Short Columns, Small Particles

Single channel 200-300 Uses short column small particle Most acceptable for both Open-access... 

Section II covers the latest trends in reducing sample preparation time, including direct sample infusion/injection and on-line solid phase extraction (SPE). In Section III, we focus on newer trends in stationary phases and how these phases hope to offer different selectivities compared to current CIS-based phases. Section IV briefly provides a few observations on how new detectors are increasing the versatility of HPLC. Finally, in Section V we examine monolithic columns, small particles packed in short columns, high-temperature LC, ultra high-pressure LC, and parallel injection techniques. 

If the operating pressure of a column is limited, simple separations will be achieved very rapidly on short columns packed with very small particles. In contrast, difficult separations will take longer and will require long columns packed with larger particles. 

Correlation was found between domain size and attainable column efficiency. Column efficiency increases with the decrease in domain size, just like the efficiency of a particle-packed column is determined by particle size. Chromolith columns having ca. 2 pm through-pores and ca. 1pm skeletons show H= 10 (N= 10,000 for 10 cm column) at around optimum linear velocity of 1 mm/s, whereas a 15-cm column packed with 5 pm particles commonly shows 10,GOO-15,000 theoretical plates (7 = 10—15) (Ikegami et al., 2004). The pressure drop of a Chromolith column is typically half of the column packed with 5 pm particles. The performance of a Chromolith column was described to be similar to 7-15 pm particles in terms of pressure drop and to 3.5 1 pm particles in terms of column efficiency (Leinweber and Tallarek, 2003 Miyabe et al., 2003). Figure 7.4 shows the pressure drop and column efficiency of monolithic silica columns. A short column produces 500 (1cm column) to 2500 plates (5 cm) at high linear velocity of 10 mm/s. Small columns, especially capillary type, are sensitive to extra-column band... 

Short column with small particles (2 to 3 flm) Use of conventional HPLC with minimal or no equipment modifications Greatest diversity of column chemistry Easy method transfer Best reproducibility and ruggedness... 

To obviate to these problems and to increase the productivity, short columns packed with small porous particles (sub-2 pm), and high flow rates that decrease the analysis time and extend the range of measurable log Poct were recently applied in HPLC and UHPLC [18-20] with a gain in terms of chromatographic performance. 

Figure 22 shows a high-throughput application in which high flow rate, a short column with very small particles packings, short and... 

The change to shorter columns packed with smaller particles is of interest for many applications in the QC department in the pharmaceutical industry. Often, the separations are executed using 25 or 15-cm columns in a 15- to 30-min time frame. In this chapter, we have demonstrated that the same separation power is available today with short columns packed with small particles. The use of short columns reduces the analysis time to a few minutes. Even faster separations, under 1 min, are possible today, but great attention needs to be paid to experimental details. 

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