Chromatographic determination parameters

Mackay, D., Shiu, W. Y., Wolkoff, A. W. (1975) Gas chromatographic determination of low concentration of hydrocarbons in water by vapor phase extraction. In Water Quality Parameters. ASTM STP 573, pp. 251-258, American Society for Testing and Materials, Philadelphia, PA. 

Przyjazny, A., Janicki, W., Chrzanowski, and Staszewki, R. Headspace gas chromatographic determination of distribution coefficients of selected organosulphur compounds and their dependence of some parameters, J. Chromatogr. A, 280 249-260, 1983. 

Determination of inorganic anions by capillary electrophoresis is critically compared with ion chromatographic determinations on the basis of recent literature in the field. After a very brief summary of the theoretical background, the selection and optimization of the running electrolyte system are discussed, especially in connection with modification of the electroosmotic flow. Preconcentration techniques are surveyed, as are the approaches to the sample introduction and analyte detection. The principal analytical parameters of the determinations are evaluated and illustrated on selected applications described in the literature. 1997 Elsevier Science B.V. 

Lombardo F, Shalaeva MY, Tupper KA et al. (2001) A tool for lipophilicity determination in drug discovery. 2. Basic and neutral compounds. J Med Chem 44 2490-2497 Nasal A, Siluk D, Kahszan R (2003) Chromatographic retention parameters in medicinal chemistry and molecular pharmacology. Curr Med Chem 10 381—426 OECD (1989) Guideline for testing of chemicals 117, (http //www.oecd.org)... 

Ashworth, A. J. Price, G. J., "Static Investigation of the Influence of Polymer Molecular Weight and Loading in the Gas Chromatographic Determination of Poly(dimethylsiloxane) Interaction Parameters," Macromolecules, 19, 358 (1986). 

Eguiazabal, J. I. Fernandez-Berridi, M. J. Iruin, J. J. Elorza, J. M., "Chromatographic Determination of Polymer Solubility Parameters," Polym. Bull., 13, 463 (1985). 

The first exploitation of this relationship in a biological context was by Boyce and Milbarrow [28], who showed a relationship between the molluscicidal activity of some A -alkyltritylamines and their Rm values on TLC plates. Many publications have reported the application of TLC to determine the relative lipophilicity of compounds. The first chapter of the book Chromatographic Determination of Molecular Interactions Applications in Biochemistry, Chemistry, and Biology [29[ summarises the theory and presents the major application fields of the TLC method. The advantage of the method for the determination of lipophilicity is that the layers can be easily covered by octanol and by using an aqueous buffer the retention parameter would be directly proportional to the octanol-water partition coefficients. The drawbacks of this method are the limited reproducibility and precision. 

Kaliszan, R., Nasal, A. and Bucinski, A. (1994). Chromatographic Hydrophobicity Parameter Determined on an Immobilized Artificial Membrane Column Relationships to Standard Measures of Hydrophobicity and Bioactivity. Eur.J.Med.Chem.,29,163-170. 

The above-described calculation method involves a time-consuming step of manual determination of the chromatographic peak parameters. This step can be automated if the signal from the chromatograph is recorded on a magnetic tape for subsequent direct entry of raw data into a computer. 

The testing procedures were developed to determine the accuracy, repeatability and rangeability of the automated process gas chromatographs. These parameters were compared for several gas chromatographs and also to a calorimeter. 

Gas Chromatographic Determination of Urinary Vanilglycolic Acid, Vanilglycol, Vanilacetic Acid and Vanillactic Acid - Chemical Parameters for the Diagnosis of Neurogenic Tumors and the Evaluation of Their Treatment... 

In this section, a more recently published variant of a quantitative relationship akin to an LFER, but without the use of given solute descriptors and based on modified system parameters, is introduced [16]. All calculated data are derived solely from H PLC measurements, which constitutes the most important difference compared to the use of the solvation equation (Eq. 5). With this method, no a priori assumptions on the role of a certain parameter and its relation to a specific retention mechanism are made. The assignment to chromatographic principles is developed in the framework of the interpretation of each determined parameter, considering the chemical properties of the contributing test analytes. It should be mentioned that the senior authors of the relevant publications, John Dolan and Uoyd Snyder, have also contributed the following chapter to this book (Chapter 2.1.6), in which the application of their strategy to a wide variety of columns is presented. In this chapter, the applied procedure is explained and the performance of this approach critically assessed. 

IL additives have been also applied as a mobile phase modifiers in RP-HPLC systems used for determination of the chromatographic lipophilicity parameters log kw of ionized forms of basic drugs (Marszall Kaliszan, 2007). The correlation of log kw versus the reference lipophilicity parameters log Po/w was evidently better when ionic liquid EMIM BF4 was added to the mobile phase at very small concentration (1.5%). 

