Separation Techniques

The selection of separation process of organic compounds is a critical issue in the chemical industry. Different conventional methods, such as coagulation, precipitation, ion exchange, electrodialysis, adsorption, ultrafiltration and liquid-liquid extraction have been used for the separation processes since last so many years, but supported liquid membrane (SLM)-based separation processes have been predicted as a promising option. Ionic liquids (ILs) are considered a new miraculous chemical due their unique properties and large variety of applications in all areas of the chemical sciences. The use of ionic liquids as a liquid membrane phase results in the stabilization of the SLMs due to their negligible vapor pressure, possibility of minimizing their solubility in the surrounding phases and greater capillary force associated with their high viscosity, which can reduce the displacement of liquids from micron pores under pressure. This review article summarizes the role of ionic liquids in supported liquid membrane technology for extraction processes, stability of the membranes and show promise in the liquid/liquid extraction of organics from water, gases, amino acids, toxic metal ions from their aqueous solution and separating isomeric organic compounds. © 2011 Elsevier B.V.

http://ac.els-cdn.com/S1385894711003469/1-s2.0-S1385894711003469-main.pdf?_tid=d038d75e-0ca1-11e4-b32d-00000aab0f01&acdnat=1405485165_222079d276960f352d8e76ad1012329d

Biodiesel production from abundant bio-sources has drawn the attention of the academic as well as the industrial communities in recent years. However, one of the most serious obstacles for using biodiesel as an alternative fuel is the complicated and costly purification processes involved in its production. The difficulties involved in the separation of glycerine and other un-reacted reactants and by-products necessitate the development of new competent low cost separation processes for this purpose. In this work, a low cost quaternary ammonium salt–glycerine-based ionic liquid is proposed as a solvent for extracting glycerine from the transesterification biodiesel product. The separation technique was tested on palm oil-based produced biodiesel with KOH as a reaction catalyst. The study investigated the effect of DES:biodiesel ratio and the DES composition on the efficiency of the extraction process. The lab scale purification experiments proved the viability of the separation technique with a best DES:biodiesel molar ratio of 1:1 and a DES molar composition of 1:1 (salt:glycerine). The purified biodiesel fulfilled the EN 14214 and ASTM D 6751 standard specifications for biodiesel fuel in terms of glycerine content. A continuous separation process is suggested for industrial scale application.

Intrusion  Detection  System  (IDS)  is  meant  to  be  a  software  application  which  monitors  the  network  or
system  activities  and  finds  if  any  malicious  operations  occur.  Tremendous  growth  and  usage  of  internet raises  concerns  about  how  to  protect  and  communicate  the  digital  information  in  a  safe  manner. Nowadays,  hackers  use  different  types  of  attacks  for  getting  the  valuable  information.  Many  intrusion detection techniques, methods and algorithms help to detect these attacks. This main objective of this paper is  to  provide  a  complete  study  about  the  definition  of  intrusion  detection,  history,  life  cycle,  types of intrusion detection methods, types of attacks, different tools and techniques, research needs, challenges and applications.

