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PubMed1999

Determination of indinavir in human cerebrospinal fluid and plasma by solid-phase extraction and high-performance liquid chromatography with column switching.

A rapid, sensitive and robust sample preparation procedure for the quantitative determination of indinavir in human cerebrospinal fluid (CSF) and plasma is described. Indinavir and the internal standard were isolated from CSF or plasma samples by cation-exchange solid-phase extraction with SCX cartridges, while the chromatographic separation was adopted from a previous method, using a cyano column connected by a switching valve to a C18 column. UV detection was set at 210 nm. The standard curve was linear over the concentration range of 2 to 2000 ng/ml in CSF and 5 to 2000 ng/ml in plasma. The intra-day coefficients of variation at all concentration levels were < or = 5.9%. The inter-day consistency was assessed by running QC samples during each daily run. The coefficients of variation for quality control samples in both matrixes were < or = 6.1%. The method has been utilized to support clinical pharmacokinetic studies.

Cations↗

PubMed2000

Determination of non-ionic surfactants and polar degradation products in influent and effluent water samples and sludges of sewage treatment plants by a generic solid-phase extraction protocol.

Non-ionic polyethoxylated surfactants (nonylphenol polyethoxylates, alcohol polyethoxylates), their breakdown products (polyethylene glycol, polyethoxylated nonylphenol carboxylates and polyethoxylated alcohol carboxylates) and other compounds were identified and measured in various waste-water treatment samples (influent, effluent and sludge). A generic protocol involving the use of sequential solid-phase extraction (SSPE) with octadecylsilica and styrene-divinylbenzene cartridges in series and differential elution was used. Fractionated extracts were analyzed by liquid chromatography-mass spectrometry (LC-MS) using atmospheric pressure chemical ionization (APCI) in the positive and negative ionization modes. For sewage treatment plant (STP) sludge, the extraction protocol involved lyophilization of the sludge followed by sonication with MeOH-CH2Cl2 (7 + 3) and final clean-up using the SSPE protocol. Limits of detection for target analytes ranging from 1.1 to 4.1 micrograms L-1 for water samples and from 0.11 to 0.28 mg kg-1 for sludge were achieved. The results obtained demonstrated the inefficient removal of the target analytes in physico-chemical STPs whereas their elimination factors in STPs with biological treatment reached average values of 77, 92 and 98% for alcohol polyethoxylates, nonylphenol polyethoxylates (NPEOs) and polyethylene glycols (PEGs), respectively. Quantitative elimination of coconut fatty acid diethanolamide (CDEA) surfactants in the activated sludge process occurred. In contrast, total removal of NPEOs led to the formation of persistent and toxic metabolites such as nonylphenol which was present in treated effluent as well as in sludge samples with average concentrations ranging from 15.0 to 251.2 micrograms L-1 and from 13.5 to 74.2 mg kg-1, respectively. Polyethoxylated carboxylates and short chain NPEOs were also detected at similar levels in the effluents and sludges. In addition, a linear correlation between the total phenolic concentration (Total Ph) measured by the 4-aminoantipyrine method and the total concentration of nonylphenolic compounds (Total NP) measured by SSPE-LC-APCI-MS was observed.

Gas Chromatography-Mass Spectrometry↗

PubMed2006

Determination of rutin deca(H-) sulfate sodium in rat plasma using ion-pairing liquid chromatography after ion-pairing solid-phase extraction.

Rutin deca(H-) sulfate sodium (RDS) is one of the most important drug candidates, which possesses very good activity as inhibitor of the complement system of warm-blooded animals and human immunodeficiency virus (HIV). In order to understand RDS metabolism and disposition, an ion-pairing coupled with solid-phase extraction technique (IP-SPE) was developed to extract RDS from rat plasma sample. Tetrabutyl ammonium bromide (TBAB) buffer (0.2 M, pH 8.0) was used as the ion-pairing extraction reagent and LC-18 was used as SPE sorbent. In addition, an ion-pairing HPLC method was established for the specific determination of RDS. A reversed phase C8 column was used for the separation of RDS and nitrendipine (internal standard). The mobile phase was composed of 10 mM phosphate buffer solution containing 25 mM TBAB-acetonitrile (52:48, v/v, pH 7.5). The calibration curve was linear from 0.3 to 30 nmol/mL. The analytical recovery from rat plasma was found to be 97.9+/-4.1% (n = 15). LOD and LOQ for RDS in plasma were calculated to be 0.12 nmol/mL and 0.30+/-0.024 nmol/mL (R.S.D. = 8.2%, n = 5), respectively. The intra- and inter-day precision was less than 9.2%. The assay was applied to a preliminary pharmacokinetic study in three male rats after those received a single intravenous bolus via caudal vein of 12 micromol/kg RDS.

