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PubMed2006

Comparison of three solid-phase extraction methods for fatty acid analysis of lipid fractions in tissues of marine bivalves.

Objective of this study was to investigate the effect of using pre-packed Si (Si), manually packed silica hydrated with water (Si-H(2)O) and pre-packed aminopropyl-bonded silica (NH(2)), at various mass ratios of lipid to sorbent, on the recovery of polar lipids following the solid-phase extraction (SPE) of a standard mixture of lipids. We also applied SPE using these sorbents to the separation of lipids from oyster tissues and compared the fatty acid (FA) composition of each fraction. Recoveries of phospholipids after SPE using Si increased with an increasing ratio of lipid to sorbent. Although the use of Si-H(2)O improved the recovery of polar lipid compared to that obtained on Si, the neutral lipid from gills and muscles of oyster showed distorted FA compositions presumably due to a leakage of polar lipids. Finally, NH(2) eluted with methanol provided good recoveries of phospholipids from the standard mixture; although polar lipids of oyster tissues showed a reduction in 20:4n-6 and MUFA likely due to the selective retention of acidic phospholipids.

Animals↗
PubMed1997

Solid-phase extraction in malondialdehyde analysis.

Malondialdehyde (MDA) has been widely used as an index of lipoperoxidation in biological and medical sciences as well as in the food industry. A solid-phase extraction (SPE) of the condensation product of the MDA with 2-thiobarbituric acid (TBA) was developed using LiChrolut C18ec, 200 mg (Merck, Darmstadt, Germany), as a SPE cartridge and methanol as an eluent for sample pretreatment before HPLC analysis. The samples of blood plasma, platelet concentrates, or erythrocyte membranes (ghosts) were deproteinized by acetonitrile in the presence of sodium hydroxide prior to the reaction with TBA. The reaction mixture was processed using SPE. The SPE extracts (800 microL of methanol) were put to dryness and after dissolution with 100 microliters of mobile phase, 50 microliters was analyzed by RP-HPLC with fluorescence detection (excitation at 514 nm, emission at 556 nm). The mean MDA concentration in plasmas of 32 healthy donors was 0.37 +/- 0.25 mumol/L and the mean MDA concentration in normal ghosts was 8.3 +/- 4.1 pmol/microgram of protein content. In the case of a patient with a severe form of beta-thalassemia, the concentration of plasma MDA was raised to 1.22 mumol/L and the amount of MDA in erythrocytal ghosts was raised to 21.05 pmol/microgram of protein content. MDA concentration in platelet concentrates (six bags) in the first day of storage was 0.46 +/- 0.18 mumol/L and in the fifth day of storage was 0.55 +/- 0.44 mumol/L.

Blood Platelets↗
PubMed1994

Automated assay for GV104326, a novel tribactam antibiotic, in human plasma by high-performance liquid chromatography and solid-phase extraction.

A highly automated, rapid, robust and specific plasma assay for GV104326, a novel tribactam antibiotic, has been developed to monitor human volunteer trials. The method involves automated solid-phase extraction with a strong anion-exchange phase and HPLC on a reversed-phase column with ultraviolet detection. The calibration range for the assay is 0.05-2 micrograms/ml. The assay is linear over this range and is specific with respect to endogenous interference and likely metabolites of GV104326. Both intra- and inter-assay variability were < 8% and intra- and inter-day bias < 10%.

Anion Exchange Resins↗
PubMed1993

Recovery of substance P and related C-terminal fragments on solid-phase extraction cartridges for subsequent high-performance liquid chromatographic separation and radioimmunoassay.

The recoveries of substance P (SP) and five related peptides were evaluated on different types of solid-phase extraction sorbent. Best results were obtained by use of a C18 silica gel cartridge. Marked differences of extraction yields occurred for the different peptide fragments and, in general, recovery increased with increasing hydrophobicity of the peptide when reversed-phase materials like C18 and C8 cartridges were used. This observation is indicative of a sorption-desorption mechanism by prevailing solvophobic interactions. A similar trend was found when phenylpropyl silica gel (CPhenyl), generally known as a reversed-phase adsorbent of lower hydrophobicity, was used. It was concluded that a substantial participation of analyte-matrix pi-pi interactions has to be taken into account when extraction yields are compared with corresponding values obtained by use of a C8 cartridge. With CN silica gel cartridges, marked differences in extraction yields were obtained by use of acetonitrile or methanol as the organic modifier. As an attempt to explain this observation, conformational effects were assumed for the sorption-desorption behaviour of the peptides on the polar matrix.

Amino Acid Sequence↗
PubMed1994

Analysis of cocaine and metabolites in brain using solid phase extraction and full-scanning gas chromatography/ion trap mass spectrometry.

