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PubMed1997

Sensitive reversed-phase high-performance liquid chromatographic method for the determination of atevirdine and its N-desethyl metabolite in human saliva or cerebrospinal fluid using solid-phase extraction.

A sensitive reversed-phase high-performance liquid chromatographic method for the determination of atevirdine and its primary metabolite in human saliva or cerebrospinal fluid using solid-phase extraction is described. Samples mixed with internal standard and sodium phosphate buffer were applied to an activated C18 solid-phase extraction column. The reconstituted eluate was injected onto a Zorbax RX C8 column utilizing a mobile phase of 100 mM ammonium acetate (pH 4.0)-isopropyl alcohol-acetonitrile (55:20:25, v/v/v). Fluorescence detection was employed with excitation at 295 nm and emission at 456 nm. Quantitation was achieved using peak-height ratios. The detection response curve was linear from 2 to 850 nM for atevirdine in both human saliva and cerebrospinal fluid and from 2 to 250 nM for the metabolite in human saliva. The method was utilized to analyze cerebrospinal fluid and saliva samples from clinical studies.

Antiviral Agents↗

PubMed2000

Immuno-affinity solid-phase extraction.

The measurement of trace organics such as drugs and pesticides at low concentration in biological and environmental samples is a challenging analytical task. Despite recent advances in instrumentation most analysts regard sample preparation as the rate-limiting step in the overall analytical method. In recent years there has been a lot of interest in immobilising antibodies onto solid supports such as silica to provide highly selective solid-phase extraction. This paper reviews the use of immuno-affinity for solid-phase extraction. It uses as examples extraction of chlortoluron and isoproturon from water and morphine and clenbuterol in urine and plasma respectively. An extensive list of other examples is given. Optimisation procedures are discussed in detail.

Chromatography, Affinity↗

PubMed2006

Selective extraction of organophosphorus nerve agent degradation products by molecularly imprinted solid-phase extraction.

The analysis of alkyl alkylphosphonic acids, the degradation products of V and G nerve agents as VX, Sarin or Soman, is an important task for the verification of compliance to the Chemical Weapons Convention. The detection of these contaminants at low concentration levels is often difficult in complex matrices due to the amount of interfering substances. Molecularly imprinted solid-phase extraction technique should allow a selective extraction of these compounds from complex samples, and thus make their detection easier. Two molecularly imprinted polymers (MIPs) prepared with methacrylic acid (MAA) as monomer and pinacolyl methylphosphonic acid (PMPA) as template molecule were synthesised and tested. The first polymer, MIP A, was prepared with ethylene glycol dimethacrylate (EGDMA) in dichloromethane. The second polymer, MIP B, was synthesised using trimethylolpropane trimethacrylate (TRIM) in acetonitrile. To evaluate the selectivity provided by these MIPs, the retention of the ethyl methylphosphonic acid (EMPA) target molecule was studied in parallel on a non-imprinted polymer (NIP). While MIP A does not show any difference compared to NIP A, a good selectivity was obtained for MIP B. After the optimisation of the extraction process, 60% of EMPA can be removed from the NIP B without affecting the retention on the MIP B. A recovery of extraction of 93% was then obtained on the MIP B. Its capacity was then measured and corresponds to 97 microg of EMPA per gram of MIP. Finally, the selectivity of MIP B was clearly demonstrated by applying it to the clean-up of a soil extract spiked with EMPA.

Chemical Fractionation↗

PubMed2002

Extraction of amphetamine and methamphetamine from urine specimens with Cerex Polycrom Clin II solid-phase extraction columns and the Speedisk 48 Pressure Processor.

Extraction of amphetamine and methamphetamine in urine was investigated using Cerex Polycrom Clin II solid-phase extraction columns and the Speedisk 48 Pressure Processor as a replacement for our liquid-liquid procedure. Linearity for urine standards extracted with the Cerex-Speedisk method ranged from 50 ng/mL for methamphetamine and from 150 ng/mL for amphetamine to 10,000 ng/mL for both. The mean recovery at the 500-ng/mL cutoff for three different lots of columns was 96.4% for AMP and 95.7% for MET. The mean of the within-run means for three batches was 495.4 ng/mL with a coefficient of variation (CV) of 1.2% or less for amphetamine and 496.4 ng/mL for methamphetamine with a CV of 1.7% or less. Thirty-six specimens containing amphetamine and the same number for methamphetamine were analyzed by both the Cerex-Speedisk and liquid-liquid methods. The correlation for specimens containing amphetamine gave an r2 of 0.9986 with a slope of 0.99; for methamphetamine, the r2 was 0.9997 with a slope of 0.98. The Cerex-Speedisk method cut extraction time in half, was less costly, and greatly reduced the volume of hazardous waste.

