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PubMedDate not supplied

Determination of amoxicillin residues in animal tissues by solid-phase extraction and liquid chromatography with fluorescence detection.

Trace levels of amoxicillin residues were determined in animal tissues by liquid chromatography (LC) with fluorescence detection. An improved solid-phase extraction (SPE) procedure requiring less flammable solvent (diethyl ether) was developed for sample preparation. Muscle samples of beef, pork, chicken, and tilapia were extracted with a phosphate buffer followed by the modified SPE procedure for cleanup and concentration prior to the LC-fluorescence analysis. Average recoveries of fortified amoxicillin at 5, 10, and 20 micrograms/kg ranged from 83.9 to 85.8% in beef, 86.1 to 88.1% in pork, 81.7 to 82.9% in chicken, and 92.5 to 95.4% in tilapia. Relative standard deviations were < 4%.

Amoxicillin↗
PubMed2005

GC/MS profiling of gamma-hydroxybutyrate and precursors in various animal tissues using automatic solid-phase extraction. Preliminary investigations of its potential interest in postmortem interval determination.

To quantify gamma-hydroxybutyrate (GHB) and its physiological metabolites, gamma-aminobutyric acid (GABA), 1,4-butanediol (1,4-BD), and gamma-butyrolactone (GBL) in various animal tissues (kidney, muscle, heart, liver, blood, brain cortex, thalamus, hypothalamus, hippocampus, or pons), an original gas chromatographic/mass spectrometric method with a automated solid-phase extraction by Oasis MCX cartridges on a Gilson Aspec Xli was developed. Using such apparatus allowed the limit of detection (LOD) of target compounds to be significantly lowered (LOD: 0.027, 0.025, and 5.7 microg/mL for GHB, 1,4-BD, and GABA, respectively, in 200 microL or microg of sample). After validation of each analytical step, the satisfactory performances of the apparatus in conjunction with the rapidity and ease of the extraction step make it suitable for simultaneous assay of GHB, 1,4-BD, GBL, and GABA. The method was used to test the correlation between GHB levels in tissues obtained at different times after death of male Sprague-Dawley rats and the postmortem interval. Preliminary results show a linear increase of GHB levels in relation to time of death in thoracic blood and central nervous system of animals kept at 15 and 20 degrees C.

4-Butyrolactone↗
PubMed2002

Accelerated solvent extraction followed by on-line solid-phase extraction coupled to ion trap LC/MS/MS for analysis of benzalkonium chlorides in sediment samples.

Benzalkonium chlorides (BACs) were successfully extracted from sediment samples using a new methodology based on accelerated solvent extraction (ASE) followed by an on-line cleanup step. The BACs were detected by liquid chromatography/ion trap mass spectrometry (LC/MS) or tandem mass spectrometry (MS/MS) using an electrospray interface operated in the positive ion mode. This methodology combines the high efficiency of extraction provided by a pressurized fluid and the high sensitivity offered by the ion trap MS/MS. The effects of solvent type and ASE operational variables, such as temperature and pressure, were evaluated. After optimization, a mixture of acetonitrile/water (6:4 or 7:3) was found to be most efficient for extracting BACs from the sediment samples. Extraction recoveries ranged from 95 to 105% for C12 and C14 homologues, respectively. Total method recoveries from fortified sediment samples, using a cleanup step followed byASE, were 85% for C12BAC and 79% for C14BAC. The methodology developed in this work provides detection limits in the subnanogram per gram range. Concentrations of BAC homologues ranged from 22 to 206 microg/kg in sediment samples from different river sites downstream from wastewater treatment plants. The high affinity of BACs for soil suggests that BACs preferentially concentrate in sediment rather than in water.

Journal Article↗
PubMed2004

In-gel digestion of proteins using a solid-phase extraction microplate.

