Figure 1 shows a schematic flow diagram of a typical preparative GC. Typical values of temperatures and pressures are given at different points of the process. The range of operating temperatures and pressures used is given in Table 1. Note that the pressure at the outlet condensers can be subatmospheric. This feature is used to increase the productivity of some separations when the vapour pressure of the sample at the operating temperature is too low. The use of vacuum raises a number of...

Process Description

A schematic diagram of a DAF process for wastewater treatment is shown in Figure 1. Its essential elements are a flocculation tank, a flotation tank, an air compressor, an air saturator, a recycling pump and a hy-drosweep system. The wastewater is pumped to the flocculation tank after being treated with coagu-lant flocculent agents such as aluminium sulfate. A portion of the clarified effluent is recycled for pressurization. Compressed air is introduced into the discharge stream of the recycle...

Chromatogram

The information obtained from a chromatographic experiment is contained in the chromatogram. When the elution mode is used this consists of a plot of the concentration or mass profile of the sample components as a function of the flow of the mobile phase or as a function of time. Typically the yy-axis will be detector response and the x-axis time or volume of mobile phase in column chromatography or migration distance in planar chromatography. The position of each peak in the chromatogram is...

Volumetric Feed Rate

The volumetric feed rate determines the vessel retention time and strongly influences vessel mixing. An increase in superficial suspension velocity results in lower gas limits as flooding will occur at lower gas rates and increases the size of microbubbles which become entrained by downward flow to the underflow. However, higher slurry velocities also decrease the negative influence of mixing on grade and recovery (higher Peclet number) and lessen the retention time difference between Rne and...

Preaeration of Feed

Optimal aeration condition for efficient particle collection and a suitable hydrodynamic environment for effective transfer of bubble particle aggregates from the remaining pulp. Unfortunately, conflicting hy-drodynamic environments are usually required for these two sub-processes. It is often difficult - if not impossible - to evaluate theoretically the relative contributions of individual collection mechanisms in a particular flotation device. The limited understanding of the aeration...

Other Devices and Processes Using Feed Slurry Aeration

Jameson cell The innovative design of the Jameson cell is based on the point of air addition and bubble generation. It utilized the concept of reactor and separator design. The downcomer into which air is aspirated and particle collection occurs is the reactor, while the cylindrical tank is the separator. The feed under high pressure is introduced at the top of the downcomer through a nozzle, producing a high speed slurry jet which entrains air into the downcomer. In Figure 6 Fine silica...

Fundamental Basis of Feed Aeration

A theoretical analysis of aeration in a flotation system is complicated. As a result, the development of aeration techniques in flotation is largely based on phe-nomenological correlations. The feed aeration and subsequent particle collection during the aeration are the combination of features of dispersed and dissolved air flotation. Particle collection by air bubbles in flotation is a multi-step process, involving three phases with interactions among solid liquid, solid gas and liquid gas in...

Feed Conditioning

The feed is introduced into the column where the temperature and composition roughly match the column profile. The feed is at higher pressure in order to flow into the column. The location of the feed stream can be optimized with a few judicious choices with a process simulator. The feed quality and location can also be adjusted within limits to lower the reboiler or the condenser duty, but not both. The best opportunities for utilizing feed exchangers are during revamps when there is excess...

The General Elution Problem

A typical chromatogram for the separation of a mixture of components is shown in Figure 1. This illustrates the characteristics of chromatography, often referred to as the 'general elution problem'. The properties illustrated by the chromatogram, which must be explained by any theory of chromatography, are the components of the mixture elute from the column at different times (retention) peak widths increase with retention time (peak shape and broadening) the separation of pairs of peaks is not...

Development

In 1917 PA Kober published a paper in which he described his observation that 'a liquid in a collodion bag, which was suspended in the air, evaporated, although the bag was tightly closed'. Kober was not the first researcher to observe this phenomenon, but the first to realize its potential for the separation of liquid mixtures which otherwise are difficult to separate, and to separate them under moderate conditions. He introduced the terms 'Pervaporation', and 'Perstil-lation', and the first...

Incorporation of Impurities

Impurities obviously reduce the purity of the crystalline product and are seldom beneficial to the crystallization processes or the product characteristics. As with the design of additives, it is important to understand how the impurities are incorporated in the crystalline product to reduce their uptake. In general an impurity is included in the crystalline product through either direct incorporation in the lattice (solid solubility), the formation of inclusions, surface adsorption or poor...

