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PubMed2001

Examination of postmortem fluids and tissues for the presence of methylecgonidine, ecgonidine, cocaine, and benzoylecgonine using solid-phase extraction and gas chromatography-mass spectrometry.

BACKGROUND: During the smoking of crack cocaine (COC), methyl ecgonidine (MED) is formed as one of the pyrolysis products. Once in the body, MED is converted to ecgonidine (ED) through several processes that include spontaneous hydrolysis and enzymatic hydrolysis. The presence of MED and/or ED could provide valuable information to help determine antemortem conditions in cases where COC is involved. Our goal was to examine postmortem tissues and fluids for the presence of MED, ED, COC, and benzoylecgonine (BZ). METHODS: Liver, brain, blood, and urine specimens obtained from 15 postmortem cases were extracted using solid-phase extraction, derivatized, and analyzed using gas chromatography-mass spectrometry with selective-ion monitoring. RESULTS: Median concentrations (range) of drugs observed in postmortem liver, brain, blood, and urine were 0 (0-10) ng/g, 7 (0-92) ng/g, 0 (0-42) microg/L, and 62 (0-2030) microg/L, respectively, for MED; 655 (90-3274) ng/g, 22 (0-52) ng/g, 119 (13-773) microg/L, and 456 (109-7452) microg/L, respectively, for ED; 57 (0-503) ng/g, 187 (0-1403) ng/g, 12 (0-88) microg/L, and 1208 (37-28 062) microg/L, respectively, for COC; and 821 (45-4980) ng/g, 524 (46-5153) ng/g, 458 (30-2071) microg/L, and 6768 (917-116 430) microg/L, respectively, for BZ. MED was detected in 12 of 15 postmortem cases. The concentrations were highest in urine compared with liver, brain, and blood. The hydrolysis product ED was detected in all postmortem cases, and the concentrations were substantially higher than MED in all liver, blood, and urine specimens. CONCLUSION: ED may be a more useful indicator of crack COC smoking.

Body Fluids↗
PubMed2005

On-line electrochemically controlled solid-phase extraction interfaced to electrospray and inductively coupled plasma mass spectrometry.

Electrochemically controlled solid-phase extractions of anions were interfaced on-line to electrospray mass spectrometry (ESI-MS) and inductively coupled plasma mass spectrometry (ICP-MS), using polypyrrole coated electrodes and a thin-layer electrochemical (EC) flow cell. The results indicate that electrochemically controlled solid-phase extraction (EC-SPE) can be used as a versatile potential controlled sample preparation technique for a range of anions and that the properties of the polypyrrole coatings can be modified by altering the electrodeposition conditions. In the present study, the influence of interfering anions (i.e., fluoride and sulfate), and the anion used during the electropolymerisation, on the bromide extraction recovery was investigated for EC-SPE interfaced to ICP-MS. The results of these experiments show that the interference due to the presence of similar concentrations of sulfate can be reduced when using a polypyrrole coating electropolymerised in the presence of bromide ions. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurements were also used to study the morphology of the coatings, as well as the variations in the film thickness within the coatings. The effect of different desorption techniques on the bromide preconcentration factor in the ICP-MS on-line flow system was also examined. Stopped-flow desorption was found to give rise to significantly increased preconcentration factors in comparison with desorptions in flowing solutions. While the desorption efficiency depends on the type of desorption electrolyte (the electrolyte in which the desorption takes place), due to the competing influx of cations, the influence of the pH on the switching charge of the polypyrrole coating was found to be small, at constant ionic strength. To study the applicability of the EC-SPE technique with respect to real samples, investigations were also made with tap water samples spiked with different bromide concentrations. The results of these experiments, which were carried out using a modified thin-layer EC flow cell allowing in situ polymerisation of polypyrrole yielding a polymer plug covering the cross section of the channel, demonstrate that 3 microM concentrations of bromide could be detected in the tap water sample. This demonstrates that the extraction technique allows extractions of low concentrations of ions in the presence of significantly higher concentrations of other similar ions. The fact that the extraction and desorption steps are electrochemically controlled makes EC-SPE particularly well suited for inclusion in miniaturised lab-on-a-chip systems.