A method is described for the determination of cocaine, benzoylecgonine and cocaethylene in the human brain using Clean Screen solid phase extraction cartridges and gas chromatography/ion trap mass spectrometry with electron impact and full scan analysis. The procedure uses deuterated internal standards. Run-to-run and within-run coefficients of variation are < 7% and the sensitivity proved to be 50 ng/g from 1 g of sample. The procedure has been applied to a number of forensic cases involving cocaine intoxication. Cocaine was relatively unstable in brain tissue stored at 4 degrees C when compared to storage at -80 degrees C.

Brain Chemistry↗
PubMed2005

A rapid and validated HPLC method to quantify sphingosine 1-phosphate in human plasma using solid-phase extraction followed by derivatization with fluorescence detection.

We describe the development and validation of analytical methodology for the determination of sphingosine 1-phosphate (S1P) in plasma. It uses solid-phase extraction (SPE) followed by an automated reversed-phase gradient HPLC column-switching system with a pre-column derivatization with o-phthalaldehyde (OPA) and fluorescence detection. The limit of quantification was determined at 100 ng/ml exogenous sphingosine 1-phosphate with a relative standard deviation for precision and accuracy <15%. The within- and between-day relative standard deviation for precision and accuracy were also less than 15%. This validated method should be suitable to quantify plasma concentration of sphingosine 1-phosphate in relatively large numbers of samples.

Calibration↗
PubMed2006

Automated solid-phase extraction for the determination of polybrominated diphenyl ethers and polychlorinated biphenyls in serum--application on archived Norwegian samples from 1977 to 2003.

An analytical method comprised of automated solid-phase extraction and determination using gas chromatography mass spectrometry (single quadrupole) has been developed for the determination of 12 polybrominated diphenyl ethers (PBDEs), 26 polychlorinated biphenyls (PCBs), two organochlorine compounds (OCs) (hexachlorobenzene and octachlorostyrene) and two brominated phenols (pentabromophenol, and tetrabromobisphenol-A (TBBP-A)). The analytes were extracted using a sorbent of polystyrene-divinylbenzene and an additional clean-up was performed on a sulphuric acid-silica column to remove lipids. The method has been validated by spiking horse serum at five levels. The mean accuracy given as recovery relative to internal standards was 95%, 99%, 93% and 109% for the PBDEs PCBs, OCs and brominated phenols, respectively. The mean repeatability given as RSDs was respectively 6.9%, 8.7%, 7.5% and 15%. Estimated limits of detection (S/N=3) were in the range 0.2-1.8 pg/g serum for the PBDEs and phenols, and from 0.1 pg/g to 56 pg/g serum for the PCBs and OCs. The validated method has been used to investigate the levels of PBDEs and PCBs in 21 pooled serum samples from the general Norwegian population. In serum from men (age 40-50 years) the sum of seven PBDE congeners (IUPAC No. 28, 47, 99, 100, 153, 154 and 183) increased from 1977 (0.5 ng/g lipids) to 1998 (4.8 ng/g lipids). From 1999 to 2003 the concentration of PBDEs seems to have stabilised. On the other hand, the sum of five PCBs (IUPAC No. 101, 118, 138, 153 and 180) in these samples decreased steadily from 1977 (666 ng/g lipids) to 2003 (176 ng/g lipids). Tetrabromobisphenol-A and BDE-209 were detected in almost all samples, but no similar temporal trends to that seen for the PBDEs were observed for these compounds, which might be due to the short half-lives of these brominated flame retardants (FR) in humans.

Adult↗
PubMed2004

A validated LC method for the determination of vesamicol enantiomers in human plasma using vancomycin chiral stationary phase and solid phase extraction.

An enantioseparation high performance liquid chromatographic (HPLC) method was developed and validated to determine D-(+)- and L-(-)-vesamicol in human plasma. The assay involved the use of a solid phase extraction for plasma sample clean up prior to HPLC analysis utilizing a C18 Bond-Elute column. Chromatographic resolution of the vesamicol enantiomers was performed on a vancomycin macrocyclic antibiotic chiral stationary phase (CSP) known as Chirobiotic V with a polar ionic mobile phase (PIM) consisting of methanol:glacial acetic acid:triethylamine (100:0.1:0.05 (v/v/v)) at a flow rate of 1.0 ml/min and UV detection set at 262 nm. All analyses were conducted at ambient temperature. The method was validated over the range of 1-20 microg/ml for each enantiomer concentration (R2>0.999). Recoveries for D-(+)- and L-(-)-vesamicol enantiomers were in the ranges of 96-105% at 3-16 microg/ml level. The method proved to be precise (within-run precision ranged from 1.3 to 2.7% and between-run precision ranged from 1.5 to 3.4%) and accurate (within-run accuracies ranged from 0.8 to 3.4% and between-run accuracies ranged from 1.7 to 5.0%). The limit of quantitation (LOQ) and limit of detection (LOD) for each enantiomer in human plasma were 1.0 and 0.5 microg/ml (S/N=3), respectively.