Further Reading

Bezuidenhout G (1995) The Bateman flotation machine. XIX International Mineral Processing Congress 3 231-236. Degner VR (1988) Flotation machine design. In Klimpel RR and Luckie PT (eds) Proceedings of Industrial Practice of Fine Coal Processing, SME AIME, ch. 16, pp. 135-146. Somerset, CA. Grainger Allen TJN (1970) Bubble generation in froth flotation machines. Transactions of the Institute of Mining and Metallurgy 79 C15-C22. Harris CC (1986) Flotation machine design, scale-up and performance...

Ultrafiltration and Microfiltration Principles

Membrane selection should start with the choice of a high quality vendor since robustness, reliability and reproducibility of manufacturing operations are of paramount importance in most bioprocessing applications. Consistent membrane and device characteristics can be as important to product quality, yield and economics as the inherent differences between various membranes and devices. Cellulosic membranes are attractive for many bioprocessing applications because of their low protein...

Miscellaneous Nitrogen Compounds

Because of the possible presence of nitroso carcinogens in foods, the separation and determination of Table 6 Retention data (hRF) of indole derivatives under different experimental conditions3 Table 6 Retention data (hRF) of indole derivatives under different experimental conditions3 aEluents A methyl acetate-isopropanol-25 ammonium hydroxide (9 7 4) B chloroform-96 acetic acid (95 5) C water-methanol-acetic acid (59 40 1) D 0.1M NH4OH in 40 methanol E n-hexane-ethyl acetate-acetic acid (72 27...

Nucleic Acids

LLPC in aqueous two-phase systems has been successfully used for DNA fractionation by size, topology and by base sequence, as well as for the fractiona-tion of 'soluble' and ribosomal RNAs (Table 4). Hence, LLPC may provide resolutions unattainable by any other method. Size DNA fragments, linear relationship for fragments up to about 4000 base pairs Various RNAs from natural sources, e.g. soluble RNAs from tomato plants Ribosomal RNA up to about 30 S Base composition Eco RI generated fragments...

Introduction

Industrially, centrifuges are used for a variety of purposes related to separation of materials on the basis of density. This separation usually involves separation of insoluble particulates from supernatant liquids, but can also include extraction of dissolved substances from one immiscible liquid to another of different density, separating the mixed liquids centrifugally. The blending of the liquids, transfer of the solute and separation of the immiscible phases are sequentially carried out...

Extracorporeal Therapy Modes Used in ESRD Patients Figure

In a typical haemodialysis procedure, although transmembrane mass transfer occurs predominantly by diffusion, a modest degree of convective mass transfer is also achieved in association with the ultrafiltered plasma water. However, the recent recognition of ft2M and other low molecular mass proteins as important uraemic toxins has prompted interest in using dialytic therapies with increased convective removal capabilities for these poorly diffusible solutes. In haemodialysis, the total...

Liquid Mixing Redistribution and Maximum Bed Height

Initial liquid distribution is essential to achieve good packed tower efficiency. Hoek suggested that at a given flow rate, each packing has its natural distribution determined by its radial spreading coefficient. Although this effect does spread the initial liquid distribution, this effect is not sufficient to correct poor initial distribution. Radial concentration gradients already established at the top of the bed cannot be compensated by additional packing. The result is permanent...

Mechanism of Membrane Separation

The property of membranes used in separation processes is their ability to control the permeation of different species. Most membranes fall into one of the two broad categories illustrated in Figure 5. In microporous membranes, permeants are separated by pressure-driven flow through tiny pores. A separation is achieved between different permeants because one of the permeants is excluded (filtered) from some of the pores through which the smaller permeants move. In solution-diffusion membranes...

Flotation Chemistry

The search for new flotation reagents for various mineral separation systems has been one of the major aims in flotation chemistry development. Although xanthate, first used more than 70 years ago, remains the principal collector for sulfide mineral flotation, long chain surfactant has been introduced as the collector in oxide, silicate and sparingly soluble salt mineral flotation systems. The early trial-and-error approach in screening and searching for a new flotation collector has evolved...

Gasphase UV Spectrophotometry

The spectral region of the UV electromagnetic absorption of interest to the analytical chemists extends from about 160 to 330 nm. Molecules in which all valence shell electrons are involved in single bonds, such as the straight chain saturated hydrocarbons, show absorption maxima in the region of 160-170 nm. Their spectra are observed only as 'end absorptions' because of instrumental limitations. The other groups of nonaromatic hydrocarbons are bathochromic-shif-ted and possess their absorption...

