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PubMed1993

Gas chromatographic determination of alkyl lysophospholipids after solid-phase extraction from cell culture media.

The gas chromatographic determination of 1-O-octadecyl-2-O-methyl-DL-glycero-3-phosphorylcholine (Et-18-OMe), an anti-invasive alkyl lysophospholipid, in cell culture media is described. Sample clean-up was performed by solid-phase extraction on a weak cation-exchange column of the CBA type (carboxylic acid). For quantitation, the structural analogue Et-16-OMe as the internal standard was used after derivatization with trimethylsilyl bromide. The described method was free of interferences in cell culture media. The overall precision for twenty determinations was 14.99%.

Cells, Cultured↗
PubMed2001

Determination of phenytoin in plasma by molecularly imprinted solid-phase extraction.

A molecularly imprinted polymer (MIP) using phenytoin as template and methacrylamide as the functional monomer was prepared. The selectivity was measured by comparing capacity factors of phenytoin and other structurally related compounds. The polymer was evaluated as a selective sorbent in molecularly imprinted solid-phase extraction (MISPE). Several washing solvents were tested to study their ability to disrupt the non-specific interactions occurring between the sample and the polymer matrix and the role of water in the recognition process was also investigated. It was shown that the key step of successful sample extraction is the right choice of the washing solvent. Plasma samples spiked with phenytoin were analyzed by the MISPE methodology developed in this work. Method validation (intra- and inter-day precision, recovery, specificity) was carried out. The calibration curve showed good linearity in the 2.5-40 microg/ml range corresponding to therapeutically relevant plasma levels. The intra- and inter-day precision values were below the 15% limit established for bioanalytical methods. The results showed that the method could be successfully applied for the determination of phenytoin in plasma samples.

Anticonvulsants↗
PubMed2004

Formation of Cu(I) in estuarine and marine waters: application of a new solid-phase extraction method to measure Cu(I).

Cu(II) is a key species with respect to the bioavailability and hence toxicity of copper. Therefore, it is important to elucidate the factors that control Cu(I) steady-state concentrations in natural waters. In this study, a solid-phase-extraction-based method was developed that allows Cu(I) measurements at ambient concentrations. Cu(I) is selectively enriched as a bathocuproine complex on a hydrophobic polymer column, whereas Cu(II), bound to ethylenediamine, is not retained on the column. After elution with acidic methanol, Cu is analyzed with graphite-furnace atomic absorption spectroscopy. The detection limit of the whole analytical procedure is below 1 x 10(-9) M, and the mean recovery of Cu(I) is approximately 70%. We then applied this method to determine Cu(I) in water samples collected from the River Scheldt estuary and the North Sea. Upon irradiation of these filtered water samples in the laboratory (with approximately 5 kW m(-2)), Cu(I) steady-state concentrations ([Cu(I)]ss) were established within a few minutes, and [Cu(I)]ss ranged from 5% to 80% of total dissolved copper, depending on the origin of the water samples. Measured [Cu(I)]ss can be interpreted by considering light-induced reduction of Cu(II) and stabilization of Cu(I) by chloride at high salinity, thermal reduction of Cu(II) by sulfide-containing compounds at low salinity, and fast reoxidation of Cu(I) due to stabilization of Cu(II) by strong organic ligands present at intermediate salinity.

Biological Availability↗
PubMed2001

Microanalysis of propofol in human serum by semi-microcolumn high-performance liquid chromatography with UV detection and solid-phase extraction.

OBJECTIVE: To develop a simple analytical method for monitoring the low serum levels of propofol found when administered for the sedation of patients in the intensive care unit (ICU). METHODS: A high-performance liquid chromatographic method (HPLC) was used with UV detection. Solid-phase extraction (SPE) cartridges and a semi-microcolumn (TSK gel ODS-80Ts, 2.0 mm i.d. x 25 cm, 5 microm) were used to improve sensitivity. Propofol in the eluate obtained from the SPE cartridge was concentrated to about five times the initial concentration. RESULTS: The sensitivity using the semi-microcolumn was amplified by about three-fold. The assay showed a good linearity with a quantification limit 20 ng/mL. Intra- and inter-assay coefficients of variation were less than 2.2% and 10.0%, respectively. The mean recoveries ranged from 97.6 to 109.5%. CONCLUSION: The HPLC method described should be useful for measuring the low serum propofol levels found when the drug is used for ICU sedation.

