Tailing of chromatographic peaks

Surface coverage by silanization is limited to 4 pmol/m or less because of steric effects, The unre-acied SiOH groups, unfortunately, impart an undesirable polarity to the surface, which may lead to tailing of chromatographic peaks, particularly for basic solutes. To lessen this cffcci. siloxane packings are frequently capped by further reaction with chlorotrtmethylsilane that, because of its smaller size, can bond some of the unreacted silanol groups. 

Why does silanization reduce tailing of chromatographic peaks ... 

Table, circular rotating sampie, 943 Tailing of chromatographic peaks, 769,788,829,849 Tandem mass spectrometry, 573, 575,576,582,584,800, 828.947... 

Most published capillary electrophoresis (CE) methods use buffers containing an organic solvent such as acetonitrile in order to prevent micelle formation. The micelles have different electrophoretic mobility than the isolated surfactant molecules (1). Since individual surfactant molecules are also present, the presence of micelles causes severe tailing of chromatographic peaks (2). Organic eluents also minimize the adsorption of the surfactant to the walls of the capillary. 

For good quantitative results from analytical hplc (or gc, see below) you should aim to produce chromatographs with symmetrical peaks. Tailing of the peaks is usually caused by overloading and can thus be avoided by reducing the quantity of sample applied. If this does not solve the problem and the tail of a component is long and drawn out, there may be an incompatibility between the compoimd and the stationary phase, a problem which is less easy to rectify. 

High speed countercurrent chromatography (HSCCC) produces highly efficient chromatographic separations of solutes without the use of solid supports Thus the method eliminates all complications caused by the solid support, such as adsorptive loss and deactivation of samples, tailing of solute peaks, contamination, etc. As with other CCC schemes, HSCCC utilizes two immiscible solvent phases, one as a stationary phase and the other as a mobile phase, and the separation is highly dependent on the partition coefficient values of the solutes, i.e., the ratio of the solute concentration between the mobile and stationary phases. Therefore the successful separation necessitates a careful search for the suitable two-phase solvent system that provides an ideal range of the partition coefficient values for the applied sample. 

Figure 30-10 Illustration of fronting and tailing in chromatographic peaks.

A tail at the beginning of a chromatographic peak, usually due to injecting too much sample. 

An analytical method vahdation study should include demonstration of the accuracy, precision, specificity, limits of detection and quantitation, linearity, range, and interferences. Additionally, peak resolution, peak tailing, and analyte recovery are important, especially in the case of chromatographic methods (37,38). 

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