Offline versus Online Arrangements

It is also necessary to differentiate between offline and online arrangements (Table 2). In the offline mode the reactions occur away from the high performance liquid chromatography (HPLC) system, although there may be some examples that could be defined as either offline or online (e.g. in a sample vial in a carousel as part of an automated derivatization-injec-tion system in LC). In the online mode the reaction chemistry occurs as part of the HPLC system, integrated into the instrumentation...

The Effect of Water Chemistry on Mineral Solution Equilibrium

When mineral particles are in contact with water, they undergo dissolution, the extent of which is dependent on the type and concentration of chemicals in solution. The dissolved mineral species can undergo further reactions such as hydrolysis, complexa-tion, adsorption and precipitation. The complex equilibria involving all such reactions can be expected to determine the interfacial properties of the minerals and their flotation behaviour. The equilibria that con trol the dissolution of...

Reversed Phase Applications

As mentioned before, two types of polysaccharide phases which are specifically designed for reversed-phase applications are currently on the market. This type of phase is extremely interesting for the direct injection of aqueous solutions (ionic products, plasma samples, etc.). Furthermore, the columns are useful in column-coupling techniques (for example, an octadecylsilica column followed by a polysacchar-ide column) to solve difficult separation problems. The manufacturer recommends on this...

Selection of Two Phase Solvent System

Among the purification of natural products, the isolation of antibiotics is one of the most difficult tasks since the crude sample often contains, in addition to numerous impurities, a set of closely related components that tend to exhibit similar partition behaviour in a given solvent system. Consequently, successful separation necessitates a painstaking search for a suitable solvent system, which often requires days, weeks and even months of hard trial. Once a suitable solvent system is...

Principles

Electrophoresis is a very separation technique which involves the separation of charged species (molecules) on the basis of their movement under the influence of an applied electric field. It is widely used by chemists and biochemists in studies related to medical technology, environmental research, food and water analysis, pollution control and forensic investigations. The development and applications of electrophoretic separation methods are an example of the fruitfulness of using physical...

1 k2

A value of Rs 1.5 is normally considered to represent baseline separation for Gaussian shaped peaks. To achieve the maximum peak resolution, both high selectivity and column efficiency (giving narrow bands) are required. Increased resolution can always be achieved by an increase in column length since the peak separation (AtR) is proportional to the distance of migration down the column, but peak width is only propor where the subscript 2 refers to the second peak. Conditions for obtaining...

Elution

Having retained the compound or macromolecule of interest on the immobilized antibody, elution can be accomplished by a variety of methods. If the antibody is covalently bound to the support, relatively strong eluotropic conditions can be used including organic solvents such as ethanol, changes in buffer concentration and or pH, or the use of chaotropic reagents. For speed and sharp elution profiles of the analyte prod-uct, a rapid change in eluent composition from conditions promoting...

Introduction to Ion Pair Chromatography

Ion pair chromatography (IPC) is an effective rever-sed-phase liquid chromatographic (RPLC) technique for separation of organic ions and partly ionized organic analytes. The technique utilizes the same types of stationary phases and mobile phases as RPLC the main characteristic for IPC is that an ion pair reagent is added to the mobile phase. The ion pair reagent is usually an alkylsulfonate, an alkylsulfate or an alkylammonium salt. The high efficiency of RPC columns compared with columns used...

Others

They all protect in one way or another, alone or in combination, the original quality of the product to be freeze-dried. As an example of a CPA the influence of glycerol concentration is shown on the right-hand side of Figure 1. The temperature of homogenous nucleation Figure 1 Phase diagram, water-glycerine. On the left-hand side the dependence of the phase transformation time from the ice temperature is shown at -140 C amorphous ice transforms into cubic ice in approximately 10 min. (From...

Amphoteric Ion Exchangers

Ion exchangers which contain both acidic and basic groups are called amphoteric resins. Usually their matrix has some structural units with acidic groups and other units with basic groups. Very interesting amphoteric resins are the so-called 'snake-cage polyelectrolytes'. One feature distinguishes the snake-cage polyelectrolytes from other amphoteric resins, namely the acidic and basic groups are not attached to the same matrix. For example, a snake-cage polyelectrolyte is prepared by...

