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PubMed1998

Assay for etoposide in human serum using solid-phase extraction and high-performance liquid chromatography with fluorescence detection.

An HPLC assay for etoposide in human serum was developed. Serum, spiked with podophyllotoxin (internal standard), was treated with sodium dodecyl sulphate prior to solid phase extraction. Analysis was performed on a 300x3.9 mm Bondclone 10 C18 column coupled with a fluorometric detector (lambda(ex) 230 nm, lambda(em) 330 nm). The retention times for etoposide and podophyllotoxin were 14 and 28 min respectively. The range of assay was 0.5 to 20 microg/ml with a detection limit of 0.2 microg/ml. This assay is suitable for use in clinical studies with etoposide.

Antineoplastic Agents, Phytogenic↗
PubMed1998

Determination of the glucocorticoid fluticasone propionate in plasma by automated solid-phase extraction and liquid chromatography-tandem mass spectrometry.

A sensitive, robust and high throughput mass spectrometry based method is described for the determination of the glucocorticoid fluticasone propionate in plasma. The method employs solid-phase extraction in 96 well microtitre plate format which has been automated by means of a custom built Zymark robotic system. The extracts are analysed by liquid chromatography-tandem mass spectrometry using thermally and pneumatically assisted electrospray ionisation and selected reaction monitoring. The method is both accurate and precise with both intra- and inter-assay precision (C.V.) of less than <6%. The method provides a lower limit of quantification of 20 pg/ml from 0.5 ml of human plasma, sufficient to monitor systemic concentrations of inhaled fluticasone propionate at therapeutic doses.

Androstadienes↗
PubMed2003

Fully automated on-line quantification of quetiapine in human serum by solid phase extraction and liquid chromatography.

A quantitative method for determination of quetiapine (QTP) in human serum is presented. The method is fully automated and based on high performance liquid chromatography (HPLC) with on-line solid phase extraction (SPE). The extraction procedure is based on a C2 cartridge, which is eluted with methanol. The eluate is injected onto a silica column with a mobile phase consisting of methanol:20 mM NH(4)CH(3)COO, pH 5.0 (99:1). Quetiapine is quantified by ultra-violet (UV) absorbance at 257 nM with trifluoperazine as the internal standard (I.S.). The extraction recoveries for quetiapine and trifluoperazine were 69 and 57%, respectively. The total inter day coefficient of variation was 11.1, 3.8 and 3.1% at 20, 500 and 1000 nM, respectively. The detection limit was 10.3 nM quetiapine. The method has been used in our therapeutic drug monitoring (TDM) laboratory where co-administered drugs often are observed. In an investigation of analytical interference from co-administered drugs, demethyl-mianserine was the only drug which interfered with the internal standard. There was no interference with quetiapine itself. The method showed good agreement with mass spectrometric quantification of quetiapine.

Antipsychotic Agents↗
PubMed2003

Automated flow injection analyzer with on-line solid-phase extraction and chemiluminescence detection for the determination of dodecylamine in diesel fuels.

This paper describes the development of a portable, automated flow injection-chemiluminescence (FI-CL) analyzer incorporating on-line solid-phase extraction (SPE) for the determination of dodecylamine (detergent) in diesel fuels. The method is based on the peroxyoxalate/sulforhodamine 101 chemiluminescence reaction, with SPE required to remove indigenous compounds within the diesel fuel matrix that interfere with the CL response. The automated analyzer achieved a detection limit of 2.9 mg L(-1) and a linear range of 2.9-50 mg L(-1), which was suitable for determinations of dodecylamine at levels typically present in fully formulated diesel fuels (40 mg L(-1)). Analyses of base fuels from five different sources demonstrated that an automated FI-CL-SPE system could provide a portable instrument for monitoring the presence/absence of dodecylamine in diesel fuels.

Journal Article↗
PubMedDate not supplied

Solid-phase extraction and GC/MS confirmation of barbiturates from human urine.