Bromides↗
PubMed1989

Comparative yields of mutagens from cigarette smokers' urine obtained by using solid-phase extraction techniques.

Urine from cigarette smokers was prepared for mutagenicity testing by extracting mutagens with solid-phase extraction columns. Commercially available prepacked bonded silicas (octadecyl, cyclohexyl, cyanopropyl) were compared for their ability to concentrate the urinary mutagens. Recovered urinary metabolites were evaluated for mutagenic activity by using a microreversion assay with Salmonella typhimurium. Dose-response data indicated that while mutagens were recovered by all three adsorbents, samples prepared by using the bonded cyanopropyl columns yielded the most bioactivity and/or the least amount of test organism toxicity. Varying pH of the urine was found to influence only the basified samples in terms of mutagenic recovery with the cyanopropyl base. Combinations of different adsorbents were not found to offer significant advantages over use of a singular extraction adsorbent.

Adult↗
PubMed2004

Selective extraction of benzoic acid from landfill leachate by solid-phase extraction and ion-exchange chromatography.

In this work a simple method was described for selective extraction of benzoic acid from landfill leachate samples. The samples were submitted to solid-phase extraction (SPE) with XAD-4 resin as the stationary phase and ion-exchange chromatography (IEC) using the ion-exchange resin Amberlyst A-27. The instrumental analysis was performed by gas chromatography with mass spectrometric detection (GC-MSD). Benzoic acid was isolated, identified and quantified. The extraction process is rapid, simple and of low cost. It was also environmental friendly, that is, it was used a minimum amounts of hazardous organic solvents and produced also minimum quantities of residues.

Benzoic Acid↗
PubMed1999

Determination of streptomycin residues in food by solid-phase extraction and liquid chromatography with post-column derivatization and fluorometric detection.

A reliable and sensitive procedure is presented for the analysis of streptomycin (STP) in food of animal origin, like meat, milk and honey. The method is based on a separation by ion-pair liquid chromatography with beta-naphthoquinone-4-sulfonate (NQS) postderivatization and fluorescence detection. The clean-up of the extract is done by solid-phase extraction, firstly with a cation-exchange cartridge and secondly with an octadecyl cartridge. The selectivity is very good and not many interfering peaks are observed for various food matrices. The streptomycin recovery of the total procedure is superior to 80%. The procedure is quantitatively characterized and repeatability, linearity, detection and quantification limits are very satisfactory. A special focus is given to STP residues in honeys and a survey on 64 commercial honeys is presented. For honey analysis, the HPLC method is compared with an immunoassay test (ELISA), and the possibility of using this test for screening with and without solid-phase extraction clean-up is also discussed.

Animals↗
PubMed2000

Development of a solid-phase extraction method for phenoxy acids and bentazone in water and comparison to a liquid-liquid extraction method.

A rapid solid-phase extraction (SPE) method was developed for the determination of bentazone and the phenoxy acids 2,4-D, dichlorprop, MCPA, and mecoprop in Norwegian environmental water samples. Cartridges with a high-capacity cross-linked polystyrene-based polymer were used for off-line preconcentration. The effects of elution solvent, elution volume, sample volume, sorbent mass, pH, and flow rate on the recoveries of the pesticides were investigated using HPLC. Average recovery of >90% was achieved with 500 mg sorbents using 2 mL of methanol with 5% NH3 as elution solvent. The recoveries were independent of sample pH in the tested range of pH 1-7. Using a sample volume of 200 mL, the limits of determination for the phenoxy acids and bentazone are 0.02 microg/L. Sample volumes up to 2000 mL at a flow rate of 60 mL/min could be handled without any loss of analytes, which makes it possible to lower the limits of determination. The SPE method was compared to a routinely used liquid-liquid extraction method. Three different water matrices spiked at 1.0 and 0.05 microg/L were extracted, and the quantification was performed by GC-MS. Both methods permitted the determination of phenoxy acids and bentazone in distilled water, creek water, and well water down to a level of 0.05 microg/L with recoveries >80% for 200 mL samples. Important advantages of the SPE method compared to the liquid-liquid extraction method were the short extraction times, lack of emulsions, use of disposable equipment, and reduced consumption of organic solvents.

