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HPLC , generally

Methods for the analysis of aromatic amines in synthetic azo dyes and in food and beverages colored with these dyes have been developed. High-performance LC or GC methods are generally employed, often with the help of derivatization reaction and fluorimetric detection, with HPLC generally regarded as the best technique for the determination of aromatic amines. [Pg.902]

Our model has also been used to devdop a systematic apinoach to laige-molecule HPLC. General rules for mmhod devdopment have been derived, and the model can be further used to simulate separations of specific sam- pies, i.e., accurate predictions of separation as a function of conditions, without running actual samples. The design of future columns for improved macromolecule HPLC is discussed in the context of our model... [Pg.155]

This group of compounds refnesents the most common analytes in HPLC. Generally, a separation can be accomplished by a number of suitable techniques. Candidates are listed in Table 7.2. [Pg.75]

The presented examples emphasize the importance of careful temperature control in order to achieve reproducible separations in chiral chromatography. Although reversals in enantioselectivity are rare in HPLC, general predictions of the enantiomeric elution order on CSPs should be critically considered, especially if the extent of chiral recognition is marginal. [Pg.764]

Part One presents the fundamental concepts of HPLC, generally in the context of biological macromolecules. Both theoretical and practical aspects arc presented to aid in understanding the material. Part Two integrates the concepts of... [Pg.821]

Ion-exchange columns can be substituted into the general HPLC instrument shown in Eigure 12.26. The most common detector measures the conductivity of the mobile phase as it elutes from the column. The high concentration of electrolyte in the mobile phase is a problem, however, because the mobile-phase ions dominate the conductivity, for example, if a dilute solution of HCl is used as the mobile phase, the presence of large concentrations of H3O+ and Ck produces a background conductivity that may prevent the detection of analytes eluting from the column. [Pg.592]

The efficiency of separation of solvent from solute varies with their nature and the rate of flow of liquid from the HPLC into the interface. Volatile solvents like hexane can be evaporated quickly and tend not to form large clusters, and therefore rates of flow of about 1 ml/min can be accepted from the HPLC apparatus. For less-volatile solvents like water, evaporation is slower, clusters are less easily broken down, and maximum flow rates are about 0.1-0.5 ml/min. Because separation of solvent from solute depends on relative volatilities and rates of diffusion, the greater the molecular mass difference between them, the better is the efficiency of separation. Generally, HPLC is used for substances that are nonvolatile or are thermally labile, as they would otherwise be analyzed by the practically simpler GC method the nonvolatile substances usually have molecular masses considerably larger than those of commonly used HPLC solvents, so separation is good. [Pg.79]

Several new oxalates have been developed for use ia analytical appHcations. Bis(2,6-difluorophenyl) oxalate (72) and bis(4-nitro-2-(3,6,9-trioxadecylcarbonyl)phenyl) oxalate (97) have been used ia flow iajection and high performance Hquid chromatography (hplc) as activators for chemiluminescence detectors. These oxalates are generally more stable and show better water solubiUty ia mixed aqueous solvents yet retain the higher efficiencies ( ) of the traditional oxalates employed for chemiluminescence. [Pg.268]

With eluent MeOH H O = 40 60% w (flow rate -1 ml/min) full sepai ation was achieved within acetylated and non-acetylated on amino group of eight thioesters of 4-aminobenzenthiosulfinic acid with retention in next order for R - = -CH3, -C,H3,-CH,-CH=CH, -C3H3by RP-HPLC on Spherisorb-ODS-2 (250x4,6 mm). The chromatograms were obtained at 254 and 289 nm. Retention was generalized by In = In - S-(p (cp - MeOH volume pai t in range near 0.4-0.6) as shown in Fig. [Pg.146]

Generally it was found that resolution R is practically the same for isoeluotropic mixtures methanol and acetonitrile with water. The dependencies were obtained between capacity factors for derivatives of 3-chloro-l,4-naphtoquinone at their retention with methanol and acetonitrile. Previous prediction of RP-HPLC behaviour of the compounds was made by ChromDream softwai e. Some complications ai e observed at weak acetonitrile eluent with 40 % w content when for some substances the existence of peak bifurcation. [Pg.286]

The application of pressure to the liquid phase in liquid chromatography generally increases the separation (see HPLC). Also in PIC improved efficiency of the column is observed if pressure is applied to the mobile phase (Wittmer, Nuessle and Haney Anal Chem 47 1422 1975). [Pg.21]

Polypeptides. These are a string of a-amino acids usually with the natural 5(L) [L-cysteine is an exception and has the R absolute configuration] or sometimes "unnatural" 7f(D) configuration at the a-carbon atom. They generally have less than -100 amino acid residues. They can be naturally occurring or, because of their small size, can be synthesised chemically from the desired amino acids. Their properties can be very similar to those of small proteins. Many are commercially available, can be custom made commercially or locally with a peptide synthesiser. They are purified by HPLC and can be used without further purification. Their purity can be checked as described under proteins. [Pg.560]

Other properties of solvents which need to be considered are boiling point, viscosity (lower viscosity generally gives greater chromatographic efficiency), detector compatibility, flammability, and toxicity. Many of the common solvents used in HPLC are flammable and some are toxic and it is therefore advisable for HPLC instrumentation to be used in a well-ventilated laboratory, if possible under an extraction duct or hood. [Pg.222]

The packings used in modern HPLC consist of small, rigid particles having a narrow particle-size distribution. The types of packing may conveniently be divided into the following three general categories. [Pg.223]

As alkanesulfonates are mixtures of homologs as well as isomers, high-performance liquid chromatography (HPLC) proves to be a general method for an exact analysis. For identifying the raw material basis (carbon number cut of normal paraffins used), the carbon number distribution of the homologs can be... [Pg.165]


See other pages where HPLC , generally is mentioned: [Pg.16]    [Pg.135]    [Pg.538]    [Pg.213]    [Pg.185]    [Pg.479]    [Pg.107]    [Pg.16]    [Pg.135]    [Pg.538]    [Pg.213]    [Pg.185]    [Pg.479]    [Pg.107]    [Pg.578]    [Pg.69]    [Pg.446]    [Pg.27]    [Pg.201]    [Pg.226]    [Pg.334]    [Pg.480]    [Pg.481]    [Pg.371]    [Pg.71]    [Pg.117]    [Pg.355]    [Pg.9]    [Pg.390]    [Pg.25]    [Pg.73]    [Pg.503]    [Pg.504]    [Pg.469]    [Pg.228]    [Pg.532]    [Pg.216]    [Pg.220]    [Pg.222]    [Pg.223]    [Pg.226]    [Pg.934]    [Pg.92]   


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General Equations of Gradient Elution in HPLC

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