Amphetamine↗

PubMed1999

Development and validation of a sensitive solid-phase extraction and high-performance liquid chromatography assay for the novel antitumour agent CT2584 in human plasma.

A HPLC assay and solid-phase extraction technique from human plasma has been developed and validated for the novel anticancer agent CT2584, 1-(11-dodecylamino-10-hydroxyundecyl)-3,7-dimethylxanthine, which has recently completed a phase I trial at the Christie Hospital, Manchester under the auspices of the CRC phase I/II committee. Following addition of CT2576, 1-(11-octylamino-10-hydroxylundecyl)-3,7-dimethylxanthine, as internal standard, a solid-phase extraction cartridge (100 mg cyanopropyl) was used to isolate the drug CT2584 from human plasma. Analysis was performed by reversed-phase chromatography. CT2576 was used as internal standard at a concentration of 4 microg ml(-1) for the quantification of CT2584 from plasma for the duration of this work. The lower limit of quantification for the drug CT2584 in buffer using this assay was found to be 0.0122 microM (0.008 microg ml(-1)) and 0.048 microM (0.027 microg ml(-1)) when extracted from human plasma.

Antineoplastic Agents↗

PubMed2002

Poly(methyloctadecylsiloxane) immobilized on silica by gamma radiation for use in solid-phase extraction.

This work presents a fast, easy and effective procedure to obtain silica-based C18 type sorbents for use in solid-phase extraction (SPE). The solid-phase was made by depositing a polymer, poly(methyloctadecylsiloxane) (PMODS), on the silica support followed by immobilization using gamma irradiation. The method presents an application of green chemistry in the analytical laboratory, since there are no toxic residues after the synthesis. Water samples spiked with a mixture of pesticides (benomyl, tebuthiuron, diuron, simazine, atrazine and ametryn) were extracted in the off-line mode in order to evaluate the performance of this sorbent.

Absorption↗

PubMed2006

Molecularly imprinted solid-phase extraction method for the high-performance liquid chromatographic analysis of fungicide pyrimethanil in wine.

A method for molecularly imprinted solid-phase extraction (MISPE) of the fungicide pyrimethanil from wine samples has been investigated. The molecular imprinted polymer was obtained by iniferter-mediated grafting on porous chloromethylated polystyrene beads, using methacrylic acid as the functional monomer and ethylene glycol dimethacrylate as the cross-linker. The imprinted beads were evaluated for use as a solid-phase extraction sorbent, in order to develop the extraction protocol in aqueous standards and red wine samples. The optimised extraction protocol resulted in a reliable MISPE method suitable for HPLC analysis (stationary phase: Cromolith Performance C18 column, 100 mm x 4.6 mm; mobile phase: acetonitrile-water (3:2, v/v), flow-rate: 1.00 ml/min; detection 270 nm). It was selective for pyrimethanil and the related pyrimidinic fungicides cyprodinil and mepanipyrim, while the non-pyrimidinic fungicides benalaxyl, chlozolinate, furalaxyl, iprodione, metalaxyl, nuarimol, procymidone and vinclozolin were not extracted. Recoveries performed on a wine matrix spiked with pyrimethanil at three different concentration levels were reproducible and were in good agreement with the recoveries performed on buffer, coming out between 80 and 90% (85+/-7.0% at 0.50 microg/ml, 79+/-1.6% at 2.0 microg/ml and 87+/-5.6% at 20 microg/ml). Preconcentration and quantitative extraction of pyrimethanil from wine samples was shown to be feasible down to 0.1 microg/ml.

Chromatography, High Pressure Liquid↗

PubMed1989

Rapid and specific RIA of serum estrone sulfate with selective solid phase extraction.

