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PubMed1992

On-line solid-phase extraction and high-performance liquid chromatographic determination of nortriptyline and amitriptyline in serum.

An isocratic reversed-phase high-performance liquid chromatographic method with on-line solid-phase extraction for the simultaneous determination of amitriptyline and nortriptyline in serum has been developed. A 250-microliters serum sample is injected directly onto a commercially available CN cartridge and, after a washing step, the retained solutes are backflushed onto a bonded-phase CN column using a column-switching technique and a mobile phase composed of acetonitrile (26%) and 0.05 M phosphate buffer with diethylamine. Serum is diluted with 0.1 M sodium lauryl sulphate and centrifuged before the injection. Detection at 210 nm ensures sufficient sensitivity. The recovery is almost quantitative and the relative standard deviation ranges from 2.8 to 8.0% for concentrations of 200-40 ng/ml. Being rapid and simple, the method is convenient for routine use.

Amitriptyline↗
PubMedDate not supplied

An enzymic digestion and solid-phase extraction procedure for the screening for acidic, neutral, and basic drugs in liver using gas chromatography for analysis.

Analysis of liver specimens is an important issue in forensic toxicology, but suitable workup and extraction methods for general screening purposes have been lacking until now. A workup and extraction scheme based on a recently developed procedure for the screening of biological fluids was developed that can be used for the screening of acidic, neutral, and basic drugs in liver. This method uses a single solid-phase extraction (SPE) column and gas chromatography-flame ionization detection (GC-FID) for the final analysis. First, the homogenized liver sample is sonicated and centrifuged; the resulting supernatant is applied to the SPE column. Elution of acidic, neutral, and some weakly basic drugs is then performed with acetone-chloroform and analyzed by GC-FID. Next, the pellet of tissue material obtained from the centrifugation is enzymically digested by subtilisin Carlsberg. This frees the drugs bound to the liver tissue. The resulting clear liquid is brought to the reconditioned SPE column. A wash step is introduced to remove acidic and neutral interferences and the basic drugs can then be eluted with ammoniated ethyl acetate. Using 100-mg wet liver samples spiked with 2 micrograms of amounts of various drugs, recoveries were 70-102% with relative standard deviations less than 9%. The resulting GC-FID chromatograms were virtually free of endogenous interferences. GC-nitrogen-phosphorous detection detected smaller amounts of nitrogen-containing drugs, again without endogenous interferences. With the SPE columns currently used, which contain a bed mass of 130 mg, the liver samples should be smaller than 200 mg because the endogenous compounds obtained after the digestion of the tissue will overload the column, which results in a lower recovery of the drugs of interest. Drugs that decompose under the digestion conditions (pH 10.5 at 60 degrees C for 1 h) may be lost in the present procedure. This phenomenon is being investigated further.

Flame Ionization↗
PubMed2000

Quantitative determination of Cu-thionein from human fluids with application of solid-phase extraction on covalent affinity chromatography with thiol-disulphide interchange support.

The aim of our investigation was to carry out quantitative isolation of Cu-thionein (Cu-Th) in human body fluids (urine, plasma and breast milk) in order to determine the level of exposure to heavy metals. In the experiment covalent affinity chromatography with thiol-disulphide interchange gel (CAC-TDI) was used as a solid phase extraction (SPE) support for preconcentration of Cu-thionein (Cu-Th) protein and Cu bonded with MT from water and human fluids samples. The present paper is a continuation of early experiments on the quantitation of Hg-thionein (Hg-Th), Cd-thionein (Cd-Th) and Zn-thionein (Zn-Th) in human body fluids such as urine, plasma and breast milk.

Animals↗
PubMed2000

Highly selective and efficient determination of US Environmental Protection Agency priority phenols employing solid-phase extraction and non-aqueous capillary electrophoresis.

Non-aqueous capillary electrophoresis has been used in the separation of a complete list of 26 priority phenols included in the 8041 US Environmental Protection Agency method and the 76/464/EEC European Union directive. A highly selective and efficient separation was obtained when the background electrolyte used was 150 mM ammonium acetate dissolved in N-methylformamide-acetonitrile (75:25). Solid-phase extraction was successfully assayed as an enrichment strategy for the analysis of low-concentration samples. A styrene-divinylbenzene functionalized cartridge provided excellent recoveries of phenols from water samples at neutral pH. The limits of quantification obtained permit the application of the proposed method to the determination of priority phenols in wastewater samples.

Electrophoresis, Capillary↗
PubMed2002

Solid-phase extraction method for the determination of free and conjugated phenol compounds in human urine.

