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100% - Super-critical Fluid Chromatography (SFC) >
This article can be downloaded as a pdf file for easy printing. Polysaccharide phases and especially the Chiralpak AD column prove to be succesful SFC phases, the role of the modifier on the selectivity is very important and you have to test different alcohols. In most cases we are successful in ... >>
88% - Chiral Chromatography >
The definitions have been mostly taken from the IUPAC recommendations of 1997 for "Analytical chiral separation methods". Click here to link to this page. >>
72% - Chiral Chromatography >
The basic rationale for the separation of enantiomers is common for all the various separation technologies: Enantiomers are converted to diastereomers or diastereomeric associates which differ in their physicochemical properties and can therefore be separated. Two general modes can be pursued: ... >>
70% - Chiral Chromatography >
If 18-crown-6 has one or two ethylene-bridges substituted by a chiral moiety such as an enantiomeric binaphthyl derivative (Crownpak CR) or tartaric acid synthon (Chirosil RCA), the resultant crown ether is chiral. When such chiral crown ethers are immobilized to a chromatographic support, CSPs ... >>
69% - Chiral Chromatography >
In general, the quantitation methods described above can be applied as well. However, one should consider the following if enantiomeric impurities of 0.1% or less must be analyzed: A relatively high mass of solute needs to be usually injected in order to be able to detect the minor impurities. ... >>
69% - Chiral Chromatography >
Links to important column suppliers for enantioselective chromatography A huge variety of distinct companies are now selling enantioselective columns. Links to a few important column suppliers are given below. Chiral Technologies ASTEC REGIS Technologies http://www.registech.com/chiral/ ... >>
68% - Chiral Chromatography >
In general, we may distinguish various types of chiral stationary phases which are schematically illustrated below a single defined selector moiety may be covalently linked via a spacer to the silica support (brush-type phases) a polymeric chiral selector may be processed in an appropriate way ... >>
64% - Chiral Chromatography >
Chiral Technologies recently commercialized a set of columns under the tradename Chiralpak QN-AX and Chiralpak QD-AX. These columns make use of selectors that are derived from quinine and quinidine and offer excellent chiral resolving power for chiral acids, preferentially in polar organic phase ... >>
64% - Chiral Chromatography >
These CSPs have been commercialized, e.g. as Chiralpak MA+ by Chiral Technologies They are based on chelating selectors which are often derived from proline or hydroxyproline. A metal-ion (Me) such as Cu2+ is added to the mobile phase. Solutes also having chelation properties such as alpha-amino ... >>
63% - Chiral Chromatography >
Chiral separation can be used for example if one needs to know the enantiomer composition of chemical substances prepared by asymmetric synthesis or biocatalysis. Another important application is the detection and analysis of enantiomeric impurities in single enantiomer products such as chiral ... >>
63% - Chiral Chromatography >
The utility of the indirect enantiomer separation method is connected to a number of requirements: First of all, the selectand i.e. the analyte to be separated must contain a (relatively easily) derivatizable functional group such as a hydroxyl, amine, carboxylic, carbonyl group. Some common ... >>
55% - Super-critical Fluid Chromatography (SFC) >
SFC is a mode of chromatography that makes use of specific types of mobile phases, namely supercritical or subcritical fluids. In general, Chromatographic separations are based on several properties of the different parts involved in the process: the solutes, the stationary and the mobile phases. ... >>
55% - Chiral Chromatography >
Since something like a generic method does not exist for enantiomer separation, the most critical and difficult task is to select the most suitable enantioselective column from the variety of commercially available ones. For the beginner in the field of chiral analysis this may appear like looking ... >>
52% - Chiral Chromatography > 6. Macrocyclic antibiotics CSPs >
In 1994 D. W. Armstrong introduced a new, important CSP class, the macrocyclic antibiotic CSPs. They are based on macrocyclic glycopeptides such as vancomycin, teicoplanin or ristocetin which are covalently immobilized on silica gel. A number of different variants are commercially available under ... >>
49% - Super-critical Fluid Chromatography (SFC) >
Independent of the stationary phase (non-polar, polar, chiral or achiral) and whatever the modifier percentage, temperature change induces retention and selectivity changes: For mobile phases having low modifier percentages (supercritical behaviour), a decrease in temperature generally reduces ... >>
46% - Chiral Chromatography >
A new set of polysaccharide-based CSPs was developed to overcome the limited solvent compatibility of the coated polysaccharide CSPs described above and were launched in 2005. CHIRALPAK® IA is based on amylose tris(3,5-dimethylphenylcarbamate), (a coated polysaccharide CSP) which is covalently ... >>
46% - Chiral Chromatography >
The most important feature of the immobilized polysaccharide CSPs is their extended solvent compatibility. They can be used with the standard eluents commonly used also with the coated versions of the polysaccharide CSPs as well as non-standard eluents listed below in order of increasing elution ... >>
46% - Chiral Chromatography >
The most prominent examples of protein phases are: Chiral AGP: The CSP is based on alpha-1 acid gylcoprotein which is a plasma protein. It has a broad applicability spectrum for the separation of various acidic, neutral and basic drugs. Ultron ES OVM: It is based on ovomucoid, a chicken egg-white ... >>
