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PubMed1997

Use of reduced sorbent bed and disk membrane solid-phase extraction for the analysis of pharmaceutical compounds in biological fluids, with applications in the 96-well format.

Significant improvements in the isolation of pharmaceutical compounds from plasma, serum and urine, have been achieved using ultra low mass sorbent bed and thin disk solid-phase extraction (SPE) material. The use of low sorbent masses or disk SPE material has allowed a significant reduction in solvent usage and extraction times. The reduction in solvent volumes required has allowed elution volumes to be reduced to as low as 30 microl with high and consistent analyte recovery. Several SPE RP-HPLC methods have been developed using these materials, including LC-MS methods. When the chromatographic conditions allow the eluent to be injected directly or injected after dilution with distilled water Empore disks are the extraction media of choice due to the materials low elution volume requirements. When operated in the 96-well microtitre format this micro-extraction provides a very efficient throughput and requires little sample manipulation.

Androstadienes↗
PubMed2002

Determination of hyperforin in human plasma using solid-phase extraction and high-performance liquid chromatography with ultraviolet detection.

Hyperforin is one of the most important active components in St. John's wort (Hypericum perforatum), a botanical dietary supplement used as an alternative treatment modality for mild to moderate depression. A solid-phase extraction (SPE) and an isocratic high-performance liquid chromatography (HPLC) analysis with ultraviolet (UV) detection were developed to determine hyperforin in human plasma samples. Benzo[k]fluoranthene was used as an internal standard. The absolute recovery for hyperforin was more than 89% for plasma concentrations ranging from 25 to 500 ng/ml. The linearity of calibration curves, inter-day and intra-day relative standard deviations were investigated. The limit of detection (LOD) of hyperforin was 4 ng/ml in plasma and the limit of quantitation (LOQ) was 10 ng/ml. Hyperforin concentrations in human plasma following St. John's wort administration were analyzed. The result suggests that this method is rapid, sensitive, reproducible and capable of quantitative analysis of hyperforin plasma concentrations.

Bridged Bicyclo Compounds↗
PubMed2004

On-line solid-phase extraction with surfactant accelerated on-column derivatization and micellar liquid chromatographic separation as a tool for the determination of biogenic amines in various food substrates.

A sensitive method was developed for the determination of biogenic amines at very low levels by combining solid phase extraction (SPE) and derivatization on-line with HPLC. The on-line derivatization and SPE were performed simultaneously on a commercially available ODS guard column, which was installed instead of the filling loop on the HPLC apparatus. Resolution of the peaks and quantification was further enhanced with micellar liquid chromatography and sensitization of the benzene ring absorption at 254 nm. Detection limits of the benzoyl derivatives of biogenic amines were in the vicinity of 0.1 microg L(-)(1), which is even lower than those obtained by fluorescence detection and is unparallel to any other UV approach. The correlation coefficients of determinations were 0.9850-0.9998. The method was applied to the determination of Biogenic amines, that is, putrescine, cadaverine, agmatine, tyramine, tryptamine, phenylethylamine, spermine, spermidine and histamine in fish, chicken, and wine samples. Recovery of the proposed method ranged from 94 to 106%.

Amines↗
PubMed2006

Solid-phase extraction in packed beds on glass microdevices.

This chapter provides a detailed description of a network of channels that includes a chamber for trapping beads in a microfluidic device. Instructions are included for the packing and use of the bead bed for solid-phase extraction (SPE). The SPE procedure may be used, e.g., as a filter to clean up a dirty sample prior to analysis, or as a means of pre-concentration for a dilute sample. Once the bead bed is in place, it may be used multiple times without sample breakthrough.

Glass↗
PubMedDate not supplied

Multiresidue determination of pesticides in drinking and related waters by gas chromatography/mass spectrometry after solid-phase extraction: interlaboratory study.

