IPC theory

The IPC theory [10] gives a clear and easy rationalization of analyte retention dependence on the presence of ILs used as additives in the mobile phase in low concentrations. In this case, their specific properties as non-molecular polar solvents are not important. In fact, they are salts characterized by a dual nature because of the different properties of the cation and anion. Both contribute to solute retention and... 

This does not mean that the earliest predictions of Sperm Competition Theory have all been supported. In particular, it now seems that there are many more elements to a competitive ejaculate than simply sperm number, with sperm size, sperm morphology and now sperm age being just three that have so far been implicated. It also seems, from this paper, that the most strategic ejaculate may well be different for the IPC male and the EPC male. 

Data are thus considered to be any information that contributes to, or is relevant to, a particular exposure assessment.3 The term encompasses not just numerical values or estimates, but also information provided in other forms, such as default values adopted for regulatory purposes, theory developed from first principles or basic science, computer programs, surveys, demographic data, census information, graphs, mathematical formulae, subjective expert judgements and descriptive summaries. More detail on the diversity of information that contributes to exposure assessment may be found in the other IPCS risk assessment documents, shown in Figure 1 (IPCS, 2000, 2004, 2005 Part 1 of this document). 

Although the daily grind of processing large sample sets translates chromatography into a practical analytical tool, the theory is not a regression to the earlier days of IPC. This section critically and, as far as possible, chronologically reviews the theoretical... 

Two genuine electrostatic non-stoichiometric theories were developed one by Stahlberg and co-workers and the other by Cantwell and co-workers. They considered the processes involved in IPC as based solely on the formation of the electrical double layer and disregarded the ion-pairing process in the bulk eluent. 

The development of most ion-pairing chromatography (IPC) methods started with optimization of the mobile phase composition after an appropriate column was selected. The theory described in Chapter 3 assists the chromatographer to perform educated guesses. Chapters 7 through 10 discuss the main qualitative and quantitative attributes of tunable mobile phase parameters to illustrate their influence on the global performance of the method. 

The retention of ionogenic analytes in RP-HPLC is obviously dependent on the eluent pH. The pH value is an important optimization parameter because it controls the extent of ionization of the solute and hence the magnitude of electrostatic interactions. Varying the acidity of the mobile phase can lead to extreme changes in selectivity. Many interdependent parameters can be modulated in IPC and their optimization requires a theory-driven procedure. 

The general theory of indirect detection was recently put forward [14] and its mechanism stimulated pioneering model makers to provide a realistic, practical and rational description of IPC [15,16]. For example, a UV-absorbing mobile phase containing potassium hydrogen phthalate and triethanolamine allowed the indirect detection of sulfur and nitrogen anions in atmospheric liquids separated on a cetylpyridinium-coated C18 column [17]. Crystal violet was used as the IPR in the... 

Class IV (a 0, b<0, and c O) exhibits the strongest departures from the predictions of FH theory since the dependence of both t and ipc on M deviates significantly from those emerging from FH theory. The critical properties of class IV blends approach different limits depending on the sign of c. The scaling laws in the M -> 00 limit for c < 0 are... 

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