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PubMed2006

Solid-phase extraction and elution on diamond (SPEED): a fast and general platform for proteome analysis with mass spectrometry.

This paper presents a new solid-phase extraction and elution platform based on surface-functionalized diamond nanocrystallites. Compared with conventional methods, the platform facilitates purification and concentration of intact proteins and their enzymatic digests for ensuing sodium dodecyl sulfate-polyacrylamide gel electrophoresis or matrix-assisted laser desorption/ionization mass spectrometry analysis without prior removal of the adsorbent. One-pot work flow involving reduction of disulfide bonds, protection of free cysteine residues, washing off residual chemicals, and proteolytic digestion of adsorbed proteins can be performed directly on the particles. The utility and versatility of this protein workup platform were demonstrated with liquid chromatography-electrospray ionization tandem mass spectrometry in proteome analysis of human urine. The proteome analysis of each urine sample can be completed in 8 h.

Amino Acid Sequence↗
PubMed2004

Determination of limonin D-ring lactone hydrolase activity by solid phase extraction with indirect fluorescence detection.

A method for the evaluation of limonin D-ring lactone hydrolase activity is described. The method utilizes solid phase extraction (SPE) for the isolation of limonin A-ring limonoate (LARL), which is subsequently converted to limonin and quantitated by fluorescence. The fluorescence method is capable of quantifying the formation of LARL in concentrations as low as 75 ng and is applicable to both purified and crude enzyme preparations. The coupling of SPE with fluorescence detection allows for the simple and rapid analysis of samples.

Citrus↗
PubMed1999

Determination of organochlorine pesticide residues in foods using solid-phase extraction clean-up cartridges.

Fourteen organochlorine pesticide residues in fatty foods were determined using a simple and rapid procedure based on solid-phase extraction (SPE) clean-up cartridges with octadecyl (C18)-bonded porous silica, a tandem C18 and Florisil column, Alumina-N and Florisil. A Florisil cartridge eluted with 12 ml petroleum ether-ethyl ether (95 + 5) was the most efficient clean-up procedure capable of eliminating the matrix interference and satisfying the agreed acceptable recovery for the large numbers of organochlorine pesticides in nine kinds of foods having different fat contents. Average recoveries of organochlorine pesticides in shellfish, fish and meats ranged from 77 to 105%, 84 to 98% and 85 to 107%, respectively. In addition, analysis of a certified Standard Reference Material (SRM 1945) verified the satisfactory performance of Florisil clean-up cartridge. This SPE method not only yielded comparable results for nonfatty foods, but also provided a reliable separation and quantification of organochlorine pesticides for analyzing a large number of foods with a wide range of fat content.

Chromatography, Gas↗
PubMed1996

Determination of morphine, morphine-3-glucuronide and morphine-6-glucuronide in human serum by solid-phase extraction and liquid chromatography-mass spectrometry with electrospray ionisation.

A high-performance liquid chromatographic (HPLC) method for the simultaneous determination of morphine and two of its metabolites, morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G), in serum is described. The compounds are extracted from serum using Sep-Pak light C18 solid-phase extraction cartridges, separated on an ODS C18 analytical column (100 x 4.6 mm I.D.) and detected by electrospray ionisation mass spectrometry. The separation was achieved by running a linear gradient from 4 to 70% acetonitrile with formic acid added as modifier. The flow-rate in the column was 1.0 ml/min. After the column, the eluate was subjected to a 1:50 split, with 20 microliters/min delivered to the mass spectrometer and 980 microliters/min delivered to waste. The compounds were detected in the mass spectrometer by selected-ion monitoring for m/z 286.2 for morphine and 462.2 for M3G and M6G. The spray voltage was 2.4 kV and the sampling cone was set at 40 V. The compounds have been quantified in serum over a concentration range of 2.9-60 nmol/l (0.84-17 ng/ml) for morphine, 11-1080 nmol/l (5.0-500 ng/ml) for M3G and 4.3-220 nmol/l (2.0-100 ng/ml) for M6G using external standardisation. Intra-assay and inter-assay precision were in the range of 2.4-9.0% for all compounds. The major advantage with the present LC-MS method was the shorter analysis time, 10 min per sample compared to 45 min per sample with our previous LC method with dual detectors. The LC-MS method has proved to have both the selectivity and sensitivity needed for pharmacokinetic studies.

Calibration↗
PubMed2006

Determination of antihyperglycemic biguanides in serum and urine using an ion-pair solid-phase extraction technique followed by HPLC-UV on a pentafluorophenylpropyl column and on an octadecyl column.