Animals↗

PubMed2000

Pesticide trace analysis using solid-phase extraction and gas chromatography with electron-capture and tandem mass spectrometric detection in water samples.

Gas chromatography (GC) with electron-capture detection (ECD), mass spectrometry (MS) and tandem mass spectrometry (MS-MS) were employed for the identification of 12 pesticides in water samples. For this purpose, a solid-phase extraction procedure with C18 cartridges was used, optimising the breakthrough volume and the saturation concentration. In GC-MS-MS, the lowest detectable concentrations for the pesticides were between 2 and 26 ng l(-1), recoveries ranged from 70 to 133% in water samples spiked at 100 ng l(-1) and the relative standard deviations were in the range 5.3 to 17.4%. The proposed analytical methodology was applied to analyse pesticides in wetland samples from Almería (Spain).

Gas Chromatography-Mass Spectrometry↗

PubMed2002

Analysis of betamethasone in rat plasma using automated solid-phase extraction coupled with liquid chromatography-tandem mass spectrometry. Determination of plasma concentrations in rat following oral and intravenous administration.

A method is described for the determination of betamethasone in rat plasma by liquid chromatography-tandem mass spectrometry (LC-MS-MS). The analyte was recovered from plasma by solid-phase extraction and subsequently analyzed by LC-MS-MS. A Packard Multiprobe II, an automated liquid handling system, was employed for the preparation and extraction of a 96-well plate containing unknown plasma samples, standards and quality control samples in an automated fashion. Prednisolone, a structurally related steroid, was used as an internal standard. Using the described approach, a limit of quantitation of 2 ng/ml was achieved with a 50 microl aliquot of rat plasma. The described level of sensitivity allowed the determination of betamethasone concentrations and subsequent measurement of kinetic parameters of betamethasone in rat. Combination of automated plasma extraction and the sensitivity and selectivity of LC-MS-MS offers a valuable alternative to the methodologies currently used for the quantitation of steroids in biological fluids.

Administration, Oral↗

PubMed1997

Evaluation of reduced solvent volume solid-phase extraction cartridges with analysis by gas chromatography-mass spectrometry for determination of 11-nor-9-carboxy-delta 9-THC in urine.

A sensitive and reliable method was developed for the identification and quantitation of 11-nor-9-carboxy-delta 9-tetrahydrocannabinol (THCCOOH) in urine using a microbed solid-phase extraction (SPE) column. Extensive method validation is presented that evaluates the recovery, linearity, precision, limit of quantitation, limit of detection, and capacity of THCCOOH in urine extracts using CLEAN SCREEN reduced solvent volume (RSV) SPE columns followed by gas chromatographic-mass spectrometric analysis. The mean recovery of THCCOOH at concentrations of 2, 3, 5, 15, 50, and 150 ng/mL was found to be 91% with coefficients of variation of 7.3% or less. Linearity of the method ranged from 1.95 to 1000 ng/mL with sensitivity at 1 ng/mL for THCCOOH. The sorbent was found to retain at least 1000 ng/mL of THCCOOH with no analyte breakthrough using the described method. Reduction in both processing times and total solvent volume is shown. The RSV SPE columns showed excellent efficiency and performance while demonstrating recoveries, cleanliness, and dynamic ranges comparable with standard SPE products.

Dronabinol↗

PubMedDate not supplied

Rapid method for the solid-phase extraction and GC-MS analysis of flunitrazepam and its major metabolites in urine.