Benzothiadiazines↗
PubMed1987

Selective solid-phase extraction of mexiletine from human serum prior to its GLC analysis.

A rapid and sensitive method for the GLC determination of mexiletine in human serum is described. The liquid-liquid extraction was replaced by the solid-phase extraction procedure for sample preparation using Separcol SI C 18 cartridges. The two-step elution of the cartridges after serum application was used-first with 50% acetonitrile in water for eluting endogenous compounds from serum, then with methanol to displace purified mexiletine. The recovery by this procedure was 83.6%. This selective solid-phase extraction offers an acceptable alternative to liquid extraction, and in combination with GLC-FID analysis is suitable for clinical pharmacokinetic studies of mexiletine.

Chromatography, Gas↗
PubMed2004

Rapid biomonitoring of heterocyclic aromatic amines in human urine by tandem solvent solid phase extraction liquid chromatography electrospray ionization mass spectrometry.

A rapid and facile tandem solvent solid phase extraction method was established to isolate the heterocyclic aromatic amines (HAAs) 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (8-MeIQx), 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine, and 2-amino-9H-pyrido[2,3-b]indole from urine. The HAAs were separated by reversed phase liquid chromatography and quantified by electrospray ionization tandem mass spectrometry (ESI/MS/MS) using selected reaction monitoring. The limits of detection and quantitation of these HAAs approached 1-3 and 2-8 pg/mL, respectively, using only 0.3 mL of urine for analysis. Full product ion spectra were acquired to corroborate analyte identities. The pretreatment of urine from human volunteers that had consumed a grilled beef meal with acid or base at 70 degrees C increased the concentration of HAAs by as much as 6-fold, indicating the presence of phase II conjugates of the parent compounds. HAAs containing an N-methylimidazole moiety undergo facile cleavage of the N-methyl group under collision-induced dissociation conditions, and MS/MS analysis in the constant neutral loss scan mode monitoring the transition [M + H](+) --> [M + H - CH(3)(*)](+) revealed the presence of two other HAAs. 2-Amino-3-methylimidazo[4,5-f]quinoxaline (IQx) was identified by coelution of the analyte with synthetic IQx and by acquisition of the product ion spectrum. The second HAA was present in a relatively high abundance in urine. The molecule had the same nominal mass as 8-MeIQx (MH(+) at m/z 214), and the product ion spectrum was similar to that of 8-MeIQx. This novel HAA was also found in the grilled meat consumed by the volunteers at a concentration of 8 parts per billion. The accurate mass measurement and product ion spectrum of this molecule by ESI quadrupole time-of-flight mass spectrometry revealed that it was an isomer of 8-MeIQx. This tandem solvent solid phase extraction LC/ESI/MS/MS procedure may be used to rapidly assess the daily exposure to a variety of HAAs in urine.

Amines↗
PubMed2005

Analysis of Delta9-tetrahydrocannabinol in oral fluid samples using solid-phase extraction and high-performance liquid chromatography-electrospray ionization mass spectrometry.

An analytical method using solid-phase extraction (SPE) and high-performance liquid chromatography-mass spectrometry (LC-MS) has been developed and validated for the confirmation of Delta(9)-tetrahydrocannabinol (THC) in oral fluid samples. Oral fluid was extracted using Bond Elut LRC-Certify solid-phase extraction columns (10 cm(3), 300 mg) and elution performed with n-hexane/ethyl acetate. Quantitation made use of the selected ion-recording mode (SIR) using the most abundant characteristic ion [THC+H(+)], m/z 315.31 and the fragment ion, m/z 193.13 for confirmation, and m/z 318.00 for the protonated internal standard, [d(3)-THC+H(+)]. The method proved to be precise for THC, in terms of both intra-day and inter-day analyses, with coefficients of variation less than 10%, and the calculated extraction efficiencies for THC ranged from 76 to 83%. Calibration standards spiked with THC between 2 and 100 ng/mL showed a linear relationship (r(2)=0.999). The method presented was applied to the oral fluid samples taken from the volunteers during the largest music event in Portugal, named Rock in Rio-Lisboa. Oral fluid was collected from 40 persons by expectoration and with Salivette. In 55% of the samples obtained by expectorating, THC was detected with concentration ranges from 1033 to 6552 ng/mL and in 45% of cases THC was detected at concentrations between 51 and 937 ng/mL. However, using Salivette collection, 26 of the 40 cases had an undetectable THC.

