High Separation Power Research Articles

High purification of gas in radial membrane element

The process of high purification of gas from easily penetrating impurities in a countercurrent radial membrane element is investigated theoretically and experimentally. The mathematical model of process is developed in view of longitudinal mixing impurities in both cavities of an element, and with the consider recycle of a target flow from a cavity of high in a cavity of low pressure (retentate recycle). It is found that, the researched membrane elements have the high separation power. It is shown that the retentate recycle should be realized in membrane elements with high-selectivity and low permeability of the basic component membranes. The experimental and the calculation results are in agreement.

IMPROVED IDENTIFICATION BY IN SITU UV SPECTRA IN PLANAR CHROMATOGRAPHY

Novel software was introduced for library searching in planar chromatography, based on corrected Rf values (hRf c), in situ ultraviolet (UV) spectral correlation, and spectrum maximum site comparison. Analysis of autopsy urine samples by thin-layer chromatography (TLC) and overpressured layer chromatography (OPLC) revealed that the new method was superior to the standard method using hRf c and correlation only. The advantage was more pronounced in TLC, which possessed poorer separation power and generally lower quality spectra than OPLC. In 11 cases of 47 in TLC, the hit list position of the correct finding was improved by the new method. This result indicates that the spectrum maximum site function gives a different kind of discrimination than would be obtained by only setting the correlation cut-off at a higher value. In OPLC, the hit lists were originally shorter, but an improvement in the list lengths was evident. OPLC proved to be the planar method of choice in the screening analysis of urine samples for drugs due to its high separation power and speed.

Factors affecting clients' project dispute resolution satisfaction in Hong Kong

The use of project dispute resolution satisfaction (DRS) as a project success measurement responds to the increasing concern over the spread of the dispute epidemic within the construction industry in Hong Kong. The DRS of a project is considered as favourable where disputes are resolved within the site level. With the use of 48 project data sets and the technique of multivariate discriminant analysis, a discriminant model function was derived to classify projects into favourable DRS and adverse DRS. The multivariate discriminant analysis model function identified eight discriminating variables, among which the degree of design changes offered the highest separation power. The reliability of the discrminating variables was reinforced by a separate relative importance index study. Through the use of principal component factor analysis, these variables were grouped into three factors generically described as substantive influence, facilitation and indirect influence.

Comprehensive Two-Dimensional Gas Chromatography with a Rotating Thermal Desorption Modulator and Independently Temperature-Programmable Columns

In comprehensive two-dimensional gas chromatography, two individual separations are coupled by means of a rotating thermal desorption modulator interface. The injection pulse introduced via the interface onto the second column should be as short as possible. Parameters affecting the modulator operation are studied. In the set-up used in this study, the temperature of the second column can be programmed independently from that of the first column. Optimization of the second-dimension separation to minimize peak broadening and maximize resolution is discussed and an elegant approach to determine second-dimension retention times using a non-constant modulation frequency is demonstrated. The high separation power of the comprehensive system is demonstrated by the analysis of technical and biota samples containing chlorinated biphenyls and toxaphene.

Comprehensive Two-Dimensional Gas Chromatography with a Rotating Thermal Desorption Modulator and Independently Temperature-Programmable Columns

In comprehensive two-dimensional gas chromatography, two individual separations are coupled by means of a rotating thermal desorption modulator interface. The injection pulse introduced via the interface onto the second column should be as short as possible. Parameters affecting the modulator operation are studied. In the set-up used in this study, the temperature of the second column can be programmed independently from that of the first column. Optimization of the second-dimension separation to minimize peak broadening and maximize resolution is discussed and an elegant approach to determine second-dimension retention times using a non-constant modulation frequency is demonstrated. The high separation power of the comprehensive system is demonstrated by the analysis of technical and biota samples containing chlorinated biphenyls and toxaphene.

Analysis of bisphosphonates by capillary electrophoresis–electrospray ionization mass spectrometry

Capillary electrophoresis–electrospray ionization mass spectrometry (CE–ESI-MS) was applied to the direct identification and quantitation of clodronate and its four common impurities. The coaxial interface technique and negative ion mode were used in the detection. Ion source parameters and sheath liquid composition were optimized to produce maximum abundance of singly charged deprotonated molecules used in monitoring. In addition, the effects of electrolyte composition and instrumental parameters of CE on separation were studied. The developed method provides high separation power and specificity to bisphosphonate analysis. In quantitative analysis, the method showed good linearity ( r=0.9946–0.9989), satisfactory repeatability (migration time variation: RSD=0.43–1.0%, peak area variation: RSD=2.2–9.4%) and sufficient sensitivity (detection limits: 0.08–0.22 mg ml −1) for identification of bisphosphonates from bulk material.