Recently, flunitrazepam (Rohypnol) has become an increasingly popular drug of abuse among young adults, who take it for its euphoric effects. In other cases, the drug has been used by rapists for its sedative and hypnotic effects that can induce a catatonialike trance and memory loss in potential victims; as a result, it has been nicknamed the "date-rape drug". For these reasons, the Drug Enforcement Administration recently considered adding the drug (a.k.a. "Roofies") to the same category as heroin and LSD. A selective and sensitive technique has been developed for extracting, detecting, and identifying flunitrazepam and its two major metabolites (7-aminoflunitrazepam and N-desmethylflunitrazepam) in human urine. Using a solid-phase extraction cartridge containing a "mixed-mode" bonded silica gel (Bond Elut Certify), flunitrazepam and its metabolites were selectively isolated from other urine components and quantitated and identified by gas chromatography-tandem mass spectrometry with a benchtop ion mass spectrometer. The extraction method is rapid, reproducible, and precise, and it has a broad linear working range. The overall extraction efficiency was found to be more than 90% for the parent drug as well as the two major metabolites.

Flunitrazepam↗

PubMed2005

Use of solid-phase extraction to enable enhanced detection of acyl homoserine lactones (AHLs) in environmental samples.

A challenge for understanding the role of bacterial cell-cell signalling in the environment is the detection of those signals, which are often present in low (nmol L(-1)) concentrations. We describe here a simple purification method, solid-phase extraction (SPE), for increasing the sensitivity of detection for one such group of signals, acyl homoserine lactones (AHLs), in environmental samples. Spiking of dried marine sponge tissue (Stylinos sp.) with AHLs resulted in detection down to 0.01 ppm for 3-oxo-hexanoyl homoserine lactone (3-oxo C6-HSL) and 1 ppm for hexanoyl homoserine lactone (C6-HSL). Compared with liquid extraction methods use of SPE resulted in twofold and tenfold improvements in sensitivity, respectively.

4-Butyrolactone↗

PubMed1993

Determination of nicotine and two major metabolites in serum by solid-phase extraction and high-performance liquid chromatography, and high-performance liquid chromatography-particle beam mass spectrometry.

A rapid and selective assay of nicotine, cotinine and trans-3'-hydroxycotinine in human serum, based on high-performance liquid chromatography with UV detection has been developed. The compounds were subjected to solid-phase extraction, using Extrelut 1 cartridges. Recoveries were ca. 95% for nicotine, 90% for cotinine and 50-55% for trans-3'-hydroxycotinine. The limit of quantitation observed with this method was 10 ng/ml for nicotine and 5 ng/ml for each of the metabolites. The compounds were also identified using high-performance liquid chromatography with particle beam mass spectrometry, to confirm their presence in human serum.

Chromatography, High Pressure Liquid↗

PubMed2004

Determination of fexofenadine in human plasma using 96-well solid phase extraction and HPLC with tandem mass spectrometric detection.

A fast and sensitive HPLC-MS/MS method, utilizing atmospheric pressure chemical ionization, for the determination of fexofenadine in human plasma is described. A deuterated analog, d6-fexofenadine is used as the internal standard (IS). Plasma samples are prepared using 96-well solid phase extraction with plates containing Waters Oasis HLB sorbent. The analytes are chromatographed on a Restek Ultra IBD column (3.2 mm x 50 mm, 3 microm) using a mobile phase consisting of a mixture of 90% acetonitrile and 10% 10 mM ammonium acetate buffer and 0.1% formic acid. Quantitation of the analyte is based on the response from the multiple reaction monitoring of the precursor to product ion pairs for fexofenadine (m/z 502 --> 466) and d6-fexofenadine (m/z 508 --> 472). The assay has been validated over the concentration range of 1-200 ng/ml based on the analysis of 0.5 ml aliquots of plasma. Within-day assay accuracy was between 97 and 102% of nominal, while within-day precision was better than 3.5% CV at all points on the standard curve. Analyte extraction recovery was better than 70% over the range of the standard curve. The method was found to be suitable for the analysis of human plasma samples obtained 24 h following the administration of a single 60 mg dose of fexofenadine.

Chromatography, High Pressure Liquid↗

PubMed1999

Simultaneous determination of adenosine, S-adenosylhomocysteine and S-adenosylmethionine in biological samples using solid-phase extraction and high-performance liquid chromatography.