Adolescent↗
PubMed2004

Development of a novel solid-phase extraction element for thermal desorption gas chromatography analysis.

A novel solid-phase extraction element is developed for sorptive enrichment of dilute analytes from liquid samples with high extraction efficiencies due to its larger amounts of polydimethylsiloxane (PDMS) absorbent than the conventional syringe type of solid-phase microextraction (SPME). The extraction element is made of titanium (Ti) open tubular tube (30 mm x 1.2 mm i.d. x 1.6 mm o.d.) coated with a chemically bonded layer of PDMS (500 microm in thickness). The extraction element combined with thermal desorption-gas chromatography-mass spectrometry using a pyrolysis-gas chromatography-mass spectrometry system was used to extract and analyze a typical herbicide, bethrodine in water samples over a concentration range from 2.5 to 2.5 x 10(4) ng/l. Thus obtained calibration curve showed good linearity for the tested whole concentration range with regression coefficient of 0.992. Detection limit of 0.5 ng/l level was achieved and the reproducibility of the measurements for bethrodine at 10 ng/l level was found to be fairly good with relative standard deviation below 7.5%.

Calibration↗
PubMed1994

[HPLC determination of oxacillin, cloxacillin and dicloxacillin in bovine muscle with automated cleanup by on-line solid phase extraction].

A high-performance liquid chromatographic (HPLC) method with automated cleanup by on-line solid phase extraction was developed for the determination of oxacillin, cloxacillin and dicloxacillin in bovine muscle tissue. The penicillins were extracted from the matrix with acetonitrile, transferred to phosphate buffer and automatically trapped on a RP-18 solid phase extraction column. After on-line elution onto the analytical HPLC-column, penicillins were quantified by UV (lambda = 225 nm) after isocratic separation. Mean recoveries at the MRL (0.3 mg/kg) were 92% for oxacillin, 92% for cloxacillin and 86% for dicloxacillin. The coefficients of variation for the three penicillins in the range of 0.15-0.6 mg/kg were 13.8%, 11.0%, and 7.3%, respectively. The applicability of this method for the determination of cloxacillin in milk was demonstrated.

Animals↗
PubMed1999

Ion-pair solid-phase extraction of biogenic amines before micellar electrokinetic chromatography with laser-induced fluorescence detection of their fluorescein thiocarbamyl derivatives.

Extraction conditions by ion-pair solid-phase extraction of biogenic amines from soy sauce samples were studied. The type of surfactant used as ion-pair reagent, the mode of extraction and the pH were factors studied to enhance the extraction efficiency. High recoveries were obtained using dodecylbenzenesulfonic acid as ion-pair reagent. Octanesulfonate and decanesulfonate did not provide satisfactory recoveries. A dynamic ion-pair solid-phase extraction method was also tested for comparison. The extracted amines were derivatized with fluorescein isothiocyanate, separated by micellar electrokinetic chromatography and detected by laser-induced fluorescence (MEKC-LIF). Because of sample clean-up after extraction and the very high number of theoretical plates obtained with the MEKC-LIF method, identification and quantification of biogenic amines in soy sauce samples could be accomplished. Biogenic amines in soy sauce samples could be separated and quantified with detection limits of the order of 0.1 microg/mL, depending on the sample source.

Biogenic Amines↗
PubMed2002

Determination of sodium 3,4-diaminonaphthalene-1-sulfonate, a Congo Red derivative, in plasma and brain of hamsters by high-performance liquid chromatography after solid-phase extraction and ultraviolet absorbance.