The methods commonly used to evaluate conjugated steroids require hydrolysis and chromatographic purification. To avoid these steps, a simple method involving selective solid phase extraction and RIA using a highly specific antiserum for estrone sulfate (E1S) has been evolved. A Bond-Elut C2 cartridge was used for solid phase extraction of estrone (E1) and E1S; recoveries were 80 and 90% respectively. The intra- and inter assay precision of the assay at 3 serum levels, were 6.5, 10.4 and 4.4 and 12.7, 13.9 and 7.4% respectively. Accuracy, tested by linearity and recovery tests, was acceptable. A good correlation exists between a conventional enzymatic method and the proposed method. The latter is less time consuming and more reliable, thus providing a rapid assay to evaluate E1 and E1S in the same serum sample.

Estrone↗

PubMed2004

Determination of quinolones in water samples by solid-phase extraction and liquid chromatography with fluorimetric detection.

A method is reported for the determination, in water samples, of 10 quinolones which are used as veterinary drugs. Analytes are isolated from samples by solid-phase extraction (SPE) and analysed by reversed-phase high-performance liquid chromatography using fluorimetric detection. A solid-phase extraction procedure based on retention on HBL OASIS cartridges and elution with a mixture of acetonitrile-water in basic medium is suitable for pre-concentration of the analytes. Pre-concentration factors up to 250 can be obtained. The quinolones are separated with an octyl silica-based column and mobile phases consisting of aqueous oxalic acid solutions and acetonitrile mixtures. The attained detection limits of the whole process are in the ng l(-1) level when 250 ml of water sample is processed. Recovery rates, from natural water samples spiked at 2060 ng l(-1) level, range from 70 to 100% and common standard deviation are about 6-12%.

Anti-Bacterial Agents↗

PubMed1992

Determination of benzalkonium chloride in eye care products by high-performance liquid chromatography and solid-phase extraction or on-line column switching.

Benzalkonium chloride (BAK) is a mixture of alkylbenzyldimethylammonium chlorides, which is commonly used as a bacteriostat. In this work, the three major homologues of BAK are quantitated in the over-the-counter eye care products Murine and Murine Plus using high-performance liquid chromatography (HPLC). The analytes are separated from various product excipients and concentrated by either solid-phase extraction onto Sep-Pak C18 cartridges or by an on-line column-switching technique using 1-cm reversed-phase precolumns. Absolute recoveries of BAK homologues by the solid-phase extraction technique ranged from 97.2 to 98.7% for standards and from 98.0 to 98.4% for samples. Absolute recovery of the BAK homologues by the column-switching technique was 101.3% for standards and ranged from 99.9 to 103.7% for samples. Relative recoveries were quantitative by both techniques. Assay precision (R.S.D. values) were +/- 2.2% to +/- 2.6% and +/- 0.4% to +/- 0.8% by solid-phase extraction and column-switching techniques, respectively. The method provides advantages of high sample throughput, excellent column life and automation.

Benzalkonium Compounds↗

PubMed2006

Fully automated analytical method for mycophenolic acid quantification in human plasma using on-line solid phase extraction and high performance liquid chromatography with diode array detection.

We have developed a new fully automated method for mycophenolic (MPA) acid quantification in plasma to optimize therapeutic drug monitoring of tranplant patients. This method involved solid-phase extraction on disposable extraction cartridges and reversed-phase high-performance liquid chromatography with diode array detection. Solid-phase extraction was performed automatically by an automated sample with extraction catridges system. After washing, MPA was eluted from the cartridge onto a Chromolith RP-18e column. MPA and the internal standard were detected at 306 nm. The retention time of MPA was 6.3 minutes. The developed method was linear from 0.2 to 20 microg/mL. The limit of quantification was 0.2 microg/mL. The method showed a good precision with intraday and interday variation coefficient less than 6%. The intraday accuracy ranged from 97.6% to 100.4% and the interday accuracy varied from 97.1% to 100.8%. The extraction efficiency was greater than 90%. This method is simple and shows a good specificity with respect to commonly co-prescripted drugs.

Antibiotics, Antineoplastic↗

PubMed2006

A validated method for the determination of nicotine, cotinine, trans-3'-hydroxycotinine, and norcotinine in human plasma using solid-phase extraction and liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry.