We present a new procedure for in-gel digestion of proteins introducing a combination of two different 96-well microplates. The two plates have incorporated small capillaries with a length of 2.4 mm in each well, one of which has 75-microm-inner diameter capillaries, whereas the second plate has reversed-phase-type capillaries fixed to it. The initial steps of the in-gel digestion process, comprising destaining, reduction/alkylation, dehydration, and digestion, was carried out in the plate containing 75-microm capillaries. Capillaries containing C18 reversed-phase modified monolithic silica rods of a 200-microm diameter were used for the second plate in which extraction and cleanup of peptides were carried out. Peptides were eluted directly from the solid-phase extraction plate onto the MALDI sample support. The separation of the process into two plates led to increased process stability, without compromising sensitivity, i.e. peptide recovery, making it suitable for true high-throughput protein identification. The handling of proteinases could easily be optimized, and no restrictions were made on chosen pH range through the absence of the solid phase in the initial steps of the protocol. Efficient binding of peptides to the solid phase and subsequent direct elution onto the MALDI sample support led to sensitivities in the attomole range. Performance of the process was demonstrated with tryptic digests of proteins stained with colloidal coomassie blue, silver, and the fluorescent stain SYPRO Ruby.

Animals↗
PubMed1987

Assay of vecuronium in plasma using solid-phase extraction, high-performance liquid chromatography and post-column ion-pair extraction with fluorimetric detection.

An assay has been developed and validated for the routine monitoring of vecuronium in plasma. It consists of solid-phase extraction using C18 disposables as sample pre-treatment, high-performance liquid chromatography and post-column ion-pair extraction with fluorimetric detection. The fluorescent anion 9,10-dimethoxyanthracene-2-sulphonate (DAS) is used as the counter ion. The detection limit is ca. 5 ng/ml in plasma with a signal-to-noise ratio of 10. The assay is also applicable for monitoring vecuronium and its potential metabolites in other biological media, e.g., urine, bile and tissue (liver, kidney) homogenates.

Chromatography, High Pressure Liquid↗
PubMedDate not supplied

Solid-phase extraction and HPLC-MS profiling of pyrrolizidine alkaloids and their N-oxides: a case study of Echium plantagineum.

Pyrrolizidine alkaloids and their N-oxides can be extracted from the dried methanolic extracts of plant material using dilute aqueous acid. The subsequent integration of solid-phase extraction (with a strong cation exchanger) of the alkaloids and N-oxides from the aqueous acid solution, together with analysis using HPLC-ESI/MS, provides a method for the simultaneous profiling of the pyrrolizidine alkaloids and their N-oxides in plant samples and the collection of useful structural data as an aid in their identification. The N-oxide character of the analytes may be confirmed by treating analytical samples with a redox resin and observing the formation of the corresponding parent pyrrolizidine alkaloids. The present case study of Echium plantagineum highlighted a higher ratio of N-oxides to the parent tertiary bases than has been previously reported. Furthermore, a higher proportion of acetylated pyrrolizidine-N-oxides was observed in the flower heads relative to the leaves. Six pyrrolizidine alkaloids or pyrrolizidine-N-oxides, not previously reported from E. plantagineum, were tentatively identified on the basis of MS and biogenetic considerations. Three of these, 3'-O-acetylintermedine/lycopsamine, leptanthine-N-oxide and 9-O-angelylretronecine-N-oxide, have been reported elsewhere, whilst three others, 3'-O-acetylechiumine-N-oxide, echimiplatine-N-oxide and echiuplatine-N-oxide, appear unreported from any other source.

Chromatography, High Pressure Liquid↗
PubMed2002

High-performance liquid chromatographic assay for amiodarone N-deethylation activity in human liver microsomes using solid-phase extraction.

A selective and sensitive assay for amiodarone N-deethylation activity in human liver microsomes by high-performance liquid chromatography (HPLC) with UV detection is reported. The extraction of desethylamiodarone from incubation samples was performed by means of an original solid-phase extraction (SPE) procedure using a polymeric reversed-phase sorbent (Oasis HLB). The method was validated for the determination of desethylamiodarone with respect to specificity, linearity, precision, accuracy, recovery, limit of quantitation and stability. Amiodarone N-deethylation activity from low to high substrate concentrations using human liver microsomes was precisely determined without a concentration step. This method is applicable to the study in vitro of the metabolism of amiodarone.

