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At least 793 records · Page 44Linked to original sources
PubMed1994

Selective solid-phase extraction of urinary 2,3-dinor-6-ketoprostaglandin F1 alpha for determination with radioimmunoassay.

This paper describes a method for selective two-step solid-phase extraction of urinary 2,3-dinor-6-ketoprostaglandin F1 alpha for reliable determination with radioimmunoassay. In the immunoreactivity profile of non-selectively extracted urine after HPLC separation, over 90% of the total 2,3-dinor-6-ketoprostaglandin F1 alpha immunoreactivity consisted of interfering material coeluting with 6-ketoprostaglandin F1 alpha and 2,3-dinor-6-ketoprostaglandin F1 alpha. Among the alkyl silica sorbents studied (methyl, butyl, octyl, and octadecyl), an efficient separation of 2,3-dinor-6-ketoprostaglandin F1 alpha from 6-ketoprostaglandin F1 alpha and the lowest immunoreactive concentration of analyte were achieved in extraction on the methyl silica sorbent by elution of 2,3-dinor-6-ketoprostaglandin F1 alpha with chloroform: hexane (85:15, v/v) from the cartridge. The proportion of specific immunoreactivity could be further increased by two-step extraction of sample on methyl silica cartridges, first at pH 3 and then at pH 10 using diethyl ether:hexane (85:15, v/v) and chloroform as eluent, respectively. After this, a high correlation was found with concentrations of samples determined by radioimmunoassay using three different antisera. A significant correlation of values was also observed between samples measured by radioimmunoassay and those measured by GC-MS. The values of 12-h excretion of 2,3-dinor-6-ketoprostaglandin F1 alpha in eight volunteers (268 +/- 204 ng/g creatinine, mean +/- SD) as well as the inhibitory effect of acetylsalicylic acid (74 +/- 12%) are in accordance with those reported in the literature. This selective extraction procedure provides a high validity in radioimmunoassay without requiring subsequent TLC or HPLC purification.

6-Ketoprostaglandin F1 alpha↗
PubMed1994

Determination of the coumarin anticoagulant phenprocoumon and metabolites in human plasma, urine and breast milk by high-performance liquid chromatography after solid-phase extraction.

The coumarin anticoagulant phenprocoumon (PH) and metabolites (6-, 7- and 4'-hydroxyphenprocoumon) were analysed in plasma and urine samples from anticoagulated patients using solid-phase extraction and high-performance liquid chromatography with reversed-phase columns and ultraviolet and fluorescence detection; a simpler handling of samples, higher selectivity, precision, accuracy and analytical recovery were obtained compared to analysis using liquid-liquid extraction. Similarly, a method for the analysis of PH in human breast milk was developed to assess the passage of anticoagulants into breast milk in anticoagulated lactating women.

Anticoagulants↗
PubMed2004

New hydrophilic polymeric resin based on 4-vinylpyridine-divinylbenzene for solid-phase extraction of polar compounds from water.

A 4-vinylpyridine-divinylbenzene (VP-DVB) resin was synthesized to be used for on-line solid-phase extraction process and it was tested for a group of polar compounds. The high specific surface area and the nitrogen content of the VP-DVB sorbent increased the interactions with the polar analytes in the preconcentration process. The sorbent enabled 100 ml of water to be concentrated with recoveries higher than 70% for several polar compounds (including phenol) except for oxamyl (55%) and methomyl (43%). The method was used to analyse water samples by liquid chromatography and UV detection. Linearity was good and detection limits were 0.1-0.2 microg l(-1) for all compounds. Several tap and river water and waste water treatment plant samples were analyzed; phenol and (4-chloro-2-methyl-phenoxy)acetic acid (MCPA) were tentatively determined in some samples.

Polymers↗
PubMed2006

Development and validation of a method for the quantitation of Delta9 tetrahydrocannabinol in human plasma by high performance liquid chromatography after solid-phase extraction.

A high performance liquid chromatography (HPLC) procedure for the determination of Delta9 tetrahydrocannabinol (THC) in human plasma is described. A two-step solid-phase extraction on CN cartridges was coupled with a reversed phase HPLC system. THC was eluted using a mobile phase composed of methanol, acetonitrile and tetrabutylammonium perchlorate solution (0.005 M, pH 3.2), through a C18 Nucleosil column and detected at a wavelength of 215 nm. Calibration curve was linear over the range 5-100 ng/ml with a lower limit of quantification validated at 5 ng/ml. Extraction recovery using the developed extraction procedure was higher than 85%. This method is presently used for the quantification of THC in plasma samples from regular cannabis smokers.

