Liquid chromatographic parameters

Karnka, R., Rayanakom, M., Watanesk, S., and Vaneesom, Y. 2002. Optimization of high-performance liquid chromatographic parameters for the determination of capsaicinoid compounds using the simple method. Anal. Sci. 18 661-665. 

Xt is very difficult to provide an optimum set of conditions for operation of a liquid chromatograph under overload conditions due to the coiq>lex interactions among a large number of parameters [591,592,595,608,620,625]. The following general observations seem to be applicable in most cases. The column efficiency should be as high as possible and separatimis should be carried out using concentration overload conditions. The production rate of a... 

Meier Augenstein, W., Watt, P. W. and Langhans, C. D. (1996) Influence of gas chromatographic parameters on the measurement of 13C/12C isotope ratios by gas liquid chromatography combustion isotope ratio mass spectrometry. I. Journal of Chromatography, A 752, 233 241. 

On the basis of the preceding discussion, it should be obvious that ultratrace elemental analysis can be performed without any major problems by atomic spectroscopy. A major disadvantage with elemental analysis is that it does not provide information on element speciation. Speciation has major significance since it can define whether the element can become bioavailable. For example, complexed iron will be metabolized more readily than unbound iron and the measure of total iron in the sample will not discriminate between the available and nonavailable forms. There are many other similar examples and analytical procedures that must be developed which will enable elemental speciation to be performed. Liquid chromatographic procedures (either ion-exchange, ion-pair, liquid-solid, or liquid-liquid chromatography) are the best methods to speciate samples since they can separate solutes on the basis of a number of parameters. Chromatographic separation can be used as part of the sample preparation step and the column effluent can be monitored with atomic spectroscopy. This mode of operation combines the excellent separation characteristics with the element selectivity of atomic spectroscopy. AAS with a flame as the atom reservoir or AES with an inductively coupled plasma have been used successfully to speciate various ultratrace elements. 

The chromatographic parameters discussed above were calculated for packed beds (increased dispersion and bed length), and for expanded beds with moderate, higher and lower dispersion. The results indicated that the corresponding separation parameters of packed beds and expanded beds are commensurable, therefore, expanded beds can be successfully employed in liquid chromatography even in the case of trace analysis of synthetic dyes in waste water and sludge [75],... 

Various liquid chromatographic techniques have been frequently employed for the purification of commercial dyes for theoretical studies or for the exact determination of their toxicity and environmental pollution capacity. Thus, several sulphonated azo dyes were purified by using reversed-phase preparative HPLC. The chemical strctures, colour index names and numbers, and molecular masses of the sulphonated azo dyes included in the experiments are listed in Fig. 3.114. In order to determine the non-sulphonated azo dyes impurities, commercial dye samples were extracted with hexane, chloroform and ethyl acetate. Colourization of the organic phase indicated impurities. TLC carried out on silica and ODS stationary phases was also applied to control impurities. Mobile phases were composed of methanol, chloroform, acetone, ACN, 2-propanol, water and 0.1 M sodium sulphate depending on the type of stationary phase. Two ODS columns were employed for the analytical separation of dyes. The parameters of the columns were 150 X 3.9 mm i.d. particle size 4 /jm and 250 X 4.6 mm i.d. particle size 5 //m. Mobile phases consisted of methanol and 0.05 M aqueous ammonium acetate in various volume ratios. The flow rate was 0.9 ml/min and dyes were detected at 254 nm. Preparative separations were carried out in an ODS column (250 X 21.2 mm i.d.) using a flow rate of 13.5 ml/min. The composition of the mobile phases employed for the analytical and preparative separation of dyes is compiled in Table 3.33. 

An overview of HPLC instrumentation, operating principles, and recent advances or trends that are pertinent to pharmaceutical analysis is provided in Chapter 3 for the novice and the more experienced analyst. Modern liquid chromatographs have excellent performance and reliability because of the decades of refinements driven by technical advances and competition between manufacturers in a two billion-dollar-plus equipment market. References to HPLC textbooks, reference books, review articles, and training software have been provided in this chapter. Rather than summarizing the current literature, the goal is to provide the reader with a concise overview of HPLC instrumentation, operating principles, and recent advances or trends that lead to better analytical performance. Two often-neglected system parameters—dwell volume and instrumental bandwidth—are discussed in more detail because of their impact on fast LC and small-bore LC applications. 

