Comparison of high-performance liquid chromatography, supercritical fluid chromatography and capillary zone electrophoresis in drug analysis

Bis(acetylacetone)ethylenediiminepalladium(II) (PdAA2en) was examined as a mixed stationary phase with OV-1 on Chromosorb G/NAW 60-80 mesh size for the GC separation of aromatic hydrocarbons, heteroaromatics, alcohols, aldehydes, ketones, esters, and nitro compounds. Forty-two compounds were examined and the GC results were compared with those obtained with 3% OV-1 on Chromosorb G/NAW 60-80 mesh size under similar operating conditions. Improved resolution, peak asymmetry, theoretical plate numbers, and Kovats indices were obtained on the mixed stationary phase of 3% OV-1 + 5% PdAA2en compared to 3% OV-1 column. The stability constant (Km), enthalpies (deltaH), entropies (deltaS), and Gibbs free energies (deltaG) of the GC elution on the column (2 m x 3 mm id) packed with 3% OV-1 + 5% PdAA2en on Chromosorb G/NAW 60-80 mesh size have been calculated. Donor-acceptor complexation in the gas phase is indicated by negative values of enthalpy (-deltaH) within 5.81 to 10.89 kcal/mol and Gibbs free energy (-deltaG) from 1.34 to 4.08 kcal/mol. The retention time transformations on both the phases were calculated and the ratios obtained from the stationary phases 3% OV-1 and 3% OV-1 + 5% PdAA2en were plotted on the x-axis and the y-axis, respectively, and the coefficients of determination for alkanes, aromatic and heteroaromatics, ketones, and alcohols were observed to lie within 0.5253 to 0.9742, indicative of some different kinds of interaction of the two stationary phases with the solutes.

Section: Methodsmentioning

confidence: 99%

Palladium(II) chelate of tetradentate Schiff base as mixed stationary phase for gas chromatography

Laghari

Khuhawar²,

Ali

2007

“…www.jss-journal.com described by Steuer et al [24]. The data X(NP) and X(RP) together with the log p values are summarised in Table 1.…”

Section: Nplc6rplc Of the Pharmaceutical Samplementioning

confidence: 99%

Considerations on the possibilities and limitations of comprehensive normal phase–reversed phase liquid chromatography (NPLC×RPLC)

François¹,

Villiers²,

Sandra³

2006

A comprehensive normal phase system LC-reversed phase LC (NPLC x RPLC) was evaluated for the separation of a pharmaceutical mixture and citrus oil extracts. NPLC was performed on a 25 cm x 1 mm ID x 5 microm dp diol phase. In the second dimension, an RP 18 monolithic column (10 cm L x 4.6 mm ID x 2 microm macropore size) and an octadecyl silicagel-packed column (5 cm L x 4.6 mm ID x 3.5 microm dp) were applied for the analyses of the pharmaceutical sample and the citrus oil extracts, respectively. A two-position/ten-port switching valve was used as interface. Under optimised LC conditions, the high degree of orthogonality between NP and RP resulted in peak capacities of 300 for the pharmaceutical sample and of 450 for the citrus oil extract composed of lemon and orange oil. Despite the features of NPLC x RPLC, several shortcomings related with the solvent incompatibility between the two LC modes were identified and the practical consequences were discussed.

“…However, the fingerprint feature is essentially the key aspect of this software. This fingerprint function -normalised 2-D chromatogramswas developed according to some basic principles adapted from information theory [29] and adapted here into the software design. Essentially, the process of operation involves: (1) Injection of the sample into the first dimension; (2) sample transport to the second dimension; (3) collection of chromatographic information in both dimensions, the corresponding time of the transportation to the second dimension being recorded by the software and the second dimension retention time being calculated; (4) possible removal of system peaks, which simplifies the visual response; and (5) normalisation of the data according to the method of Steuer [29], see Eq.…”

Section: Data Collection and Analysismentioning

confidence: 99%

Multidimensional liquid chromatography for sample characterisation

Toups

Gray

Dennis

et al. 2006

While LC finds enormously widespread use in almost all areas of chemical science, the technique is limited as a means of identification because compounds do not elute with unique retention times. This limitation spurred the growth of hyphenated instrumental methods of analysis, such as LC-MS/MS, which because of the MS/ MS detection became a method of identification. However, techniques like LC-MS/ MS are specialised and require high initial purchase and running costs, inhibiting the more widespread growth of the technique. In an attempt to increase the separation power of LC, multi-dimensional LC was developed. This expanded the separation space and subsequently has allowed the development of methods with fingerprinting ability due to the lower probability of component overlap. The work in this study illustrates the application of 2-D LC as a means of chemical fingerprinting. We employed a sample base of various low molecular weight oligostyrenes and their diastereomers that represent a population of compounds whose selectivities in a one-dimensional separation are almost unity and hence essentially impossible to separate. Yet in a 2-D domain almost all individual components occupy unique 2-D retention times.