Composition of mobile phase

The type of plate, chamber system, composition of mobile phase, running time and detection reagent used must naturally all be recorded The sample protocol illustrated in Figure 62 can be employed... 

Suggest a gradient that would improve each of the chromatograms in Fig. 4.3k. You do not need to worry about the detail, like the exact shape of the gradient, or how long it will take. Concentrate on the composition of mobile phase that is needed at the start and at the end of each chromatogram. 

Ruggedness testing evaluates how small changes in the method conditions affect the measurement result, e.g. small changes in temperature, pH, flow rate, composition of mobile phase, etc. The aim is to identify and, if necessary, better control method conditions that might otherwise lead to variation in measurement results, when measurements are carried out at different times or in different laboratories. It can also be used to improve precision and bias. 

Signals for methyl paraben were monitored with UV detection at 254 nm. The signal for rhodamine 110 chloride was monitored via fluorescence detection with an excitation filter of 482 nm (35 nm bandwidth) and emission filter of 535 nm (40 nm bandwidth). A gradient method (same as the one in Figure 6.16) was used. The compositions of mobile phases A and B were 5 95 H20 CH3CN with 0.1 HCOOH and CH3CN with 0.085% HCOOH, respectively, with a total flow rate of 300 fiL/ min (corresponding to 12.5 /rL/min for each column). 

Composition of mobile phases 1 = toluene-ethyl acetate-(98-100%) formic acid (36 12 5. v/v) 2 = cyclohexane-ethyl acetate-(98-100%) formic acid 3 = toluene-ethyl acetate-glacial acetic acid (36 12 5, v/v) 4 = cyclohexane-ethyl acetate-glacial acetic acid (31 14 5, v/v) 5 = n-hexane-ethyl acetate-(98-100%) formic acid (31 14 5, v/v) 6 = toluene-acetone-(98-100%) formic acid (38 10 5, v/v) 7 = n-hexane-ethyl acetate-glacial acetic acid (31 14 5,v/v) 8 = petroleum ether(40-70°C)-ethyl acetate-(98-100%) formic acid (30 15 5, v/v) 9 = carbon tetrachlo-ride-acetone-(98-100%) formic acid (35 10 5, v/v) 10 n-hexane-ethyl acetate-glacial acetic acid (30 20 1.5. v/v) 11 = chloroform-methanol-(98-100%) formic acid (44.1 3 2.35, v/v). Reprinted with permission from I. Jasprica et al. [141]. 

Normal-phase TLC has been employed for the control of the synthesis of some new reactive azo dyes containing the tetramethylpiperidine fragment. The chemical structure of the basic molecule and the substituents of the new derivatives are shown in Fig. 3.16. The new derivatives were characterized by their RF values determined in different mobile phases. Compositions of mobile phases were n-propanol-ammonia (1 1, v/v) for dye 1.2 (Rp = 0.84) n-propanol-ammonia (2 1, v/v) for dyes 1.3 (RF = 0.50) and 1.4 (RF = 0.80) and n-heptane-diethyl ether (1 1, v/v) for dyes 1.5 (RF = 0.80) and 1.6 (RF = 0.76). The results indicated that together with other physicochemical methods such as IR and H NMR, normal-phase TLC is a valuable tool for the purity control and identification of new synthetic dyes [96],... 

Separation of mixtures of compounds with high molecular weights, such as synthetic polymers, proteins, and other biopolymers whose retention changes markedly for small changes in the composition of mobile phases... 

Step elution is similar to gradient elution in that the composition of the mobile phase changes during the separation process. However, in step elution the change is not continuous. It involves a sudden change in the composition of mobile phase followed by a period where the mobile phase is held constant. This procedure results in a mobile phase profile that resembles a series of steps. 

APPLICATIONS (compositions of mobile phases are described using volume proportions, i.e., v/v)... 

A stainless column packed with Lichrospher lOORP-18 was used to analyze Acanthoside-D from the solvent extraction. The composition of mobile phase in analytical HPLC was experimentally determined and it was water/acetonitrile/methanoi=80/14/6 vol.%. From the chromatogram, retention time of Acanthoside-D was found to be 12 min. Figure 1 shows the analysis of Acanthoside-D from the extraction of the trunk of Acanthopanax senticosus. The flow rate of mobile phase and injection volume were 1 nt(/min and 20pl, respectively. 

