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PubMed2005

Stability of benzalkonium surfactants on hemimicelle-based solid-phase extraction cartridges.

The capability of hemimicelle-based solid-phase extraction cartridges for the preservation of organic compounds after their concentration from water samples was investigated for the first time. The approach is illustrated by studying the stability of benzalkonium homologue (C12, C14 and C16) surfactants (BAS) on monolayers of dodecyl sulphate (SDS) hemimicelles formed on alumina. The stability study included storage of cartridges at room temperature, at 4 and -20 degrees C, during a period of up to 3 months. The influence of water matrix components was also investigated from parallel experiments using spiked distilled, river and wastewater samples. Complete recovery of BAS was obtained for all storage conditions tested. Recoveries were independent on the alkyl chain length of BAS homologues and water matrix. The SPE of BAS on the SDS hemimicelles had a strong stabilizing effect for the target compounds and their analysis can be accomplished after at least 3 months without the necessity of special storage conditions for cartridges. Because of the lack of data, an additional stability study was carried out for BAS in an aqueous matrix using traditional preservation methods such as acidification (pH 2)/refrigeration, addition of formaldehyde (5%)/refrigeration, and freezing (-20 degrees C). Only combination of chemical addition (e.g. nitric acid or formaldehyde)/refrigeration was found effective to preserve BAS in the short term (e.g. for a week), then losses up to 40% were observed for these target compounds after a month.

Benzalkonium Compounds↗
PubMed2005

Efficient approach for the reliable quantification and confirmation of antibiotics in water using on-line solid-phase extraction liquid chromatography/tandem mass spectrometry.

The potential of solid-phase extraction coupled on-line to liquid chromatography/electrospray tandem mass spectrometry (SPE-LC-ESI-MS/MS) has been investigated in this paper for the efficient sensitive quantification and confirmation of 16 antibiotics in water. The list of targeted analytes included 10 quinolones (oxolinic acid (OXO), nalidixic acid (NAL), flumequine (FLU), marbofloxacine (MAR), ofloxacine (OFLO), enrofloxacine (ENR), pefloxacine (PEF), ciprofloxacine (CIP), pipemidic acid (PIPE), norfloxacine (NOR)) and 6 penicillins (penicillin G (PEN), oxacillin (OXA), dicloxacillin (DIC), piperacillin (PIP), cloxacillin (CLO) and ampicillin (AMP)) that were determined in ground and surface water. The procedure is based on the injection of 9.8 mL of sample into the SPE-LC-MS/MS system and the measurement of antibiotics by selected reaction monitoring mode, using a triple quadrupole analyser. The method has been validated at realistic low concentrations that might be present in environmental water, i.e. 10 and 100 ng L(-1), obtaining recoveries between 74% and 123% with relative standard deviation lower than 14%. Matrix effects were not relevant in most of cases, except for ampicillin in surface water, where notable signal suppression was observed. The limits of detection were as low as 0.4-4.3 ng L(-1). The method developed allows the rapid screening and quantification of all the analytes selected by acquiring one MS/MS transition (normally the most sensitive) for each compound. It was applied to a number of actual surface and groundwater samples with several compounds being detected, mainly quinolones, at low ng L(-1) levels. Special attention was given to the confirmation of compounds detected in water due to the difficulties of obtaining confident confirmation at low ng L(-1). This matter has been of growing concern in the last few years as reflected by recent papers and correspondence. The acquisition of several MS/MS transitions for each compound detected in a second independent analysis allowed the unequivocal confirmation of identity, avoiding reporting false-positives. Finally, the potential of QTOF instruments to confirm positive samples has also been evaluated and compared with triple quadrupole analysers.

Anti-Bacterial Agents↗
PubMed2006

Determination of four benzodiazepine residues in pork using multiwalled carbon nanotube solid-phase extraction and gas chromatography-mass spectrometry.

