Some important chromatographic terms

Symbols/names/formulas for the calculation What does this mean What can I do with it  

C or o m Dead time, very often in the lab. jargon front Lq-Er L = F = Retention time of a solvent molecule or an inert substance (no interaction with the stationary phase) in the system that is the time from the injection of a non-retarded substance to the appearance of a peak in the detector (apex of the peak). Change of means (a) either change of flow rate (pump, leakage, see Tip No. 26) or (b) change of the column dimensions or the packing density. 

R Resolution 4 a k+1) The degree to which one peak is separated from another. Distance between peaks at the peak bases. This is the separation criterion for a chromatographic system, since everything depends on the resolution, which influences the separation capacity, selectivity and efficiency. 

I d Dead volume A symbol for the dead volume very rarely used. V = F t Volume of the equipment from the injection to the detector cell - without the column (See Tip No. 9) Important for isocratic equipment. Sometimes one says dead volume and means the above-described volume including the column. The smaller the dead volume, the sharper are the peaks. Rules of thumb Ca. 20-25 p.1 very good, ca. 30-60 p.1 good enough for a 4 mm column considerable tailing at 2 mm columns and/or 3 pm material. From ca. 70 pi unnecessary band broadening, above all at the early peaks. 

N Efficiency rate for the band broadening of a substance in the system do 1 get sharp or broad peaks  

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Some important chromatographic terms are explained below and illustrated by a schematic diagram based on a diagram by Geiss [4] (Fig. 57) ... 

As mentioned above, the basic principle of NLC is the same as for conventional techniques. The separation is identified and characterized by measuring retention times, capacity, separation, and resolution factors. Therefore, it is necessary to explain the chromatographic terms and symbols by which the chromatographic speciation can be understood and explained. Some of the important terms and equations of the chromatographic separations are discussed below. The chromatographic separations are characterized by retention (k), separation (a), and resolution factors (Rs). The values of these parameters can be calculated by the following standard equations [92]. 

It is important to note the elution at 48% THF Retention becomes completely independent of molecular mass, and all fractions elute with the column s liquid voliune Vf. At this transition point, which is termed critical point of adsorption (CPA), entropy driven size-exclusion effects are completely compensated by enthalpic adsorption interactions. Although both types of interaction strongly depend on molecular weight, this mutual compensation phenomenon leads to molecular weight independent retention at CPA. This phenomenon allows for practical implementation of isocratic polymer separation other than sec. Thus, because of chromatographic invisibility of a main polymer chain, effective separation of telechehc polymers based on types of end-groups can be performed (Ref 7, p. 125). The same principle is applied for isocratic separation of some block copolymers (Ref 7, p. 151). 

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