In the search for compounds with similar or greater activity than Congo Red (CR) in protecting normal prion protein from being converted into the pathological form, we have synthesized various compounds which derive from CR. One of these is the sodium 3,4-diaminonaphthalene-1-sulfonate (RCA) which has an activity similar to CR in preliminary experiments. This study describes a method to determine RCA in plasma and in brain tissue by high-performance liquid chromatography (HPLC), using a solid-phase extraction and UV detection. RCA is an amphoteric molecule difficult to separate from biological matrices. Extraction was achieved by solid-phase extraction (ENV+ columns) together with the use of a counter ion. The resulting solid-phase extraction is efficient and rapid. RCA was separated on a Symmetry C18 250 x 4.6 mm I.D. 5 lm column at 1 ml/min using a 50 mM NaSO4 in 5 mM tetra-n-butylammoniumiodide (TEBA) in water-methanol (82:18, v/v) mobile phase. Retention times of RCA and I.S. were 21 and 24 min. The UV detector was set at 210 nm. The limit of quantitation was 0.5 microg/ml. The method has intra-assay and inter-assay accuracies higher than 95%, coefficients of variation ranging between 2.8 and 8.6%, and recovery rates between 74.3 and 80.1% in plasma and in brain tissue. A linear response to quantities of RCA from 0.5 to 100 microg/ml or 10 microg/g in plasma or brain was obtained. The present method allows the study of the pharmacokinetics of RCA in plasma after i.p. administration, and the distribution of the compound into the brain at the peak time.

Animals↗
PubMed2005

Cigarette filter as sorbent for on-line coupling of solid-phase extraction to high-performance liquid chromatography for determination of polycyclic aromatic hydrocarbons in water.

An on-line solid-phase extraction (SPE) protocol using the cigarette filter as sorbent coupled with high-performance liquid chromatography (HPLC) was developed for simultaneous determination of trace naphthalene (NAPH), phenanthrene (PHEN), anthracene (ANT), fluoranthene (FLU), benzo(b)fluoranthene (BbF), benzo(k)fluoranthene (BkF), benzo(a)pyrene (BaP), and benzo(ghi)perylene (BghiP) in water samples. To on-line interface solid-phase extraction to HPLC, a preconcentration column packed with the cigarette filter was used to replace a conventional sample loop on the injector valve of the HPLC for on-line solid-phase extraction. The sample solution was loaded and the analytes were then preconcentrated onto the preconcentration column. The collected analytes were subsequently eluted with a mobile phase of methanol-water (95:5). HPLC with a photodiode array detector was used for their separation and detection. The detection limits (S/N = 3) for preconcentrating 42 mL of sample solution ranged from 0.9 to 58.6 ng L(-1) at a sample throughput of 2 samples h(-1). The enhancement factors were in the range of 409-1710. The developed method was applied to the determination of trace NAPH, PHEN, ANT, FLU, BbF, BkF, BaP and BghiP in local river water samples. The recoveries of PAHs spiked in real water samples ranged from 87 to 115%. The precisions for nine replicate measurements of a standard mixture (NAPH: 4.0 microg L(-1), PHEN: 0.40 microg L(-1), ANT: 0.40 microg L(-1), FLU: 2.0 microg L(-1), BbF: 1.6 microg L(-1), BkF: 2.0 microg L(-1), BaP: 2.0 microg L(-1), BghiP: 1.7 microg L(-1)) were in the range of 1.2-5.1%.

Chemical Fractionation↗
PubMed2006

Preparation of the capillary-based microchips for solid phase extraction by using the monolithic frits prepared by UV-initiated polymerization.

A microfluidic solid phase extraction (SPE) array for sample enrichment was prepared by a simple method, a hot embossing technique. Five fused-silica capillaries (250 microm i.d., 380 microm o.d.) were partly embedded parallel in a polymethyl methacrylate (PMMA) microchip to serve as the extraction channels. Within each of the channels, a 2-mm-long monolithic porous polymer was prepared by in-situ photoinitiated polymerization. This then acted as the frit for packing of the extraction materials (octadecylsilica beads, ODS). By defining the light-exposure window on the channels, one can easily control the length and location of the polymer frits and the ODS beads can be packed at the desired location. With this method, solid phase extraction channels for microfluidic use can be easily prepared without complex fabrication of microstructures. Several SPE channels can be conveniently made in one microchip since the frits can be prepared in different channels through one polymerization; packing of the different channels can also be performed simultaneously. With the use of dilute ephedrine solutions, the sample loading capacity, linearity, and reproducibility were characterized. Coupled with the fast capillary electrophoresis separation, this microchip SPE array was applied for the detection of ephedrines in human urine.

