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PubMed2006

Simultaneous measurement of intracellular triphosphate metabolites of zidovudine, lamivudine and abacavir (carbovir) in human peripheral blood mononuclear cells by combined anion exchange solid phase extraction and LC-MS/MS.

All nucleoside reverse transcriptase inhibitors (NRTI) must first be metabolized to their triphosphate forms in order to be active against HIV. Zidovudine (ZDV), abacavir (ABC) and lamivudine (3TC) have proven to be an efficacious combination. In order simultaneously to measure intracellular levels of the triphosphates (-TP) of ZDV, ABC (carbovir, CBV) and 3TC, either together or individually, we have developed a cartridge-LC-MS/MS method. The quantitation range was 2.5-250 pg/microl for 3TC-TP, 0.1-10.0 pg/microl for ZDV-TP and 0.05-5.00 pg/microl for CBV-TP. This corresponds to 0.1-11.0 pmol 3TC-TP per million cells, 4-375 fmol ZDV-TP per million cells and 2-200 fmol CBV-TP per million cells, extracted from 10 million cells. Patient samples demonstrated measured levels in the middle regions of our standard curves both at pre-dose and 4h post-dose times.

Chromatography, High Pressure Liquid↗
PubMed2004

Application of solid-phase extraction to determination of polycyclic aromatic hydrocarbons in sewage sludge extracts.

The study presents the efficiency of sewage sludge sample clean-up with the application of SPE columns with various types of adsorbents. Six columns were tested: C8-octyl, C18 PolarPlus, C18-octadecyl, silicagel (SG), phenyl, cyano. The highest efficiency of recovery was observed for C18-octadecyl. Then, using C18, the method was optimised by changing the following parameters: eluent type and volume, column drying and effect of washing of cartridge.

Osmolar Concentration↗
PubMed2005

Solid phase extraction and determination of sub-ppb levels of hazardous Hg2+ ions.

A simple, rapid and reliable method has been developed to selectively separate and concentrate ultra trace amounts of mercury(II) ions from aqueous samples for its highly sensitive measurement by cold vapor atomic absorption spectrometry (CV-AAS). The Hg(2+) ions were adsorbed selectively and quantitatively during the passage of aqueous samples through octadecyl silica membrane disks modified by isopropyl 2-[(isopropoxycarbothiolyl)disulfanyl]ethane thioate (IIDE). The retained Hg(2+) ions were then stripped from the disk with minimal amounts of 0.5 M hydrobromic acid (two 8 ml portions) as eluent, and determined by CV-AAS. The break-through volume of the method is greater than 3000 ml, which results in enrichment factors >150. Maximum capacity of the membrane disks modified with 10mg of the ligand was found to be 350+/-30 microg of mercury(II), and the limit of detection is 0.005 ng ml(-1). The effect of various cationic interferences on the recovery of mercury in binary mixtures was studied. The method was applied to the recovery of Hg(2+) ions from different synthetic and tap water samples, as well as the determination of mercury in human hair samples.

Environmental Monitoring↗
PubMed2006

Speciation of Cr(III) and Cr(VI) in environmental samples by solid phase extraction on Ambersorb 563 resin.

A simple and sensitive method for the speciation, separation and preconcentration of Cr(VI) and Cr(III) in natural water, soil and sediment samples was developed. Cr(VI) has been separated from Cr(III) and preconcentrated as Cr(III)-diphenylcarbazone complex by using Ambersorb 563 resin and determined by spectrophotometric method at 540 nm. Effect of analytical parameters such as sulfuric acid concentration, ligand volume, type of elution solution, sample volume, amount of resin and foreign ions were investigated. The presented procedure was successfully applied for the chromium speciation in various environmental samples with successfully results.

Absorption↗
PubMed2000

Solid-phase extraction followed by high-performance liquid chromatography-ionspray interface-mass spectrometry for monitoring of herbicides in environmental water.

In this work we developed a sensitive and specific multiresidue method, based on reversed-phase liquid chromatography-mass spectrometry, with an ionspray interface (LC-ISI-MS), for determining 52 of most representative compounds of herbicides in water samples. The procedure used involved passing 0.5 l of surface water, 2 l of ground water and 4 l of drinking water samples, respectively, through a 0.5 g graphitized carbon black (GCB) extraction cartridge. Base-neutral and acid herbicides were differential eluted from GCB cartridge and follow analyzed by HPLC-ISI-MS apparatus. A conventional 4.6-mm-ID reversed-phase LC C18 column, operating with a mobile phase flow-rate of 1 ml/min, was used to chromatograph the analytes. A flow of 100 microl/min of the column effluent was diverted to the ISI source. The study demonstrates the sensitivity of the technique, with detection limit under 10 ng/l in drinking water samples. Performance data for the method such as recovery and precision are also reported.

Chromatography, High Pressure Liquid↗
PubMed2000

Solid-phase extraction of sugar cane soot extract for analysis by gas chromatography with flame ionisation and mass spectrometric detection.