Molecular Sieves

Molecular sieves are synthetic and naturally occurring zeolites with well-defined structures that have found extensive use for the separation of permanent (or fixed) gases. Molecular sieves have a pore size that is defined by the particular ion used in the preparation Table 1 General application fields of adsorbents Table 1 General application fields of adsorbents Volatile polar and nonpolar compounds CO and CO2 in air impurities in ethylene hydrocarbon and semipolar impurities of the material...

Separation Strategy and Typical Applications

Operational electrolyte conditions should be optimized to obtain the best quality of separation by changing electrolyte parameters so that the difference of the effective mobilities of the target components should be as large as possible. Strictly speaking, the separability depends on the mobility difference in the mixed zone (see Figure 1). However, to a first approximation, the mobility differences at the steady state or the difference of the RE values may be used for the criterion for...

Advantages of TLE

Thin-layer chromatography has proved to be one of the most successful chromatographic techniques ever devised. This success owes largely to its simplicity and versatility compared with column techniques. The main drawback of TLC is the low solvent velocity achieved through capillary action. This leads to long separation times and means that the optimum flow velocity (for chromatographic efficiency) is seldom reached. Electric fields can be used to cause the migration of the analyte, either by...

Resins

Water treatment The annual production of ion exchange resins has been estimated at 500 000 m3, of which at least 90 goes to industrial water treatment. The various end uses in this area will now be described. Softening The removal of calcium and magnesium ions from water supplies is a requirement for many industries. Laundries, dye-houses and cleansing plants are examples of specific industries but the need can be generalized to many hot water circuits, heat exchangers and low pressure boilers....

Collector Collector Interactions

The use of mixtures of collectors has long been recognized in plant practice and has been shown to enhance flotation performance. These benefits have been reported for a wide range of collector mixtures (anionic, cationic and nonionic) and include lower dosage requirements, improved selectivity and rates and extents of recovery and an increase in the recovery of coarse particles. In many cases an optimum ratio of constituent collectors was shown to exist. Dithiophosphates are a class of thiol...

Freezing Rates

The freezing time can be estimated by an equation developed by Steinbach where tf freezing time AJ enthalpy difference between the initial freezing point and the final temperature AT difference of temperature between the freezing point and the cooling medium d thickness of the product parallel to the direction of prevailing heat transfer ps density of the frozen product thermal conductivity of the frozen product and Ksu surface heat transfer coefficient between cooling medium and the freezing...

Diffusion in Solids

When extracting solutes from solid samples, one must not only overcome the solute-sample attraction, but the solute must diffuse with the solvent back out of the porous solid sample. This diffusion through the pores of a solid sample is influenced by the geometry or tortuosity of the pore structure (e.g. the diffusion path length). Diffusion in solids, assuming weak solute-sample sorption (i.e., a linear isotherm), is expressed by Deff ( D) y(KD + 1), where Deff is the effective (or apparent)...

Sedimentation in a Centrifugal Field

A particle moving in a circular path continuously experiences a centrifugal force, Fc. This force acts in the plane described by the circular path and is directed away from the axis of rotation. The centrifugal force may be expressed as where m is the particle mass (g) a is the acceleration (cm s 2) w is the angular velocity (radians s_1 2n rpm 60) and x is the radial distance from the axis of rotation to the particle (cm). Thus, centrifugal force is proportional to the square of the angular...

Inorganic Oxide Adsorbents and their Applications

The most important adsorbents for extraction and matrix simplification are silica gel, alumina, Florisil and diatomaceous earths. Silica gel, prepared from sodium silicate using the sol-gel procedure, is the most widely used general-purpose adsorbent. Silica gels used for solid-phase extraction have surface areas of about 300-800 m2 g-1, pore sizes from 4-10 nm, and an apparent pH of 5.5-7.5. The apparent sorbent pH is characterized as the observed pH of a 5 (w w) aqueous suspension. Alumina is...

Modes of Paper Chromatography

In most of its practical aspects (e.g. sample application, equipment such as developing tanks and visualization procedures), paper chromatography somewhat resembles TLC. The most noticeable difference is that, as the paper is not rigid, it must either be suspended from an appropriate support during development or arranged in such a way as to be self-supporting. Only the major types of paper chromatography are described below, but it should be noted that there were many minor variants of the...

Hydrocyclones

This device is particularly unique as it separates solids and liquids by centrifugal principles, but contains no moving parts. The principle of the machine is illustrated in Figure 5. The slurry or fluid to be separated is pumped at high speed and enters the conically shaped machine tangentially. The conical shape causes the flowing liquid to swirl or rotate within the cone, with the result that suspended solids move to the wall while clarified liquid remains in the centre of the cone. This...