Multistructure sequencing of N-linked fetuin glycans by capillary gel electrophoresis and enzyme matrix digestion.

Oligosaccharide sequencing by specific enzymatic digestion of N-linked fetuin glycans using a carefully designed exoglycosidase matrix in conjunction with separation of the combined digests by high performance capillary gel electrophoresis is described. Due to the extremely high separation power and excellent reproducibility of capillary gel electrophoresis, in most instances no isolation of the individual oligosaccharides is necessary, enabling multistructure sequencing from a released glycan pool. By comparing the positions of the separated exoglycosidase digest fragments to maltooligosaccharides of known size, relative migration times and migration shifts are easily calculated. Hence, the particular sequence of each oligosaccharide in a released glycan pool can be proposed with high confidence. Additionally, with the use of high sensitivity laser-induced fluorescence detection, complete sequence information can be attained from picomolar amounts of purified glycoproteins.

Demonstration of an integrated capillary electrophoresis—laser-induced fluorescence fiber-optic sensor

A unique integrated separation-based fiber-optic sensor for remote analysis, that incorporates capillary electrophoresis (CE) directly at the fiber sensing terminus is described for the first time. Based on laser-induced fluorescence detection, the sensor offers the potential for high sensitivity. Although the broad-band nature of fluorescence spectra limits selectivity, the high separation power of CE provides a unique dimension of selectivity, while permitting a design of diminutive size. Previously reported fluorescence-based sensors that utilize a chemical reagent phase to impart selectivity tend to be inflexible (not readily adaptable to the detection of different species) and “one-measurement-only” sensors. Conversely, the CE-based fiber-optic sensor described here is both versatile and reusable. The analysis speed and the potential for remote control are further attributes which make the system amenable to remote sensing. A “single-fiber” optical detection arrangement and a “single-reservoir” CE system with the fiber-optic probing the outlet of the separation capillary are employed. A preliminary evaluation of the separation characteristics of this CE-based sensor is presented. Highlights include an observed separation efficiency of up to 3000 theoretical plates (8 cm separation capillary) and migration time reproducibility of less than 10% for frontal mode CE separations. The potential utility of the sensor for remote analysis is demonstrated with separations involving the CE analysis of charged fluorescent dyes, CE analysis of metal complexes based on in situ complexation and micellar electrokinetic capillary chromatographic analysis of neutral fluorescent compounds.

On-line coupling of PIXE with capillary zone electrophoresis (CZE)

During recent years most of the new knowledge about the biological function of trace elements has been obtained from studies involving the determination of the chemical bonding or oxidation states of these elements (speciation). The combination of a molecule separation process with a method for trace element analysis creates a powerful tool for this kind of observation. We studied the on-line coupling of capillary zone electrophoresis (CZE), with its high separation power, and proton induced X-ray emission (PIXE), with its high inherent sensitivity. A CZE-PIXE detection system is described and preliminary results will be presented.

Determination of D- and L-amino acids in biological samples by two-dimensional column liquid chromatography

A two-dimensional, column liquid chromatographic system is used for the determination of the D- and L-enantiomers of amino acids in biological samples. Separation of the amino acids is first on ion-exchange column by gradient elution with a sodium citrate-sodium chloride buffer. Enantioseparation is by subsequent injection of 3 µl heart-cuts of the individual amino acids onto a second column with a chiral crown ether stationary phase. Finally, fluorescence detection is after post-column labelling of the amino acids using ano-phthalaldehyde-2-mercaptoethanol reagent solution. The high separation power and selectivity of the system allow processing of complex samples with hardly any additional treatment and the determination of small quantities of D-amino acids in the presence of excess L-form. Applicability of the system is illustrated by the determination of D- and L-aspartate, serine, glutamate and alanine in various complex biological samples, such as protein hydrolysates, urine and biotechnological and food samples. Data are given on detectability, repeatability and linearity.

