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PubMed1994

High-performance liquid chromatographic assay for sematilide in plasma using solid-phase extraction microcolumn technology.

A simple and sensitive high-performance liquid chromatographic assay for quantification of sematilide in rabbit plasma was developed. After extraction of samples via solid-phase extraction on C8 microcolumns, baseline resolution was achieved on a reversed-phase 5 microns Inertsil ODS-2 column using isocratic conditions with mobile phase consisting of water-glacial acetic acid-acetonitrile-methanol-triethylamine (93.5:4.0:1.5:0.5:0.5) and UV detection at 254 nm. The assay did not require evaporation or reconstitution steps. The injection interval was 8 minutes. The inter-day coefficient of variation for replicate analysis of spiked samples was less than 7.6% and the accuracy was more than 97% over the standard curve range (0.128 to 3.191 microM) using 0.5 ml of plasma. The assay has been successfully applied to pharmacokinetic studies in rabbits.

Animals↗
PubMedDate not supplied

Recovery of atrazine, bromacil, chlorpyrifos, and metolachlor from water samples after concentration on solid-phase extraction disks: interlaboratory study.

An interlaboratory comparison was conducted in 1997 and 1998 to examine the feasibility of using C18 solid-phase extraction disks (Empore) to simultaneously determine the herbicides atrazine, bromacil, and metolachlor and the insecticide chlorpyrifos in water samples. A common fortification source and sample processing procedure were used to minimize variation in initial concentrations and operator inconsistencies. The protocol consisted of paired laboratories in different locations coordinating their activities and shipping fortified water samples (deionized or local surface water) or Empore disks on which the pesticides had been retained and then quantitating the analytes by a variety of gas chromatographic methods. Average recoveries from all laboratories were >80% for atrazine, bromacil, and metolachlor, and >70% for chlorpyrifos. Detection of bromacil was unachievable at some locations because of chromatographic problems. Shipping samples between cooperating laboratories did not affect the recovery of atrazine, chlorpyrifos, or metolachlor in either matrix. Recoveries tended to be higher from disks shipped to cooperating laboratories compared with those from fortified water. Shipping disks eliminated many problems associated with the shipment of water samples, such as bottle breakage, higher shipping cost, and possible pesticide degradation. Recoveries of bromacil and metolachlor were lower from fortified surface water samples than from fortified deionized water samples. This collaborative research demonstrated that pesticides in water samples can be concentrated on solid-phase extraction disks at one location and quantitated under diverse analytical conditions at another location. The extraction efficiencies of the disks were comparable with or better than the recoveries obtained from the shipped water samples, and the problems associated with shipping water samples were eliminated by using the disks.

Acetamides↗
PubMed2004

Simultaneous determination of albiflorin and paeoniflorin in rat urine by solid-phase extraction and high-performance liquid chromatography following oral administration of Si-Wu decoction.

A high performance liquid chromatographic method (HPLC), together with solid phase extraction (SPE), was developed for simultaneous determination of albiflorin and paeoniflorin in rat urine after oral administration of Si-Wu decoction. The samples were pretreated with solid phase extraction using Extract-Cleantrade mark cartridges. Analysis of the extract was performed on a reversed-phase C18 column and a mobile phase made up of acetonitrile and 0.03% formic acid (17:83, v/v). UV detection was set at 230 nm. The assay was linear over the range 2.625-52.50 mg/mL for albiflorin and 3.875-77.50 microg/mL for paeoniflorin. The average percentage recoveries of three spiked urines were 97.01 +/- 3.32 and 102.32 +/- 6.97 for albiflorin and paeoniflorin, respectively. The intra-day precision (RSD) ranged from 0.21 to 1.79% at concentrations of 4.20, 10.50, 26.25 and 39.375 microg/mL of albiflorin and 0.12 to 2.92% at concentrations of 3.875, 10.85, 23.25 and 58.125 microg/mL of paeoniflorin, and inter-day precision (RSD) was from 1.02 to 1.86% for albiflorin and 0.94 to 3.30% for paeoniflorin, at the same four concentrations. This method was applied in order to analyze albiflorin and paeoniflorin in rat urine following oral administration of traditional Chinese medicinal preparation of Si-Wu decoction.

Animals↗
PubMed1993

Solid-phase extraction followed by high-performance liquid chromatographic analysis for monitoring herbicides in drinking water.