EXTRACTION xtraction is a process whereby a mixture of several substances in the liquid phase is at least partially separated upon addition of a liquid solvent in which E the original substances have different solubilities. When some of the original substances are solids, the process is called leaching. In a sense, the role of solvent in extraction is analogous to the role of enthalpy in distillation. The solvent-rich phase is called the extract, and the solvent-poor phase is called the raffinate. A high degree of separation may be achieved with several extraction stages in series, particularly in countercurrent flow. crystallization, or adsorption sometimes are equally possible. Differences in solubility, and hence of separability by extraction, are associated with differences in chemical structure, whereas differences in vapor pressure are the basis of separation by distillation. Extraction often is effective at near-ambient temperatures, a valuable feature in the separation of thermally unstable natural mixtures or pharmaceutical substances such as penicillin. The simplest separation by extraction involves two substances and a solvent. Equilibria in such cases are represented conveniently on triangular diagrams, either equilateral or right-angled, as for example on Figures 14.1 and 14.2. Equivalent representations on rectangular coordinates also are shown. Equilibria between any number of substances are representable in terms of activity coefficient correlations such as the UNlQUAC or NRTL. In theory, these correlations involve only parameters that are derivable from measurements on binary mixtures, but in practice the resulting accuracy may be poor and some multicomponent equilibrium measurements also should be used to find the parameters. Finding the parameters of these equations is a complex enough operation to require the use of a computer. An extensive compilation of equilibrium diagrams and UNlQUAC and NRTL parameters is that of Sorensen and Ark (1979-1980). Extensive bibliographies have been compiled by Wisniak and Tamir (1 980-198 1). The highest degree of separation with a minimum of Processes of separation by extraction, distillation, On a ternary equilibrium diagram like that of Figure 14.1, the limits of mutual solubilities are marked by the binodal curve and the compositions of phases in equilibrium by tielines. The region within the dome is two-phase and that outside is one-phase. The most common systems are those with one pair (Type I, Fig. 14.1) and two pairs (Type 11, Fig. 14.4) of partially miscible substances. For instance, of the approximately lo00 sets of data collected and analyzed by Sorensen and Arlt (1979), 75% are Type I and 20% are Type 11. The remaining small percentage of systems exhibit a considerable variety of behaviors, a few of which appear in Figure 14.4. As some of these examples show, the effect of temperature on phase behavior of liquids often is very pronounced. Both equilateral and right triangular diagrams have the property that the compositions of mixtures of all proportions of two mixtures appear on the straight line connecting the original solvent is attained with a series of countercurrent stages. Such an assembly of mixing and separating equipment is represented in Figure 14.3(a). and more schematically in Figure 14.3(b). In the laboratory, the performance of a continuous countercurrent extractor can be simulated with a series of batch operations in separatov funnels, as in Figure 14.3(c). As the number of operations increases horizontally, the terminal concentrations E, and R3 approach asymptotically those obtained in continuous equipment. Various kinds of more sophisticated continuous equipment also are widely used in laboratories; some are described by Lo et a/. (1983, pp, 497-506). Laboratory work is of particular importance for complex mixtures whose equilibrium relations are not known and for which stage requirements cannot be calculated. In mixer-separators the contact times can be made long enough for any desired approach to equilibrium, but 80-90% efficiencies are economically justifiable. If five stages are required to duplicate the performance of four equilibrium stages, the stage efficiency is 80%. Since mixer-separator assemblies take much floor space, they usually are employed in batteries of at most four or five units. A large variety of more compact equipment is being used. The simplest in concept are various kinds of tower arrangements. The relations between their dimensions, the operating conditions, and the equivalent number of stages are the key information. Calculations of the relations between the input and output amounts and compositions and the number of extraction stages are based on material balances and equilibrium relations. Knowledge of efficiencies and capacities of the equipment then is applied to find its actual size and configuration. Since extraction processes usually are performed under adiabatic and isothermal conditions, in this respect the design problem is simpler than for thermal separations where enthalpy balances also are involved. On the other hand, the design is complicated by the fact that extraction is feasible only of nonideal liquid mixtures. Consequently, the activity coefficient behaviors of two liquid phases must be taken into account or direct equilibrium data must be available. mixtures. Moreover, the relative amounts of the original mixtures corresponding to an overall composition may be found from ratios of Line segments. Thus, on the figure of Example 14.2, the amounts of extract and raffinate corresponding to an overall composition M are in the ratio E , / R N = M R N / E , M. Experimental data on only 26 quaternary systems were found by Sorensen and Arlt (1979), and none of more complex systems, although a few scattered measurements do appear in the literature. Graphical representation of quaternary systems is possible but awkward, so that their behavior usually is analyzed with equations. To a limited degree of accuracy, the phase behavior of complex mixtures can be predicted from measurements on binary mixtures, and considerably better when some ternary measurements also are available. The data are correlated as activity coefficients by means of the UNIQUAC or NRTL equations. The basic principle of application is that at equilibrium the activity of each component is the same in both phases. In terms of activity coefficients this 459

Developing a lithium mining project is a complex challenge which requires a careful planning, involving a multidisciplinary team. Each stage needs to be considered in planning, including resource exploration, production process design, basic and detailed engineering, financing, over to construction, commissioning, personnel training and process performance verification.

Though many educators and officials in Israel have agreed that for gifted children who participate in regular classes supplementary means should be applied, only a small minority of children identified as gifted have been educated in special classes. Unfortunately, the special gifted classes do not satisfy the intellectual, social, or emotional needs of many gifted children. We shall hereby describe some of the gifted sub-populations whose academic, social, or emotional needs cannot be fulfilled in gifted classes, and come to the conclusion that the pull-out program, when gifted children learn in special settings one morning per week, is the best possible way to satisfy the need of as many gifted children as possible.