Synthetic Multiple Interaction Pirkle Stationary Phases

Figure 1 Enantiomer separation on CSPs is made possible by formation of transient diastereomeric adsorbates with differing free energies. In this illustration, the analyte enantiomers are depicted as right and left hands, and the CSP is depicted as immobilized right-handed gloves. Figure 1 Enantiomer separation on CSPs is made possible by formation of transient diastereomeric adsorbates with differing free energies. In this illustration, the analyte enantiomers are depicted as right and left...

Mode of Air Entry

In mechanical cells there are two modes by which air is introduced into the cells one is the forced air entry mode carried out using a blower and the other is the self-induced air entry mode, in which air is sucked into the cell by vortexing. The two cell designs can be distinguished by the difference in vertical location of the impeller in the cell. In the forced air-type machine, the impeller is located close to the cell bottom with a deeper impeller submergence, and an external air blower is...

Solvents

The solvent, besides acting as the medium in which the polymerization is performed, has an important secondary role as a porogen. It controls the porous structure of the polymer matrix to a large extent, and a good porogen is essential if one wants the porous structure in the polymer to be well developed. Sometimes, however, a good porogenic solvent can be a bad solvent for the analyte, so once again a compromise is sometimes required. Common imprinting solvents include toluene, chloroform and...

High Performance Liquid Chromatography HPLC Analysis

The development of sophisticated HPLC instrumentation and of precise pumps with low pulsation as well as improved sensitivity of the detection systems along with new column materials have made this technique well suited for routine laboratory work. Over the last 20 years, a number of different HPLC methods for determination of bile acids in all kinds of biological fluids have been published, each of them with special advantages and disadvantages. Early HPLC work was based on polar column...

Conclusion For Liquid Chromatography

Large scale preparative GC is a real purification tool. It is now reliable and economically viable for industrial production. Columns with internal diameter as large as 600 mm are available. The efficiencies Figure 4 Purification cost breakdown for a production of 36 tonnes per year of injected crude on a 400 mm i.d. column. Open segments, investment costs shaded segments, operating costs. Figure 4 Purification cost breakdown for a production of 36 tonnes per year of injected crude on a 400 mm...

Reversal of EOF

The separation of anionic solutes in CE may lead to extended time of analysis due to their migration in the direction opposite to EOF. One method of decreasing the analysis time is to reverse the EOF, thus making the anions migrate in the same direction as the EOF. In aqueous CE, the addition of long alkyl chain trimethylammonium ions is used for this purpose, e.g. in the analysis of inorganic anions and phenols. This principle may also be used in NACE. However, the long alkyl chain...

Control of Batch Crystallizers

Batch crystallizers are used extensively for crystallization procedures that are of small capacity and have a high added value, and often when multipurpose reactors are used for the crystallization process. Therefore the control of a batch process differs considerably from that of a continuous process. In addition, although a batch crystallizer can be described by a similar model to the continuously operated crystal-lizer, because of the inherently nonstationary process conditions and the...

Air Liquefaction Distillation

Herron, Air Products and Chemicals, Hamilton Boulevard, Allentown, PA, USA Copyright 2000 Air Products and Chemicals, Inc Oxygen, nitrogen and argon, the major components of air, have been separated by distillation at cryogenic temperatures for nearly a century. Air was commercially liquefied as early as 1895 by Carl von Linde and also by William Hampson. Linde separated oxygen from air by distillation in a single column in 1902. A commercial plant producing pure nitrogen...

Detector Response to Low Molecular Weight Components

The differential refractive index for a polymer solvent combination is normally independent of molecular weight at high molecular weight. However, while it is generally known that the refractive index detector response varies with low molecular weight polymers this variation is commonly ignored. As a consequence, SEC results for polymers containing low molecular weight material often do not give an appropriate consideration to the low molecular weight components this has important implications...

Attenuation of Sound in a Liquid Medium

The intensity of the ultrasonic wave decreases with increasing penetration into the medium. Molecular vibration induced by the sound wave results in loss of intensity of the wave, which is transformed into heat. Heating occurs in the sites of compression and cooling at the sites of rarefaction. Since the compressibility of liquids is small, there is little heating caused by ultrasound as waves pass through the medium. The heating effect is caused by the degradation of acoustic energy due to...

