UHPLC

UHPLC for LC x LC High Speed Versus High Peak Capacity... 

TABLE 8.2 Summary of the Data from Three LC x UHPLC Separations of an E. coli Lysate... 

Figure 9.3 shows an impurity separation under conventional pressures with a 5 /mi particle, 2.1 x 150 mm column, and the same separation performed via UPLC using a 2.1 x 50 mm column with 1.7 /im particles. The run time was improved by a factor of six, with overall resolution comparable to that of the original separation on the 5 /an column. The application of UHPLC technology to impurity profile analysis can exert a significant impact on laboratory productivity by achieving a... 

Another potential benefit of UHPLC is its capability of solving the most challenging separation tasks in pharmaceutical analysis. Figure 9.4 shows a UPLC method developed to analyze pharmaceutical formulations used to treat the common cold. Cold products often contain multiple active ingredients to treat different symptoms and can contain decongestants, antihistamines, pain relievers, cough suppressants, expectorants, and numerous excipients of various polarities. The analysis of a total of 20 components was achieved within 10 min. 

FIGURE 9.5 Increasing efficiency HT UHPLC with three linked 2.1 x 150 mm 1.7 pm columns. (Courtesy of Waters Corp.)... 

UHPLC (600 to 1000 bar) Significant runtime reduction for ultra-fast separation minimal solvent consumption Five-fold increase in speed for SIM Significantly higher efficiency for most complex separations Higher mass sensitivity Rapid method development... 

To minimize unacceptable interruptions in highly regulated work flows, the smooth transfer of legacy methods from conventional to fast LC methods (via geometric transfer or method redevelopment) is a critical issue for implementing fast LC for pharmaceutical applications. Method transfer from HPLC to UPLC is discussed in detail in the literature.52,53 Moreover, method transfer software that provides parameter conversion between UHPLC and conventional HPLC is available from instrument vendors. 

The first physical change to consider with UHPLC is the compression of the eluent in the piston chamber that produces thermal heating. The change in temperature related to a change in pressure (dT/dP) can be estimated per Equation 13.2 in which Cp represents eluent heat capacity, a is the thermal compression/expansion coefficient, T is the temperature in K, and V is molar volume. 

In addition to thermal and viscosity changes, a third and perhaps the most important physical consideration in UHPLC is the influence of pressure on the solvent structure of the hydroorganic... 

FIGURE 14.4 Chromatograms of high speed isocratic capillary LC elution of three components. Column 15 cm x 320 /im inner diameter, 5 /im C18 particles. Column head pressure 6800 psi at 48 /(L/min flow rate. System XTS two-dimensional splitless ultrahigh pressure nano UHPLC, Micro-Tech Scientific, Vista, California. 

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