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PubMed1998

Confirmation of spectinomycin in milk using ion-pair solid-phase extraction and liquid chromatography-electrospray ion trap mass spectrometry.

A confirmation procedure is described for residues of spectinomycin in bovine milk. Spectinomycin is extracted from raw milk using ion-pair reversed-phase solid-phase extraction. The extracts are ion-pair chromatographed on a polymeric reversed-phase column and analyzed on a quadrupole ion trap mass spectrometer equipped with an electrospray interface. MS-MS data are acquired in the scan mode of product ions deriving from m/z 333, the protonated molecular ion. The estimated limit of confirmation is between 0.05 and 0.1 microg/ml. The procedure was validated with control milk, fortified milk (0.1-5.0 microg/ml), and milk from cows dosed with spectinomycin.

Animals↗
PubMedDate not supplied

Determination of penicillin G in feeds by liquid chromatography with solid-phase extraction.

A liquid chromatographic method was developed for the determination of penicillin G in feeds. The method involves extraction of penicillin G with methanol, concentration under a stream of nitrogen, and cleanup using Phenomenex Strata-X solid-phase extraction cartridge. Analyte separation and quantification were achieved by gradient reversed-phase liquid chromatography and ultraviolet absorbance at 230 nm. Average spike recoveries for samples prepared at 3 spiking levels (25, 50, and 200 g/ton) were 96.3, 92.1, and 88.6%, respectively. The overall method precision at each of the 3 spiking levels was < or = 5.39% relative standard deviation. The limits of detection and quantititation (g/ton formulation) were 3.89 and 13.0 g/ton, respectively.

Acetates↗
PubMed2001

Determination of nonsteroidal anti-inflammatory drugs in biological fluids by automatic on-line integration of solid-phase extraction and capillary electrophoresis.

A new, automatic method for the clean-up, preconcentration, separation, and quantitation of nonsteroidal anti-inflammatory drugs (NSAIDs) in biological samples (human urine and serum) using solid-phase extraction coupled on-line to capillary electrophoresis is proposed. Automatic pretreatment is carried out by using a continuous flow system operating simultaneously with the capillary electrophoresis equipment, to which it is linked via a laboratory-made mechanical arm. This integrated system is controlled by an electronic interface governed via a program developed in GWBasic. Capillary electrophoresis is conducted by using a separation buffer consisting of 20 mM NaHPO4, 20 mM beta-cyclodextrin and 50 mM SDS at pH 9.0, an applied potential of 20 kV and a temperature of 20 degrees C. The analysis time is 10 min and the detection limits were between 0.88 and 1.71 microg mL(-1). Automatic clean-up and preconcentration is accomplished by using a C-18 minicolumn and 75% methanol as eluent. The limit of detection of NSAIDs can be up to 400-fold improved when using sample clean-up. The extraction efficiency for these compounds is between 71.1 and 109.7 microg mL(-1) (RSD 2.0-7.7%) for urine samples and from 77.2 to 107.1 microg mL(-1) (RSD 3.5-7.1%) for serum samples.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1987

Automated solid-phase extraction and high-performance liquid chromatographic determination of ranitidine from urine, plasma and peritoneal dialysate.

Ranitidine is an H2-receptor antagonist primarily used to treat peptic ulcer. The present automated solid-phase extraction technique involves sorbent conditioning of a cyano (CN) cartridge with 0.5 ml of methanol and 1.0 ml of extraction buffer (0.005 M phosphate, pH 9). Plasma samples were applied by passing 1.0 ml of plasma through the cartridge and subsequently washing with 2 ml of the extraction buffer. Appropriate larger volumes of dialysate were used to concentrate ranitidine onto the cartridge so that the amount eluted was increased to within detectable limits. Urine samples were deluted with distilled water to decrease the ranitidine concentration to within the range of the standard curve. The high-performance liquid chromatographic method (mobile phase 88-89% of 0.02 M phosphate buffer pH 3 and 11-12% of methanol; Spherisorb phenyl cartridge column, 10 cm X 0.46 cm I.D., 5 micron particle diameter, flow-rate 1.1 ml/min; detection at 228 nm) is sensitive to 2 ng/ml in 1 ml of sample. The internal standard of choice was determined to be n-propionylprocainamide as compared to cimetidine and lidocaine. The method was cost-efficient, rapid and simple due to the automated sample processing. The coefficient of variation on replicate assays was less than 10% over all concentrations studied. Recoveries were between 97 and 110%, and the method was linear over the range 1.90-687.20 with a mean correlation coefficient of 0.999.

