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Results for “Solid Phase Extraction”

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At least 1,711 records · Page 95Linked to original sources
PubMed1989

A strategy for the determination of beta blockers in plasma using solid-phase extraction in combination with high-performance liquid chromatography.

This paper describes a general approach for the therapeutic drug monitoring of 13 different beta blockers in plasma. The chromatographic system contains a cyanopropyl-bonded phase as a stationary phase in combination with a mobile phase composed of acetonitrile and phosphate buffer (pH = 3, mu = 0.05). Two modes of detection are used, namely, UV detection and fluorescence detection. The sample pretreatment is performed with a nitrile-sorbent in combination with methanol-phosphate buffer (pH = 3, mu = 0.05) or with methanol containing 0.1% propylamine as eluent. Acceptable recoveries are obtained for practolol, acebutolol, pindolol, oxprenolol, mepindolol, atenolol, propranolol, prenalterol, alprenolol, metoprolol, sotalol and nadolol. For labetalol, however, the elution recovery has to be improved. Finally, this approach is illustrated by the assay of nadolol in the plasma of patients suffering from hypertension, who had received an oral formulation of the drug.

Adrenergic beta-Antagonists↗
PubMed1990

The influence of properties of packing materials upon the recovery of biological substances isolated from urine by solid-phase extraction.

A series of packing materials with alkyl phase chemically bonded to silica gels of various porosity have been prepared. These packings have been used to isolate the test substances 5-hydroxyindole-3-acetic acid (5-HIAA) and serotonin (5-HT) from urine. The influence of the support porosity, structure of chemically bonded phase, length of alkyl chain, and coverage density on the recovery of isolated substances was studied.

Chemical Phenomena↗
PubMed1993

Determination of ivermectin in bovine plasma by column-switching LC using on-line solid-phase extraction and trace enrichment.

Ivermectin is a potent avermectin anthelmintic, derived from the soil organism Streptomyces avermitilis. Because of its potency, it is administered in very low doses (200 micrograms kg-1), giving rise to plasma levels in the ppb region, and hence sensitive methods are required for its determination in biological samples. A method is described for the determination of ivermectin in bovine plasma, based on a commercially available C18 column employing a mobile phase composed of acetonitrile-water-isopropanol (40:40:35, v/v/v). Extraction from plasma is carried out on-line using coupled-column technology; switching between the extraction and analytical columns is achieved using a six-port column-switching valve. The method is linear over the range 2-100 ng ml-1 (r = 0.9994) and has a limit of detection of 0.8 ng ml-1 (signal-to-noise ratio = 3). Reproducibility of the method, expressed as the overall mean relative standard deviation, is 6.7% (intra-assay) and 3.8% (inter-assay). The mean recovery of the drug from plasma is 76.4%. The method is simple and economical in its execution and is sufficiently reproducible to obviate the need for an internal standard.

1-Propanol↗
PubMed1995

A comparison between solid phase extraction and supercritical fluid extraction for the determination of fluconazole from animal feed.

The application of supercritical fluid extraction with carbon dioxide and modified carbon dioxide for the determination of fluconazole from an animal feed was studied. A fractional factorial design approach was used to examine the significant experimental variables for quantitative extraction of fluconazole. Gas chromatography with either flame ionisation or mass selective detection was used for quantitation of the extracts. The results indicated that modifier (methanol) had the greatest effect on the recovery of fluconazole from the animal feed.

Animal Feed↗
PubMed1993

Measurements of leukotrienes in human plasma by solid phase extraction and high performance liquid chromatography.

Leukotrienes (LTs) are biologically active compounds derived from lipoxygenase catalyzed metabolism of arachidonic acid in mammalian tissues. The present report describes a simple method for extraction and isolation of dihydroxy-LTs; LTB4, LTB5 and the peptido-LTs; LTC4, LTD4 and LTE4 from human plasma, using a pretreatment cartridge which utilizes both hydrophobic and ion-exchange interactions. 5 ml acidified plasma or acetate buffer containing commercially available LT standards were passed through the cartridges under suction, and the absorbed LTs were subsequently eluted in a stepwise manner with acetate buffer containing increasing amounts of methanol. The eluted LTs were analyzed by reversed-phase high performance liquid chromatography (HPLC) on octadecylsilyl (ODS)-silica, using a Waters HPLC unit. Both with plasma and acetate buffer the present methodology resulted in good separation of the LTs with a total run-time of less than 32 min. Recovery of dihydroxy-LTs was approximately 80% (range 73-82%) both when the standards were dissolved in plasma and in acetate buffer. Recovery of the peptido-LTs was, however somewhat lower (47-50%). It should be noted that the present method has the advantage that exposure to chemicals of high toxicity is avoided.

Chemical Phenomena↗