As part of a project funded by the European Commission (EC) for the development and evaluation of multiresidue methods for analysis of drinking and related waters, 15 European laboratories evaluated a method using styrene-divinylbenzene co-polymer solid-phase extraction followed by gas chromatography/mass spectrometry. The main aim of the study was to evaluate whether the method meets the requirements of EC Directive 98/83 in terms of accuracy, precision, and detection limit for 22 pesticides according to the following requirements: limit of detection, < or = 0.025 microg/L; accuracy, expressed as recovery between 75 and 125%; and precision, expressed as repeatability relative standard deviation of the method of < 12.5% and as reproducibility relative standard deviation of the method of < 25%. Analyses for unknown concentrations were performed with fortified commercial bottled and tap waters. All laboratories were able to achieve detection limits of 0.01 microg/L for all pesticides except dimethoate and desisopropylatrazine (0.02 microg/L). The criteria for repeatability were met for all compounds except trifluralin, dimethoate, and lindane in bottled water and chlorpyrifos, dimethoate, and lindane in tap water. The criteria for reproducibility were met for all compounds except trifluralin, dimethoate, and lindane in bottled water and pendimethalin, chlorpyrifos, dimethoate, terbutryn, and lindane in tap water. In terms of accuracy, the method meets the requirements for all pesticides in both matrixes, except for lindane in bottled water and lindane and chlorpyrifos in tap water.

Algorithms↗
PubMed1998

Determination of organonitrogen pesticides in large volumes of surface water by liquid-liquid and solid-phase extraction using gas chromatography with nitrogen-phosphorus detection and liquid chromatography with atmospheric pressure chemical ionization mass spectrometry.

During a recent study to determine the fluxes and fates of contaminants in the St. Lawrence River, the majority of organonitrogen pesticides analysed in samples of surface water were found in the dissolved phase. This paper compares two extraction techniques and two analytical techniques for 10 chemicals (metolachlor, seven triazines and two degradation products of atrazine-cyanazine-propazine and simazine) in the dissolved phase in large volumes of surface water, using a fibre glass filter with 0.7 micron porosity. Samples of filtered surface water (1-20 l) were extracted by means of a liquid-liquid technique using the Goulden large-sample extractor, and by means of a solid-phase extraction technique, using cartridges filled with 500 mg of a large particle-size graphitized carbon black as adsorbent: Carbopack B (500-666 microns). The pesticides were analysed by gas chromatography on two DB-5 and DB-210 capillary columns with nitrogen-phosphorus detection (GC-NPD) and by liquid chromatography coupled with mass spectrometry equipped with an atmospheric pressure chemical ionization interface (LC-APCI-MS). The recoveries were high (67-100%) for the majority of the target pesticides in a volume of 17.85 l of Milli-Q water, compared to recoveries in the same volume of filtered surface water (51-102%). The detection limits ranged from 0.4 to 4 ng/l and from 0.6 to 3 ng/l for GC-NPD and LC-ACPI-MS techniques, respectively.

Chromatography, Gas↗
PubMedDate not supplied

Solid-phase extraction and reversed-phase high-performance liquid chromatography of the five major alkaloids in Narcissus confusus.

A novel, fast and precise method, combining solid-phase extraction and reversed-phase high-performance liquid chromatography is described for the quantitative determination of five alkaloids (galanthamine, N-formylnorgalanthamine, haemanthamine, homolycorine and tazettine/pretazettine) from bulbs of wild Narcissus confusus, a high galanthamine-containing plant species growing in the Iberian Peninsula.

Alkaloids↗
PubMed1996

A radioimmunoassay combined with solid-phase extraction for the determination of a novel anti-obesity agent, ARL 15849XX, in dog plasma.

A radioimmunoassay has been developed for the determination of ARL 15849XX, a cholecystokinin-8 (CCK-8) analogue, in dog plasma. The method incorporates solid-phase sample extraction and is suitable for the determination of the analyte at picogram per millilitre concentrations. The antiserum was raised in Suffolk-cross sheep following primary and booster immunisations with an immunogen prepared by conjugating ARL 16935XX, an analogue of ARL 15849KF, to bovine serum albumin. The radioligand was prepared by the no-carrier-added 125I iodination of a non-sulphated derivative, ARL 15745XX. The solid-phase extraction procedure, carried out using ion-exchange aminopropyl and octadecyl sorbents sequentially, was introduced to remove matrix interferences in the plasma and to enhance the method sensitivity. The calibration range is 20-1000 pg ml-1, using a 1 ml sample of undiluted dog plasma.

