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PubMed2005

Determination of commonly used herbicides in surface water using solid-phase extraction and dual-column HPLC-DAD.

The present study describes the application of different solid-phase extraction techniques for the extraction, separation, and quantitative determination of 10 commonly used herbicides with different chemical structures (chlorsulfuron, diuron, bentazone, linuron, chlorpropham, fenoxoprop-ethyl, MCPA, diclofop-methyl, fluazifop-butyl, trifluraline) in water. Octadecyl (C(18)) Empore extraction disks, octadecyl (C(18)), and stryene divinylbenzene (SDB) Bond Elut Env cartridges were compared for solid-phase extraction efficiency. Herbicides were separated and quantified by reversed-phase high performance liquid chromatography with diode-array detection (HPLC-DAD) with simultaneous separation on two columns of differing polarity (C(18) and CN) to confirm identification. Analytical separation was performed simultaneously on C(18) and CN columns. Reanalysis of the sample extracts on a (cyano) CN column were used to confirm the identity of these compounds. Method optimization and validation parameters were presented in this work. Recoveries varied from 76.0% to 99.0% for C(18) disks, from 75.1% to 100.0% for C(18) cartridges, and from 54.0% to 98.0% for SDB cartridges over concentrations at 0.025--0.4 microg L(-1). The limits of detection were 0.012--0.035 microg L(-1).

Chromatography, High Pressure Liquid↗
PubMed2005

Determination of quinolones and fluoroquinolones in hospital sewage water by off-line and on-line solid-phase extraction procedures coupled to HPLC-UV.

In this work, the development of two solid-phase extraction procedures (off-line and on-line formats) for the identification and quantification of several (fluoro)quinolones in hospital sewage water by HPLC-UV is described. Both procedures are based on the use of C18 and anion exchange (SAX) sorbents for the preconcentration and clean-up steps, respectively, and all variables influencing both steps were optimised. In the off-line format, after its pH was adjusted to 2.5, sample was preconcentrated on a C18 cartridge and eluted with 4 mL of methanol/ammonia (94/6). The methanolic extract must be diluted up to 10 mL with water to allow quantitative retention of the analytes on the SAX cartridge. In the on-line format, the addition of 2.5% of NH4Cl to the sewage water sample (pH = 2.5) was necessary to increase the breakthrough volumes of the analytes in the C18 precolumn. Quantitative transfer of the (fluoro)quinolones from the C18 precolumn to the SAX precolumn was accomplished by pumping 2 mL of a mixture methanol/water (40/60, pH = 9.2) at 2 mL min(-1). Elution of the analytes from the SAX precolumn by means of the chromatographic mobile phase required the inclusion of an additional isocratic step at the beginning of the gradient program. Both off-line and on-line solid phase extraction procedures coupled to HPLC-UV were applied to the analysis of a sewage water sample collected in the sewer system at the output of the St Dimphna Hospital (Geel, Belgium). The fluoroquinolone ciprofloxacin was found in this sample and quantified at 5.8 +/- 0.4 microg L(-1) (off-line method) and 5.6 +/- 0.5 microg L(-1) (on-line method). The analysis of spiked samples containing the seven (fluoro)quinolones studied provided quantitative recoveries in all cases with low RSD values (from 6 to 12%), and all the analytes could be identified by means of their UV spectra with match factors varying from 950 to 985 depending on the (fluoro)quinolone.

Chromatography, High Pressure Liquid↗
PubMed1996

[Studies on solid phase extraction of bile acids from biological matrix].

To quantify bile acids in biological samples, a solid phase extraction method was examined. This method is known as simpler procedures with less contamination compared with solvent extraction methods. Rat bile, feces and urine were used as biological samples. Since Bond Elut C18 and C8 were proved to be more suitable than the other phases (CH and SAX) so far examined using standard bile acids, Bond Elut C18 was used for biological samples. Quantification of biological sample was carried out by gas chromatography after the extracted sample was derivatized to methyl ester by treatment with trimethylsilyldiazomethane then to trifluoroacetyl ester by trifluoroacetic anhydride. On the gas chromatography, two columns (Rtx-50 and Rtx-200) were connected to the injector with Y-tube for elimination of interference. Except for a few bile acids, high recovery with less biological contamination was obtained by this solid phase extraction method.

