Reversed-phase chromatographic system

Welerowicz, T., Buszewski, B. The effect of stationary phase on lipophilicity determination of 3-blockers using reverse-phase chromatographic systems. Eiomed. Chromatogr. 2005, 39, 725-736. 

Each constant in the equation above represents single equilibrium process, which is assumed to be independent on other equilibria in the column. Equation (2-93) describes the retention of basic ionizable analytes in reversed-phase chromatographic system with binary eluents and liophilic counteranions added. Similar expression could be derived for the behavior of anionic analytes in the presence of liophilic countercation. 

Synthetic and petroleum sulfonates are analyzed by the same reversed-phase chromatographic system used for the analysis of alkyl ether sulfate surfactants. Similar to alkyl ether sulfates, the sulfonate mixtures are separated into three fractions inorganic salt, sulfonates, and unreacted oil. The analysis of two petroleum sulfonates, NaPS-1 and NaPS-2, is shown in Table 4. Good separation was obtained between the inorganic salt and the sul-fonated components. The oil present in NaPS-1 and NaPS-2 surfactants consisted of low-molecular-weight components, which were totally volatile under the detector operating conditions and, therefore, could not be detected. These two sulfonates are considerably different in molecular structure distribution. However, their elution characteristics were the same as those observed for the synthetic single-component sulfonates. 

Smilde AK, Multivariate calibration of reversed-phase chromatographic systems. Ph.D. thesis, University of Groningen, 1990,... 

The selectivity of a reversed phase chromatographic system is markedly dependent on the nature of the organic modifier. If a sufficient separation of a mixture of solutes is not achieved by using methanol as the modifier, acetonitrile or tetrahydro-furan may be tried, bearing in mind that the concentrations should be decreased... 

In biochemical analysis a reversed phase chromatographic system will often be the best choice, since such a system allows for the direct analysis of biological samples. If at all possible isocratic elution should be used, since isocratic systems are more stable than gradient elution systems, and give better reproducibility in quantitative analysis. Furthermore the necessity of solvent purity is not as strict in isocratic elution as in gradient elution, and less expensive equipment is needed. 

An example of part of the output for fitting the solvation parameter model to a reversed-phase chromatographic system by multiple linear regression analysis... 

Fig. 11.8.5). The eluting folates were detected by monitoring their UV absorbance at 284 nm. Reversed phase chromatographic systems have been used to detect folates in serum (Birmingham and Green, 1983) and in multivitamin preparations (Holcombe and Fusari, 1981). 

Early studies of the disposition and metabolism of heroin in humans and animals were performed with PC and TLC. Heroin, 6-acetylmorphine, and morphine were separated by normal-phase and reversed-phase chromatographic systems. The analytes were visualized by spraying with iodopla-tinate, Folin-Ciocalteu reagent, or Dragendorff s reagent. 

Forgacs, E. Comparison of reversed-phase chromatographic systems with principal component and cluster analysis. Anal. Chim. Acta 1994,296, 235. 

C. Kradjel and E. W. Ciurczak, Further Parameters of a NIR/HPLC Detector. Part I Limits of Analytical Sensitivity for Reverse Phase Chromatographic Systems, presented at 1st Pan American Chemical Conference, San Juan, PR, October 1985. 

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