A rapid flow system for automatic sample conditioning for the determination of phenol compounds in human urine has been developed and optimised. Free phenols are detected directly in urine samples while total phenols require acid hydrolysis to convert their conjugate fraction into free phenols, all compounds then being cleaned up and preconcentrated by solid-phase extraction. Separation and determination are done by gas chromatography, using mass spectrometry operating in the selective ion monitoring mode for quantitation. The linear range was 1-160 ng/ml of urine for most of the phenols. Limits of detection for phenol compounds (phenol, alkylphenols and chlorophenols) in the nanogram-per-millilitre range (0.3-0.6 ng/ml) are thus achieved by using 1 ml of urine; also, the repeatability, as RSD, is less than 6.5%. Based on the results for urine samples from unexposed individuals, 2-methylphenol, 2-chlorophenol and 2,4-dichlorophenol are largely detected in hydrolysed urine samples, whereas phenol and 4-methylphenol are detected in hydrolysed and unhydrolysed urine. Other chlorophenols such as trichlorophenols and pentachlorophenol are not detected. The results obtained in the analysis of urine from an individual before and after dietary intake reveal that the levels of phenol compounds in urine look related to food intake.

Calibration↗
PubMed2002

Non-covalent and semi-covalent molecularly imprinted polymers for selective on-line solid-phase extraction of 4-nitrophenol from water samples.

Two molecularly imprinted polymers (MIPs) have been synthesised for the selective extraction of 4-nitrophenol (4-NP) from water samples. One polymer was synthesised via a non-covalent approach and the other via a semi-covalent approach. The selectivity of the polymers for 4-NP was evaluated when these polymers were applied in on-line solid-phase extraction (MISPE) coupled to reversed-phase HPLC. The MISPE conditions for both MIPs were optimised and a clean-up step was included to eliminate non-specific interactions. Differences between the two MIPs were observed with the non-covalent MIP being the more selective of the two, whereas the recoveries were slightly higher for the semi-covalent MIP. The performance of the imprinted polymers in the MISPE of real water samples was also evaluated.

Chromatography, Liquid↗
PubMed1997

Simplified solid-phase extraction method for determination of dihydroergotamine in rabbit and human serum using high-performance liquid chromatography with fluorescence detection.

A rapid, selective and sensitive method for the determination of dihydroergotamine (DHE) in serum was developed. Dihydroergocristine (DHEC) was used as an internal standard. Human and rabbit serum samples were extracted using commercial solid-phase cyano (CN) columns. Proteins were washed from these columns with pure acetonitrile, resulting in clean extracts. Extracts were subsequently separated by HPLC in an isocratic way, using a reversed-phase C18 analytical column. Fluorometric detection was performed at excitation and emission wavelengths of 277 and 348 nm, respectively. Calibration curves with amounts of DHE ranging from 2 to 32 ng, were linear. The limit of detection found for DHE was 0.2 ng, extracted from 0.5 ml rabbit or from 2.5 ml human serum. The limit of quantification in serum of both species was 0.7 ng. The method has been shown to be suitable for monitoring DHE in serum during pharmacokinetic studies in rabbits.

Analgesics, Non-Narcotic↗
PubMed1993

A sensitive radioimmunoassay, incorporating solid-phase extraction, for fluticasone 17-propionate in plasma.

Antibodies were produced in rabbits immunized with fluticasone 17-propionate (FP) conjugated to bovine thyroglobulin via its 3-carboxymethoxime with isobutylchloroformate. The antibodies were used to develop a sensitive and specific radioimmunoassay (RIA) for FP in human plasma. The limit of quantitation of the RIA is 50 pg per assay tube. This translates to 50 pg ml-1 plasma when a solid-phase extraction preceded the RIA. The interassay and intraassay relative standard deviations were < 15% in the centre of the assay concentration range rising to < 25% at the lower and upper limits (50 and 250 pg ml-1). No appreciable binding was seen between the antibodies and the metabolite of FP that has been identified in man. The RIA was used to study the time course of plasma concentrations in man following inhalation of FP.

Absorption↗
PubMed1994

Fully automated assay for the determination of GR117289X in human plasma using mixed mode solid-phase extraction and high-performance liquid chromatography with ultraviolet detection.