A highly selective and sensitive procedure has been developed for isolating and identifying barbiturates in human urine. With a new disposable bonded silica gel solid-phase extraction (SPE) column and hexobarbital as an internal standard (IS), amobarbital, butabarbital, pentobarbital, phenobarbital, secobarbital, and methaqualone were selectively isolated from endogenous urine components. Capillary gas chromatography/ion trap mass spectrometry (GC/MS) analysis of the extracts generated a full mass spectrum for the detection, identification, and quantitation of barbiturates. Linear quantitative response curves for the drugs have been generated over a concentration range of 20-500 ng/mL. Overall extraction efficiencies for drugs averaged greater than 90%, and the quantitative response curves exhibited correlation coefficients of 0.996 to 0.999.

Amobarbital↗
PubMed2004

[Study on solid phase extraction and spectrophotometric determination of vanadium in environmental samples with 2-(2-quinolinylazo)-1,3-dihydroxidebenzene].

Based on the color reaction of 2-(2-quinolinylazo)-1,3-dihydroxidebenzene (QADHB) with vanadium (v) and the solid phase extraction of its colored complex with C18 cartridge, a new method for the determination of vanadium was studied. In the presence of CTMAB and citric acid-sodium hydroxide buffer solution (pH 3.5) medium. QADHB reacts with vanadium(II) to form a stable 2:1 complex. The colored complex was extracted by C18 cartridge and eluted the retained chelate from cartridge with ethanol (containing 2% of acetic acid), then can be determined by spectrophotometry at 552 nm. Beer's law is obeyed in range of 0-1.0 mg/l. This method can be applied to the determination of vanadium in environmental samples with good results.

Azo Compounds↗
PubMedDate not supplied

Determination of niacin in infant formula and wheat flour by anion-exchange liquid chromatography with solid-phase extraction cleanup.

Niacin content must be included on food labels of infant formula products and bakery products containing enriched flour. Liquid chromatographic (LC) determination of niacin in complex food matrixes is complicated by the presence of endogenous compounds that absorb at the commonly used wave-length of 260 nm. Also, the presence of particulate matter in the standard sulfuric acid extraction procedure results in reduced life of LC columns and precolumns. A simple, rapid, solid-phase extraction (SPE) procedure for separation and cleanup of niacin from a complex food matrix digest has been developed. By using a vacuum manifold with the SPE column system, multiple samples can be processed quickly and efficiently for LC analysis, compared with gravimetric column cleanup. Sulfuric acid sample digest is passed over an aromatic sulfonic acid cation-exchange (ArSCX-SPE) or a sulfonated Florisil SPE column. Niacin is eluted with 0.25M sodium acetate-acetic acid, pH 5.6 buffer in vacuo. LC chromatograms of the resulting eluate are free of interference from other components absorbing at 260 nm at the retention time of niacin. Validation of the method was obtained from agreement of analytical results on available reference materials. For both SPE methods, values for niacin in SRM 1846 Infant Formula (milk-based powder) were within uncertainty ranges of the certified value. Use of several calibration procedures (the LC computer program, a peak area response graphic standard curve, or the method of standard additions) with both SPE procedures resulted in niacin values for 3 RM-Wheat Flours (not certified for niacin) in agreement (90-105%) with their respective values reported in the literature. Several commercial wheat flours showed a broad 260 nm interference, resulting in high niacin values. Niacin recoveries from spiked soy-based liquid infant formulas ranged from 95-107% with the ArSCX-SPE column. Calibration curves of niacin were linear up to 400 micrograms/mL, with a detection limit of 0.2 microgram/mL.

Chromatography, Ion Exchange↗
PubMed1989

Solid phase extraction of the zwitterionic detergent chaps.