Animals↗
PubMed2005

Development of a high-throughput format for solid-phase extraction of enantiomers using an immunosorbent in 384-well plates.

An antibody-based solid-phase extraction method for filtered 384-well plates was developed for a medical drug candidate having two enantiomeric forms in order to demonstrate the potential of the use of recombinant antibody fragments as specific and efficient immunosorbents. An immobilization method using a six-histidine tag of the antibody fragment and mild oxidation was applied in order to immobilize antibody fragments in an oriented and kinetically stable way that ensured high capacity of the antibody support. Phosphate buffer or plasma spiked with enantiomers were used as samples. Selective solid-phase extraction was followed by liquid chromatography-mass spectrometry analysis. Average recoveries for buffer and plasma samples ranged from 79 to 122% and 80 to 108%, respectively. Good linearity was observed in the concentration range of 30-3000 ng/mL of the enantiomer.

Antibodies↗
PubMed2005

The isolation of soyasaponins by fractional precipitation, solid phase extraction, and low pressure liquid chromatography.

Bioactive soyasaponins are present in soybean (Glycine max). In this study, the isolation of soyasaponins in relatively pure form (>80%) using precipitation, solid phase extraction and reverse phase low pressure liquid chromatography (RP-LPLC) is described. Soy flour soyasaponins were separated from non-saponins by methanol extraction and precipitation with ammonium sulphate. Acetylated group A soyasaponins were isolated first by solid phase extraction followed by RP-LPLC (solvent: ethanol-water). Soyasaponins, from a commercial preparation, were saponified and fractionated into deacetylated group A and group B soyasaponins by solid phase extraction (methanol-water). Partial hydrolysis of group B soyasaponins produced a mixture of soyasaponin III and soyasapogenol B monoglucuronide. RP-LPLC of deacetylated group A soyasaponins separated soyasaponin A1 and A2 (38% methanol); of group B soyasaponins isolated soyasaponin I (50% ethanol); and of the partial hydrolysate separated soyasaponin III from soyasapogenol B monoglucuronide (50% ethanol). This methodology provides soyasaponin fractions that are suitable for biological evaluation.

Chromatography, Liquid↗
PubMed1994

Solvent and solid-phase extraction of natural and synthetic corticoids in human urine.

Optimization of the main variables that affect solvent and solid-phase extraction processes, using disposable C18 cartridges and the non-ionic polymeric resin Serdolit AD-2, of human urine containing natural and synthetic corticoids is described. The data were obtained from different HPLC separations of these compounds using calibration graphs obtained before and after extraction of these compounds. The procedures, including sample preconcentration, showed efficiencies over 90%. NaCl was used to avoid emulsion formation in solvent extraction. The results achieved using solvent and solid-phase extraction are discussed.

Adrenal Cortex Hormones↗
PubMed2005

Solid phase extraction and liquid chromatographic determination of sildenafil and N-demethylsildenafil in rat serum with basic mobile phase.

HPLC method for the determination of sildenafil and its metabolite (N-demethylsildenafil) in rat serum has been developed. The technique included a solid phase extraction of the serum samples on a [poly(divinylbenzene-co-N-vinylpyrrolidone)] solid phase extraction sorbent. After conditioning, the cartridge was loaded with 0.5 mL of buffered serum containing internal standard. Elution was made with 1 mL of acetonitrile. After evaporation of the eluates to dryness and reconstitution with methanol, the samples were analyzed on Kromasil C18 column phase with phosphate buffer 0.05 M/acetonitrile: 54/46, pH 8. Detection was carried out using a photodiode array detector. For sildenafil and demethylsildenafil, full validation of the proposed method was provided (linearity range, calibration curves, average extraction efficiency; average intra-day and interday variabilities, limit of detection, limit of quantification, specificity). The proposed method was successfully utilised to quantify sildenafil and N-demethylsidenafil in rat serum for a pharmacokinetic study.