Krause, A.A. and Niemczyk, H.D. Gas-liquid chromatographic analysis of chlorthal-dimethyl herbicide and its degradates in turfgrass thatch and soil using a solid-phase extraction technique, J. Environ. Sci Health, B25(5) 587-606, 1990. Kresheck, G.C., Schneider, H., and Scheraga, H.A. The effect of DzO on the thermal stability of proteins. Thermod3mamic parameters for the transfer of model compounds from HzO to DzO, J. Phys. Chem., 69(9) 3132-3144, 1965. 

Several studies attempted to relate the partition coefficient P of a solute in a liquid chromatographic or a gas chromatographic system with the composition of the two phases, one of which has a varying composition [19-23]. Tijssen et al. [24] and Schoenmakers [25] derived a relation between the partition coefficient and a binary mobile phase in reversed-phase HPLC from the solubility parameter theory of Hildebrand et al. [26]. Similarly, a relation can be derived for liquid-liquid extraction with extraction liquids composed of three components ... 

The various applications of micellar liquid chromatography are listed alphabetically in Table 1 according to sample type. The chromatographic parameters, instruments used for detection and elements analyzed are summarised. 

In order to optimize separations on coupled-column liquid chromatographic systems under the conditions of solvent modulation, we need to consider the parameters which affect the resolution, as follows. 

A sensitive, simple, and specific liquid chromatographic method coupled with electrospray ionization-mass spectrometry for the determination of donepezil in plasma was developed, and its pharmacokinetics in healthy, male, Chinese was studied [34]. Using loratadine as the IS, after extraction of the alkalized plasma by isopropyl alcohol-n-hexane (3 97, v/v), solutes are separated on a Cig column with a mobile phase of methanol-acetate buffer (pH 4.0) (80 20, v/v). Detection is performed with a TOF mass spectrometer equipped with an electrospray ionization source operated in the positive-ionization mode. Quantitation of donepezil is accomplished by computing the peak area ratio (donepezil [M + H](+) m/z 380-loratadine [M + H](+) mlz 383) and comparing them with the calibration curve (r = 0.9998). The linear calibration curve is obtained in the concentration range 0.1-15 ng/ml. The limit of quantitation is 0.1 ng/ml. The mean recovery of donepezil from human plasma is 99.4 6.3% (range 93.4-102.6%). The inter- and intra-day RSD is less than 15%. After an oral administration of 5 mg donepezil to 20 healthy Chinese volunteers, the main pharmacokinetic parameters of donepezil are as follow T(max), 3.10 0.55 h tV2j 65.7 12.8 h C(max), 10.1 2.02 ng/ml MRT,... 

Arpino, P. J. Guiochon, G. Krien, R Devant, G. 1979. Optimization of the instrumental parameters of a combined liquid chromatograph-mass spectrometer, coupled by an interface for direct liquid introduction. . /. Chromatogr., 185,529-547. 

Visky, D., Y. Vander Heyden, T. Ivanyi, et al. 2002. Characterisation of reversed-phase liquid chromatographic columns by chromatographic tests. Evaluation of 36 test parameters Repeatability, reproducibility and correlation. J. Chromatogr. A 977 39-58. 

The determination of substance J and related compounds in tablets will be transferred according to the tests described in this protocol. The chromatographic parameters for these experiments are as stated in the method, assay of substance J and the determination of related compounds in tablets by high-performance liquid chromatography. ... 

Braumann, T., Weber, G., Grimme, H. (1983) Quantitative structure-activity relationship for herbicides. Reversed-phase liquid chromatographic retention parameter log kw versus liquid-liquid partition coefficient as a model of the hydrophobicity of phenylureas s-tria/ines and phenoxycarbonic acid derivatives. J. Chromatogr. 261, 329-343. 

A liquid chromatographic column packed with 5.00 fim diameter solid support particles and having a porosity e = 0.400 is found to have a flow resistance parameter 750. Calculate the specific permeability K0. Assume that the flowrate/pressure drop relationship is identical to that of a bundle of identical parallel capillaries whose axes are spaced (in a square cross-sectional array) a distance of 5.00 /im from one another. What is the single capillary diameter of the hypothetical bundle ... 

Body fluids are analyzed for T3 and T4 by a variety of radioimmunoassay procedures (31) (see Immunoassays). The important clinical parameter for estimating thyroid function, the protein-bound iodine (PBI), is measured as described in treatises of clinical chemistry. High performance liquid chromatographic (hplc) methods have replaced tic (32,33). 

---