Amiodarone↗
PubMedDate not supplied

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

A method was developed for the determination of tylosin in feeds. The method involves extraction of tylosin with methanol, concentration under a stream of nitrogen, and cleanup using Phenomenex C18 solid-phase extraction cartridge. Analyte separation and quantitation were achieved by gradient reversed-phase liquid chromatography and UV absorbance at 285 nm with a reference wavelength of 320 nm with column temperature of 45 degrees C. Average spike recoveries for samples prepared at 4 spiking levels (22.7, 181, 907, and 1000 g/ton) were 111.0, 94.9, 96.2, and 98.6%, respectively. The overall method precision at each of the 4 spiking levels was < or = 7.85% relative standard deviation. The limits of detection and quantitation (g/ton) were 2.16 and 7.20 g/ton, respectively.

Animal Feed↗
PubMed2005

Fully automated online solid phase extraction coupled directly to liquid chromatography-tandem mass spectrometry. Quantification of sulfonamide antibiotics, neutral and acidic pesticides at low concentrations in surface waters.

A fully automated online solid phase extraction-liquid chromatography-tandem mass spectrometry (SPE-LC-MS/MS) instrumental setup has been developed for the quantification of sulfonamide antibiotics and pesticides in natural water. The direct coupling of an online solid phase extraction cartridge (Oasis HLB) to LC-MS/MS was accomplished using column switching techniques. High sensitivity in the low ng/L range was achieved by large volume injections of 18 mL with a combination of a tri-directional auto-sampler and a dispenser system. This setup allowed high sample throughput with a minimum of investment costs. Special emphasis was placed on low cross contamination. The chosen approach is suitable for research as well as for monitoring applications. The flexible instrumental setup was successfully optimised for different important groups of bioactive chemicals resulting in three trace analytical methods for quantification of (i) sulfonamide antibiotics and their acetyl metabolites; (ii) neutral pesticides (triazines, phenylureas, amides, chloracetanilides) and (iii) acidic pesticides (phenoxyacetic acids and triketones). Absolute extraction recoveries from 85 to 112% were obtained for the different analytes. More than 500 samples could be analyzed with one extraction cartridge. The inter-day precision of the method was excellent indicated by relative standard deviations between 1 and 6%. High accuracy was achieved by the developed methods resulting in maximum deviation relative to the spiked amount of 8-15% for the different analytes. Detection limits for various environmental samples were between 0.5 and 5 ng/L. Matrix induced ion suppression was in general smaller than 25%. The performance of the online methods was demonstrated with measurements of concentration dynamics of sulfonamide antibiotics and pesticides concentrations in a little creek during rain fall events.

Anti-Bacterial Agents↗
PubMed2004

Rapid quantitation of fluoxetine and norfluoxetine in serum by micro-disc solid-phase extraction with high-performance liquid chromatography-ultraviolet absorbance detection.

A rapid, robust and sensitive method for the extraction and quantitative analysis of serum fluoxetine (FLX) and norfluoxetine (N-FLX) using a solid-phase extraction (SPE) column and high-performance liquid chromatography (HPLC) with ultraviolet (UV) detection was developed and validated. The sample clean-up step was performed by simple micro-disc mixed-mode (non-polar and strong cation exchange (SCX)) SPE cartridges. Separation of analytes and internal standard (IS) clomipramine (CLO) from endogenous matrix interference was achieved using a Waters Symmetry C(8) (150 mm x 2.1 mm i.d., 5 microm) reversed-phase narrow bore column. The relative retention times were 8.5, 9.6 and 10.5 min for FLX, N-FLX and CLO, respectively with a low isocratic flow rate of 0.3 ml/min. Chromatographic run time was completed in 15 min and peak area ratios of analytes to IS were used for regression analysis of the calibration curve. The latter was linear from 10 to 4000 nmol/l using 0.5 ml sample volume of serum. The average recovery was 95.5% for FLX and 96.9% for N-FLX. The lowest limit of quantitation (LLOQ) for serum FLX and N-FLX was 10 nmol/l (on-column amount of 200 fmol). The method described was used to analyse serum samples obtained from rats given chronic FLX treatment and to examine the relationship between steady state serum drug concentrations and neurochemical changes in several brain regions.

Chromatography, High Pressure Liquid↗
PubMed2002

Use of solid phase extraction for the isolation and clean-up of a derivatised furazolidone metabolite from animal tissues.

