Semi-automated Solid-phase Extraction Research Articles

Study of semi-automated solid-phase extraction for the determination of acaricide residues in honey by liquid chromatography

A solid-phase extraction (SPE) method followed by a reversed-phase high-performance liquid chromatography (HPLC) procedure is reported for the assay of a wide polarity range acaricide residues in honey. After selection of suitable chromatographic and detection conditions, most steps of the SPE procedure that may affect to the recovery were investigated. Honey sample was buffered at pH 6 and then applied to the preconditioned C 18 sorbent. A washing step was performed with 1 ml of a mixture of tetrahydrofuran (THF)–phosphate buffer (10:90, v/v) and finally, the analytes were eluted with 1 ml of THF. The extract was evaporated to dryness, reconstituted in mobile phase and chromatographed on a reversed-phase C 18 column with diode array detection. The recoveries of the more polar acaricides were higher than 80% and 60–70% for the more apolar ones. Limits of detection obtained ranged from 1 to 200 ng/g.

High-throughput analysis of everolimus (RAD001) and cyclosporin A (CsA) in whole blood by liquid chromatography/mass spectrometry using a semi-automated 96-well solid-phase extraction system.

A semi-automated solid-phase extraction (SPE) liquid chromatography/mass spectrometry (LC/MS) procedure was validated for the simultaneous determination of everolimus (RAD001) and cyclosporin A (CsA) in human blood. Whole blood samples (350microL) were pretreated with acetonitrile/zinc sulfate mixture to precipitate the sample proteins. The samples were centrifuged and the resulting supernatants were manually transferred to a 96-well plate format. All subsequent sample transfer and solid phase extraction was automated using a Tomtec Quadra 96 workstation. Samples were analyzed by LC/MS using an atmospheric pressure chemical ionization (APcI) interface. In order to enhance sensitivity, the MS method used negative ion mode for RAD001 ([M]-) and its internal standard and positive ion mode for CsA ([M + H]+) and its internal standard. The lower limit of quantitation was 0.375 ng.ml(-1) for RAD001 and 6.95 ng.ml(-1) for CsA. The reproducibility of the method was evaluated by analyzing six replicates at five or more quality control (QC) levels over the nominal concentration range 0.375 to 253 ng.ml(-1) for RAD001 and 6.95 to 1,530 ng.ml(-1) for CsA. The inter- and intra-day accuracy was found to range from 89.7 to 114% with precision (% CV) of less than 12% for both compounds. The sensitivity, small sample volume needed and high sample throughput of this method make it an attractive option for pharmacokinetic studies in pediatric patients.

Study of the solid-phase extraction of diclofenac sodium, indomethacin and phenylbutazone for their analysis in human urine by liquid chromatography

A selective semi-automated solid-phase extraction (SPE) of the non-steroidal anti-inflammatory drugs diclofenac sodium, indomethacin and phenylbutazone from urine prior to high-performance liquid chromatography was investigated. The drugs were recovered from urine buffered at pH 5.0 using C 18 Bond-Elut cartridges as solid sorbent material and mixtures of methanol–aqueous buffer or acetonitrile–aqueous buffer as washing and elution solvents. The extracts were chromatographed on a reversed-phase ODS column using 10 m M acetate buffer (pH 4.0)–acetonitrile (58:42, v/v) as the mobile phase, and the effluent from the column was monitored at 210 nm with ultraviolet detection. Absolute recoveries of the anti-inflammatory drugs within the range 0.02–1.0 μg/ml were about 85% for diclofenac and indomethacin, and 50% for phenylbutazone without any interference from endogenous compounds of the urine. The within-day and between-day repeatabilities were in all cases less than 5% and 10%, respectively. Limits of detection were 0.007 μg/ml for diclofenac sodium and indomethacin and 0.035 μg/ml for phenylbutazone, whereas limits of quantitation were 0.02 μg/ml for diclofenac and indomethacin and 0.1 μg/ml for phenylbutazone.

Semi-automated solid-phase extraction procedure for the high-performance liquid chromatographic determination of alinastine in biological fluids

A solid-phase extraction (SPE) method for sample clean-up followed by a reversed-phase HPLC procedure for the assay of alinastina (pINN) in biological fluids is reported. The effects of the sample pH, composition of the washing and elution solvents and the nature of the SPE cartridge on recovery were evaluated. The selectivity of SPE was examined using spiked rat urine and plasma samples and the CH and PH cartridges gave rise to the cleanest extracts. The recoveries obtained in spiked rat urine and plasma samples were 91.2±2.7 and 99.9±2.8%, respectively. The proposed SPE method coupled off-line with a reserved-phase HPLC system with fluorimetric detection was applied to the quantitation of alinastine in real rat urine samples. The analytical method was also applied and validated for the determination of alinastine in dog plasma. The recovery from spiked dog plasma samples using the PH cartridge was around 65%. The within-day and between-day precisions were 7 and 12%, respectively. The detection and quantitation limits in dog plasma were 0.024 and 0.078 μg/ml, respectively.