A liquid chromatographic-mass spectrometric method for the simultaneous determination of nicotine, cotinine, trans-3'-hydroxycotinine, and norcotinine in human plasma was developed and validated. Analytes and deuterated internal standards were extracted from human plasma using solid-phase extraction and analyzed by liquid chromatography/atmospheric pressure chemical ionization-mass spectrometric detection with selected ion monitoring (SIM). Limits of detection and quantification were 1.0 and 2.5 ng/ml, respectively, for all analytes. Linearity ranged from 2.5 to 500 ng/ml of human plasma using a weighting factor of 1/x; correlation coefficients for the calibration curves were > 0.99. Intra- and inter-assay precision and accuracy were < 15.0%. Recoveries were 108.2-110.8% nicotine, 95.8-108.7% cotinine, 90.5-99.5% trans-3'-hydroxycotinine, and 99.5-109.5% norcotinine. The method was also partially validated in bovine serum, owing to the difficulty of obtaining nicotine-free human plasma for the preparation of calibrators and quality control (QC) samples. This method proved to be robust and accurate for the quantification of nicotine, cotinine, trans-3'-hydroxycotinine, and norcotinine in human plasma collected in clinical studies of acute nicotine effects on brain activity and on the development of neonates of maternal smokers.

Atmospheric Pressure↗

PubMed2000

Determination of vitamin D2 in emulsified nutritional supplements by solid-phase extraction and column-switching high-performance liquid chromatography with UV detection.

This paper deals with a method for solid-phase extraction of trace amounts of vitamin D2 (VD2, 19 ng/g) from emulsified nutritional supplements, which contain 50 kinds of compounds, followed by column-switching high-performance liquid chromatography (HPLC) with UV detection at 265 nm. VD2 is present at 1000-20,000,000 times lower concentration than other components. Bond Elut C18 cartridge was chosen as for the emulsified nutritional supplements after comparison with eight other types. A sample solution was applied to the solid-phase extraction cartridge and VD2 was eluted by methanol followed by HPLC. The effects of sample pH, eluent composition and eluate volume on the retention and elution of VD2 on Bond Elut C18 cartridge were examined. The resulting method was simple, rapid (analysis time: approximately 20 min), sensitive (detection limit: approximately 0.1 ng per injection (200 microl) at a signal-to-noise ratio 3:1), and reproducible (relative standard deviation: approximately 6.2%, n=5). The calibration graph for VD2 was linear in the range of 0.1-3 ng per injection (200 microl). Recovery of VD2 was approximately 80% by the standard addition method.

Calibration↗

PubMed1996

Determination of sumatriptan succinate in human plasma by high-performance liquid chromatography with coulometric detection and utilization of solid-phase extraction.

Sumatriptan succinate (the analyte) and naloxone (the internal standard) were extracted from plasma with a solid-phase extraction technique. Chromatography and detection were performed by isocratic reversed-phase high-performance liquid chromatography with coulometric end-point detection. The standard curve was linear over the range 0-100 ng/ml of sumatriptan succinate in plasma. The reproducibility (as defined by the coefficient of variation, C.V.) over the range of the standard curve was 4.9-7.3%. The recovery averaged 83%. The sensitivity was 0.25 ng of sumatriptan on column (allowing a concentration of 0.5 ng/ml to be determined from a 1-ml plasma sample volume). Plasma profiles of the analyte following subcutaneous (s.c.) administration in eight normal male volunteers, are presented.

Chromatography, High Pressure Liquid↗

PubMed2002

Miniaturized solid-phase extraction as a sample preparation technique for the determination of phthalates in water.

Miniaturized solid-phase extraction (SPE) has been developed and successfully employed for the determination of organic species in water samples by liquid chromatography (LC). The method is based on the concept of a microscale extraction technique using a fused-silica capillary column for gas chromatography (GC), so-called in-tube solid-phase microextraction (SPME). The extraction conditions, such as the extraction time and flow-rate for the extraction and desorption process, were investigated as well as the effect of the internal structure of the extraction capillary on the efficiency. By inserting a stainless steel wire into the extraction capillary to reduce the internal volume of the capillary with the same surface area of the coating, an improved extraction and pre-concentration effects were obtained. Further pre-concentration was accomplished by the extraction device with a novel fiber-in-tube configuration. The direct coupling of the extraction method with a LC system has made it possible to determine low levels of phthalates in water samples without high consumption of organic solvents. The system developed must have potential applications for the analysis of environmental and biological samples in aqueous sample matrices.