A sensitive and rapid method for measuring simultaneously adenosine, S-adenosylhomocysteine and S-adenosylmethionine in renal tissue, and for the analysis of adenosine and S-adenosylhomocysteine concentrations in the urine is presented. Separation and quantification of the nucleosides are performed following solid-phase extraction by reversed-phase ion-pair high-performance liquid chromatography with a binary gradient system. N6-Methyladenosine is used as the internal standard. This method is characterized by an absolute recovery of over 90% of the nucleosides plus the following limits of quantification: 0.25-1.0 nmol/g wet weight for renal tissue and 0.25-0.5 microM for urine. The relative recovery (corrected for internal standard) of the three nucleosides ranges between 98.1 +/- 2.6% and 102.5 +/- 4.0% for renal tissue and urine, respectively (mean +/- S.D., n = 3). Since the adenosine content in kidney tissue increases instantly after the onset of ischemia, a stop freezing technique is mandatory to observe the tissue levels of the nucleosides under normoxic conditions. The resulting tissue contents of adenosine, S-adenosylhomocysteine and S-adenosylmethionine in normoxic rat kidney are 5.64 +/- 2.2, 0.67 +/- 0.18 and 46.2 +/- 1.9 nmol/g wet weight, respectively (mean +/- S.D., n = 6). Urine concentrations of adenosine and S-adenosylhomocysteine of man and rat are in the low microM range and are negatively correlated with urine flow-rate.

Adenosine↗

PubMed2000

Analysis of drugs of abuse in hair by automated solid-phase extraction, GC/EI/MS and GC ion trap/CI/MS.

In our laboratory, analysis of human hair for the detection of drugs of abuse was first performed in 1995. Initially, requests for hair analysis were few, and it is only since 1997 that these analyses have become routine. As demand grew, we developed an automatic solid-phase extraction method; the use of a robot ASPEC allowed us to drop certain fastidious manipulations, and to treat a large number of samples at a time. This method is described, along with analysis by gas-chromatography-mass spectrometry (GC/MS) in selected ion monitoring mode (SIM), for the following drugs: codeine, 6-monoacetylmorphine (6-MAM), morphine, cocaine, methadone, ecstasy (MDMA) and Eve (MDE). This requires prior derivatization with propionic anhydride. The different validation parameters, linearity, repeatability, recovery and detection limits are described, as well as the application of this method to some real cases. Analysis of these cases is also performed by an ion trap GC/MS in chemical ionization mode (GC/IT/CI/MS) in order to demonstrate the usefulness of this technique as a complement to routine analysis. Analysis by GC/IT/CI/MS indeed avoids the risk of false-positive results by the identification of metabolites.

Automation↗

PubMedDate not supplied

Determination of acetaldehyde in blood by solid phase extraction and high performance liquid chromatography.

A simple method has been developed for the measurement of acetaldehyde in blood. Samples were treated with perchloric acid to precipitate proteins. After centrifugation, the supernatant, together with the internal standard (crotonaldehyde), were reacted with 2,4-dinitrophenylhydrazine reagent. The derivatized acetaldehyde was then isolated by solid phase extraction and followed by high performance liquid chromatography quantitation. This method had a minimal detectable concentration of 0.28 microM, and displayed an intra-assay precision of 2.23% and an inter-assay precision of 5.18%. The recoveries of acetaldehyde at added concentrations of 1.42 and 7.14 microM were 106.7% and 101.9%, respectively.

Acetaldehyde↗

PubMed2003

Simultaneous solid-phase extraction combined with liquid chromatography with ultraviolet absorbance detection for the determination of remifentanil and its metabolite in dog plasma.

To establish pharmacokinetic/pharmacodynamic relationships, a selective and specific high-performance liquid chromatographic method was developed for the quantitation of remifentanil and its metabolite in dog plasma. The assay involves a solid-phase extraction and a reversed-phase chromatographic separation with ultraviolet detection (lambda=210 nm). The calibration curves are linear in the range of 7.89-1500 ng ml(-1). Intra-day assay variability is less than 7% for all standards evaluated. Good recovery, linearity, accuracy, and precision were achieved with the assay that proved readily applicable to pharmacokinetic studies in dogs.

Analgesics, Opioid↗

PubMed1995

Analysis of cocaine and its metabolites from biological specimens using solid-phase extraction and positive ion chemical ionization mass spectrometry.