GR117289X, 3-(3-Bromo-2-[2-(1H-tetrazol-5-yl)-phenyl]-bezofuran-5-yl methyl)-2-butyl- 5-chloro-3H-imidazole-4-carboxylic acid, 1, is an angiotensin II receptor antagonist. A sensitive, accurate and precise assay for the determination of 1 in human plasma and validation data is described. The assay consists of a novel solid-phase extraction using Certify II followed by a reversed-phase gradient HPLC separation with UV detection. The extraction procedure has been fully automated by a Zymate XP robot and linked on-line to the HPLC system. The analytical range for the assay is 5-250 ng ml-1 over which the assay is linear and specific for 1 with respect to endogenous plasma components and its tetrazole N2 glucuronide, the major circulating metabolite 2. For the fully automated procedure the intra-assay data indicate a maximum bias and coefficient of variation across the calibration range of +8.0 and 9.4%, respectively. The inter-assay data indicate a maximum bias and coefficient of variation across the calibration range of +8.0 and 11.1%, respectively. The extraction efficiency of the assay was approximately 75%. Both a manual and fully automated assay were applied to the analysis of 1 in plasma of volunteers from a number of clinical studies. The assay has been shown to be robust in sustained use over several months.

Angiotensin Receptor Antagonists↗
PubMed1998

Monitoring of pesticide residues and their metabolites in surface and underground waters of Imathia (N. Greece) by means of solid-phase extraction disks and gas chromatography.

Seasonal variations of pesticide residues in surface waters and ground waters of the Imathia area of Central Mecedonia (N. Greece) were determined for the period from May 1996 to April 1997. The sampling cruises included eight sites in rivers Aliakmon, Loudias, Tripotamos, Arapitsa and Canal-66, seven water springs in the mountain Vermion, seven rainfall water collection stations and one hundred underground points. Solid-phase extraction disks followed by gas chromatographic techniques with flame thermionic detection, electron capture detection and mass-selective detection were used for the monitoring of various pesticides their transformation products in environmental waters. The most commonly encountered pesticides in underground waters, were alachlor, atrazine, desethylatrazine (DEA), metolachlor, molinate, propanil, simazine, carbofuran, diazinon and parathion methyl. The above compounds including propazine, trifluralin, malathion, parathion ethyl, lindane, alpha-benzene hexachloride (alpha-BHC), beta-BHC, 4,4'-DDE and heptachlor were determined in river waters. The higher concentrations in underground waters were measured during the period from May to August, 1996, following seasonal application and diminished significantly during the autumn and winter. Water pollution by triazine and chloroacetanilides was highest in the estuarine areas; showing that many of these compounds are transported significant distances from their application sites. The major inputs of atrazine, alachlor, simazine and metolachlor occurred in May and June just after their application. Atrazine, DEA, diazinon and metolachlor were also detected in spring waters at concentration levels below 0.006 microgram/l. Finally, atrazine, DEA, carbofuran, simazine, diazinon, parathion ethyl and parathion methyl were detected in rainfall water samples collected in the agricultural area of Imathia (central part of the plain).

Agriculture↗
PubMed1996

Determination of trace lithium in biological fluids using graphite furnace atomic absorption spectrophotometry: variability of urine matrices circumvented by cation exchange solid phase extraction.

A graphite furnace atomic absorption spectrometry method has been developed for the quantitative determination of submicromolar endogenous concentration of lithium in human plasma and urine using pyrolitically-coated graphite tubes in combination with ammonium nitrate matrix modification. This latter treatment could not completely abolish the interferences caused by the matrix, notably in urine samples. The variability of the urinary matrices required an additional standardization procedure by solid-phase extraction on strongly acidic cation exchange cartridges. Matrix-matched samples were used for the establishment of calibration curves with the addition-calibration method. Calibration curves were linear up to 0.72 mumol/l (1.0 > r2 > 0.99). The described method enables accurate measurements of trace-lithium in biological samples at concentrations down to 0.03 mumol/l with intra- and inter-day variabilities < 10%. The method was applied to the determination of trace-lithium levels in urine and plasma samples from healthy individuals enabling the calculation of its fractional excretion (FeLi) (median range 17.3%), a value which reflects the functional capacity of the kidney to reabsorb sodium and water at the proximal tubular portion of the nephron. This sensitive method can thus be used as an investigative and diagnostic tool in various renal pathophysiological conditions, in clinical research, and may also be applied to studies on the trace-lithium status of population in connection with psycho-affective disorders.

Cations↗
PubMed1993

On-line fully automated determination of clozapine and desmethylclozapine in human serum by solid-phase extraction on exchangeable cartridges and liquid chromatography using a methanol buffer mobile phase on unmodified silica.