Composition of mobile phase, regeneration solution and load solution... 

The robustness of an analytical procedure is a measure of its capacity to remain unaffected by small, but deliberate variations in method parameters and provides an indication of its reliability during normal usage. During the development phase of the analytical procedure, susceptible parameters should be identified, for example, stability of analytical solutions, extraction time, pH and composition of mobile phase, column lots and suppliers, temperature, flow rate, etc. A factorial design is encouraged. 

Several kinds of flavonoids are efficiently separated and analyzed using packed or capillary column supercritical fluid chromatography. The composition of mobile phase, stationary phase, temperature, and pressure aU affect the resolution. This article mainly focuses on the separation of polymethoxylated flavones, polyhydroxyl flavonoids, and flavonol isomers. 

Flavonol isomers, which differ only in the position of hydroxyl group on their chemical structures, showed different chromatographic behaviors. Liu et al. separated three flavonol isomers (3-hydroxyflavone, 6-hydroxy-flavone, and 7-hydroxyflavone) by a lab-constmcted packed column SFC system with carbon dioxide modified with ethanol containing 0.5% (V/V) phosphoric acid as the mobile phase. The effects of temperature, pressure, composition of mobile phase, and packed-column type on... 

A successful chromatographic analysis depends on the precise performance of the HPLC instmmentation, i.e., control of pressure, the composition of mobile phase, the performance of the analytical column, the detector, the injector or autosampler, and the electronic data handling system. 

Separation (CZE) Absence of separations -1+ Ionic force and composition of mobile phase Adapt composition of mobile phase, buffer, current conditions... 

Depending upon the different forms of chromatography, optimization can be more or less rapid. In gas phase chromatography optimization is easier to achieve than in liquid chromatography in which the composition of mobile phase must... 

Elution with the selected and degassed solvent as mobile phase can be done in two different methods. The first method is simplest, but cannot be used for all samples especially those containing complicated mixtures of compounds in crude oil fractions. As such, this method is only rarely used. It is called isocratic elution. In this method, the same composition of mobile phase is used during the entire analysis time. The main property of samples that can be analyzed by this method is that the components in the sample have approximately the same polarity. The second elution method is called gradient elution. This method can be used for complicated mixtures of compounds which have different polarities and which... 

Chromatograms of Phenol and Benzoic Acid in Different Compositions of Mobile Phase Solvent... 

Detection is evidently an important step in chromatographic analyses because, without it, we would not have any results. As with the modes of separation, the types of columns that we can use, and the compositions of mobile phases that we can use, detectors are no different. A number of different detectors can be used but, ultimately, the compoimds being analysed will determine this. Ihis is because the detector must be able to detect the compounds eluting from the chromatographic column. 

The enclosed CD-ROM contains everything needed to run MICHROM. This software is able to take the results obtained with a set of compounds and several compositions of hydro-alcoholic micellar phases, and calculate the affinity constants to predict the results for compositions of mobile phase (surfactant concentration, modifier concentration and pH). 

Similarly to LC with traditional detectors, LC-MS also mainly employs reverse-phase LC with modified silica stationary phases however, the composition of mobile phases is rather limited to methanol or acetonitrile as principal organic modifiers and to volatile additives (buffers). 

Flavonol isomers, which differ only in the position of hydroxyl group on their chemical structures, showed different chromatographic behaviors. Liu et al. ° separated three flavonol isomers (3-hydroxyflavone, 6-hydro-xyflavone, and 7-hydroxyflavone) by a lab-constructed packed column SFC system with carbon dioxide modified with ethanol containing 0.5% (VAO phosphoric acid as the mobile phase. The effects of temperature, pressure, composition of mobile phase, and packed-column type on the separation were studied. It was indicated that the addition of phosphoric acid to the mobile phase enabled flavonol isomers to be eluted from the column. It was also shown that a phenyl-bonded silica column was better and the ODS column was not as effective for the isomer separation. Increasing pressure shortened the retention time of each compound, with good resolution, and higher temperature led to longer retention times, and even the loss of the bioactivities of these components. Under selected conditions, the separation of these isomers was very satisfactory, as illustrated in Fig. 2. 

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