Acetonitriles↗
PubMed1990

Determination of warfarin in drinking water by high-performance liquid chromatography after solid-phase extraction.

A method for the determination of 0.1 micrograms/l of warfarin in drinking water involving concentration by solid-phase extraction is described. A 1000-ml volume of drinking water is aspirated through a solid-phase extraction column and warfarin is eluted to 1.0 ml. The eluate is analysed by reversed-phase high-performance liquid chromatography with UV detection. The detection limit is 0.02 micrograms/l. Recoveries of greater than 90% were obtained when tap water was spiked with warfarin.

Chromatography, High Pressure Liquid↗
PubMed2001

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

Benzoylecgonine (BZE) extraction from urine was explored using Cerex Polycrom Clin II solid-phase extraction (SPE) columns and the Speedisk 48 Pressure Processor as an alternative to the Prep1 automated sample processor and XTRX Type RP/W columns. Linearity for urine standards extracted using the Cerex-Speedisk method ranged from 20 to 3000 ng/mL. The mean recovery at the 100-ng/mL cutoff for three lots of columns was 92%. The mean of the within-run means for three batches, which had coefficients of variations of 1.8% or less, was 101.3 ng/mL at the 100-ng/mL cutoff level. Forty-six specimens known to contain BZE were analyzed by both the Prep1-Type RP/W and Cerex-Speedisk methods. The correlation for specimen BZE concentrations between the two methods gave an r2 of 0.9999 and a slope of 1.03. The Cerex-Speedisk system is an inexpensive alternative to the Prep1-Type RP/W system. It is less costly, requires little maintenance, has a small footprint, is hood compatible, and can process four times the number of specimens in a given time.

Automation↗
PubMed1998

[Solid-phase extraction coupled with high-field proton nuclear magnetic resonance spectroscopy: application to the analysis of brodimoprim metabolites in rat urine].

The use of coupled solid-phase extraction and high-field proton nuclear magnetic resonance spectroscopy (SPE-1HNMR) for the detection and identification of the urinary metabolites of brodimoprim is described. Urine was obtained from Wistar rats following a dose of 200 mg.kg-1 of brodimoprim. Analysis was performed on partially purified extracts obtained by solid-phase extraction onto C-18 bonded silica gel. As each spectrum was often given by a mixture of more than two kinds of metabolites, stepwise identification of the individual metabolites was achieved by sorting out signal sets having invariant proportionality. Five kinds of metabolites of the drug were found by the analysis.

Animals↗
PubMed2003

Automated solid-phase extraction and liquid chromatographic method for retinoid determination in biological samples.

In this study, a method for partly automated sample preparation and fully automated solid-phase extraction method for plasma, kidney and liver samples for various retinoids like all-trans-4-oxo-retinoic acid, 13-cis-4-oxo-retinoic acid, 13-cis-retinoic acid, 9-cis-retinoic acid, all-trans-retinoic acid, retinol and retinyl palmitate was established. Plasma, embryo-, kidney-and liver-homogenates were automatically mixed and extracted on multiple usage solid-phase (C2) extraction cartridges immediately before HPLC analysis. Automated cleaning, preconditioning and incorporation of the loaded cartridge to fully automated HPLC separation and quantification of the various retinoids in a single HPLC run was established. The recovery of the retinoids was generally between 80 and 90%. Intra-day repeatability was < 11.7%. As little as 1.2 ng/ml could be quantified in lipid-mixture standard samples. This method allows a highly automated sample preparation and a fully automated solid-phase extraction with good selectivity for the study of endogenous retinoids and retinoids after nutritional supplementations and pharmacological applications in several biological samples.

Animals↗
PubMed2006

Determination of sulfonamide compounds in sewage and river by mixed hemimicelles solid-phase extraction prior to liquid chromatography-spectrophotometry.

