Traditional IPRs

Conventional IPC separations were achieved by adding organic amines and ammonium salts of varying chain lengths as cationic IPRs for anionic analytes and alkyl or aryl sulfonates and sulfates as anionic IPRs for cationic solutes. Since these IPRs exhibit good tensioactive properties, IPC was originally named soap chromatography [1]. 

The molecular architecture and the chain length of the IPR greatly affect analyte retention enhancement. At constant eluent composition, log k of an analyte oppositely charged to the IPR raises linearly with the number of carbon atoms in the chain of the alkyl sulfonate [2,3]. The shorter the IPR side chain, the lower its adsorption onto the stationary phase. This involves a lower potential difference between the electrified stationary phase and bulk eluent that in turn results in a lower driving force for analyte retention [4-7]. To attain comparable retention, the effect played by a higher concentration of a less hydrophobic IPR is tantamount to that of a lower concentration of a more lipophilic IPR [8-10]. However, the relationship between adsorbophilicity and chain length of the IPR is only part of the story. 

Interestingly, a slightly different retention of a probe analyte can be obtained when the stationary phase concentrations of IPRs of different chain lengths are the same [11]. This phenomenon cannot be explained by electrostatic theories because the potential established at the stationary phase is only a function of the surface 

B sulfonate salts B ammonium salts m mixture of positive and negative iPRs 

FIGURE 7.2 Adsorption isotherms of two hypothetical IPRs of different hydrophobicities under the same experimental conditions. 

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Liquid chromatography mass spectrometry (LC-MS) is now routinely used in analytical laboratories. Traditional IPRs are non-volatile salts that are not compatible with MS techniques because they play a major role in source pollution that is responsible for reduced signals. Moreover the final number of charged ions that reach the detector is impaired by ion-pair formation actually IPRs added to the mobile phase to improve analytes retention exert a profound effect on analyte ionization. Chromatographers who perform IPC-MS must optimize the eluent composition based on both chromatographic separation and compatibility with online detection requirements. 

At variance with traditional IPRs that tend to stick very strongly to the stationary phase and to impair the initial column properties also when their presence in... 

Equation 7.1 parallels Equation 3.5 (see Chapter 3, also for symbols meaning) that holds when [LC], that is the surface concentration of the counterions C, is negligible compared to [LH], as in the case of most traditional IPRs. 

We are also trying a new drug for SLE patients. Cordyceps sinensis (CS) is a traditional Chinese medicine with immunomodulatory effect. We have shown that MRL Ipr/lpr mice treated daily with HI-A extract of CS for 8 weeks show progressivly reduced anti-dsDNA production (Y3). Although there was no change in immune complex formation, there were less mesangial proliferation (Y3). 

Yet the trips Agreement has also proved to be problematic from a developed-country perspective. The developed countries have traditionally stood behind their prominent pharmaceutical companies and supported them in their quest for establishing a strong global iprs regime. However, the recent anthrax scare in the usa and the aids crisis in Africa may have altered this relationship. The iprs standards that trips establishes severely limit the government s ability to introduce a radical policy initiative. This can emerge as an unwelcome constraint for any country in crisis. 

Catalytic oxidation of alcohols with molecular oxygen has attracted much attention as an alternative to traditional oxidation methods such as Dess-Martin [195], Jones [196] or Swern [197] oxidations, which require the use of stoichiometric toxic reagents and/or low temperatures. Significant advances have been made in Pd-catalyzed aerobic alcohol oxidations in the last few years [198-200] Sigman and co-workers have shown the broad scope of two IPr-Pd(II) complexes with low catalyst loadings and mild temperatures [201,202]. Some representative examples are summarized in Table 7. 

Note that co-elution of the analyte and IPR in the form of an ion-pair is not a rule. A dynamic distribution equilibrium of both the IPR and analyte between the plug of injected sample and the stationary phase may also involve a separation of the ion-pair partners if their retention free energies are very different. Moreover, since the hydrophobicities of the analyte and the ion-pair between analyte and IPR differ, a split, broad, or asymmetric peak may also be observed. This happens if the rate of interconversion between the free and paired analyte is slow compared to the chromatographic retention time scale and this downside can be observed in Figure 11.1 [25]. In this case, the analyte-IPR ion-pair would not be detected via MS [26]. Interestingly, analyte retention increased with the alkyl chains of the IPR in the reconstitution solution, similar to traditional IPC [26]. 

NOTE AGR - Access to Genetic Resources ESB - Equitable Sharing of Benefits arising out of the utilization of genetic resources CTU - Customary or Traditional Use of genetic resources IPR - Intellectual Property Rights NRM Bio - Natural Resource Management and Biodiversity Conservation PIC - Prior Informed Consent... 

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