Isocratic separation, high-powered

Fig. 1. Plot of plate count analysis time for high-powered isocratic separations.

HPLC, when compared to other instrumental methods, presents significant advantages for the simultaneous analysis of creatinine and purine derivatives. The variety of instrumental and experimental conditions (columns, buffers, organic modifiers, detectors, etc.) of these methods reported in the literature offers versatility and flexibility. Chromatographic conditions for these analytes are not complicated when reversed-phase columns are employed. New stationary phases with high separation power provide short analysis times. The mobile phases used are also very simple ones (organic-water mixmres with controlled pH) both isocratic elution and gradient elution are recommended. Different sensitivity detectors (UV, electrochemical, fluorescence, and combined techniques such as HPLC-MS) are very valuable for the... 

In summary, gradient elution is a powerful method for the separation and analysis of complex mixtures containing components with a wide variety of polarities and hydrophobicities. It can also be used to help establish an isocratic mobile phase for the analysis of simpler mixtures. In either case, utmost care must be taken in the selection and use of solvents of high purity and selectivity. 

An important apphcation for the power-generating industry is the ability to determine trace concentrations of sodium in the presence of high concentrations of monoethanolamine. Figure 4.45 shows the separation of a simulated sample that contains 3000 pg/L monoethanolamine spiked with 0.25 pg/L sodium A sample volume of 3mL was loaded onto a TCC-LPl concentrator colvunn prior to switching this concentrator column in line with the analytical separator. As shown in Figure 4.45, the sodium peak is well resolved from monoethanolamine using 3 mmol/L methanesulfonic acid as an eluent under isocratic conditions. 

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