The objectives of the reviews are the collection, concise description, comparison and evaluation of the various chromatographic technologies using natural and modified cyclodextrins for the increase the seperation capacity of various chromatographic separation systems.

This research was funded by, and implemented within, a UK national research organisation, while the author was the KE and Impact Evaluation Manager responsible for assessing impact on a £15m UK government-funded research programme.

This work was also submitted as the authors MBA dissertation which was accepted and awarded in 2009.

ABSTRACT: A methodology and methods ‘toolbox’ is proposed for conducting impact research and assessment from within research programmes. The emphasis is upon how to clarify and assess the wider impacts from the early stages onwards.

The approach explicitly acknowledges, and attempts to address, the known issues and challenges of impact assessment while drawing upon the resources and opportunities available to research managers and researchers within such programmes.

The study has two triangulating foundations. Firstly, it examines the academic literature to help identify and design the pilot methodology and methods. Secondly it trials these in a real programme to both test and improve them.

The study was conducted over one year within one leading UK research organisation, where two research programmes (and around 60 research projects of £15m total value) were being assessed for their impacts. The study draws upon actual impact management experience and reflection, prospective (ex ante) and retrospective (ex post) assessments, participatory contributions from leading researchers undergoing assessment, and consultation with external users. The findings of this study outline the pilot and its first iteration. Recommendations are made for improvement to the methodology and methods.

A subsequent follow-on bid to UK government incorporating the impacts identified from implementing this methodology, successfully led to a further £15m of government funding.

It is expected the pilot methodology and methods will be applicable to other organisations, conducting and funding such research programmes, required to research and assess the wider research impacts.

Although primary focus of implemetation trials was upon research in physical sciences, technology, high-tech engineering, computing/IT, and environment, the wider literature study, the methodology design and justification, the methods proposed and used, and the resulting general recommendations and lessons are expected to apply more broadly to many other research areas, where the impact is to be found more widely in the society, economy, government or public sector or within organizations, policies, professions or the public.

Interest in this work is expected from research programme managers, impact managers and assessors, management consultants advising in this area, and government funding managers, all seeking to embed a developing approach to understand, capture, and enhance wider impact.

Microwave heating reduces the preparation time and improves the adsorption quality of activated carbon. In this study, activated carbon was prepared by impregnation of palm kernel fiber with phosphoric acid followed by microwave activation. Three different types of activated carbon were prepared, having high surface areas of 872 m(2) g(-1), 1256 m(2) g(-1), and 952 m(2) g(-1) and pore volumes of 0.598 cc g(-1), 1.010 cc g(-1), and 0.778 cc g(-1), respectively. The combined effects of the different process parameters, such as the initial adsorbate concentration, pH, and temperature, on adsorption efficiency were explored with the help of Box-Behnken design for response surface methodology (RSM). The adsorption rate could be expressed by a polynomial equation as the function of the independent variables. The hexavalent chromium adsorption rate was found to be 19.1 mg g(-1) at the optimized conditions of the process parameters, i.e., initial concentration of 60 mg L-1, pH of 3, and operating temperature of 50 degrees C. Adsorption of Cr(VI) by the prepared activated carbon was spontaneous and followed second-order kinetics. The adsorption mechanism can be described by the Freundlich Isotherm model. The prepared activated carbon has demonstrated comparable performance to other available activated carbons for the adsorption of Cr(VI).

http://umexpert.um.edu.my/file/publication/00002645_105212.pdf

In most microfluidic techniques, channel width must be in range of few tens of micrometers for the device to work properly. With these dimensions, low-cost mass-production of microfluidic devices for use in point-of-care test is an issue. Here we present a hydraulic jump-based technique for size-selective microparticle or cell sorting in which working mechanism is not affected by channel width. Similar to converting kinetic energy to potential energy in macro scale, high-speed flow in a microfluidic channel is intentionally transformed into a flow with high potential energy by adjusting the channel height, inducing hydraulic jump. Depending on the strength of this energy transformation, particles with appropriate sizes can be trapped in a designed location as a result of sedimentation. With properly designing lengths of multiple expanded-height chambers and controlling the flow rate, it is possible to trap and release particles or cells selectively based on their size. To demonstrate application of our technique, we enriched 9.77 and 4.95 μm microbeads as well as WBCs and RBCs in separate chambers. Experimental results showed > 90 % selective enrichment of microbeads based on size. In addition, 69 % of WBCs and 80 % of RBCs were trapped in the first and second chamber, respectively.