The incomplete combustion of biomass is one of the most important sources of emissions of organic compounds into the atmosphere, like polycyclic aromatic hydrocarbons (PAHs) which show genotoxic activity. Since environmental samples generally contain interferents and trace amounts of PAHs of interest, concentration and clean-up procedures are usually required prior to the final chromatographic analysis. This paper discusses the performance of Sep-Pak cartridges (silica gel and RP18) on clean-up of sugar cane soot extract. The best results were obtained with a silica Sep-Pak cartridge. The recoveries ranged from 79% (benzo[b]fluoranthene) to 113% (benzo[e]pyrene).

Carbon↗
PubMed2000

Purification of crude DNA oligonucleotides by solid-phase extraction and reversed-phase high-performance liquid chromatography.

Purification of target oligodeoxyribonucleotides from failure sequence by-products of synthesis is often required for polymerase chain reaction primers, DNA sequencing and other oligonucleotide applications. We have developed purification protocols based on a reversed-phase mechanism ("trityl on" purification) using a 96-well Oasis HLB extraction plate. The Oasis HLB sorbent combines excellent pH stability with a high loading capacity allowing for single-step purification of 0.2 microM scale synthesis. After sample loading and washing, the oligonucleotide trityl group is cleaved on the plate with 2% trifluoroacetic acid. Target DNA is eluted with acetonitrile-0.36 mM triethylamine acetate, pH 11.3 (10:90, v/v). Typical yield of purified product is 60-95%. Final purity, measured by capillary gel electrophoresis, was found to be 90% or greater. Alternatively, highly pure oligonucleotides can be obtained by a RP-HPLC "trityl off" method using an XTerra C18 column. The use of volatile triethylamine acetate buffer as an ion-pair for RP-HPLC eliminates the need for further desalting.

Chromatography, High Pressure Liquid↗
PubMed1989

Isotachophoretic determination of short-chain fatty acids in drinking water after solid-phase extraction with a carbonaceous sorbent.

A macroporous carbon sorbent, packed into disposable columns (Separcol-Carb), was investigated for the off-line preconcentration of short-chain fatty acids from drinking water in conjunction with their determination by capillary isotachophoresis (ITP). Of the acids investigated (C1-C9), butyric acid and higher homologues could be enriched into a high degree from samples of drinking water. Their detection limits from the ITP conductivity detector were in the low parts per 10(9) range when an amount equivalent to 8 ml of the sample was taken for analysis. The lowest homologues (C1-C3) were not adsorbed sufficiently to achieve their reasonable enrichment by the sorbent under the working conditions employed (acidification of the sample to pH 2.0). Acetone and diethyl ether were employed for the elution of the adsorbed analytes. The latter was more convenient in the analysis of practical samples as it co-eluted a considerably smaller number of the adsorbed anionic constituents. Octadecyl-bonded silica, evaluated in parallel, was found to be of only very limited utility for the same purpose.

Electrophoresis↗
PubMed2001

Analysis of oxytetracycline, tetracycline, and chlortetracycline in water using solid-phase extraction and liquid chromatography-tandem mass spectrometry.

A method using liquid chromatography-tandem mass spectrometry has been developed for determination of trace levels of tetracycline antibiotics in ground water and confined animal feeding operation waste water. Oxytetracycline (OTC), tetracycline (TC), and chlortetracycline (CTC) were extracted from water samples using both polymeric and C18 extraction cartridges. The addition of a buffer containing potassium phosphate and citric acid improved tetracycline recoveries in lagoon water. Method detection limits determined in reagent water fortified with 1 microg l(-1) OTC, TC, and CTC were 0.21, 0.20, and 0.28 microg l(-1). Method detection limits in lagoon water samples fortified at 20 microg l(-1) for OTC, TC, and CTC were 3.6, 3.1, and 3.8 microg l(-1). Variability in recovery from laboratory fortified blanks ranged from 86 to 110% during routine analysis.

Chlortetracycline↗
PubMed1988

Improved solid-phase extraction and liquid chromatography with electrochemical detection of urinary catecholamines and 5-S-L-cysteinyl-L-dopa.

We describe a rapid, precise, accurate liquid chromatographic procedure for determining urinary catecholamines and 5-S-L-cysteinyl-L-dopa. The catecholamines (norepinephrine, epinephrine, and dopamine) and 5-S-L-cysteinyl-L-dopa are extracted from 1.0 ml of urine together with internal standards, by using a Bond-Elut strong cation-exchange (SCX) and an affinity phenylboronic acid (PBA) extraction column in series. The eluate obtained from PBA column is then chromatographed on a reversed-phase C18 column with a mobile phase containing pentane- and heptanesulfonate as ion-pair reagents. The detection is achieved with an amperometric detector set at an oxidation potential of +0.55 V. The chromatography is complete is less than 8 min for catecholamines and less than 5 min for cysteinyldopa. The method can measure less than 2 micrograms/l for catecholamines and 5 micrograms/l for cysteinyldopa. Analytical recoveries of catecholamines and cysteinyldopa added to urine pool ranged from 90-107%. Between run coefficient of variation ranged from 4.7 to 8%. None of the drugs and catecholamines metabolites tested interfered with the assay.