A solid-phase extraction (SPE)/GC-MS method using multiwalled carbon nanotubes (MWCNTs) was developed for the determination of four benzodiazepine residues including diazepam, estazolam, alprazolam and triazolam in pork. The analytes were extracted by ultrasonic assistant extraction using acetonitrile, concentrated and purified by MWCNTs packed cartridge, and determined by GC-MS. Ultrasonic extraction conditions, which included temperature, time, power, and solvent volume, were optimized. Comparative studies showed that MWCNTs were superior to C18 for the adsorption of drugs. Parameters influencing SPE efficiency, such as sample amounts, variety and volume of the eluent, were also optimized. Electron ionization (EI) operating in time program-selected ion monitoring mode (SIM) was used for GC-MS identification. The analytes were quantified with external standard calibration curve method. Lower limit of detection and quantification was obtained by the new method. Linear calibration curves were obtained in the concentration range from 10 ng/mL to 500 ng/mL for diazepam and from 20 ng/mL to 1000 ng/mL for estazolam, alprazolam and triazolam with calibration coefficients of 0.99 and above. The average recoveries for the four benzodiazepines spiked in pork were 75% to 104% and their relative standard deviations were between 1.3% and 10%. The limits of detection were 2 microg/kg for diazepam and 5 microg/kg for estazolam, alprazolam and triazolam in pork, respectively.

Adsorption↗
PubMed2005

Chromium speciation in environmental samples by solid phase extraction on Chromosorb 108.

In the present work, a solid phase extraction system has been proposed for speciation of Cr(III) and Cr(VI) in the real samples. The procedure based on the adsorption of chromium(III) as dithizonate chelate on the Chromosorb 108 resin. After reduction of Cr(VI) by concentrated H2SO4 and ethanol, the system was applied to the total chromium. Cr(VI) was calculated as the difference between the total Cr content and the Cr(III) content. The influences of the analytical parameters including pH of the aqueous solution, amounts of dithizone, eluent type, sample volume and flow rates of the sample and eluent solution were investigated. No considerable interferences have been observed from other investigated anions and cations on the chromium speciation. The adsorption capacity of sorbent was 4.50 mg/g Cr(III). The detection limit of Cr(III) is 0.75 microg/L. The proposed method was applied to the speciation of chromium in environmental samples including natural waters and total chromium preconcentration in microwave digested Turkish tobacco, coffee and soil samples with satisfactory results. In order to verify the accuracy of the method, two certified reference materials (NIST SRM 1573a Tomato Leaves and RTC-CRM 025-050 Metals on Soil) were analyzed and the results obtained were in good agreement with the certified values. The relative errors and relative standard deviations were below 5% and 9%, respectively.

Adsorption↗
PubMed2001

Separation of plant membrane lipids by multiple solid-phase extraction.

Plant membrane lipids were separated by multiple solid-phase extraction (SPE) in a single run. Elution was performed continuously through the modulated stationary phase employing only non-aqueous solvent systems. At the different stages of the glycerolipid separation the SPE manifold combined arninopropyl, arninopropyl/silica gel and silica gel/aminopropyl weak anion exchanger columns. The glycerolipid extract of pigment-containing plant tissues was cleared from the pigments onto the aminopropyl column. The aminopropyl column with the glycerolipid extract was then connected to a silica gel column from which monogalactosyldiacylglycerol, phosphatidylethanolamine, phosphatidylglycerol and digalactosyldiacylglycerol were eluted as individual fractions. The elution was performed under polarity, pH and temperature gradient conditions. To continue the separation, the aminopropyl column was discarded and the silica gel column containing the remaining glycerolipid extract was connected to an aminopropyl anion exchanger column. Individual fractions of sulfoquinovosyldiacylglycerol, phosphatidylcholine and phosphatidylinositol were now eluted. The separation process was supported by ammonium counter ions and by the polarity gradient of the elution systems used. The membrane lipids were isolated from pigment-containing (rice and maize leaves and rice leafy stems) and pigment-free (rice roots) tissues. The repeatability for a standard glycerolipid mixture was 2-6% (n=7), and for rice leaf lipid extracts, 3-7% (n=5). Glycerolipid recovery was 87-95%.

Chromatography, Thin Layer↗
PubMed1999

Simultaneous determination of antifouling herbicides in marina water samples by on-line solid-phase extraction followed by liquid chromatography-mass spectrometry.

Solid-phase extraction (SPE) coupled on-line with either liquid chromatography-diode array detection (LC-DAD) or liquid chromatography-atmospheric pressure chemical ionization mass spectrometry was applied to the simultaneous analysis of several antifouling herbicides such as diuron, TCMTB (2-thiocyanomethylthiobenzothiazole), Irgarol and chlorothalonil in seawater samples. SPE was carried out on polymeric cartridges (PLRP-s) after the percolation of 100 ml of seawater sample, with recoveries ranging from 96 to 111% for the antifouling compounds. LC-MS detection was used in negative and positive ion mode. In positive ion mode, additional structural information for diuron and Irgarol was obtained by increasing the fragmentor voltage, thus permitting the unequivocal identification of these compounds in environmental waters. Method detection limits were in the range of 0.005 microg/l. This methodology was also compared to LC-DAD in terms of selectivity and sensitivity. Finally, the method was evaluated for the analysis of environmental seawater samples, from the Ebre Delta area and Masnou marina, in Catalonia (Spain).