Autoanalysis↗
PubMed2005

Quantitative analysis of multiple illicit drugs in preserved oral fluid by solid-phase extraction and liquid chromatography-tandem mass spectrometry.

We present a validated method for the simultaneous analysis of basic drugs which comprises a sample clean-up step, using mixed-mode solid-phase extraction (SPE), followed by LC-MS/MS analysis. Deuterated analogues for all of the analytes of interest were used for quantitation. The applied HPLC gradient ensured the elution of all the drugs examined within 14 min and produced chromatographic peaks of acceptable symmetry. Selectivity of the method was achieved by a combination of retention time, and two precursor-product ion transitions for the non-deuterated analogues. Oral fluid was collected with the Intercept, a FDA approved sampling device that is used on a large scale in the US for workplace drug testing. However, this collection system contains some ingredients (stabilizers and preservatives) that can cause substantial interferences, e.g. ion suppression or enhancement during LC-MS/MS analysis, in the absence of suitable sample pre-treatment. The use of the SPE was demonstrated to be highly effective and led to significant decreases in the interferences. Extraction was found to be both reproducible and efficient with recoveries >76% for all of the analytes. Furthermore, the processed samples were demonstrated to be stable for 48 h, except for cocaine and benzoylecgonine, where a slight negative trend was observed, but did not compromise the quantitation. In all cases the method was linear over the range investigated (2-200 microg/L) with an excellent intra-assay and inter-assay precision (coefficients of variation <10% in most cases) for QC samples spiked at a concentration of 4, 12 and 100 microg/L. Limits of quantitation were estimated to be at 2 microg/L with limits of detection ranging from 0.2 to 0.5 microg/L, which meets the requirements of SAMHSA for oral fluid testing in the workplace. The method was subsequently applied to the analysis of Intercept samples collected at the roadside by the police, and to determine MDMA and MDA levels in oral fluid samples from a controlled study.

Chromatography, Liquid↗
PubMed2006

Application of a semi-automated 96-well format solid-phase extraction, column-switching, fluorescence detection protocol for the determination of alendronate in human urine samples obtained from a bioequivalence study.

In the current study, a semi-automated, 96-well format, solid-phase extraction (SPE), analytical column-switching method for alendronate determination in human urine is developed, validated and applied to a bioequivalence study. The current protocol was a substantial improvement of an existing classical method. A robotic liquid handling system was employed to simplify and reduce the time of sample preparation procedure. Automated SPE was carried out using a 96-well cartridge plate and a vacuum control system. Urine samples were determined by applying a column-switching protocol with fluorescence detection. Analysis time, due to the column-switching procedure, was about half of the conventional LC approach (11.5 min instead of 21 min). The method application required the determination of alendronate in urine samples obtained from 96 healthy volunteers as part of a bioequivalence study of two 70 mg alendronate sodium tablets. All major pharmacokinetic parameters of the bioequivalence study were estimated and reported.

Alendronate↗
PubMed2001

High-performance liquid chromatographic determination of diclofenac in human plasma after solid-phase extraction.

A novel high-performance liquid chromatographic (HPLC) method for the quantification of diclofenac in human plasma was set up. Samples, added with ibuprofen (used as internal standard) were purified by solid-phase extraction using Abselut Nexus cartridges (Varian) not requiring pre-conditioning. Drugs of interest were eluted directly into the autosampler vials and injected. The recovery of diclofenac was 92%, the analysis lasted 7 min with a sensitivity of 5 ng/ml and intra- and inter-day RSDs of 3 and 8%, respectively. The pharmacokinetics of diclofenac after oral and rectal administration in 10 healthy volunteers are reported.

Administration, Oral↗
PubMed2003

Quantitative determination of the HIV protease inhibitor atazanavir (BMS-232632) in human plasma by liquid chromatography-tandem mass spectrometry following automated solid-phase extraction.