Intercalation Properties

Over time, research on layered phosphates has moved from the study of their ion exchange properties to that of their intercalation properties in great part determined by the presence of Br+nsted acid groups in the interlayer region. Both a- and y-zirconium phosphates are excellent intercalating agents of Lewis bases. The intercalation chemistry of the former has been more widely investigated and we will be mainly concerned with a-zirconium phosphate. Many molecules belonging to various classes...

Chiral Mobile Phase Additives

There are no fundamental differences between the techniques using chiral stationary phases and chiral Table 3 Chiral selectors used as mobile-phase additives L- or D-Proline Cu(II), L-Phenylalanine Cu(II), W-Methyl-L-phenylalanine Cu(II), W,W-Dimethyl-L-phenylalanine Cu(II), (R, R)-Tartaric acid mono-1-octylamide Cu(II) (R, R)-Tartaric acid mono-1-octylamide Cu(II) 1,1 '-Binaphthyl derivatives of 18-crown-6 Cyclodextrins a-Cyclodextrin -Cyclodextrin Propranolol, pseudoephedrine, salsolinol,...

Silylating Agents

Silylation is the most widely used method for metabolic profiling, especially for urinary organic acids. On the other hand its use for amino acids has a number of disadvantages as already mentioned. For some applications, silylating agents are too powerful in that they are able to react with compounds which will not elute from the column. The most popular reagents are listed in Table 3 and many others are described in detail in the Fluka handbook edited by van Look (see Further Reading). For...

Packed Column Description

Figure 2 illustrates a tower with structured packing. In addition to the packing itself, packed columns require other internals to assure the performance of the packing. These internals are Liquid feed pipes to deliver the fluid to the liquid distributors, as seen at the top of the tower and at the intermediate distributor. Liquid collection and mixing as shown below the top bed. Liquid draw-off sump and pipe as shown below the top bed. Liquid redistributors, as presented between the two beds....

The BOSS and Big Boss Diffusion Denuder Samplers

Diffusion denuder sampling systems for the determination of total fine particulate organic material have been developed at Brigham Young University. The objectives which guided the development of these 1. The sampling system should have a flow rate sufficient to enable measurement of low concentrations of particulate carbonaceous material and to allow the detailed chemical characterization of particulate organic material, e.g. flow rates of from 30 to 300 L min_i were considered desirable. 2....

SEC Concentration Detectors and Sample Concentration

A number of detector types for specific additional information will be considered later but the most basic SEC application requires a concentration detector to monitor the polymer as it emerges from the column. The most common form of concentration detector encountered in SEC is a differential refractive index (DRI) detector. These detectors are a cost-effective option which are nearly universal in application but they have limited sensitivity and require a very good temperature control. Since...

Classification of Chiral Stationary Phases

Enantiomer separation by GC is mainly performed on three types of CSPs chiral amino acid derivatives via hydrogen bonding chiral metal chelates via coordination (complexa-tion GC) cyclodextrin derivatives via inclusion. Initially, the chiral selectors were used as involatile neat liquids or as solutions in squalane or poly-siloxanes, respectively. Subsequently, a number of chiral selectors have been chemically linked to poly-siloxanes (Chirasil-type stationary phases). Chiral Stationary Phases...

Nonlinear Extended pH Gradients

IPG formulations have been given only in terms of rigorously linear pH gradients. While this has been the only solution adopted so far, it might not be the optimal one in some cases. Altering the pH slope in some portions of the gradient might be required in those pH regions overcrowded with proteins. The reasons for resorting to non-linear pH gradients are given in the histogram of Figure 7. With the relative abundance of different species it is clear that an optimally resolving pH gradient...

The Separation Membrane

The dialytic transport across thin membranes can be described in eqn 33 C,MD and ci,MA are the solute concentrations in the membrane at the interfaces with the donor and the Objectives in a microanalytical scale Donor solution Acceptor solution Objectives in a microanalytical scale Donor solution Acceptor solution Flowing or stirred, large sample volume Slowly flowing or gently stirred, small volume Stirred or flowing, large reagent volume Quiescent or slowly flowing, small volume Quiescent or...

Anomalous Migration in Sdspage

The precise structural relationship of SDS to protein during SDS-PAGE is unknown but various studies have indicated that a wide variety of proteins all bind a relatively constant amount of SDS (+1.4 g SDS g_1 protein) and adopt a similar flexible rod shape regardless of their native configuration. It is this supposedly constant very high and uniform charge-mass ratio which allows for reliable molecular weight determination since migration rate therefore depends on molecular sieving alone....