Chromatography, Liquid↗
PubMed1997

Determination of kinetic and retention properties of cartridge and disk devices for solid-phase extraction.

The kinetic properties of cartridge and disk solid-phase extraction devices are determined by forced-flow liquid chromatography. Typical cartridges provide about 5-15 theoretical plates per cm of bed height and particle-loaded membranes provide about 4-9 theoretical plates for a 0.5-mm-thick membrane. It is shown that cartridge devices fail to provide their maximum trapping performance because of inadequate packing density and that the required packing density could be easily achieved in practice with particles of a standard size. The retention properties of common sorbents for extraction from water and air are characterized with the solvation parameter model. For predominantly aqueous solutions a favorable cavity term results in increased retention while polar interactions tend to reduce retention. Retention on porous polymer sorbents is more complicated because of their capacity to absorb significant amounts of the sample processing solvent resulting in solvent-dependent changes in retention properties. For trapping organic volatiles from air cavity formation and dispersion interactions are important, and in the case of Tenax its capacity for induction interactions is also significant.

Adsorption↗
PubMed1997

Moclobemide fatalities: report of two cases and analytical determinations by GC-MS and HPLC-PDA after solid-phase extraction.

We have described a rapid and simple solid-phase extraction on C18 cartridges of moclobemide suitable for the analysis of post-mortem whole blood and urine. The methods used for identification were GC-MS and HPLC-PDA. Quantification was performed by the HPLC-PDA technique with detection at 238 nm. The limit of detection was 0.012 microgram/ml in blood. A between-day precision study gave relative standard deviations which were always less than 4.7% over the entire range of calibration (0.2 to 20.0 micrograms/ml). The method was applied in a case of moclobemide overdose due to a deliberate ingestion of 4.5 g of the drug. A second case concerned a polyintoxication including moclobemide as one of the main toxins. The post-mortem whole blood concentrations were 15.5 and 13.8 micrograms/ml respectively. Determination of the drug in other biological specimens is also reported.

Adult↗
PubMed1999

Validation of an automated liquid chromatographic method for omeprazole in human plasma using on-line solid-phase extraction.

An automated system using on-line solid-phase extraction and HPLC with UV detection has been validated in order to determine omeprazole in human plasma. The extraction was carried out using C18 cartridges. After washing, omeprazole was eluted from the cartridge with mobile phase onto an Inertsil ODS-2 column. The developed method was selective and linear for drug concentrations ranging between 5 and 500 ng ml(-1). The recovery of omeprazole ranged from 88.1 to 101.5%, and the limit of quantitation (LOQ) was 5 ng ml(-1). The intraday accuracy ranged from 93.1 to 106.2% and the interday accuracy varied from 95.4 to 105.1%. For the LOQ, good values of precision (8.7 and 17.5% for intraday and interday, respectively) were also obtained. This automated system has been applied to determine omeprazole in human plasma samples from bioequivalence studies.

2-Pyridinylmethylsulfinylbenzimidazoles↗
PubMedDate not supplied

Solid-phase extraction of drugs from biological tissues--a review.

Solid-phase extraction procedures are being used increasingly in all types of drug testing laboratories, including those which carry out forensic toxicology. The advantages of such procedures include decreased operator time, reduced solvent volumes, and increased extraction efficiency. The application of existing techniques, however, has not yet been applied to tissues that are widely available postmortem. Tissue analysis can make the task of interpretation of drug levels much easier, particularly where unstable drugs are involved (e.g., cocaine). This review article explores the possibilities of applying existing extraction procedures to human tissue samples. We also consider the reasons why forensic laboratories have been slow to investigate such possibilities. We hope to stimulate interest in alternative tissue extraction procedures by reviewing reported procedures that apply to both human and animal tissue.

Animals↗
PubMedDate not supplied

Analysis of urinary benzodiazepines using solid-phase extraction and gas chromatography-mass spectrometry.