A selective, accurate, and reproducible LC-MS-MS assay was developed for the determination of the HIV protease inhibitor atazanavir (BMS-232632) in human plasma samples. The method involved automated solid-phase extraction of atazanavir and a stable isotope analog internal standard (I.S.) using Oasis HLB 10 mg 96-well SPE plates. A portion of the reconstituted sample residue was injected onto a C(18) HDO analytical column which was configured with a triple quad mass spectrometer for analyte determination by positive ion electrospray. The assay was linear from 1.00 to 1,000 ng/ml with a lower limit of quantitation of 1.00 ng/ml. The inter- and intra-day coefficients of variation (C.V.) for the assay were <4%, and the accuracy was 99-102%. Atazanavir was stable in human plasma for at least 109 h at room temperature and for at least 1 year at -20 degrees C.

Atazanavir Sulfate↗
PubMed1988

A modified assay for cyclosporin in blood using solid-phase extraction with high-performance liquid chromatography.

A modified procedure for measuring cyclosporin in whole blood by high-performance liquid chromatography is described and evaluated for clinical use. Sample preparation uses solid-phase extraction cartridges that can be reused. Life of the reverse-phase analytical column exceeds 1,000 injections at 70 degrees C. Cyclosporins A and D (internal standard) elute after 5.6 and 7.6 min, respectively. Calibration plots are linear from 50 ng/ml to at least 2,000 ng/ml. Within-day and between-day imprecision is less than 9% (coefficient of variation). Minimum measurable concentration is 50 ng/ml.

Chromatography, High Pressure Liquid↗
PubMed2002

Analysis of the antioxidant butylated hydroxytoluene (BHT) in water by means of solid phase extraction combined with GC/MS.

The antioxidant 3,5-di-tert-butyl-4-hydroxy-toluene (BHT) is widely used as an additive to increase the tenability of food and plastics. BHT is degraded to 3,5-di-tert-butyl-4-hydroxybenzaldehyde (BHT-CHO) in mammals, as well as in the natural environment such as in water and soils. BHT-CHO has been studied extensively in terms of their potential toxicities. The present investigation was carried out to quantify BHT and BHT-CHO in river, ground, rain and drinking water obtained from several locations in Germany. Apart from the compounds mentioned above, 1,2-bis-(3,5-di-tert-butyl-4-hydroxyphenyl)ethane (2-BHT), which is a dimer of BHT, was also detected in the extracts of some ground water samples. The applied analytical method is based on solid phase extraction (SPE) to concentrate trace compounds from water samples followed by gas chromatography/mass spectrometry (GC/MS) of the extracts. A total of 51 of the respective water samples were used for extraction purposes and analyte recoveries were all > or = 80%. The determination limit for BHT was 5 ng l(-1) and for BHT-CHO 16 ng l(-1). The standard deviations for the analytical procedure were 6% for BHT and 10% for BHT-CHO. The use of the antioxidant BHT in Germany has resulted in water concentrations of 7-791 ng l(-1) in the rivers Rhine, Elbe, Main, Oder, Nidda and Schwarzbach. The degradation product BHT-CHO was also detected in the river water samples at concentrations between 29 and 223 ng l(-1). The concentrations of BHT measured in German rivers are lower compared to values measured in the USA and Japan 20 years ago. In ground water, levels for BHT varied from non-detectable up to 2156 ng l(-1) and for BHT-CHO from non-detectable up to 674 ng l(-1). Both compounds were also detected in rain water in Frankfurt/Main at a concentration of 1797 ng l(-1) for BHT and 59 ng l(-1) for BHT-CHO.

Antioxidants↗
PubMed1998

Quantitative determination of tricyclic antidepressants and their metabolites in plasma by solid-phase extraction (Bond-Elut TCA) and separation by capillary gas chromatography with nitrogen-phosphorous detection.

An analytical method for the simultaneous determination of amitriptyline, nortriptyline, imipramine, desipramine, clomipramine, and desmethylclomipramine in human plasma using promazine as internal standard is described. The method is based on a solid-phase extraction procedure using the Bond-Elut TCA columns followed by separation and detection using capillary gas chromatography with a specific nitrogen phosphorous detector (GC/NPD). Using the new extraction procedure, the problem of adsorption losses was overcome, and good recoveries were achieved for all compounds tested (>87%). Furthermore, clean extracts free of chromatographic interferences were obtained. Complete separation of underivatized, tricyclic antidepressant compounds was achieved in <11 minutes with reliable chromatographic performance. The limits of detection ranged from 1.2 to 5.8 microg/l. Calibration curves, showing good linearity, were prepared covering the therapeutic concentrations range expected (20 to 500 microg/l). The interassay precision values (RSD) ranged from 4.5% to 9.8%. It is concluded that extraction of amitriptyline, nortriptyline, imipramine, desipramine, clomipramine, and desmethylclomipramine, with Bond Elut TCA solid-phase columns followed by their detection using GC/NPD provides a sensitive and reproducible method that can be easily automated for immediate and routine analysis of clinical samples.