A multiresidue analytical method based on C18 solid-phase extraction and one-run HPLC determination has been developed for the analysis of eleven acidic, neutral and weak basic herbicides in drinking water. A 1-1 sample of water was preconcentrated by passage through a 500-mg C18 solid phase extraction column. The retained compounds were eluted from the column with 1 ml of methanol. After concentration of the extract the pesticides were separated and quantified by reversed-phase HPLC with UV detection. Bentazone, 2,4-D, MCPA, fluazifop-acid, metoxuron, monolinuron, metobromuron, diuron, linuron, atrazine and simazine were determined simultaneously in a single run on a C18 HPLC column. Reanalyses of the sample extracts on a second cyano column were used to confirm the identity of the neutral and basic compounds. The limit of determination, defined as four times the baseline noise, varied between 0.01 microgram/l and 0.1 microgram/l depending on the compound, the detection sensitivity of the instrument and the type of HPLC column used.

Chromatography, High Pressure Liquid↗
PubMed1991

Separation and determination of saturated very-long-chain free fatty acids in plasma of patients with adrenoleukodystrophy using solid-phase extraction and high-performance liquid chromatographic analysis.

An improved method was developed for the isolation of very-long-chain free fatty acids (VLCFFAs) in plasma and their separation and determination by high-performance liquid chromatography (HPLC). The method includes sample clean-up using solid-phase extraction, fluorophoric labelling of the FFAs and reversed-phase HPLC separation. The solid-phase extraction was carried out with aminopropyl-bonded phase columns. The FFAs were then derivatized with 9-anthryldiazomethane (fluorescent) reagent and separated by HPLC on an RP-18 column with methanol as the mobile phase. Using this method, the concentrations of C20:0, C22:0, C24:0 and C26:0 were determined in the plasma of five adrenoleukodystrophy (ALD) patients, one obligatory heterozygote, four healthy male volunteers and one child with cerebral leukodystrophy but without any other ALD symptoms. Statistically significant differences were found in the levels of C24 and C26 and in the ratios C24/C22 and C26/C22 in ALD patients and in normal controls. The values were higher in patients with X-ALD. This method therefore provides a rapid and accurate procedure for the laboratory confirmation of X-ALD.

Adrenoleukodystrophy↗
PubMed1993

High-performance liquid chromatography versus solid-phase extraction for post-derivatization cleanup prior to gas chromatography-electron-capture negative-ion mass spectrometry of N1,N3-bis-(pentafluorobenzyl)-N7- (2-[pentafluorobenzyloxy]ethyl)xanthine, a product derived from an ethylene oxide DNA adduct.

N7-(2-Hydroxyethyl)xanthine (N7-HEX), as a standard, has been measured at the low picomole level by the following sequence of steps: (1) derivatization with pentafluorobenzyl bromide; (2) post-derivatization sample cleanup by reversed-phase high-performance liquid chromatography (HPLC) or silica solid-phase extraction; and (3) separation/detection by gas chromatography electron-capture negative-ion mass spectrometry (GC-ECNI-MS). The average yield of product from the two sample cleanup procedures applied to 95 pg (0.48 pmol) of N7-HEX was comparable: 60% for HPLC; 56% for solid-phase extraction. The reaction blanks (0 pg N7-HEX) showed an interfering GC-ECNI-MS peak after HPLC cleanup. This problem was not encountered with solid-phase extraction, which, along with its greater convenience, made it the preferred technique for post-derivatization sample cleanup.

Chromatography, High Pressure Liquid↗
PubMed2004

Synthesis and application of molecularly imprinted polymer on selective solid-phase extraction for the determination of monosulfuron residue in soil.

A novel sample clean-up procedure using molecularly imprinted polymer as the solid-phase extraction material for the determination of monosulfuron residue in soil samples has been developed. The molecularly imprinted polymer (MIP) was synthesized by non-covalent method with monosulfuron as the template. The selectivity and affinity of the MIP was evaluated by equilibrium adsorption and HPLC experiments, which demonstrated that the MIP has specific affinity for the template. The template-MIP interaction was studied by investigating the influence of different mobile phases on the retention of the template, which provided basic knowledge for the selection of the washing and elution solutions in the molecularly imprinted solid-phase extraction (MISPE) process. The study indicated that polar organic solvents with hydrogen bonding abilities have stronger eluting strength for the monosulfuron. After the MISPE procedure, a clean baseline was obtained in the HPLC quantification analysis. The recoveries of the method using the combination of MISPE and HPLC were above 93% and the R.S.D. was less than 3.2% in the soil sample determinations. Low detection limit (0.08 microg g(-1), when defined as 3 times of the noise) was also obtained in the method evaluation study.