A solid-phase extraction and GC-MS confirmation method was developed for certain urinary diazolo- and triazolobenzodiazepines, including the metabolites of lorazepam, clonazepam, alprazolam, and triazolam. The latter two do not form benzophenones, and the others are not readily confirmed by conventional thin-layer chromatography or GC-MS techniques. Samples were hydrolyzed with glucuronidase at 37 degrees C, adjusted to pH 4.5, extracted with Bond Elut Certify columns, dried, and derivatized using BSTFA with 1% TMCS. Sample preparation time averaged 4 hours. A GC-MS selected-ion-monitoring acquisition method targeting retention time, molecular ion abundances, and qualifier ion ratios was used to determine positive results. The recovery of 7-NH2-clonazepam was 95%, and recoveries of alpha-hydroxyalprazolam, alpha-hydroxytriazolam, and lorazepam were greater than 66%. Linearity was demonstrated from 0.1 to 1.0 microgram/mL for each drug. Within-run CVs were less than 11%, and between-run CVs were less than 16%. Using this technique, we have been able to confirm suspected cases of abuse that had not been confirmed by previous techniques.

Anti-Anxiety Agents↗
PubMed2003

Liquid chromatographic determination of oxcarbazepine and its metabolites in plasma of epileptic patients after solid-phase extraction.

A method based on high-performance liquid chromatography with UV detection in combination with solid-phase extraction for sample pretreatment has been developed for the simultaneous analysis of the antiepileptic drug oxcarbazepine and its main metabolites in human plasma. The extraction of the analytes from plasma samples was carried out by means of a selective solid-phase extraction procedure using hydrophilic-lipophilic balance cartridges. The separation was obtained on a reversed-phase column (C(18), 150x4.6 mm I.D., 5 micrometer) using a phosphate buffer-acetonitrile-methanol-triethylamine mixture (final apparent pH* 3.5) as the mobile phase. Under these chromatographic conditions, oxcarbazepine and its metabolites 10,11-dihydro-10-hydroxycarbamazepine, 10,11-dihydro-10,11-dihydroxycarbamazepine and the internal standard are baseline separated in less than 9 min. The extraction yield values were >94% for all analytes and the precision, expressed by the RSD%, was in the low percentage range. For the entire method, including sample pre-treatment and HPLC determination, the linearity of the calibration lines, expressed by the linear correlation coefficient, was better than 0.995; the limit of quantitation was 15 ng ml(-1). The method was applied to plasma samples from patients undergoing chronic treatment with oxcarbazepine, both in monotherapy and in polytherapy. Based on the analytical parameters precision, accuracy, limit of quantitation and analysis time the method is suitable for routine application in therapeutic drug monitoring.

Anticonvulsants↗
PubMed2005

A new and simple solid-phase extraction method for LC determination of pyronaridine in human plasma.

A new approach using a simple solid-phase extraction technique has been developed for the determination of pyronaridine (PND), an antimalarial drug, in human plasma. After extraction with C18 solid-phase sorbent, PND was analyzed using a reverse phase chromatographic method with fluorescence detection (at lambda(ex)=267 nm and lambda(em)=443 nm). The mean extraction recovery for PND was 95.2%. The coefficient of variation for intra-assay precision, inter-assay precision and accuracy was less than 10%. The quantification limit with fluorescence detection was 0.010 microg/mL plasma. The method described herein has several advantages over other published methods since it is easy to perform and rapid. It also permits reducing both, solvent use and sample preparation time. The method has been used successfully to assay plasma samples from clinical pharmacokinetic studies.

Administration, Oral↗
PubMed1989

A solid-phase extraction procedure for DNA purification.

The preparation and use of particulate materials for the removal of proteins from nucleic acid samples by solid-phase extraction procedures are described. The solid-phase extraction procedure is analogous to the classical phenol extraction for DNA purification, with the exception that the phenol is replaced with insoluble particulate materials that are chemically similar to phenol and thus function in an analogous manner. These particulate materials have a very high affinity for proteins and a very low affinity for nucleic acids. With these materials, it is possible to remove large quantities of proteins (i.e., tens of milligrams) from minute quantities (submicrogram) of nucleic acid and quantitatively recover the latter in a biologically active state. Compared to other procedures that are currently used to purify nucleic acids, the protocols using these materials offer the advantages of speed, quantitative DNA recovery, safety, and convenience.

Alkaline Phosphatase↗
PubMed2006

A microfluidic fluorous solid-phase extraction chip for purification of amino acids.