Calibration↗
PubMed1998

Gas chromatographic determination of aromatic amines in water samples after solid-phase extraction and derivatization with iodine. I. Derivatization.

A new method for the selective determination of aromatic amines is presented, which is based on the solid-phase extraction at pH 9 and subsequent derivatization of the analytes to the corresponding iodobenzenes. These can selectively and sensitively be determined with gas chromatography and electron-capture detection. Separation of at least 30 compounds in a single chromatographic run in 30 min is possible. With this method, 56 aromatic amines were investigated, and only in six cases no derivatives were obtained. Limits of quantitation were between 0.5 and 8 micrograms 1(-1), but may still be lowered with higher sample volumes or different injection techniques. The application to water samples revealed the suitability for the investigation of ground, leachate and wastewater.

Amines↗
PubMed2001

Quantitation of promethazine and metabolites in urine samples using on-line solid-phase extraction and column-switching.

A chromatographic method for the quantitation of promethazine (PMZ) and its three metabolites in urine employing on-line solid-phase extraction and column-switching has been developed. The column-switching system described here uses an extraction column for the purification of PMZ and its metabolites from a urine matrix. The extraneous matrix interference was removed by flushing the extraction column with a gradient elution. The analytes of interest were then eluted onto an analytical column for further chromatographic separation using a mobile phase of greater solvent strength. This method is specific and sensitive with a range of 3.75-1400 ng/ml for PMZ and 2.5-1400 ng/ml for the metabolites promethazine sulfoxide, monodesmethyl promethazine sulfoxide and monodesmethyl promethazine. The lower limits of quantitation (LLOQ) were 3.75 ng/ml with less than 6.2% C.V. for PMZ and 2.50 ng/ml with less than 11.5% C.V. for metabolites based on a signal-to-noise ratio of 10:1 or greater. The accuracy and precision were within +/- 11.8% in bias and not greater than 5.5% C.V. in intra- and inter-assay precision for PMZ and metabolites. Method robustness was investigated using a Plackett-Burman experimental design. The applicability of the analytical method for pharmacokinetic studies in humans is illustrated.

Humans↗
PubMed1998

Solid-phase extraction of 18beta-glycyrrhetinic acid from plasma and subsequent analysis by high-performance liquid chromatography.

A new method is described for the solid-phase extraction of 18beta-glycyrrhetinic acid from plasma or serum, with subsequent analysis by HPLC. New aspects of the method include the use of commercially available 18alpha-glycyrrhetinic acid as the internal standard and the use of a Bond Elut C2 (ethyl) extraction column, to avoid the need to use large volumes of organic solvent to elute the isolates from the columns. Separation was achieved on a Shandon Hypersil BDS C18 analytical column, with a mobile phase consisting of acetonitrile-0.02 M phosphate buffer, pH 5.7 (55:45, v/v). The column effluent was monitored at 248 nm. Compared with previous methods, the procedure is much easier to carry out, whereas the sensitivity (limit of detection, 10 ng/ml, and limit of quantitation, 50 ng/ml), the precision (0.3-6.2%) and the accuracy (97.2-101.9%) are of the same order of magnitude.

Calibration↗
PubMed1998

Solid-phase extraction method with high-performance liquid chromatography and electrochemical detection for the quantitative analysis of oxycodone in human plasma.

A sensitive and reproducible solid-phase extraction (SPE) method for the quantification of oxycodone in human plasma was developed. Varian Certify SPE cartridges containing both C8 and benzoic acid functional groups were the most suitable for the extraction of oxycodone and codeine (internal standard), with consistently high (> or =80%) and reproducible recoveries. The elution mobile phase consisted of 1.2 ml of butyl chloride-isopropanol (80:20, v/v) containing 2% ammonia. The quantification limit for oxycodone was 5.3 pmol on-column. Within-day and inter-day coefficients of variation were 1.2% and 6.8% respectively for 284 nM oxycodone and 9.5% and 6.2% respectively for 28.4 nM oxycodone using 0.5-ml plasma aliquots.

Analgesics, Opioid↗
PubMed1999

Solid-phase extraction and high-performance liquid chromatographic determination of articainic and its metabolite articainic acid in human serum.