A semi-automated solid-phase extraction and radioreceptor assay for the analysis of scopolamine in urine and plasma

In a double-blind placebo-controlled cross-over study, we evaluated the therapeutic efficacy of transdermal scopolamine in ten patients with reversible airways obstruction. They received a patch (Scopoderm ® TTS) behind the ear for three days and samples of blood and urine were taken. A highly sensitive method was developed and validated to measure the low levels of free and total scopolamine in urine and plasma. The procedure consisted of a semi-automated solid-phase extraction followed by the analysis using radioreceptor assays. The mean plasma concentrations, taken every third patch day, of free and total scopolamine were 43.6 pg/ml and 229.0 pg/ml, respectively. In 24-h urine, collected every second patch day, 6.3 μg of free scopolamine and 83.4 μg total scopolamine was excreted. This means that 70% of the delivered dose (120 μg in 24 h) is excreted in urine. For urine samples, the limit of detection (LOD) of the assay is 550 pg/ml and the limit of quantitation (LOQ) is 610 pg/ml. For plasma samples, the LOD is 16 pg/ml and the LOQ is 38 pg/ml.

Clinical evaluation of Toxi · Prep™: a semiautomated solid-phase extraction system for screening of drugs in urine

A prototype Toxi.Prep (TP) system that utilizes solid-phase extraction (SPE) has been developed as a method for broad-spectrum drug screening and identification of tetrahydrocannabinol (THC) metabolites in urine. TP can simultaneously extract up to seven specimens while automating the process of sample extraction, washing, and elution onto a chromatogram. TP was compared with the Toxi. Lab A (TL-A) system for extraction of basic drugs only. In a blind study, 33 distinct drugs and metabolites were detected in 55 urines over 13 runs. Of the drug occurrences, 68.8% (141 of 205) were detected on both TP and TL-A. Of the 13 runs, quinidine and quinine, nortriptyline metabolites, and diphenhydramine were noted more frequently on TP than TL-A, whereas nicotine and metabolites, morphine, and methadone metabolites were more frequently noted on TL-A. Twenty specimens were analyzed for THC metabolites. Of the cases positive for THC metabolites, 100% (16 of 16) were positive by both methods. Time and motion studies for all runs proved an overall labor reduction for extraction and spotting by approximately 40%.

Evaluation of Automated Extraction of Organochlorine Contaminants from Freshwater

A semiautomated solid phase extraction (SPE) system fitted with reverse phase disks was evaluated for the extraction and concentration of trace contaminants in water. Organochlorine compounds of environmental interest and covering a wide range of log Kow values were dissolved in laboratory water of low dissolved organic carbon (DOC) concentration and extracted using a variety of solvents and conditions based on a survey of the literature. The most successful eluent was 15% diethyl ether in n-pentane which recovered 64−91% of the analytes. We tested the influence of DOC from a Canadian Shield humic lake on the recovery of organochlorine compounds by this SPE technique. Recoveries of analytes from high DOC lake water were lower by SPE (42−69%) than by a shake-flask liquid−liquid extraction method (59−98%). An additional 2−11% of analytes were recovered by solvent rinses of containers. Breakthrough, assessed by liquid−liquid extraction of water of SPE sample effluent, ranged from 6 to 38% for lake water samples. These results indicate that the DOC is a principle factor affecting SPE recoveries of organic contaminants in freshwater. Application of the optimized SPE method for analysis of organochlorine contaminants in lake enclosure experiments, however, yielded higher concentrations and better recoveries of surrogates than a large volume liquid−liquid extraction system.

An on-line semi-automated solid-phase extraction procedure for high-performance liquid chromatographic determination of lonidamine in serum

A semi-automated solid-phase extraction procedure on-line with gradient elution reversed-phase chromatography permits the determination of lonidamine and its metabolite in human serum. The average recovery from serum at the 2.5 μg ml −1 level was (92.8 ± 3.4)%. The limit of quantitation for a 100 μl sample size was 50 ng ml −1. The within-day ( n = 5) and between-day ( n = 5) relative standard deviations for lonidamine determination in serum samples spiked at the 2.5 μg ml −1 level were 2.7% and 4.5%, respectively.

Semi-automated solid-phase extraction procedure for drug screening in biological fluids using the ASPEC system in combination with Clean Screen DAU columns

The use of a semi-automated solid-phase extraction system (ASPEC) for the screening of drugs in plasma and urine on a single mixed-mode column (Clean Screen DAU) is described. The processes of column preconditioning, sample application, column wash, pH adjustment and elution of the drugs were accomplished by the ASPEC. After off-line evaporation, the residues were injected into a wide-bore capillary gas chromatograph. The recoveries of the tested drugs were in the range of 73–96%, with relative standard deviations less than 5% at a concentration level of 2 μg/ml.