A method is presented for the determination of protein-bound residues of furazolidone in animal tissue. The use of furazolidone in food-producing animals has been banned in the EU. Illegal use of furazolidone can be monitored most effectively by testing for bound residues containing the 3-amino-2-oxazolidone (AOZ) moiety which, unlike the parent drug, is stable and can be detected for prolonged periods after cessation of treatment. This paper reports the development of an extraction and clean-up procedure for AOZ from liver using solid phase extraction. The method replaces solvent extraction and provides extensive sample clean-up with removal of approximately 99% of the derivatising agent, 2-nitrobenzaldehyde, which may interfere with the determination. It also offers the advantage of being suitable for automation, thereby increasing throughput of samples. The extraction procedure may be used for HPLC and ELISA screening techniques. The method has been validated in fortified and incurred pig liver samples, yielding mean recovery of AOZ in excess of 60%.

Animals↗
PubMedDate not supplied

Chromium speciation by surfactant assisted solid-phase extraction and flame atomic absorption spectrometric detection.

A new procedure has been developed for chromium speciation in aqueous solution by the use of micellar, ion-association, solid-phase extraction techniques (SPE) followed by flame atomic absorption spectrometry. The method was based on the use of C-18 bonded phase silica SPE disks for retention of ion-associated Cr(VI) with cetyl trimethyl ammonium bromide (CTAB), elution of the retained species and subsequent detection by flame atomic absorption spectrometry (FAAS). Cr(III) was oxidized by potassium persulfate to Cr(VI), then the total chromium was retained on the disk and determined by FAAS. The amount of Cr(III) was calculated by the difference between the total and Cr(VI) values. The calculated limit of detections (LOD) (based on 3sigma) are 15 microg L(-1) and 20 microg L(-1) for Cr(VI) and Cr(III) respectively. No considerable interferences have been observed from other investigated anions and cations and the method has been successfully applied to water samples taken from the Karoon River in Khuzestan province.

Chromium↗
PubMed2004

In-capillary micro solid-phase extraction and capillary electrophoresis separation of heterocyclic aromatic amines with nanospray mass spectrometric detection.

A miniaturised technique to analyse and detect heterocyclic aromatic amines (HAs) using micro solid-phase extraction ( microSPE) coupled on-line (in-capillary) to capillary electrophoresis (CE) separation with nanospray (nESI) mass spectrometry (MS) detection has been developed. HAs are mutagenic and carcinogenic compounds formed at low levels in protein-rich food during cooking. Due to the low concentrations of HAs and the high complexity of the matrix in which they exist, sensitive and selective analytical methods are required for quantification. microSPE was performed on a packed bed of C(18 )particles inside the CE capillary, which minimised the dead volume. The on-line coupling of SPE, CE and nESI-MS reduced the time for extraction and identification to less than half an hour, which will allow for screening of several samples per day. The new technique provides short analysis time, low sample and solvent consumption, and HAs in standard solutions were easily detected at 12-17 fmol injections, and in spiked urine samples at 750-810 fmol injections.

Journal Article↗
PubMed1996

Determination of alternariol and alternariol methyl ether in apple juice using solid-phase extraction and high performance liquid chromatography.

The present work describes a new method for determination of alternariol (AOH) and alternariol methyl ether (AME) in apple juice using solid-phase extraction (SPE) columns for extraction and cleanup of samples for high-performance liquid chromatography (HPLC). Chromatograms of spiked samples show that both toxins can be easily detected without interferences, and good recoveries for AOH (82.8 +/- 7.4%) and AME (91.9 +/- 6.1%) with detection limits as low as 1.6 and 0.7 micrograms/l, respectively, were obtained.

Beverages↗
PubMed1994

Sensitive determination of methotrexate in monkey plasma by high-performance liquid chromatography using on-line solid-phase extraction.

