Column, capillary resolving power

Popular techniques for the analysis of small ions include ion-exchange chromatography and flame atomic absorption spectrometry but CE is becoming more popular for such applications due to its simplicity and speed of method development and analysis, elimination of the need for specialized columns, high resolving power, and simple sample treatment steps (typically, the sample just needs to be diluted in the background electrolyte and injected onto the capillary). Commercial ion analysis... 

In 1993, Jorgenson s group improved upon then earlier reverse phase HPLC-CZE system. Instead of the six-port valve, they used an eight-port electrically actuated valve that utilized two 10-p.L loops. While the effluent from the HPLC column filled one loop, the contents of the other loop were injected onto the CZE capillary. The entii e effluent from the HPLC column was collected and sampled by CZE, making this too a comprehensive technique, this time with enhanced resolving power. Having the two-loop valve made it possible to overlap the CZE runs. The total CZE run time was 15 s, with peaks occurring between 7.5 and 14.8 s. In order to save separation space, an injection was made into the CZE capillary every 7.5s,... 

Extremely high resolving power (capillary columns)... 

As most polymers contain relatively few additives, the high resolving power of capillary SFC columns is... 

The concept of the effective plate number was introduced and employed in the late nineteen fifties by Purnell (7), Desty (8) and others. Its introduction arose directly as a result of the development of the capillary column, which, even in 1960, could be made to produce efficiencies of up to a million theoretical plates (9). It was noted, however, that these high efficiencies were were only realized for solutes eluted close to the column dead volume, that is, at very low k values. Furthermore, they in no way reflected the increase in resolving power that would be expected from such high efficiencies on the basis of the performance of packed columns. This poor performance, relative to the high efficiencies produced, can be shown theoretically ( and Indeed will be, later in this book) to result from the high phase ratio of capillary columns made at that time. That is the ratio of the mobile phase to the stationary phase in the column. The high phase ratio was... 

Citrus volatiles have been extensively examined over the last several decades and several reviews have summarised composition and concentration data which existed at that time [1-7]. Careful attention should be paid to the analytical technology employed in each study cited. Many of the early studies employed packed-column gas chromatography (GC) which had limited resolving power. Results from these studies should therefore not be accepted uncritically. Studies employing high-resolution capillary GC are less prone to coelution and are probably more reliable. 

MS techniques, mainly because of its ease of operation, the commercial availability of advanced instrumentation, and the high resolving power of capillary column GC that allows one to carry out specific high-resolution measurement at extremely low levels. The GC-MS techniques are, however, not applicable to all compounds, especially the thermolabile compounds, such as N-nitrosamides, or the nonvolatile NOC. Furthermore, direct HPLC-MS analysis of nonvolatile NOC eliminates the need for derivatization. 

Although LC separation does not normally provide the same high resolving power as GC with long capillary columns, it can be better tuned to achieve the necessary resolution. In addition to the... 

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