Amino Acid Sequence↗
PubMed1996

Stereospecific determination of amisulpride, a new benzamide derivative, in human plasma and urine by automated solid-phase extraction and liquid chromatography on a chiral column. application to pharmacokinetics.

Amisulpride, a drug belonging to the benzamide series, demonstrates antischizophrenic and antidepressant (antidysthymic) properties in man. For the pharmacokinetic studies of the racemic drug in man, a method of determination based on solid-phase extraction (SPE) from plasma and HPLC on a stereoselective column was developed. For this aim, one millilitre of plasma, after the addition of the internal standard, tiapride or metoclopramide, is diluted with a borate buffer at pH 9, then automatically loaded onto a SPE C18 100-mg column. The column is washed with different solvents, then eluted with 0.5 ml of methanol. After evaporation of the eluted fraction, the residue is reconstituted in 0.25 ml of eluent mixture. An aliquot is injected onto the HPLC column, a Chiralpak AS, equilibrated with an eluent mixture constituted by n-hexane-ethanol, (67:33, v/v) containing 0.2% (v/v) of diethylamine (DEA) or n-heptane-ethanol, (70:29.8, v/v) containing 0.2% of DEA and connected to a UV detector set at 280 nm or to a fluorimetric detector set at lambda ex = 280 nm and lambda cm = 370 nm. The limit of quantitation (LOQ) in human plasma is 2.5 ng ml-1 for both S-(-)- and R-(+)-amisulpride isomers with both detection methods. The method has been demonstrated to be linear in the range 2.5-320 ng ml-1 for both R-(+)- and S-(-)-amisulpride in human plasma with both UV and fluorescence detection. Absolute recovery of S-(-)- and R-(+)-amisulpride enantiomers from human plasma, as well as selectivity, precision and accuracy have been demonstrated to be satisfactory for pharmacokinetics in man and equivalent for both the proposed methods that have been cross-validated on real dosed human plasma samples. The methods have been used for clinical pharmacokinetic studies allowing pharmacokinetic parameters for amisulpride enantiomers in agreement with those obtained for the racemate to be obtained. After dilution with water, urinary samples from subjects treated with amisulpride racemate can be analysed according to the method used for plasma.

Amisulpride↗
PubMed2005

Novel solid-phase extraction protocol for 11-nor-9-carboxy-delta9-tetrahydrocannabinol from urine samples employing a polymeric mixed-mode cation-exchange resin, Strata-X-C, suitable for gas chromatography-mass spectrometry or liquid chromatography-mass spectrometry analysis.

A novel solid-phase extraction (SPE) method was developed for extraction and cleanup of 11-nor-9-carboxy-delta9-tetrahydrocannabinol (THC-COOH), the major metabolite of the active principle of marijuana, delta9-tetrahydrocannabinol, from urine samples. The protocol utilizes a polymeric mixed-mode cationic sorbent, Strata-X-C, which exhibits strong retention for the metabolite facilitating a more rigorous organic wash to eliminate matrix components/endogenous materials. Acetonitrile containing acetic acid was used as the elution solvent and is compatible with both LC-MS and GC-MS modes of analysis. The hydrophobic retention of Strata-X-C was demonstrated to be higher than a neutral polymeric sorbent, Strata-X, of the same backbone but devoid of the cation-exchange moiety (sulfonic acid), by LC studies employing homologous paraben probes. Simultaneously, the polar (non-ionic) interaction capability of Strata-X-C is also greater than that of Strata-X, as assessed through regioisomeric nitrophenol probes. These two features enable the metabolite to be retained strongly on Strata-X-C. Good linearity and precision was obtained for THC-COOH by GC-MS analysis of its trimethylsilyl derivative in the range 1-50 ng. A simplified room temperature instantaneous derivatization procedure was developed that is suitable for high-throughput screening of THC-COOH.