Chromatography, High Pressure Liquid↗
PubMed2006

Determination of Olanzapine in rat brain using liquid chromatography with coulometric detection and a rapid solid-phase extraction procedure.

A sensitive and selective method was developed for the determination of the antipsychotic drug Olanzapine levels in rat brain tissue, based on HPLC with electrochemical detection. The analyses were carried out on a C8 reversed phase column (150 mm x 4.6 mm, 5 microm), using a mobile phase composed of methanol and a phosphate buffer (44.0 mM, pH 3.5), containing triethylamine (21:79, v/v), flowing at 1.2 mL min(-1). A high sensitivity coulometric detection analytical cell containing two flow-through low volume working electrodes was used: electrode 1 was set at +0.350 V and electrode 2 at -0.200 V. Olanzapine, administered to rats in different doses or in different times, was extracted from tissue homogenate of either the whole brain or specific areas (cortex, hyppocampus, nucleus striatum) with a rapid solid phase extraction procedure (SPE) on Oasis HLB cartridges. The method provided a high extraction yield of Olanzapine and internal standard (2-methylolanzapine) from brain tissue homogenate with absolute recovery values higher than 90.0%. The detector response was linear over a concentration range of 0.2-100.0 ng mL(-1) of Olanzapine. The limit of quantification (LOQ) was 0.2 ng mL(-1). Precision results, expressed by the intra-day and the inter-day relative standard deviation values, were satisfactory, better than 4.6%. Accuracy was satisfactory as well. This method proved to be suitable for the analysis of Olanzapine in rat brain tissues and for the study of distribution and pharmacokinetics of Olanzapine in rat brain after a single treatment with the antipsychotic drug.

Animals↗
PubMed1991

On-line solid-phase extraction of piroxicam prior to its determination by high-performance liquid chromatography.

A direct method for the determination of piroxicam in plasma is described. Plasma is directly injected onto the extraction column (10 mm x 2 mm I.D., packed with 40-microns Bond Elut C2) where proxicam is separated from the plasma concomitants using a solid-phase extraction procedure. Using a laboratory-made on-line column-switching system, the drug is quantitatively transferred and separated on the analytical column (15 cm x 4.6 mm I.D., Supelcosil LC18 DB, 5 microns) followed by determination using ultraviolet absorption at 331 nm. Validation of the method demonstrated a good recovery (100%), sensitivity (limit of determination 0.2 microgram/ml, based on a 20-microliters sample volume), accuracy and precision (better than 5%). The developed method has been adopted for studying the steady-state pharmacokinetics of the drug.

Chromatography, High Pressure Liquid↗
PubMed1987

Solid-phase extraction of chloramphenicol with graphitized carbon black.

The sorption and desorption properties of graphitized carbon black (GCB) were evaluated for enrichment of highly polarizable chloramphenicol (CP) from biological fluids. The distribution of CP between GCB and water lay strongly toward GCB. Among the organic solvents examined, methanol gave the lowest adsorption coefficient. The optimum packing amount of GCB, and the optimum volume and flow-rate of the eluent were deduced from the breakthrough curve and methanol elution curve, respectively. The inner diameter of GCB extraction columns was chosen from the sorption efficiency curve obtained by plotting CP recovery against column inner diameter. The solid-phase extraction method using GCB was applied to the assay of CP in serum samples in the concentration range of 5 to 50 micrograms/ml.

Absorption↗
PubMed2004

Determination of impurities in pesticides and their degradation products formed during the wine-making process by solid-phase extraction and gas chromatography with detection by electron impact mass spectrometry. I. Vinclozoline, procymidone and fenitrothion.

The presence of degradation products of vinclozoline, procymidone and fenitrothion, and of impurities from their commercial formulations, was studied in white and red wines elaborated from spiked must. After solid-phase extraction the nature of the residues was established by gas chromatography with mass spectrometric detection. The structures of several degradation products and impurities are discussed and elucidated on the basis of their electron impact spectra. In elaborated wines the concentrations of the degradation products and impurities are lower than those of the original active ingredients. Aminofenitrothion and acetylamino-formyl-fenitrothion-oxon are the main residues of fenitrothion in wine. For dicarboximides, an alcohol derivative of vinclozoline was found in addition to 3,5-dichloroaniline.

Bridged Bicyclo Compounds↗
PubMed1991

Solid-phase extraction and direct high-performance liquid chromatographic determination of metoprolol enantiomers in plasma.

