Ion-pair reverse-phase chromatography

A combination of different modes of chromatography can provide excellent resolution for those components that chromatograph poorly with a single mode [108,109]. The chromatographic separation of baclofen (I) from its potential transformation product (II) with dual mode chromatography entailing ion-pair reversed-phase chromatography and... 

S. Ahuja, Retention Mechanism Investigations on Ion-pair Reversed Phase Chromatography, American Chemical Society meeting, Miami, April 28, 1985. 

W.R. Melander and Cs. Horvath, Mechanistic study of ion-pair reversed-phase chromatography , J. Chromatogr., 1980, 201, 211. 

Aboul-Enein and Al-Duraibi (1998) employed dansyl chloride in a fluorescence assay for PUT, SP, SPD, and their acetylated derivatives by ion-pair reverse-phase chromatography. This assay could be applied to the separation of free and acetylated polyamines in biological samples. Dansyl chloride has also been used as the fluorescence reagent in the determination of polyamines in urine by Molins-Legua and colleagues (1999). Derivatization was carried out within the C18 cartridges that were used during the SPE extraction procedure. Recoveries were 80-95% for all four polyamines analyzed and the hmit of detection was 10 ng/ml. 

The elucidation of the retention mechanism in ion-pair reversed-phase chromatography using alkyl amines or alkyl sulfonates as hetaerons has evoked significant interest not only for the great potential of the method in the separation of ionic compounds but also for theoretical reasons. 

B. Do, S. Robinet, D. Pradeau and F. Guyon, Speciation of arsenic and selenium compounds by ion-pair reversed-phase chromatography with electrothermal atomic absorption spectrometry. Application of experimental design for chromatographic optimisation, J. Chromatogr. A, 918(1), 2001, 87-98. 

CEC was used to separate double-stranded DNA (dsDNA) on microchips [58,152]. In these cases, Ci8-modified PMMA microchips were employed with ion-pair reverse phase chromatography and DNA fragments with different sizes were analysed by contact conductivity detection. 

Afton, S., K. Kubachka, B. Catron, et al. 2008. Simultaneous characterization of selenium and arsenic analytes via ion-pairing reversed phase chromatography with inductively coupled plasma and electrospray ionization ion trap mass spectrometry for detection. Applications to river water, plant extract and urine matrices. J. Chromatogr. A 1208 156-163. 

J. Zheng, Y. Shibata, N. Furuta, Determination of selenoamino acids using two-dimensional ion-pair reversed phase chromatography with on-line detection by inductively coupled plasma mass spectrometry, Talanta, 59 (2003), 27-36. 

J. Zheng, Y. Shibata, A. Tanaka, Study of the stability of selenium compounds in human urine and determination by mixed ion-pair reversed phase chromatography with ICP-MS detection, Anal. Bioanal. Chem., 374 (2002), 348-353. 

Various high-performance liquid chromatography methods have been described, mainly employing ion-pair reversed-phase chromatography, with electrochemical or fluorimetric detection, most of them including sample pretreatment with solid-phase or liquid extraction. 

HPLC is commonly used for separating and purifying oligonucleotides. Separation is usually based on ion-pair, reversed-phase chromatography and is particularly useful for purifying fluorescently labeled probes guided by absorbance and fluorescent elution profiles. 

Figure 7.7. HPLC analysis of water-soluble vitamins in a beverage powder sample (Tang ) and a baby formula (Similac ) using ion-pair reversed-phase chromatography and UV detection. Reprinted with permission from reference 17.

Lindgren, K. Determination of cefaclor and cephradine in serum by ion-pair reversed-phase chromatography. J.Chromatogr., 1987, 413, 351—354... 

Trautmann, K.H. Haefelfinger, P. Determination of the cephalosporin Ro 13-9904 in plasma, urine, and bile by means of ion-pair reversed phase chromatography. J.High Res.Chromatogr., 1981, 4, 54-59... 

The vast majority of separations described for the leukotrienes have used isocratic reversed phase conditions with an ODS stationary phase, although a single report exists which used ion-pair reversed phase chromatography with gradient conditions. Examples of these separations will not be discussed, together with some of the problems associated with HPLC of the leukotrienes. 

Odink et al. (Odink et al., 1988) presented a simple method for the routine analysis of iodide in urine. Iodide was sep>arated by means of ion-pair reversed phase chromatography (RP-HPLC) and detected electrochemically with a silver electrode after a one-step sample cleanup. The coefficient of variation of a single analysis of iodide in a pooled urine sample (530 nmol/1) was 7.6%. The detection limit was 3 pmol (S/N 3), corresponding to 0.06 pmol/1. The recovery of iodide added to urine was 96 7 %. 

While ion-pairing reverse-phase chromatography is the primary separation method described in this chapter, many different types of chromatographic methods have been used to separate nucleic acid. These include gel filtration, afHnity and ion exchange [1-13]. In particular, ion-exchange chromatographic separations of nucleic acids performed on nonporous anion exchangers can be extremely rapid and useful [14-17]. 

---