Chromatography, High Pressure Liquid↗
PubMed2000

Stability of sulfonated derivatives of benzene and naphthalene on disposable solid-phase extraction pre-columns and in an aqueous matrix.

The stability of 14 sulfonated benzene and naphthalene compounds was investigated using polymeric solid-phase extraction cartridges, based on the styrene-divinylbenzene polymer Isolute ENV+. Several different storage conditions were tested to carry out the stability study in polymeric cartridges, which included storage at room temperature, at 4 degrees C and at -20 degrees C, during a period of up to 3 months. An additional stability study was carried out, not with the polymeric solid matrix, but in an aqueous matrix. This study was performed storing the samples at 4 degrees C, during 2 months under three different conditions: acidifying the water sample to pH 2.5-3 with sulfuric acid, adding 1% of formaldehyde (additive used in waste water analyses), and storing the water sample at 4 degrees C without any additives. The extraction of the SPE process is analyzed by ion-pair chromatography-electrospray mass spectrometry, in the negative ion mode. This study showed that the stability of polar aromatic sulfonic acids on disposable polymeric cartridges and in the water matrix is related to temperature and pH, respectively. Target aromatic sulfonated compounds stored in polymeric solid-phase extraction cartridges, are more stable at lower temperatures. The target analytes showed also good stability when stored in water at acidic pH. From the different analytes studied, substituted naphthalenesulfonates suffered more degradation than mononaphthalenesulfonates or benzenesulfonates under the experimental conditions of this work.

Benzene↗
PubMed1984

High-performance liquid chromatographic (HPLC) separation and quantitation of endogenous glucocorticoids after solid-phase extraction from plasma.

This study describes a method for the extraction and simultaneous measurement of cortisone, cortisol and corticosterone using dexamethasone as an internal standard. Solid-phase extraction of plasma steroids with C18 columns allows the samples to be extracted, washed and concentrated in a single step with minimal sample handling and without the use of large volumes of organic solvents. HPLC separation of the steroids is accomplished within 10 min and the individual steroid peaks are quantitated by UV detection at 239 nm. This assay was examined for linearity, extraction efficiency, precision and potential interference by commonly used drugs. Plasma values of glucocorticoids are reported for samples obtained from human subjects as well as from rats. HPLC was also compared to RIA for the determination of plasma levels of corticosterone in the rat. Solid-phase extraction and assay by HPLC provides a rapid and specific method for the simultaneous determination of plasma glucocorticoids.

Animals↗
PubMed2004

High-throughput pharmacokinetics screen of VLA-4 antagonists by LC/MS/MS coupled with automated solid-phase extraction sample preparation.

Automation of plasma sample preparation for pharmacokinetic studies on VLA-4 antagonists has been achieved by using 96-well format solid-phase extraction operated by Beckman Coulter Biomek 2000 liquid handling system. A Biomek 2000 robot is used to perform fully automated plasma sample preparation tasks that include serial dilution of standard solutions, pipetting plasma samples, addition of standard and internal standard solutions, performing solid-phase extraction (SPE) on Waters OASIS 96-well plates. This automated sample preparation process takes less than 2 h for a typical pharmacokinetic study, including 51 samples, 24 standards, 9 quality controls, and 3-6 dose checks with minimal manual intervention. Extensive validation has been made to ensure the accuracy and reliability of this method. A two-stage vacuum pressure controller has been incorporated in the program to improve SPE efficiency. This automated SPE sample preparation approach combined with liquid chromatography coupled with the high sensitivity and selectivity of tandem mass spectrometry (LC/MS)/MS has been successfully applied on both individual and cassette dosing for pharmacokinetic screening of a large number of VLA-4 antagonists with a limit of quantitation in the range of 1-5 ng/ml. Consequently, a significant throughput increase has been achieved along with an elimination of tedious labor and its consequential tendency to produce errors.