The phase diagrams of the {1-butyl-3-methylimidazolium nitrate ([Bmim][NO 3 ]) / 1-hexyl-3-methylimidazolium nitrate ([Hmim][NO 3 ]) + dipotassium hydrogen phosphate (K 2 HPO 4)}c aqueous biphasic systems (ABS) and the binodal curves of {1-octyl-3-methylimidazolium nitrate ([Omim][NO 3 ]) + K 2 HPO 4 } ABS have been determined experimentally at T = (288.15, 298.15, and 308.15) K. The Merchuk equation with three dependent-temperature adjustable parameters was used for reproducing and predicting the binodal curves. The effect of the alkyl chain length of ionic liquids (ILs) was studied. It was found that the two-phase formation in the investigated ABS is decreased with decreasing the alkyl chain length of IL in the order: [Hmim][NO 3 ] N [Omim][NO 3 ] N [Bmim][NO 3 ]. Moreover, the effect of temperature on the binodal curves and tie-lines was also discussed. It was shown that the biphasic region expanded with a decrease in temperature , whereas the absolute value of slope of the tie-lines slightly decreased with an increase in temperature. Finally, the liquid–liquid equilibrium (LLE) data for the studied systems are correlated by using the NRTL thermo-dynamic model, and good agreement was obtained between the correlation and the experimental data.

In the present work, an effort has been made to develop suitable process conditions for synthesis of carbon molecular sieve (CMS) from a locally available palm shell of Tenera type. The process involves three stages; carbonization, physical activation with steam, and carbon deposition by using benzene cracking technique. The highest micropore volume of activated carbon was obtained at 53.2% burn-off,

In this paper rapid separation methods for
strontium determination using molecular recognition technology
products 3M EmporeTM Sr disc, AnaLig Sr-01 and
extraction chromatography Sr Resin were presented and
statistical tested. The methods performance was investigated
by analysis of NPL (High Alpha–Beta 2003) and (High
Alpha–Beta 2005) intercomparison samples. The presented
results were evaluated as correct for all experimental data.
We used linear regression (with regression diagnostics),
t test and the mean of variable using 90Sr with 3M EmporeTM
Sr disc, AnaLig Sr-01 and Sr Resin.

This paper describes a rapid method of 94Nb
pre-concentration, separation and purification by using
cation and anion exchange resins. The method is suitable
for analyzing highly contaminated radioactive waste samples
in a relatively short time and high decontamination
factors. The use and effectiveness of the method was successfully
tested by analysis of samples from nuclear reactor
parts such as control rod drive shaft, shielding cassettes,
neutron in-core measurement channels (KNI), pressure
vessel construction material and fuel cassette construction
material samples.

In this study, a novel continuous reactor has been developed to produce high quality methyl esters (biodiesel) from palm oil. A microporous TiO2/Al2O3 membrane was packed with potassium hydroxide catalyst supported on palm shell activated carbon. The central composite design (CCD) of response surface methodology (RSM) was employed to investigate the effects of reaction temperature, catalyst amount and cross flow circulation velocity on the production of biodiesel in the packed bed membrane reactor. The highest conversion of palm oil to biodiesel in the reactor was obtained at 70°C employing 157.04g catalyst per unit volume of the reactor and 0.21cm/s cross flow circulation velocity. The physical and chemical properties of the produced biodiesel were determined and compared with the standard specifications. High quality palm oil biodiesel was produced by combination of heterogeneous alkali transesterification and separation processes in the packed bed membrane reactor. © 2010 Elsevier Ltd.

http://ac.els-cdn.com/S0960852410014574/1-s2.0-S0960852410014574-main.pdf?_tid=74bcbdf2-025e-11e4-8ea3-00000aab0f27&acdnat=1404356723_f959262287254ffe4bce3abeee7084d9 
http://www.sciencedirect.com/science/article/pii/S0960852410014574