Cation Exchange Resins↗
PubMed1988

Measurement of methsuximide and N-desmethylmethsuximide using solid-phase extraction and wide-bore capillary gas chromatography.

A method for the determination of the anti-epileptic drug methsuximide (MSM) and its active metabolite N-desmethylmethsuximide (NDM) is presented. 5-Methyl-5-phenylhydantoin is used as the internal standard. A simple solid-phase extraction procedure utilizing disposable reversed-phase C18 columns is described. Samples are analyzed by gas chromatography with flame ionization detection using a wide-bore capillary column with a permanently bonded, non-polar stationary phase. The MSM assay possesses linearity to 6.0 micrograms/mL, sensitivity to 0.5 microgram/mL, recovery ranging from 93 to 110%, and precision reflected by a SD of +/- 0.37 microgram/mL. The NDM assay displays linearity up to 80.0 micrograms/mL, sensitivity to 5.0 micrograms/mL, recovery of 90 to 100%, and precision reflected by a SD +/- 0.90 microgram/dL. Lack interference is documented for 6 commonly prescribed anti-epileptic drugs and 4 drugs with similar retention times on this stationary phase; only guaifenesin was found to potentially interfere with the determination of methsuximide. We conclude that the method reported here is ideally suited for monitoring therapeutic and toxic levels of this anti-epileptic drug.

Chromatography, Gas↗
PubMed2001

Determination of haloacetic acids in aqueous environments by solid-phase extraction followed by ion-pair liquid chromatography-electrospray ionization mass spectrometric detection.

Haloacetic acids (HAAs) were determined in different water samples by a new, fast and simple analysis method based on enrichment of 50-ml water samples at pH 1.8 by solid-phase extraction (SPE) followed by liquid chromatography (LC) separation and electrospray ionization mass spectrometric detection in the negative ionization mode. Deprotonated (M-H)-haloacetates and decarboxylated (M-COOH)- ions were detected. Different polymeric SPE sorbents were tested, and LiChrolut EN was found to be the best material for the extraction. Complete LC separation of all compounds could only be achieved by ion-pair chromatography using triethylamine as volatile ion-pairing reagent. The detection limits were in the low microg/l range. High microg/l concentration levels for the chlorinated and brominated haloacetates were found in drinking water from a drinking water treatment plant in Barcelona, and the corresponding tap water. In swimming pool water samples from Catalonia mg/l levels and in surface river water from Portugal microg/l values were detected. These results confirm other recent reports on the ubiquitous occurrence of HAAs in aqueous environments.

Acetates↗
PubMed1988

Liquid chromatographic determination of indolidan and its dehydro metabolite in plasma. Use of the Varian AASP for solid-phase extraction.

A method is described for the determination of indolidan and its dehydro metabolite in human plasma. Two procedures are given, one manual and one which is semi-automated by use of the Varian AASP (Automated Analytical Sample Processor). The method involves solid-phase extraction to isolate the drug, metabolite, and an internal standard from plasma. The manual procedure requires elution of the analytes from the extraction column with methanol, evaporation of the methanol to dryness, and reconstitution in mobile phase prior to injection into a reversed-phase liquid chromatographic system. Using the AASP (semi-automated procedure), the analytes are eluted from the extraction column directly into the chromatographic system, resulting in substantial savings in sample preparation time. The limit of detection for both drug and metabolite is 0.25 ng/ml in plasma. Detection was made by ultraviolet absorbance, using wavelength programming to optimize the sensitivity of the assay for each compound.

Autoanalysis↗
PubMed2005

Chlorinated phenol analysis using off-line solid-phase extraction and capillary electrophoresis coupled with amperometric detection and a boron-doped diamond microelectrode.