Comparison of Video Technology with Classical Densitometry

Classical densitometry uses the spectral range from 190 to 800 nm with high spectral selectivity. Absorption spectra for substance identification can be recorded within this whole span. In contrast, video technology functions only in the visible range. The UV region - exceptionally productive for planar chromatography - is only indirectly accessible through the use of an UV indicator embedded in the layer and in cases where samples fluoresce. In this respect video technology parallels the human...

Cyclodextrins in Capillary Electrophoresis

In the pharmaceutical industry the importance of capillary electrophoresis is continuously growing. It is a technique which is increasingly used for determination of the optical purity of intermediates and final products. Many different optically pure compounds Figure 12 Capillary GC analysis on cyclodextrin stationary phases. Experimental conditions column (A) 15 m x0.32 mm ID Chiraldex B-PH ((S)-hydroxypropyl- -cyclodextrin (Astec)) (B) 15mmx0.32mm ID Chiraldex B-DA (dipentylated...

Air

The purpose of the air loop is to control a volumetric flow of air through the column or to maintain a three-phase density within the vessel. In basic control systems air rate is controlled manually based on a monitored air flow rate. In slightly more advanced systems, the flow is controlled through an automatic valve to compensate for pressure changes (Figure 2). Figure 2 Example of air control loop. PI, pressure indicator FIT, flow indicator and transmitter FIC, flow indicator and controller...

Indirect method

This method involves reaction of the enantiomeric mixture with a suitable chriral reagent to make the corresponding diastereomeric derivatives prior to chromatography the choice of chiral selector is Table 17 values of amino acids on untreated plates and plates impregnated with metal sulfates Aminoacids Unimpregnated Plate impregnated with Mn2+ Fe2 Co2 Ni2+ Cu2 Zn2 Cd2 Hg2+ T, Tailing SF, migrates with solvent front. hRF values are the average of at least five determinations. Table 18 TLC of...

Determination of Formation Constant of CSEnantiomer Complex

The present technique has an advantage over conventional HPLC by allowing the determination of the formation constant (Kf) for the CS-enantiomer complex which is useful for developing the CS for chiral chromatography. In a schematic view of the portion of the separation column in Figure 5, enantiomers (A+ and A_) are partitioned between the organic stationary phase (upper half) and the aqueous mobile phase (lower half). In the organic stationary phase enantiomers form a CS complex CSA+...

Amino Acids

The scraped layer corresponding to each spot is extracted with 70 ethanol in a known minimum volume, and ninhydrin reaction is performed followed by spectrophotometry. Six to eight standard dilutions in an appropriate concentration range for each amino acid are prepared 2 mL of amino acid solution and 2 mL of buffered ninhydrin are mixed in a test tube, heated in a boiling-water bath for 15 min, cooled to room temperature and 3 mL of 50 ethanol is added. The extinction is read at 570 nm (or 440...

Analytical OPLC Separations

In OPLC, the most frequent modes of development are linear one- and two-directional (Figure 5A,B). Linear OPLC, however, requires a special chromato-graphic plate sealed along the edge, by impregnation, to prevent the solvent from flowing off the layer. The advantage of circular development, in which the mobile phase migrates radially from the centre of the plate to the periphery, is well known for the separation of compounds in the lower RF range, Figure 4 Schematic diagram of long-distance...

Extraction Schemes

Classification schemes are numerous and no one scheme covers all systems. The most common schemes are based on the form of the extracted element that transfers into the organic phase. This simplified classification scheme is adequate for the discussion here. However, even with simple schemes the categories are not exclusive, and some extraction agents could be classified into other categories. The experimental process of inorganic extraction of a neutral complex, regardless of the type of...

Carbenicillin Sulbenicillin and Ticarcillin

These epimeric, di-anionic -lactams are similar in physicochemical properties and are analysed under very similar conditions. For analysis of carbenicillin (Figure 3, structure 7), plasma and urine samples are loaded onto an anion exchange solid-phase extraction column. Carbenicillin epimers are eluted with 10 lithium chloride-methanol (3 2) and injected into an HPLC. Analysis is on an ODS column with a mobile phase consisting of 0.05 mol L_1 ammonium acetate-methanol (9 1). Carbenicillin...