A fully automated method for determination of clozapine and desmethylclozapine in human serum using high-performance liquid chromatography was developed. On-line solid-phase extraction was performed on an exchangeable cyanopropyl cartridge. The analytes were eluted with a methanol-ammonium acetate buffer mobile phase, separated on a silica column, and measured by ultraviolet detection at 261 nm. The total time for one analysis was 13 min. Inter-day variation was < 6% and < 8% for clozapine and desmethylclozapine, respectively. Detector response was linear in the range of 30-300 ng/ml. Comparison with liquid-liquid extraction showed good agreement. The patients had clozapine serum concentrations in the range 40-1500 ng/ml. Desmethylclozapine concentrations were 25% lower and closely related.

Autoanalysis↗
PubMed2006

Potential of a simple solid-phase extraction method coupled to analytical and bioanalytical methods for an improved determination of microcystins in algal samples.

Artemia assays and protein phosphatase assays are commonly used for the screening of microcystins (MCs) in algal samples instead of the standard mouse toxicity assay. However, it has been shown that their results are often biased because of the matrix effects. To eliminate the possible interferences in the algal matrices, a new solid-phase extraction (SPE) method using silica gel as a sorbent was developed and evaluated. Results show that this SPE method could not only reduce the toxicity of the Microcystis samples towards brine shrimp by 50-80% but also eliminate 90-100% of the endogenous phosphatase activity from Spirulina and Chlorella samples, thus improving the determination of microcystins in algal samples using either of the two bioanalytical methods. The application of this SPE method as an off-line cleanup for high-performance liquid chromatography (HPLC) with UV detection is also described in this study. After SPE, the HPLC chromatograms of Microcystis samples have clear baselines that have no interferences with the analyte peaks.

Animals↗
PubMed2000

Determination of urinary catecholamines with capillary electrophoresis after solid-phase extraction.

The stabilities of 3,4-dihydroxybenzylamine (DHBA), dopamine, 3-methoxytyramine, normetanephrine and metanephrine standards under acid, base and enzymatic hydrolysis conditions were studied. Basic incubation media were not suitable for 3,4-dihydroxy compounds, but acid and enzymatic hydrolysis conditions were applicable to all the compounds. The results of acid and enzymatic hydrolysis were comparable and the enzymatic hydrolysis was applied to a urine matrix. A method including solid-phase extraction (SPE) with a copolymer sorbent was developed for purification of the urine samples. Due to poor recovery of DHBA, the most frequently used internal standard in catecholamine analysis, this compound was replaced with the 3-O-methoxy structure. The recoveries of the compounds in spiked urine samples in SPE were between 96.4 and 124.4%. The repeatability of the combination of enzymatic hydrolysis and SPE pretreatment was good for all the compounds, except for dopamine and 3-methoxytyramine due to some matrix compounds still interfering with the separation. The analyses were performed with capillary electrophoresis in an ammonium acetate buffer with UV detection. The validation data for the compounds including limit of detection, limit of quantification, linearity and repeatability of the method are presented.

Catecholamines↗
PubMedDate not supplied

Rapid simultaneous determination of amphetamine, methamphetamine, 3,4-methylenedioxyamphetamine, 3,4-methylenedioxymethamphetamine, and 3,4-methylenedioxyethylamphetamine in urine by solid-phase extraction and GC-MS: a method optimized for high-volume laboratories.

To facilitate analysis of high sample volumes, an extraction, derivatization and gas chromatographic-mass spectrometric analysis method was developed to simultaneously determine amphetamine (AMP), methamphetamine (MAMP), 3,4-methylenedioxyamphetamine (MDA) 3,4-methylenedioxymethamphetamine (MDMA), and 3,4-methylenedioxyethylamphetamine (MDEA) in urine. This method utilized a positive-pressure manifold cation-exchange polymer-based solid-phase extraction followed by elution directly into automated liquid sampler (ALS) vials. Rapid derivatization was accomplished using heptafluorobutyric anhydride (HFBA). Recoveries averaged 90% or greater for each of the compounds. Limits of detection were 62.5 ng/mL (AMP and MDEA), 15.6 ng/mL (MAMP), and 31.3 ng/mL (MDA and MDMA) using a 2-mL sample volume. The method was linear to 5000 ng/mL for all compounds using MDMA-d5 and MAMP-d14 as internal standards. Over 200 human urine samples previously determined to contain the target analytes were analyzed using the method. Excellent agreement was seen with previous quantitations. The method was challenged with 75 potentially interfering compounds and no interferences were seen. These interfering compounds included ephedrine, pseudoephedrine, phenylpropanolamine, and phenethylamine. The method resulted in dramatic reductions in processing time and waste production.