Animals↗
PubMed1999

Sensitive method for the determination of baclofen in plasma by means of solid-phase extraction and liquid chromatography-tandem mass spectrometry.

A simple and sensitive method for the determination of baclofen in plasma is described. Baclofen and the internal standard, KM 08205, were isolated from plasma by solid-phase extraction using C18 material. After separation by reversed-phase liquid chromatography, the analytes were detected with tandem mass spectrometry. The extraction procedure was optimised regarding the solid-phase extraction material, the pH in the conditioning solution and the washing volume. The method was proven to be selective and sensitive with an absolute recovery of about 95%, a relative standard deviation below 5% and a limit of quantification of 10 nmol/1.

Baclofen↗
PubMed1997

Continuous cleanup/preconcentration procedure of hydroxyvitamin D3 metabolites in plasma as an alternative to batch solid-phase extraction.

A continuous automatable cleanup procedure coupled on-line with a liquid chromatograph and UV detector for hydroxyvitamin D3 metabolites [24,25-(OH)2, 1,25-(OH)2 and 25-(OH)] as an alternative to batch solid-phase extraction is reported. The method, based on continuous solid-phase cleanup/preconcentration of the analytes, requires only the passage of the sample through a single minicolumn, which also results in a preconcentration effect which increases the sensitivity. The proposed method is also compared with a conventional batch, two-step solid-phase extraction method previously improved by the authors. The method has been checked by applying it to plasma samples spiked with the target analytes (linear range between 0.05 and 100 ng/ml with coefficient of variation values lower than 6.5%) and acceptable recoveries ranging between 94.6 and 101% have been obtained. The sampling frequency was 4 h-1.

24,25-Dihydroxyvitamin D 3↗
PubMed2002

Toward a microchip-based solid-phase extraction method for isolation of nucleic acids.

A silica-based solid-phase extraction system suitable for incorporation into a microchip platform (nu-total analytical system; nu-TAS) would find utility in a variety of genetic analysis protocols, including DNA sequencing. The extraction procedure utilized is based on adsorption of the DNA onto bare silica. The procedure involves three steps: (i) DNA adsorption in the presence of a chaotropic salt, (ii) removal of contaminants with an alcohol/water solution, and (iii) elution of the adsorbed DNA in a small volume of buffer suitable for polymerase chain reaction (PCR) amplification. Multiple approaches for incorporation of this protocol into a microchip were examined with regard to extraction efficiency, reproducibility, stability, and the potential to provide PCR-amplifiable DNA. These included packing microchannels with silica beads only, generating a continuous silica network via sol-gel chemistry, and combinations of these. The optimal approach was found to involve immobilizing silica beads packed into the channel using a sol-gel network. This method allowed for successful extraction and elution of nanogram quantities of DNA in less than 25 min, with the DNA obtained in the elution buffer fraction. Evaluation of the eluted DNA indicated that it was of suitable quality for subsequent amplification by PCR.

DNA↗
PubMed1993

Gas chromatographic determination of zopiclone in plasma after solid-phase extraction.

A gas chromatographic technique for determining zopiclone based on a solid-phase extraction procedure with C18 cartridge for sample clean-up is presented. Quantification can be achieved with 1 ml of plasma. The method uses prazepam as internal standard. Zopiclone is separated on a 5% phenyl methyl silicone analytical column and detected with an electron-capture detector, which consequently allows a limit of quantitation of 2 micrograms/l. It is thus simple, rapid, sensitive and linear over the range 5-2000 micrograms/l.

Azabicyclo Compounds↗
PubMed2005

Determination of herbicides in mineral and stagnant waters at ng/L levels using capillary electrophoresis and UV detection combined with solid-phase extraction and sample stacking.

In this work, the combined use of solid-phase extraction (SPE) and on-line preconcentration strategies as normal stacking mode (NSM) and stacking with matrix removal (SWMR) for the ultrasensitive and simultaneous capillary electrophoresis-ultraviolet analysis (CE-UV) of five triazolopyrimidine sulfonanilide pesticides (i.e., diclosulam, cloransulam-methyl, flumetsulam, metosulam and florasulam) in different types of water is investigated. An adequate separation electrolyte for the separation and stacking of these pesticides was obtained, considering also its compatibility with MS detection, which consisted of 24 mM formic acid and 16 mM ammonium carbonate at pH 6.4. It was observed that the use of this running buffer together with the SWMR preconcentration method provided the best results in terms of sensitivity (between 6.54 and 11.9 microg/L) and peak efficiency (up to 550000 theoretical plates per meter, NTP/m). When this on-line preconcentration procedure was combined with an off-line sample preconcentration step as SPE using C18 cartridges, the selected herbicides could be detected in the ng/L range. The optimized SPE-SWMR-CE-UV method was applied to the determination of the selected group of pesticides in spiked and non-spiked mineral and stagnant waters. Recoveries ranged between 55 and 110% and limits of detection between 131 and 342 ng/L. This work shows the great possibilities of the combined use of SPE-SWMR-CE-UV to overcome the sensitivity problems usually linked to CE analysis.