Mixed hemimicelles-based solid-phase extraction was investigated for the preconcentration of five sulfonamides from environmental water samples prior to HPLC-spectrophotometry determination in this paper. A comparative study on the use of sodium dodecyl sulfate (SDS) coating gamma-alumina or octadecyltrimethylammonium bromide (OTMABr) and OTMABr coating silica as sorbent materials were presented. The five analytes (sulfadiazine (SDA), sulfathiazole (STA), sulfapyridine (SPD), sulfamethazine (SMZ) and sulfamethoxazole (SMX)) were quantitatively adsorbed on OTMABr-gamma-alumina and OTMABr-silica mixed hemimicelles, but OTMABr-gamma-alumina was not adopted because it worked at a high pH (around 10), instead, OTMABr-silica was selected to overcoming the pH restriction. The analytes retained on the cartridge were quantitatively desorbed with suitable amounts of methanol. Factors influencing the extraction efficiency, such as the amount of surfactant, pH of sample and breakthrough volume were discussed. The proposed method had been applied to determining the five sulfonamides in several environmental water samples and concentration factors of 300 and 600 for SDA and other four analytes were achieved, respectively. Detection limits obtained ranged between 0.15 and 0.35microg/L for this five sulfonamides under the optimized conditions. The accuracy of the method was evaluated by recovery measurements on spiked samples, and good recovery results (89-113%) with precision of 3-6% were achieved.

Chromatography, Liquid↗
PubMed1992

Application of solid-phase extraction on anion-exchange cartridges to quantify 5'-nucleotidase activity.

The enzyme 5'-nucleotidase (5'-ribonucleotide phosphohydrolase, EC 3.1.3.5) catalyzes a critical reaction in intermediary metabolism, the phosphohydrolysis of nucleoside 5'-monophosphates to their corresponding nucleosides. We have evaluated solid-phase extraction on pre-packed anion-exchange cartridges as a chromatographic technique with which 5'-nucleotidase activity may be detected and quantified. Chromatographic conditions were established whereby substrate nucleotide was rapidly and completely separated from its corresponding nucleoside by solid-phase extraction. Both analytes were recovered quantitatively, without loss or degradation. This chromatographic system was integrated into a discontinuous radiochemical assay for 5'-nucleotidase which enabled both substrate utilization and product formation to be assessed simultaneously. Enzyme reaction samples could be analyzed directly for 5'-nucleotidase activity without any pre-chromatography preparation. The high capacity of the solid-phase cartridges and the inability of 5'-nucleotidase to enter the packing bed during analyte elution facilitated termination of the enzyme reaction by applying the entire reaction mixture to the cartridge. Loaded cartridges could then be stored at 4 degrees C prior to chromatography and subsequently batch-eluted. The excellent resolution between substrate and product in solid-phase extraction and the sensitivity of radioisotopic counting enabled detection/quantification of low tissue levels of 5'-nucleotidase in conjunction with ancillary assays for secondary enzyme reactions with the potential to elicit the artifactual loss of 5'-nucleotidase substrate/product when crude biological preparations are examined for 5'-nucleotidase activity. Our results demonstrate that solid-phase extraction on anion-exchange cartridges with elution solvents of appropriate pH offers several unique advantages for 5'-nucleotidase determination.

5'-Nucleotidase↗
PubMed2000

Solid-phase extraction of phenols.

Sample preparation for phenol analysis using solid-phase extraction (SPE) is reviewed. The scope of the review has been restricted to the literature dealing with the analysis of phenols as the main objective. The use, advantages and disadvantages of silica sorbents, polymeric, functionalized, carbon-based and mixed available sorbents, when applied to the separation and preconcentration of phenols, as well as the available experimental devices, are discussed. Other aspects such as phenol derivatisation prior to SPE, solid-phase microextraction, matrix effects and the storage of phenols in SPE cartridges, have been also discussed.

Chromatography, Liquid↗
PubMed1994

High-performance liquid chromatography determination of clonazepam in plasma using solid-phase extraction.