A high-performance liquid chromatographic method was developed for the sensitive determination of methotrexate (MTX) in monkey plasma using direct injection and on-line solid-phase extraction. After application of a 100-microliters aliquot of plasma to a pre-treatment column, the column was washed with 0.02 M phosphate buffer (pH 7) to eliminate plasma proteins and endogenous substances, and subsequently the adsorbed MTX was eluted. The MTX fraction was transferred to an analytical column by a column-switching (heart-cutting) technique, and MTX was analyzed using ion-pair chromatography with tetrabutylammonium bromide. More than 50 injections could be performed onto one pretreatment column. The accuracy, precision, reproducibility and linearity were satisfactory over a wide range of MTX concentrations (5-1000 ng/ml). The quantitation limit was 5 ng/ml with a signal-to-noise ratio of 5. The method was suitable for the pharmacokinetic study of MTX in monkey.

Animals↗
PubMed2004

New materials for solid-phase extraction and multiclass high-performance liquid chromatographic analysis of pesticides in grapes.

Sample preparation procedures which included the use of new aminopropyl (NH2) and octadecyl (C18) solid-phase extraction (SPE) sorbents are proposed for the simultaneous multiclass determination of the fungicide benomyl and of the herbicides tebuthiuron, diuron, simazine, atrazine, and ametryn in grapes, using single wavelength high-performance liquid chromatography. Sorbent preparation uses a fast, easy, and effective procedure to obtain silica-based materials, made by depositing polysiloxanes on a silica support followed by thermal immobilization. Recovery results of the compounds, after elution from the SPE cartridges, indicate that the most efficient system employed silica loaded with 40% of an aminofunctional polydimethylsiloxane as sorbent, using dichloromethane:methanol (95:5, v/v) as eluent. Method validation, carried out in agreement with International Conference on Harmonization directives, was performed at three fortification levels (100, 200, and 1000 microg kg(-1)). Limits of detection and quantification show that the method developed can be used to detect the pesticides at concentrations below the maximum residue levels established by Codex Alimentarius, the US Environmental Protection Agency, the European Union, and Brazilian legislation.

Chromatography, High Pressure Liquid↗
PubMed2004

Selective determination of trimethylamine in air by liquid chromatography using solid phase extraction cartridges for sampling.

The selective determination of trimethylamine (TMA) in air by liquid chromatography is reported. Sampling is effected by flushing air through C18-packed solid-phase extraction (SPE) cartridges at a flow rate of 15 mL/min for 15 min. Next, TMA is desorbed from the cartridges and injected into the chromatographic system. The analyte is then selectively retained on a precolumn (20 mm x 2.1 mm i.d., packed with 30 microm, Hypersil C18 phase), and derivatized on-line by injecting 9-fluorenylmethyl chloroformate (FMOC). Finally, the TMA-FMOC derivative is transferred to the analytical column (125 mm x 4 mm i.d., LiChrospher 100 RP18, 5 microm), and monitored at 262 nm. The method was applied to the measurement of TMA in air in the 0.25-2.5 microg interval (equivalent to concentrations of TMA of 1.1-11 mg/m3), providing good linearity, reproducibility and accuracy. The mean recovery of TMA was (96 +/- 7%) (n = 12), and the limit of detection was 0.05 microg. The proposed procedure allows the selective determination of TMA in the presence of other primary and secondary short-chain aliphatic amines.

Air Pollutants, Occupational↗
PubMed2005

Evaluation of a new hypercrosslinked polymer as a sorbent for solid-phase extraction of polar compounds.

A new hypercrosslinked polymer (HXLGp) with hydrophilic character due to the presence of hydroxyl moieties has been tested as a sorbent for the solid-phase extraction (SPE) of several polar compounds from water samples. This new sorbent enables the on-line extraction of 300 ml of sample with recoveries higher than 80% for polar compounds such as oxamyl, methomyl or desisopropylatrazine (DIA). The HXLGp has also been compared to other commercially available sorbents such as Oasis HLB (hydrophilic macroporous), to hydrophobic hypercrosslinked resins and to a previously synthesized sorbent based on N-vinylimidazole-divinylbenzene. The results are consistently better with the new synthesized sorbent. The method was successfully applied to the on-line SPE-HPLC of tap and river water samples. The validation with river water samples provided good linearity range and detection limits between 0.03 for methomyl and 4-nitrophenol (4NP) to 0.2 microg l(-1) for phenol (Ph).

Chromatography↗