An HPLC-UV method was established for the determination of metformin and buformin in biological fluids. Metformin was not retained on particles packed in conventional solid-phase extraction cartridges; in contrast, buformin was retained too firmly and not eluted with a solvent for recovery. However, both drugs were retained on particles that had been treated with an ion-pair reagent of heptanesulfonate or dodecylsulfate and recovered almost completely. The recovered fraction was subjected to HPLC on a pentafluorophenylpropyl column which was suitable for the determination of both biguanides in serum and in urine. Limits of quantitation were low enough for clinical use, and reproducibility was high with an RSD of 0.9-2.3%. HPLC on a conventional octadecyl column was suitable only for the determination of buformin in serum since interfering peaks appeared on the chromatograms of urine samples. The method was applied to analysis of some clinical specimens.

Alkanes↗
PubMed1996

An investigation of the properties of a "shielded" phase for the solid phase extraction of acidic and basic compounds.

The extraction properties of Hisep, a novel bonded phase for solid phase extraction, have been investigated using a number of acidic and basic analytes and compared with those of a conventional ODS bonded material. Marked differences in extraction properties for the test analytes propranolol, anisic acid and ICI 128436 from aqueous buffer were noted between the two materials. Thus, extraction onto the ODS material was by both ionic and reversed-phase mechanisms whilst retention on the Hisep phase appeared to be mediated predominantly by reversed-phase hydrophobic interactions. The presence of dog plasma had no effect on the extraction of propranolol but did reduce the extraction efficiencies observed for anisic acid and ICI 128436 in a pH dependent manner.

Adrenergic beta-Antagonists↗
PubMed1997

Determination of morphine and codeine in plasma by HPLC following solid phase extraction.

A cheap simple and rapid extraction procedure followed by a UV high performance liquid chromatography (HPLC) assay is described for the simultaneous determination of morphine (M) and codeine (C) in plasma. The method is based on extraction of these opiates from plasma using reversed phase (solid phase) extractions columns followed by HPLC with UV detection at 240 nm. The extraction step provides, respectively, 85 and 80% recovery for M and C. The response of the detection system is linear for both molecules in the studied range from 50 to 750 ng ml-1. No other drugs have been found to interfere with the assay. This method offers a quick, cost effective and reliable procedure for specifically determining M and C, from a small sample volume.

Analgesics, Opioid↗
PubMed2000

Investigation into the effects of temperature and stirring rate on the solid-phase extraction of diuron from water using a C18 extraction disk.

A novel experimental method for determining the equilibrium constant, Keq, and the uptake rate constant, kup, for the solid-phase extraction (SPE) of diuron from water using a C18 Empore extraction disk is reported. Log Keq and log kup are determined at 7.0, 11.0, 18.0 and 23.0 degrees C and for stirring rates of 100, 200 and 400 rpm. From a Van 't Hoff plot of log Keq versus T-1 the enthalpy of sorption, delta H0, is shown to be negative which indicates that the thermodynamic process of uptake is exothermic. The rate of stirring has no effect on log Keq over the temperature range 7.0-23.0 degrees C. The enthalpy of activation, delta H0, calculated from Arrhenius plots of log kup versus T-1 at 100, 200 and 400 rpm show that the kinetic process of uptake is endothermic. At 100 rpm the rate of uptake is limited by the aqueous diffusion of diuron. At 200 rpm or greater the aqueous diffusion layer around the disk is sufficiently small to prevent diffusion from being a limiting factor. The method described in this paper is limited to the analysis of analytes that contain a significant UV chromophore and are relatively soluble in water, but it can also be used to investigate pH and salinity effects on the SPE of diuron from water.

Chromatography, Liquid↗
PubMedDate not supplied

Comparison of solid-phase extraction and supercritical fluid extraction for the analysis of morphine in whole blood.

A comparative study of the quantitative determination of morphine in whole blood using solid-phase extraction (SPE) and supercritical fluid extraction (SFE) is described. Comparative studies were made of the two techniques for the extraction of morphine from authentic forensic blood specimens. Quantitative results indicate that morphine levels measured using SPE correspond well to morphine levels produced using SFE. The two techniques are therefore comparable, although SFE is faster and cleaner and extracts may be produced with higher analyte recoveries than with SPE. This paper presents a comparison of the two techniques and the morphine concentrations determined in blood.

Analgesics, Opioid↗
PubMed2006

Selective solid-phase extraction of bisphenol A using molecularly imprinted polymers and its application to biological and environmental samples.