Catecholamines↗
PubMed1988

Development of a solid-phase extraction technique for alpha-human atrial natriuretic peptide in human plasma.

A reliable extraction method was developed for alpha-human atrial natriuretic peptide (alpha-hANP) using Bond Elut C8 columns in tandem. This involved activation of the columns using methanol followed by a water wash to remove the excess methanol. Plasma (1 ml) was then added and a vacuum applied until all was drawn through. Excess protein and other endogenous compounds were removed by washing the columns with water and elution of the alpha-hANP was achieved with 0.75 ml acetonitrile-water-trifluoroacetic acid (80:19.8:0.2, v/v/v). Samples were evaporated under nitrogen and reconstituted in radioimmunoassay buffer ready for analysis. The recovery of alpha-hANP from plasma using this method was found to be 90% +/- 0.6% [mean +/- standard error of the mean (S.E.M.); coefficient of variation (C.V.) = 1.5%] which will allow more precise measurement of the peptide than is presently available. With this high precision of analysis available, having a limit of detection of 0.4 fmol/ml and a range of 0 to 32 fmol/ml, a low-dose infusion of alpha-hANP was conducted and the changes in plasma concentration were followed.

Atrial Natriuretic Factor↗
PubMed1991

Determination of triazines and organophosphorus pesticides in water samples using solid-phase extraction.

Octadecyl (C18)-bonded porous silica was evaluated for the extraction of triazine and organophosphorus pesticides from natural water. The extraction results showed an effective performance when 11 of water was passed through small glass columns containing 500 mg of 50-100-microns C18 bonded porous silica. The adsorbed compounds were removed with ethyl acetate, evaporated to 200 microliters and determined by gas chromatography. The overall average recoveries were greater than 85% except for dimethoate and trichlorfon. Application of this procedure to the analysis of natural water samples gave results that agree well with those obtained by solvent extraction methods.

Chromatography, Gas↗
PubMed2002

Fast and efficient separation of cytokinins from auxin and abscisic acid and their purification using mixed-mode solid-phase extraction .

A method for separation of cytokinins from auxin and abscisic acid, which allows further separation of cytokinin ribotides from cytokinin bases, ribosides and glucosides and their purification on a single Oasis MCX column was developed. Due to the mixed reversed-phase and cation-exchange mode of the Oasis MCX sorbent the cationic cytokinin bases, ribosides and glucosides as well as the anionic auxin, abscisic acid and cytokinin ribotides are retained and can be sequentially eluted by solvents containing different concentrations of methanol and ammonium hydroxide. Characteristics of the method are high recoveries of analyzed phytohormones and their sufficient purity for quantification by HPLC-ELISA (RIA) or HPLC-MS.

Abscisic Acid↗
PubMed2002

Solid-phase extraction for the simultaneous preconcentration of organic (selenocystine) and inorganic [Se(IV), Se(VI)] selenium in natural waters.

This paper describes the combined use of a new preconcentration method using the Amberlite IRA-743 resin and high-performance liquid chromatography coupled to inductively coupled plasma mass spectrometry to determine simultaneously inorganic and organic selenium species in aquatic systems. The developed enrichment procedure, whose accuracy has been checked by recovery tests, is suitable for selenium speciation at environmental levels of 10 ng (Se) l(-1). The method has been applied to mineral and freshwater samples.

Chromatography, High Pressure Liquid↗
PubMed2003

Determination of imidacloprid and its metabolite 6-chloronicotinic acid in greenhouse air by application of micellar electrokinetic capillary chromatography with solid-phase extraction.

A method is described for the analysis of the insecticide imidacloprid [1-(6-chloro-3-pyridylmethyl)-N-nitroimidazolidin-2-ylideneamine] and its metabolite 6-chloronicotinic acid by micellar electrokinetic chromatography with diode-array detection at 270 and 227 nm, respectively. The best results were obtained using sodium dodecyl sulphate at a concentration of 60 mM and a running buffer of NH4Cl/NH3 at 15 mM (pH 8.5). The selection of instrumental parameters such as voltage at 30 kV with an injection time of 20 s gave the best resolution with an analysis time of less than 6 min. The method yields similar sensitivity for the parent compound and for the metabolite, with detection limits of 0.71 and 1.18 microg/ml for imidacloprid and 6-chloronicotinic acid, respectively. The sampling and analysis of these two pesticides in greenhouse air was carried out using personal samplers connected to XAD-2 cartridges as sampling media, investigating the dissipation of analytes in a 24-h period after their application.

Agriculture↗