Retention properties of triacylglycerols on silver ion high-performance liquid chromatography

The retention properties of series of synthetic disaturated-monounsaturated (1 to 6 double bonds) triacylglycerols and the common seed oil triacylglycerols on a silver ion high-performance liquid chromatography column have been studied in quantitative terms. Retention factors were found to increase stepwise, with a saturated dimonoenoic species being held ten times and trilinolenin ten thousand times more strongly than a disaturated monoenoic species, for example. Formation of chelate-type of pi-complexes between silver ions and double bonds, with participation of the carbonyl oxygen in the complexation, have been assumed in order to explain the high separation power and specificity of the silver ion column.

An improvement of restriction analysis of bacteriophage DNA using capillary electrophoresis in agarose solution.

Seven representatives of the serogroup B Staphylococcus aureus bacteriophages, 29, 53, 55, 83A, 85, phi 11 and 80 alpha, were examined by capillary electrophoresis (CE) for genomic homology using DNA restriction analysis. Genomic DNA of individual bacteriophages was cleaved by HindIII restriction endonuclease, and the resulting restriction fragments were separated by standard horizontal agarose slab gel electrophoresis (SGE) as well as by CE in low-melting-point agarose solutions. The number and size of restriction fragments identified by both methods were compared. The high separation power of CE makes it possible to extend the restriction fragment patterns. In most of the restriction patterns, some additional restriction fragments as small as 150 bp, not identified by SGE, were detected. With respect to speed, high separation efficiency, low sample consumption and automation, CE offers a simple procedure for processing of multiple samples cost-effectively in a reasonable time. The comparison of the complemented restriction patterns of the different phage strains and the subsequent identification of their common fragments leads to a deeper understanding of their phylogenetic relationships. The genome homologies expressed for individual phage pairs in terms of coefficient F values ranged from 15 to 69%. These values are in good accordance with the degree of DNA homology of these phages as determined by DNA hybridization studies and thermal denaturation analysis of DNA by other authors. The total size of each phage genome was estimated by adding the sizes of individual restriction fragments.

Effect of alkali metals and metal‐ammonia complexes on electroosmosis, effective field strength, and resolution in the separation of diuretics by CZE

AbstractThe counter ion in CZE separation systems affects resolution, effective field strength and electroosmosis. Alkali metals (lithium, sodium, potassium, and cesium), the ammonium ion, and several complexes of metals with ammonia ([Ag(NH3)2]+, [Cu(NH3)4]2+, [Zn(NH3)4]2+, [Cd(NH3)4]2+, [Ni(NH3)6]2+, and [Co(NH3)6]2+) have been studied for their effect on the separation of diuretics. With the alkali metals the electroosmotic flow velocity decreased and the effective field strength and resolution increased as the hydrated radius of the alkali metal decreased.All the metal‐ammonia complexes except that with silver greatly reduced the electroosmotic flow velocity (Veo) and had only a slight effect on the effective field strength (Eeff). Because these complexes had a negligible effect on the ionic strength of the buffer, they enabled high separating power to be maintained during the separation, and hence the use of more energy in the separation system. This yielded better resolution of the compounds, but the analysis time was then compromised.A simultaneous reduction in capillary length and Veo while maintaining the high voltage enabled increased resolution without an increase in analysis time. The ability to control Veo by adding small concentrations (< 100 μM) of metal complexes to the buffer solution makes it possible to adjust the analysis time and capillary length independently while employing high separation power.

A fast and compact solid radiator RICH counter

The performance of NaF as Cherenkov radiator in a RICH counter has been studied. This detector is less than 8 cm thick and represents 10% of a radiation length. It uses TMAE as photosensitive compound and is operated at low gain to minimize photon feedback. The induced pulse in the cathode plate is read out by pads. A prototype has been developed and tested with pions and protons up to 3.5 GeV/ c momentum. About 20 photoelectrons are detected per ring for β = 0.96 protons, giving high detection efficiency and good particle separation power. The low index of refraction of NaF also allows operation at normal incidence for β = 1 particles with good efficiency. The mean refractive index obtained by fitting the ring radius of experimental data to the geometrical setup depends on the beta and reduces the separation power of the detector. Such a detector would be very useful for particle separation in medium energy particle physics experiments and also an important part of an astrophysics project in space.