A method is described by which underivatized metoprolol enantiomers in plasma can be quantitated by high-performance liquid chromatography with fluorescence detection. Samples are prepared for injection using a simple solid-phase extraction procedure which is essentially 100% efficient for all analytes. The metoprolol enantiomers are resolved using a cellulose tris(3,5-dimethylphenylcarbamate) chiral stationary phase and a hexane-ethanol-diethylamine mobile phase. Samples were tested for adaptability to autoinjection and found to be stable for at least 16 h after reconstitution in mobile phase. The automated method was determined to be precise and accurate for enantiomer concentrations as low as 10 ng base per ml and was successfully employed in a pharmacokinetic investigation.

Chromatography, High Pressure Liquid↗
PubMed1994

Quantification of zidovudine and one of its metabolites in plasma and urine by solid-phase extraction and high-performance liquid chromatography.

A rapid, sensitive and selective method for the quantification of zidovudine (AZT) and one of its metabolites (the 5'-glucuronyl form of zidovudine, G-AZT) in biological fluids is described, based on high-performance liquid chromatography. Solid-phase extraction on-line with chromatographic separation was used. The limit of quantitation of the assay is 10 ng/ml of plasma or urine for G-AZT and 20 ng/ml of plasma or urine for AZT.

Chromatography, High Pressure Liquid↗
PubMed2006

Sol-gel molecular imprinted ormosil for solid-phase extraction of methylxanthines.

A organically modified molecularly imprinted silica (MIS), selective for methylxanthines, was prepared using a simple sol-gel procedure. Caffeine was used as template; 3-aminopropyltrimethoxysilane (APTMS) as functional monomer and tetraethyl orthosilicate (TEOS) as reticulating agent. The material was packed on solid-phase extraction (SPE) cartridges and evaluated with aqueous test samples, natural water and human urine; a quantitative method for methylxanthines in water, using SPE cartridges packed with the MIS coupled with HPLC-UV was developed. The MIS was highly specific for methylxanthines, with an imprinting factor of (20.5+/-1.9). The analytical method resulted in detection limits of 85 microgL(-1) for theobromine, 44 microgL(-1) for theophylline and 53 microgL(-1) for caffeine.

Chromatography, High Pressure Liquid↗
PubMed1998

Quantitative determination of endogenous retinoids in mouse embryos by high-performance liquid chromatography with on-line solid-phase extraction, column switching and electrochemical detection.

An isocratic high-performance liquid chromatographic method for the determination of 9-cis-retinoic acid, 13-cis-retinoic acid, all-trans-retinoic acid and all-trans-retinol in mouse embryos using on-line solid-phase extraction and column switching in combination with electrochemical detection has been developed. The method was validated using retinoids in albumin solutions and 13-cis-acitretin was used as internal standard. About 370 microliters of albumin solution was injected on a 10 x 2.1-mm I.D. pre-column packed with Bondapak C18, 37-53-micron particles. The proteins were washed to waste within 5 min using as mobile phase, a 1:3 dilution of mobile phase 2, which consisted of acetonitrile-methanol-2% ammonium acetate-glacial acetic acid (79:2:16:3, v/v). Components retained on the pre-column were back-flushed to and separated on the 250 x 4.6-mm I.D. Suplex pKb-100 analytical column using mobile phase 2. The retinoids were detected electrochemically at +750 mV using a coulometric electrochemical detector. The total analysis time was about 20 min. Recoveries were in the range of 86-103%. The mass limits of detection were about 10 pg and 25 pg for the retinoic acids and all-trans-retinol, respectively. The intra-assay precision, reported as relative standard deviation, was in general better than 4% (n = 6) for the four retinoids. Inter-assay precision was in the range 3-4% (n = 10). The method was applied for determination of endogenous retinoids in 9.5 day-old mouse embryos. A 340-microliter solution containing 100 microliters of embryo homogenate (1.64 embryos) was analyzed. The concentrations of all-trans-retinol and all-trans-retinoic acid were found to be 279 pg per embryo and 75.8 pg per embryo, respectively. The amount of 13-cis-retinoic acid and 9-cis-retinoic acid was below the detection limit.

Animals↗
PubMed2003

Chip-based solid-phase extraction pretreatment for direct electrospray mass spectrometry analysis using an array of monolithic columns in a polymeric substrate.