Amitriptyline↗
PubMed2005

Simultaneous determination of anabolic steroids and synthetic hormones in meat by freezing-lipid filtration, solid-phase extraction and gas chromatography-mass spectrometry.

Estradiol, testosterone, progesterone, zeranol and diethylstilbestrol including estradiol metabolites were determined simultaneously in meat. Extraction of growth hormones was carried out by ultasonication using a methanol-water mixture. The growth hormones in the meat extract can be effectively separated from lipids by freezing-lipid filtration, followed by C8-solid phase extraction (SPE). During freezing-lipid filtration, about 90% of lipids are removed without any significant loss of growth hormones. For further clean-up, silica- and aminopropyl-SPE were used. To enhance detection sensitivity, the growth hormones are derivatized with trimethylsilyl reagents. Quantitation using isotope-labelled internal standards was performed by gas chromatography-mass spectrometry in the selected ion monitoring mode. The method detection limits were 0.1-0.4 microg/kg for all growth hormones. Overall recoveries of synthetic and natural growth hormones were 68-106% with coefficients of variation of 5-16% for the complete procedure.

Anabolic Agents↗
PubMed2002

An original approach to determining traces of tetracycline antibiotics in milk and eggs by solid-phase extraction and liquid chromatography/mass spectrometry.

An original and highly specific method able to identify and quantify traces of five tetracycline antibiotics (TCAs) in milk and eggs is presented. This method uses a single solid-phase extraction (SPE) cartridge for simultaneous extraction and purification of TCAs in the above matrices. After diluting 5 mL of intact whole milk or 2 g egg samples with Na(2)EDTA-containing water, samples are passed through a 0.5-g Carbograph 4 extraction cartridge. After analyte elution from the SPE cartridge, an aliquot of the final extract is injected into a liquid chromatography/mass spectrometry (LC/MS) instrument equipped with an electrospray ion source and a single quadrupole. MS data acquisition is performed in the positive-ion mode and by a time-scheduled multiple-ion selected ion-monitoring program. With methanol as organic modifier, the in-source collision-induced dissociation (CID) process generated fragment ions able to pick up one methanol molecule. In several cases, these methanol-adduct fragment ions have m/z values higher than those of the protonated molecules. This event is rarely encountered in MS, thus making the analysis of TCAs by this method extremely specific. Compared with a conventional published method, the present protocol extracted larger amounts of TCAs from both milk and egg and decreased the analysis time by a factor of 3. Recovery of TCAs in milk at the 25-ppb level ranged between 81 and 96% with relative standard deviation (RSD) no larger than 9%. Recovery of TCAs in egg at the 50-ppb level ranged between 72 and 92% with RSD no larger than 7%. Estimated limits of quantification(S/N = 10) of the method were 2-9 ppb TCAs in whole milk and 2-19 ppb TCAs in eggs.

Animals↗
PubMed1991

Solid-phase extraction of fluoxetine and norfluoxetine from serum with gas chromatography-electron-capture detection.

A rapid, selective, and sensitive method is described for the purification and analysis of fluoxetine and norfluoxetine using a solid-phase extraction column and gas chromatography-electron-capture detection. Linear quantitative response curves for fluoxetine and norfluoxetine are generated over a concentration range of 20-200 ng/ml. Overall extraction efficiency of the extraction procedure is found to be greater than 90% and greater than 75% with correlation coefficients of 0.997 and 0.993 for fluoxetine and norfluoxetine, respectively.

Chromatography, Gas↗
PubMed1994

Determination of oxytocin in biological samples by isocratic high-performance liquid chromatography with coulometric detection using C18 solid-phase extraction and polyclonal antibody-based immunoaffinity column purification.