Calibration↗
PubMed1999

A new approach to the effective preparation of plasma samples for rapid drug quantitation using on-line solid phase extraction mass spectrometry.

A procedure that permits rapid development of an optimized solid phase extraction (SPE) method for the analysis of drugs in plasma by on-line solid phase extraction-mass spectrometry (SPE-MS) has been developed. This procedure employs the concept of manipulating the pH and the percentage of organic solvent in the chromatographic mobile phase to affect the retention behaviors of both the matrix components and the analytes of interest. This resulted in the effective removal of matrix interferences from biological samples during SPE. During a the method development, only generic HPLC gradient approaches were needed, and multiple samples were pooled so that several SPE methods could be investigated at once. The analysis time per sample was 1.3 minutes. Thus, the time involved in the entire method development (analysis of a set of samples) was less than one hour. With the knowledge of the retention behaviors of the analytes with respect to the pH and the percentage of organic, it was then possible to compose an optimized SPE-MS method. This method consisted of a base/organic and then an acid/organic washing step, followed by a rapid gradient elution step. Due to the rigorous washing procedure, most matrix interferences were removed, and analytes eluted off the SPE sorbent suffered from very little matrix interference. Thus, quantitation of drugs in plasma by a single quadrupole mass spectrometer could be accomplished, something that was not possible when only a generic gradient was used for on-line SPE-MS. In addition, both external and internal calibration curves could be obtained for the concentration range from 5 to 500 ng/mL with correlation coefficients of 0.99 (using 1/x as a weighting factor) and relative standard deviations (RSDs) less than 10%. The results achieved were comparable to those obtained by the use of a triple quadrupole mass spectrometer. Moreover, the robustness of the method was tested by continuously injecting plasma samples. During 136 runs, the absolute peak area variation for these three basic drugs was less than 15% without taking the signal variation from the mass spectrometer into account. Significantly, the on-line developed method can be directly transferred to a 96-well format SPE plate.

Calibration↗
PubMed1997

Simultaneous analysis of several non-steroidal anti-inflammatory drugs in human urine by high-performance liquid chromatography with normal solid-phase extraction.

A practical and reproducible high-performance liquid chromatographic method using normal solid-phase extraction has been developed for the simultaneous analysis of twelve non-steroidal anti-inflammatory drugs (NSAIDs) in human urine. A urine specimen mixed with acetate buffer pH 5.0 was purified by solid-phase extraction on a Sep-Pak Silica cartridge. The analyte was chromatographed by a reversed-phase Inertsil ODS-2 column using a phosphate buffer-acetonitrile at pH 5.0 as the mobile phase, and the effluent from the column was monitored at 230 or 320 nm. Absolute recoveries were greater than 73% for all of the twelve NSAIDs. The present method enabled simple manipulation and isocratic HPLC with UV analysis as well as high sensitivity of 0.005 microg/ml for naproxen, and 0.05 microg/ml for sulindac, piroxicam, loxoprofen, ketoprofen, felbinac, fenbufen, flurbiprofen, diclofenac, ibuprofen and mefenamic acid as the quantitation limit in human urine using indomethacin as an internal standard.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2003

Selective separation of active inhibitors of epidermal growth factor receptor from Caragana jubata by molecularly imprinted solid-phase extraction.

A feasibility research was performed to study the possibilities of using a molecularly imprinted polymer as sorbent material in solid-phase extraction for the separation of active inhibitors of epidermal growth factor receptor (EGRF) from Caragana Jubata, a Chinese traditional Tibetan medicine. A molecularly imprinted polymer using quercetin, an active anti-EGFR inhibitor (IC50 = 15 microM), as the template and acrylamide as the functional monomer was prepared. The polymer was evaluated as a selective sorbent in molecularly imprinted solid-phase extraction. The EtOAc extract of Caragana Jubata was loaded on the polymer, and two novel active anti-EGFR inhibitors were found to be selectively retained after washing the polymer with appropriate solvent to disrupt the non-specific interactions occurring between the sample and the polymer matrix, which were identified as (E)-piceatannol (IC50 =4.9 microM) and butein (IC50 = 10 microM). The present work affords us a new potential method for selective separation of bioactive components from herb by using molecularly imprinted polymer as a solid-phase extraction adsorbent.

Caragana↗