The analysis of chlorinated phenols (2-chlorophenol, 3-chlorophenol, 4-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, pentachlorophenol) in river water was accomplished using off-line solid-phase extraction (SPE) and capillary electrophoresis coupled with electrochemical detection. A key to the sensitive, reproducible, and stable detection of these pollutants was the use of a boron-doped diamond microelectrode in the amperometric detection mode. An off-line SPE procedure was utilized to extract and preconcentrate the pollutants prior to separation and detection, with ENVI-Chrom P, a highly cross-linked styrene-divinylbenzene copolymer, being employed as the sorbent. Pollutant recoveries in the 95-100% range with relative standard deviations of 1-4% were achieved. The diamond microelectrode provided a low and stable background current with low peak-to-peak noise. The oxidative detection of the pollutants was accomplished at +1.05 V vs Ag/AgCl without the need for electrode pretreatment. The method was evaluated in terms of the linear dynamic range, sensitivity, limit of quantitation, response precision, and response stability. A reproducible electrode response was observed during multiple injections of the chlorinated phenol solutions with a relative standard deviation of < or =5.4%. Good electrode response stability was observed over many days of continuous use with no significant electrode deactivation or fouling. The separation efficiencies for all six pollutants were greater than 170,000 plates/m. The minimum concentration detectable for all six ranged from 0.02 to 0.2 ppb (S/N > or = 3) using a 250:1 preconcentration factor.

Boron↗
PubMed2001

Identification of alkyl dimethylbenzylammonium surfactants in water samples by solid-phase extraction followed by ion trap LC/MS and LC/MS/MS.

A novel methodology was developed for the determination of alkyl (C12, C14, and C16) dimethylbenzylammonium chloride (benzalkonium chloride or BAC, Chemical Abstract Service number: 8001-54-5) in water samples. This method is based on solid-phase extraction (SPE) using polymeric cartridges, followed by high-performance liquid chromatography/ion trap mass spectrometry (LC/MS) and tandem mass spectrometry(MS/MS) detection, equipped with an electrospray interface in positive ion mode. Chromatographic separation was achieved for three BAC homologues by using a C18 column and a gradient of acetonitrile/10 millimolar aqueous ammonium formate. Total method recoveries were higher than 71% in different water matrices. The main ions observed by LC/MS were at mass-to-charge ratios (m/z) of 304, 332, and 360, which correspond to the molecular ions of the C12, C14, and C16 alkyl BAC, respectively. The unequivocal structural identification of these compounds in water samples was performed by LC/MS/MS after isolation and subsequent fragmentation of each molecular ion. The main fragmentation observed for the three different homologues corresponded to the loss of the toluyl group in the chemical structure, which leads to the fragment ions at m/z 212, 240, and 268 and a tropylium ion, characteristic of all homologues, at m/z 91. Detection limits for the methodology developed in this work were in the low nanogram-per-liter range. Concentration levels of BAC--ranging from 1.2 to 36.6 micrograms per liter--were found in surface-water samples collected downstream from different wastewater-treatment discharges, thus indicating its input and persistence through the wastewater-treatment process.

Benzalkonium Compounds↗
PubMed1997

Liquid chromatographic analysis of amphetamine and related compounds in urine using solid-phase extraction and 3,5-dinitrobenzoyl chloride for derivatization.

A chromatographic method for the analysis of amphetamine and related compounds in urine using 3,5-dinitrobenzoyl chloride (3,5-DNB) as a labeling reagent is presented. This assay is based on the employment of solid-phase extraction (SPE) cartridges for sample cleanup and derivatization. Experimental conditions are optimized for the simultaneous derivatization of ephedrine, norephedrine, pseudoephedrine, beta-phenylethylamine, amphetamine, methamphetamine, and 3-phenylpropylamine. The derivatives formed are separated in a LiChrospher 1000 RP18 (125 x 4-mm i.d., 5-microns film thickness) analytical column using a water-acetonitrile gradient elution and detected at 254 nm. Derivatization in C18 SPE disks is found to be the best option for analysis of urine samples; this method provides analyte conversions that are about 85-102% of those obtained by the analogous solution derivatization. Because the 3,5-DNB reagent is a strong pi-acid, the described method can be used in combination with a Pirkle-type donor column for chiral analysis. The practicality of the described approach is illustrated by determining amphetamine enantiomers using a Supelcosil LC-(S)-naphtylurea (250 x 4.6-mm i.d., 5-microns film thickness) column and a mobile phase of n-hexane-acetonitrile-ethyl acetate. Under these conditions, good linearity and reproducibility are observed over the 0.5-10 micrograms/ml concentration range; the limit of detection is 50 ng/mL.