An array of eight porous monolithic columns, prepared in a Zeonor polymeric chip by UV-initiated polymerization of butyl methacrylate and ethylene dimethacrylate, was tested for solid-phase extraction (SPE) cleanup of biological samples prior to directly coupled electrospray mass spectrometry (ESI-MS). The chip, fabricated by hot embossing and thermal bonding, consists of eight parallel channels (10 mm long, 360 microm i.d.) connected via external fused-silica capillaries. The monomer mixture was aspirated simultaneously into the eight channels using a homemade vacuum manifold device and polymerized in parallel for 20 min under UV irradiation. The porous monolithic columns were then characterized by scanning electron microscopy and evaluated by ESI-MS applications with respect to sample capacity, recovery, reproducibility of peak area or peak height ratios, and linearity between peak height ratio and concentration using imipramine as a pharmaceutical test compound. The average sample capacity was estimated to be 0.30 microg with a relative standard deviation (RSD) of 26.5% for the eight monolithic columns on the same polymeric chip. For two chips prepared using the same monomer mixture, the difference in average sample capacity was 7.0%. The average recovery for the eight monolithic SPE columns on the same chip was 79.1% with an RSD of 7.9%. Using imipramine-d3 as an internal standard, the RSD of peak height ratios for the eight different columns was 2.0% for a standard solution containing 1 microg/mL imipramine. A linear calibration curve (R2 = 0.9995) was obtained for standard aqueous solutions of imipramine in the range from 0.025 to 10 microg/mL. To demonstrate the analytical potential of the chip-based SPE system, two different types of real-world samples including human urine sample and P450 drug metabolism incubation mixture were tested. Similar to standard aqueous solution, a linear correlation (R2 = 0.9995) was also found for human urine sample spiked with imipramine in the range of 0.025-10 microg/ mL. When aliquots of a human urine sample spiked with 1 microg/mL imipramine were loaded onto eight different monolithic columns, the RSD of peak height ratios was 3.8%. For a P450-imipramine incubation mixture, the formation of the N-demethylated metabolite (m/z 267.2) and the monohydroxylated metabolite (m/z 297.2) of imipramine was observed following chip-based monolithic SPE sample cleanup and preconcentration.

Journal Article↗
PubMed2001

Determination of phenols, flavones, and lignans in virgin olive oils by solid-phase extraction and high-performance liquid chromatography with diode array ultraviolet detection.

A simple analytical method for the quantitative determination of phenols, flavones, and lignans in virgin olive oils was developed. The polar fraction was isolated from small amounts of oil sample (2.5 g) by solid-phase extraction (SPE) using diol-phase cartridges, and the extract was analyzed by reversed-phase HPLC coupled with diode array UV detection. Chromatographic separation of pinoresinol, cinnamic acid, and 1-acetoxypinoresinol was achieved. Repeatability (RSD < 6.5%), recovery (> 90%), and response factors for each identified component were determined. SPE on amino-phase cartridges was used for isolating acidic phenols and as an aid for phenol identification. For the first time, 2-(4-hydroxyphenyl)ethyl acetate was detected in olive oils. The aldehydic structure of the ligstroside aglycon was confirmed by NMR spectroscopy. The colorimetric determination of total o-diphenolic compounds by reaction with molybdate was consistent with their HPLC determination. Differences between results obtained by liquid-liquid extraction and SPE were not statistically significant.

Chromatography, High Pressure Liquid↗
PubMedDate not supplied

Determination of 17 beta-estradiol and its metabolites in sewage effluent by solid-phase extraction and gas chromatography/mass spectrometry.

The paper describes a simple and quantitative method for monitoring non-conjugated 17 beta-estradiol (E2) and its metabolites estrone (E1) and estriol (E3) as environmental contaminants in municipal sewage effluents. Estrogens were preconcentrated and cleaned up by solid-phase extraction using a reversed-phase C18 cartridge. They were derivatized with pentafluoropropionic acid anhydride, and the products were analyzed by gas chromatography/mass spectrometry. Recoveries from spiked distilled water and sewage were better than 87% at fortification levels of 100 and 20 ng/L. For a 1 L sewage sample and a concentration factor of 5000, detection limits were 5 ng/L for E1 and E2 and 10 ng/L for E3. In a brief survey of Canadian wastewater, these estrogens were detected in many raw sewage and effluent samples at concentrations ranging from 6 to 109 ng/L for E1, from < 5 to 15 ng/L for E2, and from < 10 to 250 ng/L for E3.