H Grajek, S Neffe, Z Witkiewicz. Chromatographic determination of the physico-chemical parameters of adsorption on activated carbon fibres. J... 

KAM 07] Kamphoff M., Thiele T., Kunz B., Influence of different extraction parameter on a solid-phase dynamic extraction for the gas chromatographic determination of d-limonene degradation products by using a fractional factorial design . Journal ofAOACInternational, vol. 90, pp. 1623-2627, 2007. 

Wadman, S.K., Ketting, D. and Voute, P.A. (1976), Gas chromatographic determination of urinary vanilglycolic acid, vanilglycol, vanilacetic acid, and vanillactic acid -Chemical parameters for the diagnosis of neurogenic tumours and the evaluation of their treatment. Clin. Chim. Acta, 72,49. 

The second important parameter is the chromatographic peak s width at the baseline, w. As shown in Figure 12.7, baseline width is determined by the intersection with the baseline of tangent lines drawn through the inflection points on either side of the chromatographic peak. Baseline width is measured in units of time or volume, depending on whether the retention time or retention volume is of interest. 

The amino group is readily dia2oti2ed in aqueous solution, and this reaction forms a basis for the assay of sulfas. Aldehydes also react to form anils, and the yellow product formed with 4-(dimethylamino)hen2a1dehyde can be used for detection in thiu-layer and paper chromatography. Chromatographic retention values have been deterrnined in a number of thiu layer systems, and have been used as an expression of the lipophilic character of sulfonamides (23). These values have corresponded well with Hansch lipophilic parameters determined in an isobutyl alcohol—water system. 

Inhalation of high concentrations of monochlorotoluenes will cause symptoms of central nervous system depression. Inhalation studies produced an LC q (rat, 4 h) of 7119 ppm for o-chlorotoluene (68). o- and Chlorotoluene are both considered moderately toxic by ingestion (Table 2). A study of the relationship between the electronic stmcture and toxicity parameters for a series of mono-, di-, and tri-chlorotoluenes has been reviewed (72). A thin-layer chromatographic method has been developed to assess the degree of occupational exposure of workers to chlorotoluenes by determining j -cblorobippuric... 

Recalling that a separation is achieved by moving the solute bands apart in the column and, at the same time, constraining their dispersion so that they are eluted discretely, it follows that the resolution of a pair of solutes is not successfully accomplished by merely selective retention. In addition, the column must be carefully designed to minimize solute band dispersion. Selective retention will be determined by the interactive nature of the two phases, but band dispersion is determined by the physical properties of the column and the manner in which it is constructed. It is, therefore, necessary to identify those properties that influence peak width and how they are related to other properties of the chromatographic system. This aspect of chromatography theory will be discussed in detail in Part 2 of this book. At this time, the theoretical development will be limited to obtaining a measure of the peak width, so that eventually the width can then be related both theoretically and experimentally to the pertinent column parameters. 

As a secondary consideration, the chromatographer may also need to know the minimum value of the separation ratio (a) for a solute pair that can be resolved by a particular column. The minimum value of (a) has also been suggested [8] as an alternative parameter that can be used to compare the performance of different columns. There is, however, a disadvantage to this type of criteria, due to the fact that the value of (a) becomes less as the resolving power of the column becomes greater. Nevertheless, a knowledge of the minimum value of (cxa/b) can be important in practice, and it is of interest to determine how the minimum value of (aA/B) is related to the effective plate number. 

Nevertheless, a number of gas chromatographic applications exist, epecially those for the determination of crude oil indicators. Such indicators are used as geochemical parameters for the thermal history of the crude as well as to indicate the possible relationship between crudes from different wells. These indicators comprise a number of isomeric aromatic species, such as the individual alkylnaphthalenes (44, 45), the individual Cio-mono-aromatics or the individual C9-mono-aromatics. The ratio between these isomers gives a definite indication of the crude oil. In general, these systems use a Deans switching unit to make a heart-cut, which then is focused, reinjected and separated on a second column with a different polarity. 

Valko et al. [37] developed a fast-gradient RP-HPLC method for the determination of a chromatographic hydrophobicity index (CHI). An octadecylsilane (ODS) column and 50 mM aqueous ammonium acetate (pH 7.4) mobile phase with acetonitrile as an organic modifier (0-100%) were used. The system calibration and quality control were performed periodically by measuring retention for 10 standards unionized at pH 7.4. The CHI could then be used as an independent measure of hydrophobicity. In addition, its correlation with linear free-energy parameters explained some molecular descriptors, including H-bond basicity/ acidity and dipolarity/polarizability. It is noted [27] that there are significant differences between CHI values and octanol-water log D values. 

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