46% - Chiral Chromatography >
Poly(meth)acrylamide CSPs: e.g. poly[N-acryloyl-(S)-phenylalanine-ethyl ester] ( ChiraSpher from Merck KGaA, Darmstadt, Germany) Tartramide CSPs (network polymer CSPs based on crosslinked tartaric acid diamides) e.g. O,O‘-bis-(3,5-dimethylbenzoyl)-N,N‘-diallyl-(R,R)-tartaric acid diamide ... >>
46% - Chiral Chromatography >
Cyclodextrin (CD) CSPs are based on α, β- or γ-cyclodextrins that are macrocylic structures made from 6, 7, and 8 glucose units, respectively. The glucose (glucopyranose) units are connected via -1,4-linkages. These cyclic molecules have the shape of a truncated cone and the number of glucose ... >>
46% - Chiral Chromatography >
Donor-acceptor phases (Brush-type or Pirkle-type CSPs) CSPs of this class are obtained by bonding a low-molecular mass neutral synthetic chiral selector via an achiral spacer to silica. Since the selector moieties are arranged perpendicularly to the silica surface like the bristles of a brush, ... >>
46% - Chiral Chromatography >
In general, it is of utmost importance in chiral analysis that no accidental alterations of the original enantiomer composition of the sample, due to the manipulations carried out in the course of sample work-up, occur. This could for example happen if crystallization steps are part of the sample ... >>
38% - Application areas > Pharmaceutical Analysis > Separation techniques in pharmaceutical analysis >
In research, development and manufacturing of pharmaceutical products separation techniques are applied to perform quantitative and qualitative analysis. In quantitative analysis the contents of active and impurities in samples are determined. In qualitative analysis samples are screened for unknow ... >>
34% - Sample prep in modern bioanalysis >
Introduction A reliable quantitative LC-MS method consist of four main steps, where each one must be carefully addressed during the method development: Sample preparation Efficient and fast chromatographic separation Sensitive and selective MS detection The choice of appropriate data processing ... >>
34% - Super-critical Fluid Chromatography (SFC) >
Some rules of thumb for setting the SFC parameters: Low temperature (below 30°C) and medium backpressure (15 MPa) are advised as starting points to develop an SFC separation. The smaller compressibility of the fluid, achieved under these conditions, ensures satisfactory chromatographic ... >>
34% - Super-critical Fluid Chromatography (SFC) >
This reference list contains the literature with more details referring to the four articles - above - by Eric Lesellier on parameters. (1)T.A Berger, W.H. Wilson, Anal. Chem. 65(1993)1451 (2) C. Bouigeon, D. Thiébaud, M. Caude, Anal. Chem. 68(1996)3622 (3) J.D. Pinkston, S.B. Marapane, G.T. ... >>
34% - Super-critical Fluid Chromatography (SFC) >
What is SFC? History In the 1980s SFC started with high expectations, it would compete – and maybe even replace - both GC and LC: the capillary SFC (columns in the order of ten micrometres), the very long columns separation would improve compared to GC analyses. Unfortunately there ... >>
34% - Super-critical Fluid Chromatography (SFC) >
SFC: the 'Sleeping Beauty' of separation science? Where previously we saw SFC only for chiral and polymer analysis, we now see more and more mainstream publications in which SFC replaces RPLC and NPLC. Agilent and Waters have taken SFC into their portfolio, and RIC, the company of Pat ... >>
34% - Home > Expert teaching >
* Paul Haddad. Ion chromatography. * Henk Claessens. RPLC and HPLC Columns * Harold McNair. GC and LC basic theory. * Hans-Gerd Janssen. Several GC topics * Sabine Heinisch. Gradiënt elution. * Nick Snow. Sample preparation (GC). * Paola Dugo. Food analysis * Yolanda Pico. ... >>
34% - Home > The Community >
The team is a group of experts that have joined forces to share information and combine it into an unbiased source of learning and reference. All contributions are refereed by independent reviewers not commercially connected to its content. On this page you will find the names of the Editorial ... >>
25% - UHPLC. Ultra High Performance Liquid Chromatography > UHPLC Columns >
Properties of UHPLC Particles Packing materials for UHPLC are prepared in a similar manner to those used in HPLC, (Click for more info on column packings) and therefore have many of the same characteristics. The major differences are the particle diameter and particle strength. The particles have ... >>
24% - LC Instrumentation. Basics > LC Separation modes >
LC is a technique that can be used for the separation of polar and non-polar compounds, for charged and neutral compounds, and for volatile and non-volatile compounds. In particular, when mixtures of compounds with different polarities, i.e., drug and their metabolites, parent compounds and their ... >>
24% - LC Instrumentation. Basics > Guidelines for method choice >
Guidelines for method choice in analytical chemistry Choosing the necessary sampling and SP steps for the determination of analytes in a complex and dirty matrices is one of the most troublesome to perform, and therefore, the degree of SP depends on quite a number of parameters. The most important ... >>
24% - Chiral Chromatography > General elution modes >
Elution of analytes is performed by either one of 3 distinct mobile phase modes: normal-phase (NP) mode. The mobile phase is composed of apolar solvents (usually hexane or heptane) and polar organic modifiers (2-propanol, ethanol, chloroform, ethylacetate, etc.) may be added to adjust the elution ... >>
18% - GC Instrumentation. Basics > Advanced: Column types > The stationary phase > Sample capacity; overloading > >
In packed columns, the selection of a suitable type of stationary phase material (selectivity) is much more important. A good separation (resolution) is only obtained if significant retention differences occur for the analytes of interest as a consequence of the moderate efficiency ... >>