Environmental Pollutants↗
PubMed2001

Solid-phase extraction and GC-MS analysis of THC-COOH method optimized for a high-throughput forensic drug-testing laboratory.

In order to facilitate the confirmation analysis of large numbers of urine samples previously screened positive for delta9-tetrahydrocannabinol (THC), an extraction, derivitization, and GC-MS analysis method was developed. This method utilized a positive pressure manifold anion-exchange polymer-based solid-phase extraction followed by elution directly into the automated liquid sampling (ALS) vials. Rapid derivitization was accomplished using pentafluoropropionic anhydride/pentafluoropropanol (PFPA/PFPOH). Recoveries averaged 95% with a limit of detection of 0.875 ng/mL with a 3-mL sample volume. Performance of 11-nor-delta9-tetrahydrocannabinol-9-carboxylic acid (THC-COOH)-d3 and THC-COOH-d9 internal standards were evaluated. The method was linear to 900 ng/mL THC-COOH using THC-COOH-d9 with negligible contribution from the internal standard to very weak samples. Excellent agreement was seen with previous quantitations of human urine samples. More than 1000 human urine samples were analyzed using the method with 300 samples analyzed using an alternate qualifier ion (m/z 622) after some interference was observed with a qualifier ion (m/z 489). The 622 ion did not exhibit any interference even in samples with interfering peaks present in the 489 ion. The method resulted in dramatic reductions in processing time, waste production, and exposure hazards to laboratory personnel.

Chemistry Techniques, Analytical↗
PubMed2006

Analysis of hormonal steroids in fish plasma and bile by coupling solid-phase extraction to GC/MS.

An analytical procedure for the simultaneous determination of twelve endogenous steroids (testosterone, androstenedione, 17beta-estradiol, estrone, pregnenolone, progesterone, dihydroandrostenedione, dihydrotestosterone, 11alpha-ketotestosterone, 17alpha-hydroxyprogesterone, 17alpha-hydroxypregnenolone, 17alpha,20beta-dihydroxy-4-pregnen-3-one) in plasma and bile samples by solid-phase extraction (SPE) and gas chromatography/mass spectrometry (GC-MS) has been developed. After enzymatic hydrolysis for bile samples only, samples were concentrated and purified using two successive SPE (C(18) and NH(2)) cartridges. Analytes were derivatized with a mixture of N-methyl-N-(trimethylsilyl)trifluoroacetamide (MSTFA) / mercaptoethanol / ammonium iodide (NH(4)I) and determined by GC-MS in selective ion monitoring mode. For most of the steroids monitored, recoveries were in the range 90-120% in plasma and in the range 60-70% in bile, and the reproducibility was below 10% for the complete procedure. Limits of detection obtained ranged from 0.1 to 0.4 ng/g in fish plasma and from 1.6 to 14 ng/g in fish bile. The developed method was successfully applied to the determination of plasma steroids in flounders (Platichthys flesus) collected from two French estuaries.

Animals↗
PubMedDate not supplied

Combined reversed phase and anion exchange solid phase extraction for the assay of the neuroprotectant NBQX in human plasma and urine.

A combination of reversed phase and anion exchange solid phase extraction (SPE) was investigated for the liquid chromatographic assay of the neuroprotectant agent NBQX in human plasma and urine. Reversed phase SPE alone using a variety of phases failed to yield sufficiently pure extracts for the assay of plasma in the low ng/mL concentration range using UV detection. However, using Bond Elut Certify II SPE columns containing a mixture of reversed phase and anion exchange functionalities markedly improved the purity of plasma extracts. Furthermore, a change of detector wavelength from UV (294 nm) to the visible region (380 nm) removed some minor interfering peaks originating from plasma. Using optimized SPE conditions with an extraction recovery of 92.3% and a high performance liquid chromatographic procedure with Lichrospher C18 as the stationary phase, the lower limit of quantitation in human plasma was 2 ng/mL (corresponding to 0.75 ng injected on-column). Intra-assay coefficients of variation ranged from 9.6% at 2 ng/mL to 1.3% at 10 ng/mL. A similar SPE procedure was applied to human urine with acceptable recovery (88.3%), but an analytical column of different selectivity (Chromspher B C18) was necessary in order to avoid interference from the urine. The limit of quantitation for the urine assay was 25 ng/mL and the intra-assay precision ranged from 4.6% at 25 ng/mL to 2.2% at 500 ng/mL.

Chromatography, High Pressure Liquid↗