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See detailKnowledge-Based System for the Automated Solid-Phase Extraction of Basic Drugs from Plasma Coupled with Their Liquid Chromatographic Determination. Application to the Biodetermination of Beta-Receptor Blocking Agents
Hubert, Philippe ULg; Chiap, Patrice ULg; Moors, M. et al

in Journal of Chromatography. A (1994), 665(1), 87-99

Techniques for the preparation of biological samples are often based nowadays on solid-phase extraction (SPE). The different SPE steps can be performed automatically on disposable extraction cartridges ... [more ▼]

Techniques for the preparation of biological samples are often based nowadays on solid-phase extraction (SPE). The different SPE steps can be performed automatically on disposable extraction cartridges (DECs) by means of a sample processor. A knowledge-based system was developed to facilitate the development of fully automated methods for the solid-phase extraction of relatively hydrophobic basic drugs from plasma, coupled with their determination by high-performance liquid chromatography (HPLC). The DEC filled with 50 mg of cyanopropyl-bonded silica phase is first conditioned with methanol and buffer solution (pH 7.4). After sample application, the DEC sorbent is washed with the same buffer. The analytes are then desorbed with an appropriate eluent and the eluate is finally diluted with the same buffer as used in the HPLC mobile phase before injection. Under these conditions, only three variables are still to be optimized: the composition and volume of the elution solvent and the volume of buffer to be added to the eluate. On the basis of this general strategy, a decision tree providing information about suggested starting conditions and guidelines for the optimization of the three variables was developed and implemented by use of a hypermedia software. This didactic expert system was evaluated using several beta-receptor blocking agents as model compounds and the operating conditions obtained for the automated SPE of these compounds are presented. A method for the determination of propranolol in plasma using the SPE conditions deduced from the knowledge-based system was validated. The absolute recovery of propranolol is ca. 93% and the limit of detection is 1.3 ng ml-1. The mean within-day and between-day reproducibilities are 2.3 and 3.6%, respectively. [less ▲]

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See detailA knowledge-based system for developping solid-phase extraction methods with the ASPEC system, chapitre #D-3
Moors, M.; Bourguignon, B.; Massart, D. L. et al

in Reid, E.; Hill, H. M.; Wilson, I. D. (Eds.) Biofluid and tissue analysis for drugs, including hypolipidaemics (1994)

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See detailFully Automated Determination of Sulfamethazine in Ovine Plasma Using Solid-Phase Extraction on Disposable Cartridges and Liquid Chromatography
Hubert, Philippe ULg; Chiap, Patrice ULg; Evrard, Brigitte ULg et al

in Journal of Chromatography. A (1993), 622(1), 53-60

An automatic sample preparation procedure followed by on-line injection of the sample extract into a HPLC system has been developed for the quantitative analysis of sulfamethazine and its N4-acetyl ... [more ▼]

An automatic sample preparation procedure followed by on-line injection of the sample extract into a HPLC system has been developed for the quantitative analysis of sulfamethazine and its N4-acetyl metabolite in ovine plasma. The sample clean-up was performed by solid-phase extraction (SPE) on C18 disposable extraction cartridges (DECs). All the sample handling operations were effected by a robotic auto-sampler. The DEC was first conditioned with methanol and phosphate buffer pH 7.4. After loading 1.0 ml of plasma sample onto the DEC, the latter was washed with the same buffer. The elution step was performed with methanol (0.25 ml) and the eluate was then diluted by adding 0.75 ml volume of phosphate buffer pH 6.4. A 20-microliters volume of the resultant solution was injected onto an octadecyl silica column preceded by a short guard column. The HPLC mobile phase was methanol-phosphate buffer pH 6.4 (25:75, v/v). Sulfamethazine and N4-acetylsulfamethazine were determined photometrically at 262 nm. Under these conditions, linear calibration curves ranging from 2 to 250 micrograms ml-1 have been obtained for both compounds. Drug recoveries were higher than 90% and typical relative standard deviation values were 0.7% (within-day) and 2.0% (between-day) at a plasma concentration of 50 micrograms ml-1. [less ▲]

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See detailKnowledge-based systems for method development in solid-phase extraction
Massart, D. L.; Hubert, Philippe ULg; Chiap, Patrice ULg et al

Conference (1993)

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See detailDetermination of verapamil and norverapamil in human plasma by liquid chromatography: comparison between a liquid-liquid extraction procedure and an automated liquid-solid extraction method for sample preparation.
Hubert, Philippe ULg; Chiap, Patrice ULg; Ceccato, Attilio ULg et al

in Journal of Pharmaceutical & Biomedical Analysis (1992), 10(10-12), 937-42

A conventional liquid-liquid extraction (LLE) procedure with high-performance liquid chromatography (HPLC) has been developed for the determination of verapamil and its main metabolite, norverapamil, in ... [more ▼]