Flow Cell Sfcftir

The flow cell approach involves connecting a high pressure flow-through cell at the end of the separation column and positioning the flow cell in the FTIR beam so that the analytes can be monitored in real time as they elute from the column and flow through Table 1 Key advances in the development and application of flow cell and mobile elimination interfaces for SFC FTIR Mobile phase elimination approach 1986 First demonstration of flow cell SFC FTIR using carbon dioxide as the mobilephase...

Kataoka S Yamamoto and

Narimatsu, Okayama University, Tsushima, Aliphatic and aromatic mono-, di- and polyamines are naturally occurring compounds formed as metabolic products in microorganisms, plants and animals, in which the principal routes of amine formation include the decarboxylation of amino acids, amination of carbonyl compounds and degradation of nitrogen-containing compounds. Accordingly, amines are important indicators of a wide variety of biochemical, clinical, toxicological and fermentation...

The Principle of Electrodialysis

The principle of electrodialysis is illustrated in Figure 1. A typical electrodialysis cell arrangement consists of a series of anion and cation exchange membranes arranged in an alternating pattern between an anode and a cathode to form individual cells. If an electrolyte solution is passed through these cells and an electrical potential is established between the electrodes, the positively charged cations migrate towards the cathode and the negatively charged anions towards the anode. The...

R2r n

It is seen that the light intensity varies inversely as the square of the distance from the particle, which would be expected from the inverse-square law. Not so obvious is the inverse dependence of the scattered light intensity on the fourth power of the wavelength of the incident light. In practice, the equation does not precisely predict the intensity of the scattered light as there are a significant number of particles present that are not greatly smaller than the wavelength of the incident...

The Ion Exchange Membranes

Ion exchange membranes are the key components in electrodialysis. They consist of highly swollen gel-type polymer structures carrying fixed positive or negative charges. Polymer structures carrying negatively charged groups are referred to as cation exchange membranes, while those carrying positively charged groups are referred to as anion exchange membranes. In a cation exchange membrane, the fixed negative charges are in electrical equilibrium with mobile cations in the interstices of the...

Hi dx a2 ORf dx z ZoRf

Figure 7 Plot of time necessary to ascend 4 cm versus percentage of water in mixtures of methanol water and acetonit-rile water. acetonitrile O, methanol. Plate LiChrosorb RP-18 (7 im). The value of cos 6' decreases rapidly as the percentage of water increases. When 6' is close to 90 the solvent is unable to ascend the plate. Even when using a relatively nonviscous organic solvent such as acetonitrile, 30 of water is the upper limit. In Figure 7, the variation of 4 cm development time with...

Benzyloxime Derivatization

Derivatization of simple aldehydes and ketones to benzyloximes was developed by Magin. The reaction proceeds as follows aPerkin-Elmer F-11 gas Chromatograph equipped with a coiled glass column, 6 ft long and 1 8 in i.d. bRelative retention times of secondary peaks. Reproduced with permission from Kallio H etal. (1972) Gas-liquid chromatographic analysis of 2,4-dinitrophenylhydrazones of carbonyl compounds. Journalof Chromatography 65 355. and a typical chromatogram of DNPHs of carbonyl...

Detection of Alkaloids

Only a few alkaloids are directly visible on the chromatogram as coloured spots and visualization methods have to be applied to detect them. In order to detect the compounds under UV light, fluorescing indicators are added to the adsorbent. Alkaloids become visible in short wavelength UV light (X 254 nm), where they appear as dark zones on a fluorescent background. This is considered to be a nonselective method of detection because, on the layer containing a fluorescent indicator, the emission...

Group IA

Solution Propranolol

As a general rule, most applications concern the brush-type CSPs having a rc-electron acceptor charac ter. This is because many compounds of pharmaceutical interest contain a rc-donor group. CSPs derived from N-(3,5-dinitrobenzoyl)amino acids are among the most widely used for enan-tiomeric separations of numerous compounds. The early commercialization of the well-known CSP ((R)-DNBPG), designed by Pirkle and co-workers in 1980, and the easy and inexpensive preparation of this type of CSP, has...

Preparative OPLC Separations

Whether or not the use of OPLC for preparative separation is necessary depends on the kind of sample to be separated. The potential of linear online OPLC on 20 cm x 20 cm plates with a separation distance of 18 cm as a preparative method is considerable. Because the average particle size of pre-coated preparative plates is too large, not all the advantages of this method can yet be realized. Generally, preparative online OPLC can be used for separation of 6-8 compounds in amounts up to 300 mg....