Multiple techniques for solid phase adsorption of 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS) were evaluated. Both the porous polystyrene divinylbenzene matrices (BioBeads SMTM) and Extracti GelTM D reduced CHAPS to significantly below its critical micellar concentration while Extracti-GelTM removed CHAPS to below detectable limits. Bio-Bead extraction of CHAPS correlated with the surface area of the bead type. SM-16 beads, with the largest effective surface area, removed nearly 97% of the detergent. For a given amount of detergent and mass of Bio-Beads, the ratio of sample to total bead volume significantly affected CHAPS adsorption. Total protein recovery with the Extracti-GelTM was approximately 97%. Protein recovery in the samples treated with Bio-Beads varied from 56-95%. Chromatographic rather than batch processing yielded optimum recoveries. CHAPS can be effectively removed from dilute protein solutions by solid phase adsorption and this technique offers significant advantages over standard dialysis or gel filtration methods.

Adsorption↗
PubMed2005

Dispersive solid-phase extraction for the determination of sulfonamides in chicken muscle by liquid chromatography.

A new, fast and low-cost sample preparation for the determination of sulfonamide (SA) residues in chicken muscle by LC technique has been developed. The procedure involves single extraction of sample with acetonitrile, followed by a rapid clean-up and was called "dispersive solid-phase extraction" (dispersive SPE). Using dispersive SPE 25 mg of octadecyl sorbent was added to 1 ml of acetonitrile extract, mixed and centrifuged. The acetonitrile layer was evaporated and residue was dissolved in acetate buffer (pH 3.5). Analysed compounds were detected by fluorescence detector after pre-column derivatization with fluorescamine. The separation of analytes was performed with gradient elution with mobile phase methanol: 2% acetic acid and RP-LC analytical column. The whole procedure was evaluated for six sulfonamides (sulfadiazine, sulfamerazine, sulfamethazine, sulfametoxypirydazine, sulfametoxazole and sulfadimetoxine) according to the European Commission Decision 2002/657/EC. Specificity, decision limit (CCalpha), detection capacity (CCbeta), trueness and precision were determined during validation process. The dispersive SPE with octadecyl sorbent was found suitable for sample preparation before sulfonamide determination in chicken muscle. As it was found the most of endogenous matrix components were removed and the analytes were isolated from spiked samples with recoveries above 90%. The used analytical conditions allow to successively separate all the tested sulfonamides with the limit of detection at the level of 1-5 microg/kg. The method is simple, rapid and more effective than conventional methods.

Animals↗
PubMed2005

[Determination of ligustrazine in human plasma by high performance liquid chromatography with solid-phase extraction].

A high performance liquid chromatographic method was developed for the determination of ligustrazine in human plasma. The chromatographic separation was performed on a Luna C18 column (150 mm x 4.6 mm i.d., 5 microm) at column temperature of 40 degrees C. The mobile phase, a mixture of methanol-acetonitrile-acetate buffer of pH 5.0 (50:8:42, v/v), was delivered at a flow rate of 1.0 mL/min. The detection wavelength was 280 nm. Plasma samples were prepared with a C8 solid-phase extraction column. Linearity was confirmed in the mass concentration range of 25-5000 microg/L with the correlation coefficient of 0.9999. The extraction recovery of ligustrazine ranged from 96.72% to 100.90%. The relative standard deviations (RSDs) of intra- and inter-day assay at the mass concentrations of 50, 500 and 3000 microg/L were less than 8.64% and the accuracies were between 99.59%-103.26%. The limit of detection (LOD) was 10 microg/L. The results of this method validation satisfactorily meet the acceptance criteria of bioanalysis and the method is applicable to the pharmacokinetic studies of ligustrazine in human beings.

Chromatography, High Pressure Liquid↗
PubMed2006

Determination of paeoniflorin in rat plasma by a liquid chromatography-tandem mass spectrometry method coupled with solid-phase extraction.