Capillary Action↗

PubMed2005

Highly selective solid-phase extraction and large volume injection for the robust gas chromatography-mass spectrometric analysis of TCA and TBA in wines.

A reliable solid-phase extraction (SPE) method for the simultaneous determination of 2,4,6-trichloroanisole (TCA) and 2,4,6-tribromoanisole (TBA) in wines has been developed. In the proposed procedure 50 mL of wine are extracted in a 1 mL cartridge filled with 50 mg of LiChrolut EN resins. Most wine volatiles are washed up with 12.5 mL of a water:methanol solution (70%, v/v) containing 1% of NaHCO3. Analytes are further eluted with 0.6 mL of dichloromethane. A 40 microL aliquot of this extract is directly injected into a PTV injector operated in the solvent split mode, and analysed by gas chromatography (GC)-ion trap mass spectrometry using the selected ion storage mode. The solid-phase extraction, including sample volume and rinsing and elution solvents, and the large volume GC injection have been carefully evaluated and optimized. The resulting method is precise (RSD (%) < 6% at 100 ng L(-1)), sensitive (LOD were 0.2 and 0.4 ng/L for TCA and TBA, respectively), robust (the absolute recoveries of both analytes are higher than 80% and consistent wine to wine) and friendly to the GC-MS system (the extract is clean, simple and free from non-volatiles).

Anisoles↗

PubMed2000

Screening and determination of benzodiazepines in whole blood using solid-phase extraction and gas chromatography/mass spectrometry.

Benzodiazepines are one of the most widely prescribed drugs for the treatment of a wide spectrum of clinical disorders. They are used as anticonvulsants, anxiolytics, hypnotics or muscle relaxants with different duration of action. In this paper, a simple and sensitive method for the determination of benzodiazepines in whole blood using solid-phase extraction and gas chromatography/mass spectrometry (GC/MS) is described. The drugs spiked in whole blood were extracted with an Oasis HLB solid-phase extraction cartridge (Waters), which contains a copolymer designed to have a hydrophilic-lipophilic balance. GC/MS analysis was performed using a Shimadzu QP-5000 equipped with a BPX5 capillary column (15 mx0.32 mm I.D., film thickness 0.25 microm, SGE). Nineteen benzodiazepines and two thienodiazepines were well separated from each other on their SIM chromatograms and also on the TIC with the exception of oxazolam to cloxazolam separation. The blank extract from whole blood gave no peaks that interfered with all benzodiazepines and thienodiazepines on the chromatogram. The calibration curves for selected benzodiazepines with fludiazepam as an internal standard showed excellent linearity over the concentration range 5-500 ng/ml blood with a correlation coefficients of >0.995. The detection limits ranged from 0.2 to 20 ng/ml blood. The method is simple and sensitive for the determination of benzodiazepines in whole blood and seems to be useful in the practice of forensic science.

Anti-Anxiety Agents↗

PubMed1998

Development and validation of a differential pulse polarographic method for quinolinic acid determination in human plasma and urine after solid-phase extraction: a chemometric approach.

A chemometric approach was applied for determining quinolinic acid in human plasma by differential pulse polarography after solid phase extraction. A fractional factorial design was used to examine the significant experimental variables for the peak height maximization. A Doehlert design, which allowed a sequential response surface methodology to be performed, was applied to the variables scan rate and drop size. The results indicated that the scan rate had the greatest effect on the response peak height. The linear range was extended from 8.52 x 10(-8) to 1.34 x 10(-5) M and the limit of detection was 2.9 x 10(-8) M. The validation process consisted of a pre-validation study followed by the main validation in the plasma matrix. The robustness and the intermediate precision were evaluated by means of experimental design. A 3(4)//9 screening symmetric matrix and a central composite design were used to optimize the solid phase extraction procedure of the analyte from human plasma using anion exchange cartridges. The goal was to select the best retention, wash and elution solvents and their volumes in order to maximize the extraction efficiency using as the response the polarographic peak height. An extraction efficiency of 90% was found. The method was also applied to the determination of quinolinic acid in urine and the mean concentration in human plasma and urine, was found to be 3.7 x 10(-7) and 4.9 x 10(-5) M respectively.

Chemistry Techniques, Analytical↗