Integrated on-line sample clean-up using cation exchange restricted access sorbent for the LC determination of atropine in human plasma coupled to UV detection

in Journal of Pharmaceutical & Biomedical Analysis (2005), 36(5), 947-954

A new, simple and fully automated liquid chromatographic (LC) method with UV detection has been developed for the direct determination of atropine in plasma. Sample clean-up was based on the use of cation ... [more ▼]

A new, simple and fully automated liquid chromatographic (LC) method with UV detection has been developed for the direct determination of atropine in plasma. Sample clean-up was based on the use of cation exchange restricted access material (RAM) in a pre-column, coupled to LC by means of a column switching system. After direct injection of a 200 microl-volume of plasma sample, the biological matrix was washed out for 10 min using a washing liquid composed of 2 mM lithium perchlorate adjusted to pH 3.0 and methanol (97:3; v/v). By rotation of the switching valve, atropine was then eluted in the back-flush mode for 2 min and transferred to the analytical column packed with octadecyl silica by the LC mobile phase constituted of a mixture of acetonitrile and potassium phosphate buffer (pH 3.0; 50 mM) containing 2 mM sodium heptanesulfonate (16:84; v/v). The UV detection was performed at 220 nm. The method was validated according to a new approach based on accuracy profile over a concentration range from 25 ng/ml, corresponding to the limit of quantitation, to 1000 ng/ml. The method was then applied for the determination of atropine in plasma after intravenous administration to hospitalised patients. [less ▲]

Evaluation of a novel anion-exchange restricted-access sorbent for on-line sample clean-up prior to the determination of acidic compounds in plasma by liquid chromatography

in Journal of Chromatography. A (2004), 1030(1-2), 95-102

A new kind of silica-based restricted-access material (RAM) with anionic properties has been tested in pre-columns for on-line solid-phase extraction of acidic compounds from directly injected plasma ... [more ▼]

A new kind of silica-based restricted-access material (RAM) with anionic properties has been tested in pre-columns for on-line solid-phase extraction of acidic compounds from directly injected plasma samples prior to their determination by reversed-phase liquid chromatography (LC), using the column-switching technique. The outer surface of the porous RAM particles contains hydrophilic diol groups while diethylaminoethyl (DEAE) groups are bound to the internal surface which gives the sorbent the properties of a weak anion exchanger towards low-molecular-mass compounds. Due to an appropriate pore diameter (about 6 nm), macromolecules, such as proteins, are physically excluded from the pores and flushed directly out during the sample clean-up process, while small compounds have access to the inner surface and can be retained mainly by electrostatic interactions. The retention capability of this novel packing material has been tested for some hydrophilic acidic compounds such as aspartic acid, glutamic acid, ascorbic acid and acetylcysteine as well as for some more hydrophobic drugs such as naproxen, ibuprofen and diclofenac, used as model compounds. The influence of the composition of the washing liquid on the retention of the analytes in the pre-column has been investigated. The efficiency of the sorbent to clean-up complex matrices was also tested using human plasma and urine samples. A generic washing liquid composition was then selected in order to obtain efficient and selective sample clean-up as well as a high recovery of the acidic analytes. (C) 2003 Elsevier B.V. All rights reserved. [less ▲]

Evaluation de nouvelles phases à accès restreint échangeuses d’ions pour l’extraction sélective de comosoés médicamenteux dans le plasma avant leur analyse chromatographique

Poster (2004)

Fully automated method for the liquid chromatographic determination of cyproterone acetate in plasma using restricted access material for sample pre-treatment

in Journal of Chromatography. B : Analytical Technologies in the Biomedical & Life Sciences (2003), 795(1), 73-82

A new fully automated method for the quantitative analysis of an antiandrogenic substance, cyproterone acetate (CPA), in plasma samples has been developed using on-line solid-phase extraction (SPE) prior ... [more ▼]

A new fully automated method for the quantitative analysis of an antiandrogenic substance, cyproterone acetate (CPA), in plasma samples has been developed using on-line solid-phase extraction (SPE) prior to the determination by reversed-phase liquid chromatography (LC). The automated method was based on the use of a precolumn packed with an internal-surface reversed-phase packing material (LiChrospher RP-4 ADS) for sample clean-up coupled to LC analysis on an octadecyl stationary phase using a column-switching system. A 200-mul volume of plasma sample was injected directly on the precolumn packed with restricted access material using a mixture of water-acetonitrile (90:10, v/v) as washing liquid. The analyte was then eluted in the back-flush mode with the LC mobile phase which consisted of a mixture of phosphate buffer, pH 7.0-acetonitrile (54:46, v/v). The elution profiles of CPA and blank plasma samples on the precolumn and the time needed for analyte transfer from the precolumn to the analytical column were determined. Different compositions of washing liquid and mobile phase were tested to reduce the interference of plasma endogenous components. UV detection was achieved at 280 nm. Finally, the developed method was validated using a new approach, namely the application of the accuracy profile based on the interval confidence at 90% of the total measurement error (bias+standard deviation). The limit of quantification of cyproterone acetate in plasma was determined at 15 ng ml(-1). The validated method should be applicable to the determination of CPA in patients treated by at least 50 mg day(-1). (C) 2003 Elsevier B.V. All rights reserved. [less ▲]

Cyclodextrins as topical permeation enhancers : in vitro and in vivo testing

Poster (2003)

The use of a novel cation exchange restricted access material for automated sample clean-up prior to the determination of basic drugs in plasma by liquid chromatography

Poster (2002)

Evaluation of a new kind of cation exchange restricted access sorbent for on-line solid phase extraction of basic drugs from plasma prior to their determination by liquid chromatography

Poster (2002)