A rapid, sensitive and selective liquid chromatography-tandem spectrometry method was developed and validated for determination of paeoniflorin in rat plasma using geniposide as the internal standard. The samples were pretreated with solid-phase extraction using Extract-Clean cartridges. Separation of paeoniflorin and IS was achieved on a reversed-phase C18 column (50x4.6 mm i.d.) with a mobile phase made up of acetonitrile and 0.05% formic acid (25:75, v/v) at a flow rate of 0.5 mL/min. Detection was carried out on a triple quadrupole tandem mass spectrometer by multiple-reaction monitoring and an electrospray ionization source was employed as the ionization source. The lower limit of quantification obtained was 4 ng/mL (n=6) using 200 microL plasma with an accuracy of -3.67% (relative error) and a precision of 4.13% (relative standard deviation). A good linearity was found in the range of 4-1000 ng/mL. The intra- and inter-day relative standard deviations in the measurement of quality control samples 10, 150 and 800 ng/mL ranged from 3.73 to 4.94% and from 4.31 to 6.56%, respectively. The accuracy was from -3.93 to -1.11% in terms of relative error. The analyte and IS were stable in the battery of stability studies. This method was successfully applied to a pharmacokinetic study of paeoniflorin after a single oral administration of 53.36 mg/kg paeoniflorin to rats.

Animals↗
PubMed2004

Solid-phase extraction of L-muscone from aqueous samples with Amberlite XAD-4 for gas chromatographic assay.

An efficient analytical method was devised for the accurate L-muscone assay in aqueous samples. It involves solid-phase extraction of L-muscone in adsorption mode using XAD-4 as the sorbent and dichloromethane modified with 10% (v/v) methanol as the eluting solvent. The gas chromatographic analysis of the eluate residue dissolved in toluene on a DB-5MS capillary column provided complete resolution of L-muscone from the co-extracted interferences. The overall method showed excellent linearity (r2 > or = 0.9994) in the range of 0.1 to 2.0 microg/mL with good intra- and inter-day precisions (% RSD = 2.5 to approximately 7.3) and with high extraction recovery rates (> or = 98.1%). When the present method was applied to a L-muscone herbal drink product, the within-batch RE (%) in the labeled concentration (1.5 microg/mL) for the three randomly chosen bottles were -2.4, -1.3 and -3.3 with high precision (% RSD < or = 3.1). The present method is considered to be suitable for quality control evaluation on liquid drinks and other complex formulations fortified with L-muscone.

Chromatography, Gas↗
PubMed1988

Determination of delta 9-tetrahydrocannabinol in plasma using solid-phase extraction and high-performance liquid chromatography with electrochemical detection.

A method for the determination of nanogram amounts of delta 9-tetrahydrocannabinol (THC) in plasma and serum is described. THC was quantitatively isolated by solid-phase extraction after addition of an aqueous solution of urea and methanol to the sample. The extracts were analysed by high-performance liquid chromatography with electrochemical detection in the oxidizing mode. The detection limit of THC is ca. 100 pg for a signal-to-noise ratio of 3. With this method, levels of 2 ng/ml of THC in plasma can be measured.

Chromatography, High Pressure Liquid↗
PubMed1992

Determination of sterols, erythrodiol, uvaol and alkanols in olive oils using combined solid-phase extraction, high-performance liquid chromatographic and high-resolution gas chromatographic techniques.

A method is described for the determination of the sterol, erythrodiol, uvaol and alkanol content in olive oils by means of solid-phase extraction and high-performance liquid chromatography, instead of liquid-liquid and thin-layer chromatographic separations, the following step being high-resolution gas chromatographic separation. This type of procedure allows the simultaneous analysis of a larger number of samples and a substantial reduction in manual operations. Comparisons were made between the two methods on 100 different olive oils and with a statistical analysis of the results (Student's t-test).

Chromatography, Gas↗
PubMed1995

Assay of tocainide enantiomers in plasma by solid-phase extraction and indirect chiral high-performance liquid chromatography after derivatization with (-)-menthyl chloroformate.