Chromatography, Liquid↗
PubMed2003

Application of new high-performance liquid chromatography and solid-phase extraction materials to the analysis of pesticides in human urine.

A method for the simultaneous determination of diuron and linuron pesticides in human urine was developed, using both solid-phase extraction (SPE) and high-performance liquid chromatography (HPLC) phases made in our own laboratory. These materials were prepared by sorption of polysiloxanes onto a silica surface, followed by immobilization. The HPLC columns were prepared from poly(methyloctylsiloxane), PMOS, immobilized onto silica with microwave radiation while the SPE cartridges where made with poly(methyloctadecylsiloxane), immobilized thermally. Method validation was performed for diuron and linuron for three fortification levels. The recoveries obtained were 85-103%, the inter- and intra-assay precisions were less than 1.6 and 1.8%, respectively. The limits of quantitation and detection for diuron were 2.4 and 8.0 microg/l and for linuron were 5.0 and 12 microg/l, respectively.

Chromatography, High Pressure Liquid↗
PubMed2003

New technique using solid-phase extraction for the analysis of aromatic amines in mainstream cigarette smoke.

A new procedure has been developed for the quantitation of aromatic amines in mainstream cigarette smoke. Two solid-phase extraction (SPE) cleanup steps using different retention mechanisms are required to process the samples. The first step uses a cation-exchange cartridge, followed by a second step that uses a cartridge with a hydrophobic retention character. The aromatic amines eluted from the second SPE cartridge are derivatized with heptafluorobutyric anhydride and analyzed with GC-MS selected ion monitoring in the negative chemical ionization mode. This new method has several advantages over other reported techniques, being sensitive, robust, and easily automated. The detection limits ranged from 0.02 ng/cigarette for tolidine to 1.41 ng/cigarette for aniline and the recoveries were from 79 to 109%.

Amines↗
PubMed1997

Solid-phase extraction with end-capped C2 columns for the routine measurement of racemic citalopram and metabolites in plasma by high-performance liquid chromatography.

An assay based on solid-phase extraction followed by high-performance liquid chromatography (HPLC) was developed for the measurement of citalopram and its main metabolites desmethylcitalopram and didesmethylcitalopram. The best extraction procedure was performed with end-capped C2 column utilising secondary silanol interactions to obtain clean extract. The HPLC analysis was done on a phenyl column with a mobile phase without any amine additives. Fluorescence detection gave a limit of detection of 0.8 nmol/l plasma for the compounds analysed.

Antidepressive Agents↗
PubMed2001

Determination of naphthenic acids in crude oils using nonaqueous ion exchange solid-phase extraction.

A method is presented for the routine, rapid, and quantitative analysis of aliphatic and naphthenic acids in crude oils, based on their isolation using nonaqueous ion exchange solid-phase extraction cartridges. The isolated acid fractions are methylated and analyzed by gas chromatography and gas chromatography/mass spectrometry. The method is effective on both light and heavy oils and is capable of providing mechanistic information of geochemical significance on the origin of the acids in the oils. Analysis of oils that were solvent extracted from laboratory and field mesocosm marine sediment oil degradation studies indicate that this new method of analyzing the products of hydrocarbon biodegradation may be a useful tool for monitoring the progress of bioremediation of oil spills in the environment.

Journal Article↗
PubMed2005

Hyphenation of solid-phase extraction with liquid chromatography and nuclear magnetic resonance: application of HPLC-DAD-SPE-NMR to identification of constituents of Kanahia laniflora.

The introduction of on-line solid-phase extraction (SPE) in HPLC-NMR has dramatically enhanced the sensitivity of this technique by concentration of the analytes in a small-volume NMR flow cell and by increasing the amount of the analyte by multiple peak trapping. In this study, the potential of HPLC-DAD-SPE-NMR hyphenation was demonstrated by structure determination of complex constituents of flower, leaf, root, and stem extracts of an African medicinal plant Kanahia laniflora. The technique was shown to allow acquisition of high-quality homo- and heteronuclear 2D NMR data following analytical-scale HPLC separation of extract constituents. Four flavonol glycosides [kaempferol 3-O-(6-O-alpha-l-rhamnopyranosyl)-beta-d-glucopyranoside; kaempferol 3-O-(2,6-di-O-alpha-l-rhamnopyranosyl)-beta-d-glucopyranoside; quercetin 3-O-(2,6-di-O-alpha-l-rhamnopyranosyl)-beta-d-glucopyranoside (rutin); and isorhamnetin, 3-O-(6-O-alpha-l-rhamnopyranosyl)-beta-d-glucopyranoside] and three 5alpha-cardenolides [coroglaucigenin 3-O-6-deoxy-beta-d-allopyranoside; coroglaucigenin 3-O-(4-O-beta-d-glucopyranosyl)-6-deoxy-beta-d-glucopyranoside; 3'-O-acetyl-3'-epiafroside] were identified, with complete assignments of 1H and 13C resonances based on HSQC and HMBC spectra whenever required. Confirmation of the structures was provided by HPLC-MS data. The HPLC-DAD-SPE-NMR technique therefore speeds up the dereplication of complex mixtures of natural origin significantly, by characterization of individual extract components prior to preparative isolation work.

