Analytical Chemistry

aldehydes < amines < alcohols and phenols < acids. During the separation process there is competition for adsorption si ...

wider range of activities than alumina and is less likely to induce chemical changes. The latter is available in a neutral form ...

In a partition system the stationary phase is a liquid coated onto a solid support (p. 97). Silica gel, kieselguhr (diatomaceous ...

relative solubilities in the stationary and mobile phases. Partition isotherms usually have a longer linear range than adsorptio ...

If the flow of mobile phase is monitored by a detector and recorder/VDU system, such as is used in gas and high-performance liqu ...

where WB is the baseline peak width and Wh/2 is the peak width measured at half of the peak height. Valid comparisons of efficie ...

Peak Asymmetry (Peak Skew) Few chromatographic peaks are perfectly Gaussian (symmetrical), most exhibiting a degree of asymmetry ...

Figure 4.14 Effects of diffusion and mass transfer on peak width. (a) Concentration profiles of a solute at the beginning of a s ...

Figure 4.15 Efficiency as a function of mobile phase velocity and the effect of each term in equation (4.46). efficiencies are a ...

Temperature Effects The choice of operating temperature can have a profound effect on a chromatographic separation due to the te ...

Figure 4.16 A typical elution profile; the separation of saturated esters by gas-liquid chromatography methyl formate 2. methyl ...

components) and very small samples (nanograms); useful for both qualitative and quantitative analysis. Relative precision 2–5%. ...

maintained when the temperature is increased during a separation. With a simple needle valve, the flow rate will decrease with a ...

Figure 4.18 Sample injection ports. (a) Flash-vaporizer. (b) Split injector with septum purge for capillary columns. (c) Direct ...

sample are collected in a cold trap at the top of the column initially held at over 100°C below the boiling point of the most vo ...

bration and changes in operating temperature are achieved by circulating the oven air with a fan. (a)— Packed Columns These rare ...

Stationary Phase The number of stationary phases suitable for gas chromatography is quite extensive, and choice is dictated larg ...

Table 4.10 Some stationary phases used in gas chromatography (b)— Capillary (Open Tubular) Columns This type of column has becom ...

transfer between the phases as this increases efficiency by reducing the C term in equation (4.46). The most efficient capillary ...

VDU screen via suitable electronic amplifying circuitry where the data are presented in the form of an elution profile. Although ...