A fast high-performance liquid chromatographic (HPLC) assay was developed for determination of tocainide enantiomers in plasma. Subsequent to solid-phase extraction of tocainide from plasma, homochiral derivatization with (-)-menthyl chloroformate enabled separation of the enantiomers by a conventional reversed-phase HPLC system. The detection was performed by UV absorption at 262 nm. An enantiomeric resolution of 1.0 was obtained. Linearity of the method was investigated and found to be good in the range from 1.0 to 20.0 micrograms/ml tocainide enantiomer and the limit of quantitation was 1.0 microgram/ml. The method was applied to a study of the distribution and elimination pharmacokinetics of tocainide enantiomers in the rabbit. No difference in distribution or elimination between the enantiomers was found nor did the enantiomers affect the disposition of one another when administered together as the racemate.

Animals↗
PubMed1996

Simultaneous quantitation of pioglitazone and its metabolites in human serum by liquid chromatography and solid phase extraction.

A high-performance liquid chromatographic (HPLC) method for the simultaneous determination of pioglitazone (U-72107) and its potential metabolites (M-1 to M-6) in human serum was developed. The method involved a solid phase extraction (SPE) of pioglitazone, its metabolites, and the internal standard (U-92573) from serum using C18 SPE columns with an elution solvent of 0.5 ml of acetonitrile-water (35:65, v/v). Separation of the eight analytes was achieved within 20 min using a reversed-phase Zorbax RX-C8 analytical column (250 mm x 4.6 mm i.d., 5 microns particle size) with a mobile phase of acetonitrile-water (40:60, v/v) containing 3 ml acetic acid per liter mobile phase (apparent pH 5.5). An ultraviolet detector operated at 269 nm was used with a linear response observed from 0.02 to 2 micrograms ml-1 for these analytes except for M-4 which was best fitted with a polynomial regression. Limit of quantitation was found to be 0.02 microgram ml-1 for pioglitazone, M-3, M-5, and M-6; 0.04 microgram ml-1 for M-2 and M-4; and 0.5 microgram ml-1 for M-1 when using a 0.5 ml serum sample for extraction. Obtained from the method validation, intra- and inter-assay precision was < or = 9% and accuracy ranged from -8.2 to 13.4% for all analytes. The applicability of this method has been demonstrated by successfully analyzing clinical serum samples. The strategies in the HPLC characterization and in the SPE procedure development for this method are discussed as well.

Chromatography, High Pressure Liquid↗
PubMed2003

Determination of lincomycin and tylosin residues in honey using solid-phase extraction and liquid chromatography-atmospheric pressure chemical ionization mass spectrometry.

An analytical method for the determination of residues of the antibiotic drugs lincomycin and tylosin in honey was developed. The procedure employed a solid-phase extraction for the isolation of lincomycin and tylosin from diluted honey samples. The antibiotic residues were subsequently analyzed by reversed-phase HPLC with atmospheric pressure chemical ionization mass spectrometric detection. Average analyte recoveries for lincomycin and tylosin ranged from 84 to 107% in replicate sets of honey samples fortified with drug concentrations of 0.01, 0.5, and 10 microg/g. The method detection limits were determined to be 0.007 and 0.01 microg/g for lincomycin and tylosin, respectively.

Atmospheric Pressure↗
PubMed2004

Determination of residues of UV filters in natural waters by solid-phase extraction coupled to liquid chromatography-photodiode array detection and gas chromatography-mass spectrometry.

This study describes a procedure for the enrichment, separation and quantification of four major UV filters in natural waters. Solid-phase extraction combined with liquid chromatography and photodiode array detection (LC-UV-DAD), and gas chromatography with mass spectroscopy (GC-MS) were employed for the analyses. LC of the four compounds with surfactant-modified hydro-organic eluents gave satisfactory resolution of overlapping peaks. In GC, a significant improvement of the detection limits was attained, but only three compounds could be detected. The method was validated for, and applied to, various water samples prone to UV filter accumulation due to recreational activities. Recoveries from real samples were 86-99% with LOQs as low as 0.5 ng/l depending on the sample volume and the analytical procedure.

Chromatography, Liquid↗