Molecularly imprinted polymers (MIPs) were prepared using bisphenol A (BPA) as a template by precipitation polymerization. The polymer that had the highest binding selectivity and ability was used as solid-phase extraction (SPE) sorbents for direct extraction of BPA from different biological and environmental samples (human serum, pig urine, tap water and shrimp). The extraction protocol was optimized and the optimum conditions were as follows: conditioning with 5 mL methanol-acetic acid (3:1), 5 mL methanol, 5 mL acetonitrile and 5 mL water, respectively, loading with 5 mL aqueous samples, washing with 1 mL acetonitrile, and eluting with 3 mL methanol. MIPs can selectively recognize, effectively trap and preconcentrate BPA over a concentration range of 2-20 microM. Recoveries ranged from 94.03 to 105.3%, with a relative standard deviation lower than 7.9%. Under the optimal condition, molecularly imprinted SPE recoveries of spiked human serum, pig urine, tap water and shrimp were 65.80, 82.32, 76.00 and 75.97%, respectively, when aqueous samples were applied directly. Compared with C18 SPE, a better baseline, better high-performance liquid chromatography separation efficiency and higher recoveries were achieved after molecularly imprinted SPE.

Animals↗
PubMed2006

Automated post-collection concentration for purified preparative fractions via solid phase extraction.

Recent advancements in preparative HPLC have improved and streamlined compound purification. However, fraction evaporation remains a bottleneck within the process. An alternative to fraction evaporation is to remove the water and reduce the overall volume of the collection by trapping the fraction onto a solid phase extraction (SPE) cartridge. This method (as opposed to analytical applications involving SPE) works by collecting and then diluting the fraction(s), passing the fraction(s) through a SPE, drying the SPE with nitrogen and ultimately eluting the concentrated fraction(s) in a small amount of 100% organic solvent. An appreciable breakthrough is not observed using this method. In addition, recovery from the SPE for the tested compounds rosmarinic acid and carvacrol, two naturally occurring antioxidants in oregano, was found to be 95-98% for a 100mg injection via preparative HPLC purification at 50mg/compound.

Antioxidants↗
PubMed1990

Analysis of lorazepam in rat brain using liquid/liquid and solid-phase extraction in combination with high performance liquid chromatography.

A method for the determination of lorazepam in rat brain is described using liquid/liquid and solid-phase extraction, followed by high performance liquid chromatography. After addition of chlordiazepoxide as the internal standard, 100 mg brain tissue was homogenized and incubated with alkaline protease. Lorazepam and chlordiazepoxide were extracted three times with toluene. After treatment through a C18-Bond Elut column, lorazepam and chlordiazepoxide were analyzed isocratically on a reversed-phase column with a mobile phase consisting of methanol +0.025 M sodium phosphate buffer (66:34, v/v). The eluted drugs were monitored by their absorption at 240 nm. The sensitivity limit of this method was 10 ng of lorazepam per 100 mg of brain tissue sample. The standard curve was linear over the range of 20 to 200 ng lorazepam. The coefficient of variation for day-to-day precision established by 21 replicate analyses was 4.5 to 13.6%.

Animals↗
PubMedDate not supplied

Liquid chromatographic determination of hyoscine (scopolamine) in urine using solid phase extraction.

A sensitive method for the determination of hyoscine (scopolamine) in urine is described. After concentration and "clean-up" on C18 and CN solid phase extraction columns, hyoscine was quantified by high performance liquid chromatography with coulometric detection (oxidation at +0.9 V). The limit of detection was 5 ng per sample and the precision for 5 mL samples containing 2 ng/mL was 12.3%. The method was applied to urine samples collected from 12 volunteers wearing Scopoderm TTS patches. The mean excretion rate of unmetabolized hyoscine was 0.45 micrograms/h and 87% of the total hyoscine was present as conjugates. Apohyoscine (aposcopolamine) was identified as a urinary metabolite. The significance of this with regard to hyoscine assays is discussed.

Chromatography, High Pressure Liquid↗
PubMed2003

Determination of stavudine in human serum by on-line solid-phase extraction coupled to high-performance liquid chromatography with electrospray ionization tandem mass spectrometry: application to a bioequivalence study.

A method based on solid-phase extraction (SPE) coupled to high-performance liquid chromatography (HPLC) with positive ion electrospray ionization tandem mass spectrometry (ESI-MS/MS) detection was developed for the determination of stavudine in human serum, using didanosine as internal standard. The acquisition was performed in multiple reaction monitoring (MRM) mode. The method was linear over the studied range (10-2000 ng/mL), with r(2) > 0.99, and the run time was 4 min. The intra- and inter-assay precisions (%) were in the ranges 0.1-13.6 and 2.6-9.9, respectively, and the intra- and inter-assay accuracies were >92%. The absolute recoveries were approximately 100% (10 ng/mL), 98% (30 ng/mL), 105% (750 ng/mL) and 105% (1500 ng/mL). The limits of detection and quantitation were 4 and 10 ng/mL, respectively. The analytical method was applied to a bioequivalence study, in which 24 healthy adult volunteers (12 men) received single oral doses (40 mg) of reference and two test stavudine formulations, in an open, three-period, randomized, crossover protocol. The 90% confidence interval of the individual ratios (test formulation/reference formulation) for C(max) (peak serum concentration), AUC(0-10) and AUC(0-inf) (areas under the serum concentration vs. time curve from time zero to 10 h and to infinity, respectively), were in the range 80-125%, which supports the conclusion that the two test formulations are bioequivalent to the reference formulation with respect to the rate and extent of stavudine absorption.