The use of high-performance liquid chromatography for therapeutic drug monitoring of clonazepam has previously been limited by low sensitivity and labor-intensive liquid-liquid extractions. The present method was developed employing a rapid solid-phase extraction, thus minimising sample workup and providing analytical sensitivity down to 2 micrograms/L using 1 ml of plasma. Plasma samples were loaded onto C18 solid-phase extraction columns, and clonazepam and its internal standard (methyl-clonazepam) were eluted with methanol, dried, and reconstituted in 130 microliters of mobile phase. Chromatographic separation was achieved using a 3-microns RP18 column at 40 degrees C and a mobile phase of 32% acetonitrile and 0.5% glacial acetic acid in distilled water at 0.5 ml/min. Detection was carried out using ultraviolet absorbance at 306 nm. Retention times for clonazepam and methyl-clonazepam were approximately 7 and 12 min respectively. Standard curves were linear over a range of 5-200 micrograms/L with intraassay coefficients of variation of 1.2 and 4.8% at 200 and 5 micrograms/L, respectively. Plasma concentrations measured in patient samples were not statistically different from those obtained using an established gas chromatographic method, and quality control specimens from the Heathcontrol EQA Scheme were consistently within +/- 1.2 SD of the group means. There was no chromatographic interference from other benzodiazepines or other drugs used for the treatment of epilepsy.

Chromatography, High Pressure Liquid↗
PubMed1992

Determination of cocaine and its metabolites in brain tissue using high-flow solid-phase extraction columns and high-performance liquid chromatography.

A new solid-phase extraction procedure for the determination of cocaine and some of its metabolites in brain tissue, using high-flow co-polymeric sorbents is reported as a substantial improvement on our recently reported procedure. The recovery of cocaine, norcocaine and cocaethylene was excellent as was the reproducibility of the extraction. The use of high-flow sorbents allowed the easy extraction of tissue without the need for a time-consuming lipase digestion, regardless of sample viscosity or physical nature. The use of these solid-phase columns provided many advantages over the more commonly used solvent extraction, including an increase in extraction speed and efficiency, reduced operator time, reduced solvent use and disposal volumes and exceptional extract quality. The procedure was successfully applied to rabbit brains spiked with cocaine, benzoylecgonine, norcocaine and cocaethylene.

Animals↗
PubMed1999

High-performance liquid chromatographic determination of benzoylurea insecticides residues in grapes and wine using liquid and solid-phase extraction.

A method for the determination of the benzoylurea insecticides diflubenzuron, triflumuron, teflubenzuron, lufenuron and flufenoxuron in grapes and wine by HPLC has been developed and validated. Grape samples (50 g) were homogenized and extracted with ethyl acetate-sodium sulfate and further cleaned-up by solid-phase extraction on silica sorbent. Wine samples (10 ml) diluted with water (1:3) were solid-phase extracted on an octadecyl sorbent using methanol as the eluent. The pesticides were separated on a reversed-phase octadecyl narrow-bore column by gradient elution and the residues were determined with a UV diode array detector. The calibration plots were linear over the range 0.05-5 micrograms/ml. Recoveries of benzoylurea pesticides from spiked grapes (0.02-2.0 mg/kg) and wine (0.01-0.2 mg/l) were 85.8-101.6% and 69.1-104.8%, respectively, and the limits of quantification for these insecticides were < 0.01 mg/kg for grapes and < 0.01 mg/l for wine. The method was applied to the determination of flufenoxuron and teflubenzuron residues in grapes from treated fields and in produced wine.

Calibration↗
PubMed1989

Improved screening method for beta-blockers in urine using solid-phase extraction and capillary gas chromatography-mass spectrometry.

An improved screening method for beta-blockers in urine is proposed, involving enzymatic hydrolysis, solid-phase extraction and capillary gas chromatography-mass spectrometry. Several extraction methods for beta-blockers, such as conventional liquid-liquid and solid-phase extraction procedures, have been evaluated for at least eight beta-blockers. Additionally, the gas chromatographic properties and mass fragmentation of the trimethylsilyl-trifluoroacetyl, trifluoroacetyl and cyclic n-butylboronate derivatives of beta-blockers have been compared and evaluated with respect to their efficiency for screening urine. The resulting screening method proved to be a specific and sensitive procedure, enabling these analytes to be detected and identified up to 48 h after the administration of a dosage, usually encountered in doping cases.

Adrenergic beta-Antagonists↗