Micellar electrokinetic capillary chromatographic separation and laser-induced fluorescence detection of 2'-deoxynucleoside 5'-monophosphates of normal and modified bases

Micellar electrokinetic chromatography is used to separate dansylated nucleotides, both normal and modified species. The high separation power allows detection of minor components present in less than 1 part per thousand of the major components. Laser-excited fluorescence is used to detect the separated components at the 6 · 10 −18 mol level or 10 −9 M injected material. Combined with high-performance liquid chromatographic enrichment prior to labeling, this technique can be used to assess DNA damage in carcinogenesis studies.

Simple high-performance liquid chromatographic methods for resolving complex mixtures

~1) had to be transferred. HPLC-GC transfer was automated, allowing the instrument to be situated in a production plant and run by non-laboratory personnel . Maris et a1.16 determined PCBs in sediment samples using HPLC for sample clean-up. Excellent agreement of the HPLC-GC results with GC results obtained with conventional sample pre-treatment was found. Volumes of 1804 were transferred into a 5-m uncoated pre-column using the retention-gap technique with efficient partially concurrent eluent evaporation (on-column interface). Results of another study17, viz. on the determination of organochlorine pesticides in surface water are shown in Fig. 3. Towards automated analysis Automation in the sense of applying autosamplers has become common practice. However, in view of the tremendous work involved in sample preparation, this represents automation of only a small portion thereof. More recently, robotics were introduced for automating simple manual routine work. However, robotics only allow automation of classical, inefficient techniques. We need higher separation power for removing by-products, to achieve more efficient sample preparation in fewer steps, and, ideally, these steps should be integrated on-line into the final analysis. Column switching techniques in HPLC are one approach towards this end. From this point of view, automated coupled HPLC-GC should become a must for all laboratories that must analyze large numbers of complex samples efficient1Y.

Simultaneous effects of amines and alkylsulphonates in reversed-phase ion-pair liquid chromatography — application to the separation of 2-imidazoline drugs

The reversed-phase liquid chromatographic separation of several pharmaceutically important 2-imidazoline derivatives using eluents containing both amines and alkylsulphonates, is described. The addition of N, N-dimethyloctylamine and sodium octanesulphonate to an acidic aqueous methanolic eluent, resulted in an eluent with much higher separation power than mobile phases containing only one modifier. The combined effect of the amine and of the alkylsulphonate enabled baseline (or nearbaseline) separations of all the 2-imidazolines studied. The use of such eluents is described in terms of efficiency, selectivity, peak symmetry and separation time and the mechanism of retention is discussed. Some separation examples are given to demonstrate the applicability of the developed technique in the quality control of these drugs in pharmaceuticals.

Combined thin-layer chromatography/mass spectrometry without substance elution: Use for direct identification of amino acids as dansylated esters

Amino acids can be identified unambiguously in form of their dansylated methyl esters by combination of thin-layer chromatography on polyamide and subsequent mass spectrometry without prior substance elution from the chromatographic polyamide carrier. The evaporation intensity of the amino acid derivatives is sufficient to get excellent mass spectra with significant structural information also with very small amounts of starting material (picomole level), which guarantee a high separation power in the TLC step. Besides the methylester derivatives, in part, products additionally methyl substituted at the sulfonamide nitrogen could be separated.

Potentials of capillary gas chromatography in toxicology today.

The usefulness, the applicability and the limitations of capillary gas chromatography in various types of toxicological analysis were discussed. Technical parameters of capillary gas chromatography, such as type of injector, type of column with regard to material, size, and stationary phase were assessed in view of the requirements of toxicological analysis. The main advantage of capillary gas chromatography, i.e. high separation power, is unfortunately counterbalanced by low loadability and/or speed of analysis. In the present situation capillary gas chromatography is a method of choice in drug screening despite some disadvantages, but in drug-oriented analysis the conventional chromatography on packed; columns is probably more useful.

Liquid chromatography in open tubes.

Liquid chromatography in open tubes is evaluated for applicability to clinical analysis. The principal advantages of this technique include high separation power, reduced solvent consumption, and small sample volume requirements. Technology for the production of columns as small as 8 micron (i.d.) is described. Preliminary results are encouraging and, with further development in column and detector technology, the technique should find wide applicability in clinical analysis.