A new method is described using solid-phase extraction (SPE) for preconcentration of articaine and the metabolite articainic acid and high-performance liquid chromatography (HPLC) for the determination of both compounds in human serum. Articaine and articainic acid were extracted in one step with SDB-RPS disk cartridges after precipitation of the serum proteins by perchloric acid. The HPLC separation was then performed on a reversed-phase C8 column using phosphate buffer-acetonitrile (88:12, v/v). UV absorption at 274 nm was used for measuring the analytes with a low limit of quantitation of about 10 ng/ml, which is appropriate for pharmacokinetic studies of low dose submucosal injections of the local anaesthetic agent articaine hydrochloride in dentistry.

Anesthetics, Local↗
PubMed1998

Rapid determination of polycyclic aromatic hydrocarbons in tea infusion samples by high-performance liquid chromatography and fluorimetric detection based on solid-phase extraction.

This paper describes a method for the determination of PAHs in black, green and decaffeinated tea infusion samples. The method is based on the solid phase extraction of the PAHs using Sep-Pak vac tC-18 cartridges. The PAHs are then eluted from the cartridges with dichloromethane. Quantification and detection are carried out by HPLC with a fluorimetric detector using a program of excitation and emission wavelength pairs. Recoveries at concentration levels in the range 190-1790 ng l-1 were higher than 65% for all PAHs except dibenz[a,h]anthracene, for which it was around 54%. The mean content of PAHs was in the range 28.7-112 ng l-1 in the tea infusions, with relative standard deviations between 2 and 18% (n = 4).

Chromatography, High Pressure Liquid↗
PubMed1996

Solid-phase extraction and HPLC determination of levamisole hydrochloride in sheep plasma.

The anthelmintic, levamisole, was determined in sheep plasma by means of ion-pair solid-phase extraction (SPE) and reverse-phase liquid chromatography. The SPE columns were conditioned with 2 ml of methanol followed by 1 ml of octane sulphonic-acid buffer. After sample application, the columns were washed with 2 ml of the same buffer, followed by elution with 90/10 acetonitrile:buffer. A phenyl reverse-phase column (Spherisorb S5 Phenyl, 250 x 4.6 mm) was used with a mobile phase of acetonitrile: 0.005 M of octane sulphonic-acid sodium salt and 0.2% triethylamine in water, pH 3.5, 38/62. Extraction recoveries of 89-94% were achieved over the range from 100-3750 ng/ml. Accuracy and precision were better than 96% and 2.6%, respectively, over said range, with a limit of quantitation of 50 ng/ ml.

Animals↗
PubMedDate not supplied

Preparation of environmental samples for determination of sulfonylurea herbicides by solid-phase extraction using a polymeric sorbent.

An analytical procedure was developed for rapid determination of sulfonylurea herbicides in water or soil. Samples were prepared by solid-phase extraction using polymeric sorbents in cartridges and analyzed by liquid chromatography with photodiode array detection. Recoveries were consistent for all sample matrixes tested and were generally > 85%, except for tribenuron methyl (75%). Detection limits were < 100 ng/L for water samples.

Adsorption↗
PubMed1997

Determination of noscapine in human plasma using solid-phase extraction and high-performance liquid chromatography.

A simple, reliable high-performance liquid chromatographic (HPLC) method has been developed and validated for the determination of noscapine in human plasma. Noscapine and the internal standard, papaverine were quantitatively extracted from plasma onto disposable extraction columns by means of an automated off-line solid-phase extraction system and were separated onto a reversed-phase column. The method was found to be precise and accurate within the range 7.2-270 ng/ml. No endogenous compounds interfered with the assay.

Antitussive Agents↗
PubMed2000

Rapid determination of trace nitrophenolic organics in water by combining solid-phase extraction with surface-assisted laser desorption/ionization time-of-flight mass spectrometry.

A rapid technique for the screening of trace compounds in water by combining solid-phase extraction (SPE) with activated carbon surface-assisted laser desorption/ionization (SALDI) time-of-flight mass spectrometry is demonstrated. Activated carbon is used both as the sorbent in SPE and as the solid in the SALDI matrix system. This eliminates the need for an SPE elution process. After the analytes have been adsorbed on the surfaces of the activated carbon during SPE extraction, the activated carbon is directly mixed with the SALDI liquid and mass spectrometric analysis is performed. Trace phenolic compounds in water were used to demonstrate the effectiveness of the method. The detection limit for these compounds is in the ppb to ppt range.

Microchemistry↗
PubMed2003

Solid-phase extraction clean-up of soil and sediment extracts for the determination of various types of pollutants in a single run.