Apocynaceae↗
PubMed2006

Influence of suspended clay minerals and humic matter on the solid phase extraction efficiency of selected pesticides from water.

The purpose of this investigation was to determine the influence of humic acids (HA) and Ca-montmorillonite (CaM) on the solid-phase extraction (SPE) efficiency of atrazine, alachlor and alpha-cypermethrin from water samples at various pH-values. The nature and intensity of binding of the studied pesticides to CaM were determined by X-ray diffraction analysis and termogravimetric analysis (TGA) test. The studied pesticides eluted from discs were analysed by thin-layer chromatography (TLC). The effects of CaM and humic acid were generally pH-dependent and acted independently in extraction efficiency influence. Lower recovery of pesticides was observed at higher pH values when CaM was > or =0.1 g and was attributed to greater dispersion of clay, increased surface area and subsequent adsorption. Concentrations of dissolved organic carbon (DOC) in humic acid had less effect on the extraction efficiency when water was at pH 8 compared to water at pH 2, which was probably due to greater nonpolar interactions of the pesticides to the charge-neutralized humic acid molecule.

Acetamides↗
PubMed1996

Comparison of solid-phase extraction and dialysis on pretreatment efficiency of blood urea analysis.

Although the analysis of urea in blood using high-performance liquid chromatography has been reported, its automated solid-phase extraction (SPE) has not been reported. In addition to these two methods, dialysis may also be used to pretreat blood samples. The separation efficiency of automated SPE is discussed and compared with automated dialysis using a condensing column. The results indicate that automated SPE and dialysis have an almost identical separation efficiency for urea analysis. However, the dialysis technique is not as efficient for the removal of admixtures eluted after urea.

Blood Urea Nitrogen↗
PubMed2002

[Study on solid phase extraction spectrophotometric determination of copper(II) with 2-(4-antipyrinylazo)-5-dimethylaminoaniline].

Based on the color reaction of 2-(4-Antipyrinylazo)-5-Dimethylaminoaniline (ADA) with copper (II) and the solid phase extraction of its colored complex with Waters Porapak(r) Sep-Park-C18 cartridge, a new method for the determination trace amount of copper(II) was studied. In the medium of Tween-80 and presence of pH = 4.5 buffer solution, ADA can react with copper (II) to form a stable 2:1 complex. The colored complex can extracted by Porapak(r) Sep-Park-C18 cartridge and eluted by ethanol contain 1% of acetic acid, then can be determined by spectrophotometer at 530 nm. Beer's law is obeyed in range of 0.05(1.0(g/ml. This method can be applied to the determination trace amount of copper in water with satisfactory results.

Aniline Compounds↗
PubMed1993

Automated solid-phase extraction of opiates from urine (II). Establishing criteria for the detection of opiate abuse.

Automation in the laboratory was taken one step further with the introduction of automated solid-phase extraction of opiates from urine using C18 bonded-phase columns as an alternative to traditional liquid-liquid partitioning. A comparison of the automated procedure with an established liquid-liquid extraction procedure showed a linear correlation between the two over the concentration range studied. Criteria for the identification of opiate abusers were established to adapt this new methodology to large-scale screening of urine specimens.

Codeine↗
PubMed2004

A new method for the quantitation of propofol in human plasma: efficient solid-phase extraction and liquid chromatography/APCI-triple quadrupole mass spectrometry detection.

Propofol (2,6-diisopropyl phenol) is widely used for the induction and maintenance of anesthesia. Analyses of its pharmacokinetics require simple and sensitive methods for quantitation of propofol in human plasma. Previously reported HPLC and GC methods are limited by cumbersome extraction steps. We describe a novel method that combines sample preparation by solid-phase extraction (SPE) with hydrophilic-lipophilic balance cartridges and analysis with a sensitive LC-APCI-triple quadrupole mass spectrometry (MS/MS) method for better quantitation. The absolute recovery of the analyte was greater than 96%. The limit of quantification for propofol in plasma at a signal-to-noise ratio of 10 was 5 ng/ml. The precision of the assay yielded coefficients of variation ranging from 2.9 to 5.3% and an accuracies of 99-105%. Our method advances the quantitative analysis of propofol in human plasma by combining simple, rapid and efficient SPE with specific and sensitive quantitation by HPLC with APCI-MS/MS detection.

Anesthetics, Intravenous↗