In this study, gas chromatography-mass spectrometry (GC-MS) following microwave distillation and solid-phase microextraction (MD-SPME) was developed for the analysis of volatile constituents from the aerial parts of Thymus vulgaris L. In order to improved headspace method, microwave powers; irradiation times and SPME fibers coating were studied. The optimal experiment parameters obtained were:
100 μm PDMS, a microwave power of 400 W and an irradiation time of 5 min. MD-SPME was compared with headspace solid-phase microextraction (HS-SPME) and conventional hydrodistillation (HD) for the extraction of volatile compounds in Thymus vulgaris L. A comparative qualitative and quantitative study on the composition
of volatile compound was carried out. Thymol, p-cymene, γ-terpinene and carvacrol were identified as major constituents of this plant in all methods. The relative standard deviation (R.S.D) values of less than 7 % showed that the MD-SPME method has good repeatability. It has been shown the extraction of volatile compounds from Thymus vulgaris L. with MD-SPME was better in terms of energy saving, extraction time, plant material, oxygenated fractions and product quality.

The soil-water partition coefficient normalized to the soil organic carbon content (KOC) is one of essential properties governing the fate of organic chemicals in the soil-water compartment. It is a parameter of utmost importance when it comes to the removal of toxic organics in the waste water management facilities or placing a new chemical on the
market. Since direct determination of KOC based on tests involving soil-sorption measurements are expensive, time-consuming, tedious, and subject to a variety of experimental difficulties and artifacts, different alternative methods have been developed for rapid indirect experimental determination and estimation of KOC values. In the scope of the present work we provide critical and historical overview of development and
application of the main chromatographic methods, both high-performance liquid chromatography (HPLC) and thin-layer chromatographic (TLC) techniques for indirect experimental determination of the soil-water partition coefficient as well as mobility assessment of environmentally important compounds in the soil. Chromatographic methods proved to be promising in this field, which is clearly demonstrated by their  implementation in official guidelines for testing the chemicals.

Potassium leakage was studied in liquid membrane systems containing various emulsifiers and
compared with emulsion stability in the storage test. The effects of various parameters upon emulsion
stability and the leakage of standard traces are discussed. The transfer of cations can be caused by
emulsion breaking, by transport with the specific carrier and/or with snrfactants used as emulsifiers.
The latter case becomes especially important when hydrophilic surfactants, e.g. ones containing
polyoxycthylene chains, are present in liquid membranes. In systems containing hydrophobie
emulsifiers the transfer of potassium is relatively low. In each case considered the effect of emulsifiers
upon the transfer of the standard tracer should be checked prior to using the leakage test to characterize
emulsion stability.

Separation of aromatics from aliphatics is a challenging process because of the close range of their boiling points and the formation of several combinations of azeotropes. Until now, no feasible separation process is available for aromatic concentrations below 20 wt%. In this work, we have investigated the possibility of using a selected deep eutectic solvent (DES) for the liquid-liquid extraction of benzene, toluene, ethylbenzene and m-xylene (BTEX) aromatics. The DES used in this work was synthesized by combining tetrabutylammonium salt and sulfolane. Equilibrium data for the ternary system consisting of BTEX aromatics, n-octane and DES were measured at 25 °C and atmospheric pressure. The results showed that the used DESs have comparable distribution ratios and selectivities to those of commercial solvents. In all tested systems, sulfolane was not present in the hydrocarbon layer. It was also found that the selectivity decreases with decreasing polarity of the aromatic compound. The Non-Random Two Liquid (NRTL) model was successfully used to correlate the experimental tie-lines and to calculate the phase compositions of the ternary systems. In addition, the performance of COSMO-RS to predict the ternary tie-lines for the studied systems was evaluated and the σ-profiles were used to explain the interaction between the DES and the aromatic compounds. This journal is © the Partner Organisations 2014.

http://pubs.rsc.org/en/content/articlepdf/2014/ra/c4ra01081g

SEDIMENTATION

INTRODUCTION - THE PHENOMENON OF SEDIMENTATION

Sedimentation is the physical process whereby solid particles, of greater density than their suspending medium, will tend to separate into regions of higher concentration under the influence of gravity. As a solids/liquids separation technique it therefore possesses the great advantage of utilizing a natural, and therefore costless, driving force. This section of the suspension processing Guide is Intended to provide an Introduction to the science of the subject, and the means to judge where and how best to exploit sedimentation as a separation (or other processing) technique.