A new sample clean-up procedure based on solid-phase extraction (SPE) sorbents was proposed for the determination of pesticides, polycyclic aromatic hydrocarbons and polychlorinated biphenyls in soils and sediments. The main purpose of the research was to find a combination of sorbents for the SPE method that would permit the determination of many types of analytes (polycyclic aromatic hydrocarbons, polychlorinated biphenyls, N-, P- and Cl-containing pesticides) in a single run. Elution profiles for both the analytes and the interfering components were determined for several types of SPE sorbents (alumina, silica and surface-modified silica) and combinations of them. The efficiency of the clean-up method developed was evaluated using real soil samples.

Acetonitriles↗
PubMed2004

Rapid determination of chlorinated pesticides in fish by freezing-lipid filtration, solid-phase extraction and gas chromatography-mass spectrometry.

An analytical method has been developed for measuring 24 chlorinated pesticides in fish tissue samples. Extraction of chlorinated pesticides was carried out by ultrasonication using an acetone-n-hexane (5:2, v/v) mixture. Most of the lipids in the extract were eliminated by freezing-lipid filtration, prior to solid-phase extraction (SPE) cleanup. During freezing-lipid filtration, about 90% of the lipids extracted from the fish samples were easily removed without any significant losses of chlorinated pesticides. For purification, SPE using Florisil was shown to be more effective than silica. Quantification was performed using gas chromatography-mass spectrometry in the selected ion monitoring mode. Spiking experiments were carried out to determine the recovery, precision, and limits of detection (LODs) of the method. The overall recovery was above 80% in the spiked fish tissue sample at 100 ng/g level. The detection limits for chlorinated pesticides were ranged from 0.5 to 5 ppb, except for endosulfan I and II which was 20 ppb. The newly developed method is demonstrated to give efficient recoveries and LODs for detecting chlorinated pesticides spiked into fish tissue with high lipid content.

Animals↗
PubMed2004

Determination of arginine-vasotocin and isotocin in fish plasma with solid-phase extraction and fluorescence derivatization followed by high-performance liquid chromatography.

A new HPLC assay for plasma arginine-vasotocin (AVT) and isotocin (IT) determination based on fluorescence detection preceded by combination of solid-phase extraction (SPE) and fluorescence derivatization is presented. Plasma samples retained on solid support were purified and then derivatized by the fluorescent compound 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F). The peptide derivatives were eluted from cartridges, pre-concentrated and analyzed by HPLC system with fluorescent detection. The separation was carried out on a reversed-phase column with solvent gradient system. The assay was linear in the range 15-220 pmol ml(-1) for AVT r2=0.998 and 10-220 pmol ml(-1) for IT r2=0.996. The detection limits for AVT and IT were 0.8 and 0.5 pmol ml(-1) (3:1, signal-to-noise), respectively. The recoveries of derivatized hormones were in the range 89-93%. Both of the inter- and intra-day assay precision were below 5.5 and 9% for AVT and IT, respectively. The assay should be also applicable to plasma and tissue samples from other animals with only minor modification.

Animals↗
PubMedDate not supplied

Determination of benomyl, diphenyl, o-phenylphenol, thiabendazole, chlorpyrifos, methidathion, and methyl parathion in oranges by solid-phase extraction, liquid chromatography, and gas chromatography.

A simple and rapid method was developed for determination of benomyl, diphenyl (DP), o-phenylphenol (OPP), thiabendazole (TBZ), chlorpyrifos, methidathion, and methyl parathion in whole oranges. These compounds were extracted from a mixture of samples and anhydrous sodium acetate with ethyl acetate. The ethyl acetate extract was concentrated and cleaned up by passing through tandem solid-phase extraction columns consisting of anion-exchange and primary/secondary amine bonded silica. The eluate was concentrated and volume was adjusted with methanol for subsequent liquid chromatography (LC) and gas chromatography (GC). Benomyl (as methyl-2-benzimidazole carbamate, MBC), DP, OPP, and TBZ residues were determined by LC with fluorescence detection. Recoveries at 3 fortified levels (0.1, 1, and 10 micrograms/g) ranged from 63.9 to 97.4%, with coefficients of variation (CVs) of 1.6 to 15.5%. Limits of detection (LODs) were 0.01 microgram/g for DP, OPP, TBZ and 0.05 microgram/g for benomyl. Chlorpyrifos, methidathion, and methyl parathion residues were determined by GC with flame photometric detection. Recoveries ranged from 90.4 to 97.0%, with CVs of 2.1 to 5.9%. LODs were 0.005 microgram/g for chlorpyrifos and methyl parathion, and 0.01 microgram/g for methidathion.

Benomyl↗