Electrophoresis, Capillary↗
PubMed2005

Analysis of triazolopyrimidine herbicides in soils using field-enhanced sample injection-coelectroosmotic capillary electrophoresis combined with solid-phase extraction.

In this work, a combined methodology using off-line solid-phase extraction (SPE), on-line field-enhanced sample injection (FESI) and coelectroosmotic capillary electrophoresis with UV detection (CE-UV) is developed for the trace analysis of five triazolopyrimidine sulfonanilide pesticides (i.e., flumetsulam, florasulam, cloransulam-methyl, diclosulam and metosulam). An adequate background electrolyte (BGE) was obtained for the separation of these pesticides using hexadimethrine bromide (HDB) as electroosmotic flow (EOF) modifier. This BGE consisted of 0.00042% HDB, 11 mM formic acid, 16 mM ammonium carbonate and 2.5 mM alpha-CD solution at pH 7.6. The use of this running buffer together with the FESI preconcentration method provided limits of detection (LODs) in the low microg/L range (i.e., between 13.0 and 31.5 microg/L). The optimized FESI-CE-UV method was combined with off-line SPE using C(18) cartridges and applied to the determination of the selected group of pesticides in soil samples. Recovery percentages ranged between 50 and 84% in these samples with LODs between 18 and 34 microg/kg. This work shows the great possibilities of the combined use of SPE-FESI-CE-UV to improve CE sensitivity allowing the achievement of LODs similar to other analytical techniques as GC or HPLC.

Anilides↗
PubMed2003

Simple liquid chromatography method for the rapid simultaneous determination of prednisolone and cortisol in plasma and urine using hydrophilic lipophilic balanced solid phase extraction cartridges.

This article describes the development and validation of a simple solid phase extraction (SPE) and HPLC method for the extraction and the specific determination of prednisolone and hydrocortisone (cortisol) in both plasma and urine using one washing step with Oasis hydrophilic lipophilic balanced (HLB) cartridges (1 ml/30 mg, 30 microm). Recoveries of prednisolone and cortisol from plasma and urine exceeded 82%. The limit of quantification (LOQ) in plasma and urine was 9.9 and 6.7 ng/ml for cortisol, respectively, and 11.6 and 8.0 ng/ml for prednisolone, respectively. The intraday and interday precision (measured by CV%) for both prednisolone and cortisol in both plasma and urine was always less than 7%. The accuracy (measured by relative error %) for both prednisolone and cortisol in both plasma and urine was always less than 8%. The advantages of the developed method are the use of a one step washing SPE utilising HLB cartridges which do not suffer the drying out problems of conventional SPE cartridges and the time saving when compared with solvent extraction (SE), in addition to the simultaneous determination of prednisolone and cortisol in both plasma and urine.

Chromatography, High Pressure Liquid↗
PubMed1997

Application of solid-phase extraction to the preconcentration of metallothionein and metals from physiological fluids.

Solid-phase extraction (SPE) with covalent affinity chromatography with thiol-disulphide interchange (CAC-TDI) gels as sorbents were used for the preconcentration of Cd-thionein (Cd-Th), Zn-thionein (Zn-Th) and Cu-thionein (Cu-Th) proteins and Cd, Zn or Cu bonded with metallothioneins (MTs) from water, plasma and human urine samples. An indirect method of quantitation of MTs, based on the analysis of metal content, for the determination of MT in human body fluids is described. In experiments, different types of CAC-TDI gels were tested. The results showed a satisfactory correlation between the concentration of MT proteins added to water or physiological fluids and the concentration of protein indirectly determined via the concentration of metals by atomic absorption spectrometry.

Adult↗