Automated extraction of drugs from biological fluids

Selective extraction of salbutamol from human plasma with the use of phenylboronic acid

An investigation was conducted on the usage of a single-step extraction procedure involving the retention of a phenylboronate-salbutamol complex on an end-capped C18 solid-phase sorbent to determine the level of salbutamol in human plasma samples. Propranolol, a beta-blocker, was chosen as the internal standard for this assay. In this solid-phase clean-up method, 50 mM sodium carbonate buffer, pH 9.60, was used for conditioning the column as well as washing the endogenous interference. Under the optimal conditions, the recovery of salbutamol from spiked plasma samples was found to be high and reproducible with mean recoveries (n = 3) of more than 90% after elution by using 50% 1 M trifluoroacetic acid in methanol. This sample clean-up step was effectively analyzed under reversed-phase high-performance liquid chromatography with fluorimetric detection. The method was successfully applied to the routine measurement of salbutamol in human plasma from the bioequivalence study on the different administration route of salbutamol. Quantification of salbutamol was convincingly reported with the correlation of coefficient of 0.9980 for the concentration range from 0 to 1000 ng ml(-1). An adequate precision was achieved with both between- and within-day precisions of less than 10% (n = 6) for 100 and 1000 ng ml(-1) and less than 15% (n = 6) for 10 ng ml(-1).

Fully automated assay for the determination of GR117289X in human plasma using mixed mode solid-phase extraction and high-performance liquid chromatography with ultraviolet detection

GR117289X, 3-(3-Bromo-2-[2-(1H-tetrazol-5-yl)-phenyl]-bezofuran-5-yl methyl)-2-butyl- 5-chloro-3H-imidazole-4-carboxylic acid, 1, is an angiotensin II receptor antagonist. A sensitive, accurate and precise assay for the determination of 1 in human plasma and validation data is described. The assay consists of a novel solid-phase extraction using Certify II followed by a reversed-phase gradient HPLC separation with UV detection. The extraction procedure has been fully automated by a Zymate XP robot and linked on-line to the HPLC system. The analytical range for the assay is 5-250 ng ml-1 over which the assay is linear and specific for 1 with respect to endogenous plasma components and its tetrazole N2 glucuronide, the major circulating metabolite 2. For the fully automated procedure the intra-assay data indicate a maximum bias and coefficient of variation across the calibration range of +8.0 and 9.4%, respectively. The inter-assay data indicate a maximum bias and coefficient of variation across the calibration range of +8.0 and 11.1%, respectively. The extraction efficiency of the assay was approximately 75%. Both a manual and fully automated assay were applied to the analysis of 1 in plasma of volunteers from a number of clinical studies. The assay has been shown to be robust in sustained use over several months.

A sensitive radioimmunoassay, combined with solid-phase extraction, for the sub-nanogram per ml determination of ondansetron in human plasma

The development of a radioimmunoassay, incorporating solid-phase sample extraction, suitable for the subnanogram per ml determination of ondansetron base in human plasma is described. The antiserum was raised in Soay sheep following primary and booster immunizations with an immunogen prepared by conjugating 9-(carboxypropyl)-ondansetron to bovine thyroglobulin. The radioligand consisted of ondansetron specifically tritium-labelled on the N-methyl group of the indole moiety. The solid-phase extraction method, using a cyanopropyl sorbent, was introduced to remove cross-reacting metabolites and to enhance assay sensitivity. The calibration range is 0.05-2.40 ng ml-1 using a 1 ml sample of human plasma; inter- and intra-assay bias and precision are < +/- 13% and < 10% over this concentration range, respectively. The assay drift, measured as the difference in concentration values for quality control samples assayed immediately before and after the sequence of test plasma samples, is < +/- 10% for run sizes of up to 54 samples.

Determination of salmeterol in rat and dog plasma by high-performance liquid chromatography with fluorescence detection

Salmeterol (as the hydroxynaphthoate) is the first of a new class of long-acting beta-adrenergic receptor agonists with both bronchodilator and anti-inflammatory actions. A sensitive, accurate, and precise high-performance liquid chromatographic method for the determination of salmeterol in rat and dog plasma is described. Samples are prepared by solid-phase extraction and, after chromatography of the extracts on a reversed-phase styrene/divinylbenzene analytical column, salmeterol is detected by fluorescence monitoring (excitation wavelength, 230 nm; emission wavelength, 305 nm). The method is sensitive to 1 ng/mL, at which concentration the coefficient of variation was 16.3% in a single assay run. Repeated analyses of quality control samples, nominally at 2 ng/mL, were carried out over a number of assay runs with a coefficient of variation of 10.4%. The method is specific for salmeterol with respect to endogenous plasma components and identified metabolites. The assay was applied to the analysis of salmeterol in plasma of rats and dogs from pharmacokinetic studies.

Determination of ondansetron in plasma and its pharmacokinetics in the young and elderly

Ondansetron is a 5-hydroxytryptamine3 receptor antagonist for the treatment of chemotherapy- and radiotherapy-induced nausea and emesis. A sensitive, accurate, and precise HPLC method for the determination of ondansetron in plasma is described. Samples are prepared by solid-phase extraction and, after chromatography of the extracts on a silica analytical column, ondansetron is detected by UV absorbance at 305 nm. The method is sensitive down to 1 ng/mL, at which concentration the coefficient of variation was 6.2% in a single assay run. Repeated analyses of quality control samples, nominally at 2 ng/mL, were carried out over a number of assay runs with a coefficient of variation of 5.5%. The method is specific for ondansetron with respect to endogenous plasma components, identified phase I metabolites, and some co-administered chemotherapeutic drugs. In sustained use over several months, and in support of the clinical development of ondansetron, the method has been shown to be robust. An application of the assay in the investigation of the pharmacokinetics of ondansetron in the young and elderly is described.

Determination of albuterol concentrations in human plasma using solid-phase extraction and high-performance liquid chromatography with fluorescence detection

A fast, simple, and accurate method for determining albuterol concentrations in human plasma has been developed and validated for use in routine clinical analyses. This method involves a solid-phase extraction procedure using silica cartridges and normal-phase high-performance liquid chromatography with fluorescence detection. Regression analysis showed the method was linear over the standard curve range 1-16 ng ml-1. The percent recovery for albuterol and the internal standard, bamethane, at 5 ng ml-1 was found to be greater than 90%. The newly developed method has been applied in the analysis of plasma samples from patients and healthy volunteers.

Analysis of albuterol in human plasma based on immunoaffinity chromatographic clean-up combined with high-performance liquid chromatography with fluorimetric detection

A method combining immunoaffinity chromatography with high-performance liquid chromatography was developed for the determination of albuterol in human plasma. The immunoaffinity chromatography, based on the specific interaction of albuterol with the immobilized antibody raised against it, was used as a clean-up step. Albuterol eluted from this immunochemical solid-phase clean-up step was analysed by reversed-phase high-performance liquid chromatography with fluorimetric detection. The performance of the assay was validated on six normal volunteers after a 4-mg oral dose of albuterol, which gave a peak plasma concentration in the range 6.67-15.31 ng/ml at 3-4 h after the dose. Plasma levels (0.79-1.56 ng/ml) of albuterol could be detected up to 24 h after the dose.