A conventional liquid-liquid extraction (LLE) procedure with high-performance liquid chromatography (HPLC) has been developed for the determination of verapamil and its main metabolite, norverapamil, in plasma. After addition of the internal standard, plasma samples were basified with phosphate buffer (pH 9.0) and extracted with a mixture of cyclohexane-dichloromethane. After centrifugation, the organic layer was separated and the analytes were extracted back into a 0.1 N sulphuric acid solution containing 2-aminoheptane. An aliquot of this aqueous phase was then injected directly onto the HPLC column. This LLE procedure has been compared with an automated liquid-solid extraction (LSE) method that has been developed in parallel. Good linearity was obtained using both extraction methods. The absolute recoveries for the two analytes were ca 95% with the automated LSE procedure and slightly lower (ca 84%) for the LLE method. The automated method gives better results with respect to detectability and precision, but the LLE procedure is simpler to develop, requires much less expensive equipment, and remains a useful alternative when the number of samples to be analysed is limited. [less ▲]

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See detailAutomated HPLC analysis of diltiazem and desacetyldiltiazem in plasma using disposabele extraction cartridges
Chiap, Patrice ULg; Hubert, Philippe ULg; Bechet, Isabelle et al

in Journal de Pharmacie de Belgique (1992), 47

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See detailAutomatic Determination of Diltiazem and Desacetyldiltiazem in Human Plasma Using Liquid-Solid Extraction on Disposable Cartridges Coupled to Hplc--Part II: Optimization of Liquid-Solid Extraction
Hubert, Philippe ULg; Chiap, Patrice ULg; Crommen, Jacques ULg

in Journal of Pharmaceutical & Biomedical Analysis (1991), 9(10-12), 883-887

An automatic liquid-solid extraction (LSE) procedure to be coupled to HPLC for the determination of diltiazem and desacetyldiltiazem in plasma has been developed. The LSE operations are performed on ... [more ▼]

An automatic liquid-solid extraction (LSE) procedure to be coupled to HPLC for the determination of diltiazem and desacetyldiltiazem in plasma has been developed. The LSE operations are performed on disposable extraction cartridges (DECs) by means of a sample processor equipped with a robotic arm holding a needle through which the different liquids are dispensed. The operating parameters of LSE have been optimized with respect to recovery, detectability and reproducibility by using, whenever possible, aqueous solutions of the analytes. Different kinds of DECs have been tested. For the compounds studied, DECs filled with 50 mg of cyanopropyl silica have been selected. The influence of the pH of the buffer used in the washing step has been studied, leading finally to the selection of the same phosphate buffer (pH 7.4) as in the HPLC mobile phase. The minimum volume of methanol which still gives a nearly complete elution of the analytes from the extraction cartridges has been determined. Under these conditions, a high sensitivity can be obtained without an evaporation step. Moreover, the volume of buffer to be added to the methanolic eluate before injection into the HPLC system has been optimized in such a way that a focusing effect is obtained at the top of the analytical column while the dilution of the extract is minimized. [less ▲]

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See detailAutomatic Determination of Diltiazem and Desacetyldiltiazem in Human Plasma Using Liquid-Solid Extraction on Disposable Cartridges Coupled to Hplc--Part I: Optimization of the Hplc System and Method Validation
Hubert, Philippe ULg; Chiap, Patrice ULg; Crommen, Jacques ULg

in Journal of Pharmaceutical & Biomedical Analysis (1991), 9(10-12), 877-882

A sensitive and automated method for the analysis of diltiazem and desacetyldiltiazem in plasma has been developed using liquid-solid extraction (LSE) on disposable extraction cartridges (DECs) in ... [more ▼]

A sensitive and automated method for the analysis of diltiazem and desacetyldiltiazem in plasma has been developed using liquid-solid extraction (LSE) on disposable extraction cartridges (DECs) in combination with HPLC. After isolation from plasma, the analytes are separated on a highly deactivated octyl silica column with a mobile phase of methanol-0.05 M phosphate buffer (pH 7.4) (62:38, v/v). The analytes are monitored photometrically at 238 nm. The complete preparation of the plasma sample as well as the injection of the final extract on to the analytical column are performed automatically by means of a sample processor equipped with a robotic arm to which is attached a needle dispensing the different liquids. The internal standard solution is first added to the plasma sample. The DEC is then conditioned successively with methanol and phosphate buffer (pH 7.4). A 1.0-ml volume of sample containing the internal standard solution is applied on an extraction cartridge filled with cyanopropyl silica (50 mg). After the DEC has been washed with the same buffer, the analytes are eluted with 0.16 ml of methanol. A 0.14-ml volume of buffer is then passed through the DEC and 0.25 ml of the final extract is injected onto the HPLC column. The absolute recoveries of the drugs are about 90% and the limit of detection for diltiazem is 0.8 ng ml-1. Relative standard deviations of 2.6% (within-day) and 3.7% (between-day) have been obtained for this compound at a plasma concentration of 50 ng ml-1. [less ▲]

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