Anti-HIV Agents↗
PubMed1992

Urinary testosterone measurement by gas chromatography after solid-phase extraction and high-performance liquid chromatography.

A method was developed for the rapid determination of testosterone in urine. The procedure consists of solid-phase extraction (SPE) followed by high-performance liquid chromatographic (HPLC) clean-up before gas chromatographic determination. Recovery was evaluated by adding [3H]testosterone (10(4) cpm) to urine samples; the mean recovery of radioactivity after SPE and HPLC was 82%. Precision was estimated by repeated measurement of testosterone in four different urine samples; the coefficient of variation was 7.9% (95% confidence limits 6.1-11.4%). Accuracy was evaluated by standard addition and dilution assays; a linear relationship was found between the expected and observed values (r2 = 0.982). The method is rapid, effective and suitable for routine analysis.

Chromatography, Gas↗
PubMed1996

Purification of fatty acid ethyl esters by solid-phase extraction and high-performance liquid chromatography.

We have developed a two-step method to purify fatty acid ethyl esters (FAEE) using solid-phase extraction (SPE), with a recovery of 70 +/- 3% (mean +/- S.E.M.) as assessed using ethyl oleate as a recovery marker from a standard lipid mixture in hexane. The first step of the SPE procedure involves application of a lipid mixture to an aminopropyl-silica column with simultaneous elution of FAEE and cholesteryl esters from the column with hexane. Gas chromatographic analysis of FAEE without interference from cholesteryl esters may be performed using the eluate from the aminopropyl-silica column, thus eliminating the need for an octadecylsilyl (ODS) column in this case. The FAEE can then be separated from the cholesteryl esters, if necessary, by chromatography on an ODS column and elution with isopropanol-water (5:1, v/v). Both the aminopropyl-silica and ODS columns were found to be effective for up to four uses. To permit isolation of specific FAEE species following isolation of total FAEE by the two-step SPE method, we have also developed a purification scheme for individual FAEE by high-performance liquid chromatography (HPLC). Thus, this simple method allows for reproducible isolation of total FAEE by SPE and isolation of individual FAEE species by HPLC.

Chromatography, High Pressure Liquid↗
PubMed2004

Development of a rapid method based on solid-phase extraction and liquid chromatography with ultraviolet absorbance detection for the determination of polyphenols in alcohol-free beers.

An analytical method based on solid-phase extraction (SPE) and followed by liquid chromatographic separation and ultraviolet detection (HPLC-UV) is proposed for the determination of 10 phenolic compounds which participate on beer stability and sensory properties in alcohol-free beers. Acetonitrile was found to be the most appropriate solvent for the elution of polyphenolic compounds adsorbed on C18 cartridges. The performance of the method was assessed by the evaluation of parameters such as absolute recovery (generally higher than 60%), repeatability (lower than 10%), linearity (r2 higher than 0.993) and limits of quantitation (ranging from 1 to 37 microg/L); no matrix effects were observed. The polyphenol content of different Spanish alcohol-free beers is presented. Five phenolic compounds such as protocatechuic, p-coumaric, ferulic, caffeic acids, and (+)-catechin were identified at levels lower than 10 mg/L.

Beer↗
PubMed2005

Determination of omeprazole, hydroxyomeprazole and omeprazole sulfone using automated solid phase extraction and micellar electrokinetic capillary chromatography.

A sensitive method for the determination of omeprazole and its metabolites has been developed. It involves an automated solid phase extraction (SPE) procedure and capillary electrophoresis with UV detection. Omeprazole, hydroxyomeprazole and omeprazole sulfone could be separated by micellar electrokinetic capillary chromatography using a background electrolyte composed of 20 mM borate buffer and 30 mM sodium dodecyl sulfate, pH 9.5. The isolation of omeprazole and its metabolites from plasma was automatically accomplished with an original SPE procedure using surface-modified styrene-divinylbenzene polymer cartridges. Good recovery data and satisfactory precision values were obtained. Responses were linear for the three analytes, from 0.08 to 2.0 microg/mL of plasma. Intra- and inter-day precision values of about 1.6% R.S.D. (n=10) and 2.5% R.S.D. (n=36), respectively, were obtained. The method is highly robust and no breakdown of the current or capillary blockages were observed during several weeks of operation. The validated method was applied to the determination of omeprazole in pharmaceutical preparations and for the analysis of plasma samples obtained from three volunteers who received oral doses of omeprazole.

2-Pyridinylmethylsulfinylbenzimidazoles↗