Amphetamines↗
PubMed2004

Determination of catechins and catechin gallates in tissues by liquid chromatography with coulometric array detection and selective solid phase extraction.

Catechins levels in organ tissues, particularly liver, determined by published methods are unexpectedly low, probably due to the release of oxidative enzymes, metal ions and reactive metabolites from tissue cells during homogenization and to the pro-oxidant effects of ascorbic acid during sample processing in the presence of metal ions. We describe a new method for simultaneous analysis of eight catechins in tissue: (+)-catechin (C), (-)-epicatechin (EC), (-)-gallocatechin (GC), (-)-epigallocatechin (EGC), (-)-catechin gallate (CG), (-)-epicatechin gallate (ECG), (-)-gallocatechin gallate (GCG) and (-)-epigallocatechin gallate (EGCG) (Fig. 1). The new extraction procedure utilized a methanol/ethylacetate/dithionite (2:1:3) mixture during homogenization for simultaneous enzyme precipitation and antioxidant protection. Selective solid phase extraction was used to remove most interfering bio-matrices. Reversed phase HPLC with CoulArray detection was used to determine the eight catechins simultaneously within 25 min. Good linearity (>0.9922) was obtained in the range 20-4000 ng/g. The coefficients of variance (CV) were less than 5%. Absolute recovery ranged from 62 to 96%, accuracy 92.5 +/- 4.5 to 104.9 +/- 6%. The detection limit was 5 ng/g. This method is capable for determining catechins in rat tissues of liver, brain, spleen, and kidney. The method is robust, reproducible, with high recovery, and has been validated for both in vitro and in vivo sample analysis.

Animals↗
PubMed1995

Determination of organophosphorus pesticides and their transformation products in river waters by automated on-line solid-phase extraction followed by thermospray liquid chromatography-mass spectrometry.

The trace-level determination of ten priority organophosphorus (OP) pesticides (e.g., chlorpyrifos-methyl, diazinon, disulfoton, fenthion, fenamiphos) and various transformation products (TPs; e.g., disulfoton sulfoxide, fenthion sulfoxide etc.) using automated on-line solid-phase extraction (SPE) with C18 precolumns followed by LC-MS and thermospray interface with time-scheduled selected-ion monitoring (SIM) was developed. Two main ions (usually [M+H]+ and [M+NH4]+ or [M+CH3CN]+) were used for each pesticide in the positive ion (PI) detection mode, while [M-H]- and [M+HCOO]- ions were used in the negative ion (NI) mode. The proposed method requires 100 ml of sample for a limit of detection (LOD) of 0.01-0.1 microgram/l. Calibration graphs were constructed by preconcentrating 100 ml of water spiked with the pesticide mixture at various concentrations (from 0.025 to 2 microgram/l). Good linearity was observed for most of the analytes studied. The experimental setup described in this paper was applied to study the kinetics of degradation of ten organophosphorus pesticides in spiked river water samples. The different samples were first analyzed by an automated on-line precolumn exchange system (OSP-2) followed by LC with diode array detection. To confirm the identity of the organophosphorus pesticides detected, the samples were then analyzed by automated on-line SPE-LC-MS. The method permitted unequivocal identification of many of the TPs formed during the experiments, e.g., the oxo-derivatives of chlorpyrifos-methyl, temephos and pyridafenthion, fenamiphos sulfoxide. Many of these TPs are here reported for the first time since previously used MS-based techniques were not sensitive enough.

Biodegradation, Environmental↗