An accurate and reliable gas chromatographic-mass spectrometric method was developed to analyze tissue, whole blood, plasma, and urine samples for cocaine (COC) and its major metabolites. COC, benzoylecgonine (BZE), and ecgonine methyl ester (EME) were isolated from the biological matrix using solid-phase extraction, and the tert-butyldimethylsilyl derivatives of BZE, EME, and their deuterium-labeled internal standards were formed. Separation of the compounds was performed by capillary chromatography, and analysis was performed by positive ion chemical ionization mass spectrometry using methane and ammonia as the reagent gases. The tert-butyldimethylsilyl derivatives of BZE and EME were stable and produced mass spectral ions with higher mass-to-charge ratios than trimethylsilyl derivatives. Recovery of COC and its metabolites exceeded 80% at all three concentrations tested. Linearity of the method was established from 2.5 to 2000 microg/L. Intra-assay precision had a coefficient of variation (CV) of less than 9% for all analytes when tested at 10, 25, 100, and 200 microg/L. Interassay precision also had a CV of less than 9% for COC, BZE, and EME at 25 and 100 microg/L. At 200 microg/L, %CVs for COC, BZE, and EME were 11.5, 12.0, and 12.7, respectively. In addition to the analysis of COC, BZE, and EME, the method was used to quantitate cocaethylene and to identify norcocaine.

Calibration↗

PubMed1988

Determination of fat-soluble vitamins in a pharmaceutical dosage form by solid-phase extraction and reversed-phase liquid chromatography.

A rapid and precise method for the determination of fat-soluble vitamins from a water-based multivitamin mixture was developed utilizing solid-phase extraction and reversed-phase high-performance liquid chromatography (HPLC). Cholecalciferol, alpha-tocopherol acetate, and retinol palmitate were extracted in a single stage from the matrix using Bond Elut C18 columns. The vitamins were then chromatographed on a Hypersil 5-microns C18 column, using a water:methanol gradient, and quantified simultaneously using individual UV absorption maxima. The recovery of added analytes varied from 92.6 to 100.6%. The assay coefficient of variation was 1.7-2.7%. The sample preparation method and HPLC assay described here are practical for pharmaceutical quality control purposes.

Cholecalciferol↗

PubMed1994

Solid-phase extraction of small drugs on apolar and ion-exchanging silica bonded phases: towards the development of a general strategy.

In connection with the development of a general strategy for solid-phase extraction (SPE) of drugs, the use of the apolar octadecyl silica bonded phase and ion-exchanging phases with a benzene sulphonic acid or quaternary amine bonded functionality is investigated for the SPE of small polar drugs. This investigation was performed on a set of 15 drugs, belonging to varying pharmacological groups and with varying structures. For each analyte, its adsorption on the C18 and the ion-exchanging phase was controlled for an aqueous solution and for a spiked plasma sample. For those analytes retained on the sorbent, different elution solvents were compared. Although SPE methods could successfully be developed for some drugs, no general solution can be proposed and no solution was found for a few drugs. The main problems are that for these few drugs no sufficient retention is obtained on any SPE phase investigated or the selectivity is too low.

Amines↗

PubMed2003

Effective pretreatment of human serum samples for dioxin analysis by solid phase extraction and blue-chitin column cleanup.

For the analysis of dioxins, polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDDs/Fs) and coplanar polychlorinated biphenyls (Co-PCBs), devising simple and economical methods is important, especially for mass screening of human exposure. Pretreatment of samples, namely the extraction and cleanup methods that are widely used at present, needs to be improved for savings in time, manpower, and solvent consumption. In the present study, we applied solid phase extraction (SPE) using octadecyl (C18) and a blue-chitin column in place of liquid-liquid extraction (LE) and an active-carbon column with serum samples, frequently used for assessment of human exposure. Efficacy of the new pretreatment methods was demonstrated by successful high resolution gas chromatography-high resolution mass spectrometry (HRGC-HRMS) of the major 17 PCDDs/Fs and 12 Co-PCBs that are on the list of WHO/IPCS (1997) hazardous dioxins with toxic equivalent factor (TEF) values. SPE is timesaving and requires less manpower and organic solvent as compared with the LE that is presently widely used. Concerning cleanup with blue-chitin, the amount of toluene applied as eluent could be reduced to 1/3, as compared with the active-carbon case. The combination of SPE and blue-chitin for pretreatment of serum saves time and manpower, is accurate and uses less organic solvent than LE with active carbon cleanup.

Chitin↗