As a scientific discipline the subject of sedimentation is vast with perspectives ranging from the field of chemical engineering through to theoretical physics being covered In the literature [1-11]. Good reviews of the subject, with a bias towards the engineering aspects, have been written by Fitch and Koz [12, 13]. A short summary of some of the more relevant contributions from the literature is also provided in GBHE-SPG-PEG-302 “Basic Principles & Test Methods”, of the Suspensions Processing Guides.
.
The sedimentation process is traditionally divided into ...

A stochastic model of transcolumn eddy dispersion along packed beds was derived. It was based on the calculation of the mean travel time of a single analyte molecule from one radial position to another. The exchange mechanism between two radial positions was governed by the transverse dispersion of the analyte across the column. The radial velocity distribution was obtained by flow simulations in a focused-ion-beam scanning electron microscopy (FIB-SEM) based 3D reconstruction from a 2.1 mm × 50 mm column packed with 2 m BEH-C 18 particles. Accordingly, the packed bed was divided into three coax-ial and uniform zones: (1) a 1.4 particle diameter wide, ordered, and loose packing at the column wall (velocity u w), (2) an intermediate 130 m wide, random, and dense packing (velocity u i), and (3) the bulk packing in the center of the column (velocity u c). First, the validity of this proposed stochastic model was tested by adjusting the predicted to the observed reduced van Deemter plots of a 2.1 mm × 50 mm column packed with 2 m BEH-C 18 fully porous particles (FPPs). An excellent agreement was found for u i = 0.93u c , a result fully consistent with the FIB-SEM observation (u i = 0.95u c). Next, the model was used to measure u i = 0.94u c for 2.1 mm × 100 mm column packed with 1.6 m Cortecs-C 18 superficially porous particles (SPPs). The relative velocity bias across columns packed with SPPs is then barely smaller than that observed in columns packed with FPPs (+6% versus + 7%). u w = 1.8u i is measured for a 75 m × 1 m capillary column packed with 2 m BEH-C 18 particles. Despite this large wall-to-center velocity bias (+80%), the presence of the thin and ordered wall packing layer has no negative impact on the kinetic performance of capillary columns. Finally, the stochastic model of long-range eddy dispersion explains why analytical (2.1–4.6 mm i.d.) and capillary (<400 m i.d.) columns can all be packed efficiently (1 <h min < 2) with particles of size larger than 2 m. In contrast, the model predicts that 0.4–1.2 mm i.d. columns and 2.1 mm i.d. columns cannot be packed well (h min >3) with sub-2 m particles and with 1 m particles, respectively.

We have fabricated partially aligned free-standing mesoporous pure anatase TiO2 nano fiber mats (TiO2-NF) for photocatalysis by electrospinning on a rotating drum collector using a blend of
titanium isopropoxide (Ti(OiPr)4), with a carrier polymer, polyvinylpyrrolidone (PVP) in acetic acid and ethanol. Calcination removes PVP and generates mesoporous TiO2-NF with fiber
diameters in the range of 25-75 nm by optimizing the electrospinning parameters like electric field strength, polymer concentration and flow rate of solution, etc. The band gap energy of TiO2 nanofibers form the UV-vis absorption spectra is found to increase with increase in the calcination temperature thus allowing band gap engineering for different applications. The
surface morphology, phase composition, crystallinity, surface area and porosity of the TiO2-NF are also investigated. We demonstrate the efficient and reusable photocatalytic action of the
partially aligned pure electrospun TiO2-NF and residual carbon containing TiO2-NF mats with an average fiber diameter ~40 nm in the photocatalytic degradation of a polycyclic aromatic
hydrocarbon (PAH) dye, naphthalene. Small carbon residue (2.54%) containing TiO2-NF is found to be about twice as efficient as the pristine TiO2-NF in photodegradation of PAH dye, but
the effectiveness declined at higher carbon content.