A specific high-performance liquid chromatographic (HPLC) method is described for the reliable quantitation of oxytocin using culture media supernatants. The procedure employs solid-phase extraction, antibody-based immunoaffinity purification and isocratic HPLC with dual channel coulometric detection (ED). The lower limit of detection for this cyclic nonapeptide was 40 pg (40 fmol). Due to its relative simplicity, specificity and precision, the HPLC-ED of oxytocin is an accurate and attractive alternative to many existing quantitative methods.

Amino Acid Sequence↗
PubMed2005

Simultaneous determination of nicotine, cotinine, norcotinine, and trans-3'-hydroxycotinine in human oral fluid using solid phase extraction and gas chromatography-mass spectrometry.

Nicotine is rapidly and extensively metabolized in humans. We present an analytical method to simultaneously quantify nicotine, cotinine, norcotinine, and trans-3'-hydroxycotinine in human oral fluid. Solid phase extraction (SPE) and GC/MS/EI with selected ion monitoring (SIM) were utilized. Linearity ranged from 5 to 1000 ng/mL of oral fluid; correlation coefficients for calibration curves were >0.99. Recoveries were 90-115% nicotine, 76-117% cotinine, 88-101% norcotinine, and 67-77% trans-3'-hydroxycotinine. Intra-assay precision and accuracy ranged from 1.6 to 5.7% and 1.6 to 17.8%, respectively. Inter-assay precision and accuracy ranged from 4.3 to 10.2% and 0 to 12.8%, respectively. Suitable precision and accuracy were achieved for the simultaneous determination of nicotine and three metabolites in the oral fluid of smokers. This assay is applicable to pharmacokinetic studies of nicotine, cotinine, and trans-3'-hydroxycotinine from tobacco smokers and can be utilized for routine monitoring of tobacco smoke exposure. 3-Hydroxycotinine requires additional investigation to determine its usefulness as a biomarker for tobacco smoke exposure.

Cotinine↗
PubMed2000

Use of molecularly imprinted solid-phase extraction for the selective clean-up of clenbuterol from calf urine.

A feasibility study was performed in order to study the possibilities in using molecularly imprinted polymers (MIPs) as sorbent material in solid-phase extraction (MISPE) for clean-up of clenbuterol from urine. A binding study of clenbuterol in several solvents was performed on a clenbuterol imprinted polymer as well as on a blank polymer. These binding experiments were used to find suitable loading, washing and elution solvents for the MISPE procedure. Extraction of clenbuterol from calf urine was performed by directly loading a 10-ml urine sample onto the MIP column. Thereafter the column was washed with 10 ml of acetonitrile containing 1% acetic acid, and finally clenbuterol was eluted with 6 ml of methanol containing 10% acetic acid. A recovery of 65% was obtained. This recovery could be increased up to 75% if a sample volume of 1 ml was used or up to 100% if urine was freeze-dried and the residue was dissolved in acetonitrile and spiked with clenbuterol prior to analysis. Chromatograms of the wash and eluate solutions show an efficient clean-up, which supports the potential of MISPE for clean-up of trace amounts of clenbuterol from calf urine.

Adrenergic beta-Agonists↗
PubMed1998

Improving the solid-phase extraction of "quat" pesticides from water samples. Removal of interferences.

A novel strategy, based on the addition of a cationic surfactant, for preventing the interferences associated with a diminution in the efficacy of solid-phase extraction (SPE) with silica cartridges of diquat, paraquat and difenzoquat in water is developed. Conditions for extraction are optimised with respect to pH, cationic surfactant and its concentration. Humic acids, anionic surfactants, inorganic salts and other organic contaminants like pesticides, phenols, polycyclic aromatic hydrocarbons and polychlorinated biphenyls produce the studied interferences. The best performance is shown in the improvement of the "quats" recovery from waters with high levels of humic acids and anionic surfactants (recovery is increased from ca. 30% to more than 80%). Unfortunately, the strong interference from inorganic salts remains. The presence in the water sample of other organic contaminants only affected the extraction efficiency of difenzoquat at high concentrations (more than 1 mg/l). Analytic utility is illustrated by selective measurements of the three herbicides, in real water samples. Overall, the results show that in spite of its drawbacks, SPE is a useful technique that allows the detection and quantification of the "quats" at limits below 100 ng/l as established by the European Union.

Aluminum Chloride↗