3,4-Methylenedioxyamphetamine↗
PubMed1990

Solid-phase extraction and liquid chromatography of torsemide and metabolites from plasma and urine.

Torsemide is a new diuretic drug with a profile of action similar to that of furosemide. The high potency of torsemide results in low dose therapy and causes problems for the pharmacokinetic study of the drug due to low plasma levels. Described here are methods for the analysis of torsemide and two metabolites in plasma and urine using solid-phase extraction and liquid chromatography. The limits of quantitation are 10 ng/mL for plasma and 20 ng/mL for urine. The relative standard deviations for precision are less than 10% for most analytes at most concentrations in the calibration range. The recoveries from plasma were 94.3, 92.9, and 95.6%, and from urine were 77.5, 66.6, and 76.5% for torsemide and metabolites M1 and M5, respectively. The method was suitable for pharmacokinetic studies. Data from a normal volunteer are presented.

Chromatography, Liquid↗
PubMed2001

Identification of photocatalytic degradation products of non-ionic polyethoxylated surfactants in wastewaters by solid-phase extraction followed by liquid chromatography-mass spectrometric detection.

The photodegradation of non-ionic surfactants (nonylphenol- and alcohol-polyethoxylates, NPEOx and CnEOx) was investigated in different waters with and without a photoinducter (Fe(III)). Deionized water and industrial effluent spiked at 0.5 mg/L with C10EO6 and NPEO9 were irradiated using a xenon arc lamp. Aliquots of the test solutions were taken at different time intervals and were preconcentrated using solid phase extraction (SPE) with C18 cartridges. Liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry (LC-APCI-MS) was used to identify the chemical species generated from phototransformation of non-ionic surfactants. The intermediates detected included nonylphenol diethoxylate (NPEO2) and nonylphenol ethoxy acetic acid (NPE2C). Much smaller amounts of degradation products of NPEO9 having only the alkyl chain carboxylated were also formed in the photocatalysis experiment. The identified C10EO6 photoproducts included fatty alcohols and acids. Polyethylene glycols (PEGs) were also formed as the consequence of the central scission of C10EO6 and the deethoxylation of NPEO9. The photodegradation in wastewater samples was more efficient than in deionized water being the half-life (t(1/2)) of C10EO6, 48 h and 29 h in deionized water and wastewater, respectively, and for NPEO9, 17 h and 14 h in deionized water and wastewater, respectively. When induced photodegradation was undertaken, the t(1/2) for NPEO9 was 21 min and 29 min in deionized water and wastewater, respectively. Disappearance of parent compounds was observed after 120 h from the beginning of the photodegradation experiment, or after 210 min of irradiation for the photocatalysis.

Journal Article↗
PubMed2002

Simultaneous determination of the six HIV protease inhibitors (amprenavir, indinavir, lopinavir, nelfinavir, ritonavir, and saquinavir) plus M8 nelfinavir metabolite and the nonnucleoside reverse transcription inhibitor efavirenz in human plasma by solid-phase extraction and column liquid chromatography.

A sensitive and selective liquid chromatographic assay has been developed for the determination of the six currently protease inhibitors approved by the U.S. Food & Drug Administration (amprenavir, indinavir, lopinavir, nelfinavir, ritonavir, and saquinavir) plus the M8 active metabolite of nelfinavir and the nonnucleoside reverse transcription inhibitor efavirenz in a single run. Pretreatment of 1-mL plasma sample spiked with internal standard was made by a solid-phase extraction procedure using a polymeric reversed-phase sorbent. Liquid chromatography was performed using a narrow-bore C18 reversed-phase column and gradient elution. Double ultraviolet detection at 265 nm (amprenavir) and at 210 nm (all other assayed drugs and internal standard) was used. Calibration curves were linear in the range 25 to 10,000 ng/mL, and the assay has been validated over the range 25 to 5,000 ng/mL. Average accuracies at four concentrations were in the range 92.4% to 103.0% and 94.4% to 103.0% for within-day and between-day, respectively, and the coefficients of variation were less than 8%. Mean absolute recoveries varied from 72.8% (ritonavir) to 93.7% (indinavir). No metabolite of the protease inhibitors was found to coelute with the drugs of interest or with the internal standard. At this time, among the tested drugs, especially all the currently licensed nucleosides and the other nonnucleoside reverse transcription inhibitor nevirapine that can be used in combination with the protease inhibitors, none was found to interfere with the assay.

Alkynes↗