Amino acids (AAs) are important biomolecules responsible for plethora of functions in both prokaryotic and eukaryotic systems. There are 22 naturally occurring amino acids, among which 20 common amino acids appear in the genetic code and known as proteinogenic amino acids, which are the building blocks of proteins. Proteinogenic amino acids exist in two isomeric forms (except glycine) and the biological activity is often attributed to a specific stereoisomer. Most of the amino acids found in protein is predominantly L-AAs. A few D-amino acids can be found in bacterial cell wall, some marine invertebrates and higher organisms including frog, snail, spider, rat, chicken and human. Besides their role in protein synthesis, different proteinogenic amino acid stereoisomers have found to perform important biological roles either by functioning as precursors of a myriad of other bioactive molecules or by indicating several biological phenomena i.e. acting as markers for different physiological conditions. Given the biological importance of Land D-amino acids (AAs), improved analytical methods for their resolution and accurate quantification remain of keen interest. Chiral analysis of amino acids in complex biological matrices poses numerous analytical challenges that are exacerbated by broad differences in polarity and ionization efficiencies of the proteinogenic amino acid stereoisomers. To date, various analytical methods are reported for chiral amino acid analysis including chromatographic, spectrometric, enzymatic, fluidic, electrophoretic and microbiological techniques. Advances in stationary phase, derivatization chemistry and instrumentation contributed to achieving baseline separation and accurate detection of trace levels of proteinogenic amino acids stereoisomers in different matrices. However, liquid and gas chromatography coupled to mass spectrometry based analytical methods remain the most popular platform in chiral amino acid analysis in terms of feasibility and performance. This review discusses different physicochemical and biological features and functions of proteinogenic amino acid stereoisomers and lists a variety of established chromatography and mass spectrometry based analytical methods for their analysis reported to date.

Flow directionality, valving and liquid routing in centrifugal microfluidics (Lab-on-CD) are typically controlled by applying centrifugal and Coriolis forces and have been the subject of active research interest in recent years. Determining and switching the flow direction at a T-junction is a common fluidic operation important for implementing several chemical and clinical assays for Lab-on-CDs. The present work describes a novel approach to route samples and control flow direction on a spinning disc that employs a guiding microstructure that relies on a two-stage valve comprised of an auxiliary inlet, which is a recess embedded at a T-junction, and a bent auxiliary outlet. The distinctive feature that makes this approach different from other types of passive capillary valves is the strong control of liquid movement, which is achieved by employing two adjustable sequential burst valves called a primary valve and a secondary burst valve. The guiding method can be used to route samples and reagents at given flow rates to a selection of receiving reservoirs, which are determined by the spinning frequency of the disc. The technique also allows for the switching of the flow direction instantaneously from the direction along the disc rotation to the opposite direction by increasing the rotational speed of the disc rather than relying on the Coriolis force, which would require reversing the spin direction. The flow routing by the proposed technique has been studied theoretically, and the flow behavior has been numerically investigated. These studies have been experimentally validated for a wide range of capillary sizes and for various liquids including di-water, mixtures of water and ethanol and bovine serum albumin (BSA).

http://pubs.rsc.org/en/content/articlehtml/2014/ra/c4ra14397c

Xylose is an abundant raw material coexists with other sugars that can be turned into useful products,
such as ethanol, xylitol and 2, 3-butanediol by microorganism such as yeasts, bacteria, and mycelial fungi.
However, more than 80 % of the production cost of these products comes solely from the production of
xylose. Presently, the separation of xylose from hemicellulose hydrolysate relies on chromatographic
separation alone. The use of nanofiltration membrane may offer alternative in recovering xylose due to
the differences in size compared to other sugars. The aim of this study is to evaluate the ability of
membrane developed by interfacial polymerization reaction between triethanolamine (TEOA) (6 % w/v)
and tri-mesoyl chloride (TMC) (0.15 % w/v) as monomers on polyethersulfone (PES) microporous
substrate to separate xylose from glucose. In this study, factors affecting the process, namely pressure,
concentration of total sugars in solution, and composition of monosaccharides in total sugar, were
investigated using two-level factorial analysis. The experiment was performed using Amicon Milipore
stirred cell (Model 8200) with constant stirring speed at 300 rpm and temperature at ambient. The glucose
and xylose concentration was quantified using high performance liquid chromatography (HPLC). It is
found that the developed nanofiltration membrane has the ability to separate xylose from glucose.The
analysis of the experimental response revealed that the total sugar concentration and composition ratio of
xylose: glucose had significant interactive effect on xylose separation factor. Overall from the present
study, it can be concluded that nanofiltration has high potential to replace currently in use
chromatographic method in xylose separation.