An electrokinetically-driven microfluidic chip was developed to realize beads-based solid-phase extraction (SPE) of amino acids. This chip uses a two-level (deep/shallow) poly(dimethylsiloxane) (PDMS) microchannel network to confine the fluorous reversed-phase silica beads within the SPE chamber. The mixture of fluorous tagged and non-tagged amino acids was carried into the fluorous solid-phase extraction (F-SPE) chamber by electrokinetic pumping and was successfully separated and extracted. By adding a reference material to the sample, the extraction efficiency of the eluted fluorous-tagged amino acid was calculated using the detection results from mass spectrometry (MS). The F-SPE microchips showed good reproducibility and efficiency, yielding an average extraction efficiency of 55% with a RSD of 10.6% under the typical experimental conditions.

Amino Acids↗
PubMed2002

Solid-phase extraction in clinical biochemistry.

In order to measure low concentrations of analytes in plasma and urine, it is often necessary to extract and concentrate them. With solid-phase extraction (SPE), this is achieved by partitioning the analytes between a solid and a liquid or headspace vapour. A wide range of high-quality materials is now available to do this, offering a variety of separation modes for different applications. These include partitioning using reversed-phase, normal-phase, ion-exchange, restricted-access and immunoaffinity sorbents or molecularly imprinted polymers and, increasingly, combinations of these processes. Solid-phase microextraction was introduced to analyse volatile and semi-volatile compounds. The range of sampling formats has expanded from simple packed syringes to cartridges, disks, SPE pipette tips and 96-well plates. These developments have facilitated automated off- and on-line sample processing. The basic principles of SPE and the recent innovations are reviewed here. This is a technological growth area. Some of the developments are finding application in clinical toxicology. However, they could also be of wider value in clinical chemistry--for example, for analyses of volatile and non-volatile metabolites, peptides, radioactive elements and trace metal speciation.

Adsorption↗
PubMed2005

An ion-imprinted functionalized silica gel sorbent prepared by a surface imprinting technique combined with a sol-gel process for selective solid-phase extraction of cadmium(II).

A new ion-imprinted thiol-functionalized silica gel sorbent was synthesized by a surface imprinting technique in combination with a sol-gel process for selective on-line, solid-phase extraction of Cd(II). The Cd(II)-imprinted thiol-functionalized silica sorbent was characterized by FT-IR, the static adsorption-desorption experiment, and the dynamic adsorption-desorption method. The maximum static adsorption capacity of the ion-imprinted functionalized sorbent was 284 micromol g(-1). The largest selectivity coefficient for Cd(II) in the presence of Pb(II) was over 220. The static uptake capacity and selectivity coefficient of the ion-imprinted functionalized sorbent are higher than those of the nonimprinted sorbent. The breakthrough capacity and dynamic capacity of the imprinted functionalized silica gel sorbent for 4 mg L(-1) of Cd(II) at 5.2 mL min(-1) of sample flow rate were 11.7 and 64.3 micromol g(-1), respectively. No remarkable effect of sample flow rate on the dynamic capacity was observed as the sample flow rate increased from 1.7 to 6.8 mL min(-1). The imprinted functionalized silica gel sorbent offered a fast kinetics for the adsorption and desorption of Cd(II). The prepared ion-imprinted functionalized sorbent was shown to be promising for on-line, solid-phase extraction coupled with flame atomic absorption spectrometry for the determination of trace cadmium in environmental and biological samples. All competitive ions studied did not interfere with the determination of Cd(II). With a sample loading flow rate of 8.8 mL min(-1) for 45-s preconcentration, an enhancement factor of 56, and a detection limit (3sigma) of 0.07 microg L(-1) were achieved at a sampling frequency of 55 h(-1). The precision (RSD) for 11 replicate on-line sorbent extractions of 8 mug L(-1) Cd(II) was 0.9%. The sorbent also offered good linearity (r = 0.9997) for on-line, solid-phase extraction of trace Cd(II).

Adsorption↗
PubMed1991

Clonazepam serum levels in epileptic patients determined simply and rapidly by high-performance liquid chromatography using a solid-phase extraction column.

We studied the use of high-performance liquid chromatography (HPLC), using a solid phase extraction column (Bond Elut cartridge column), for the simple, rapid and sensitive determination of serum clonazepam levels in epileptic patients. Extracted aliquots were analyzed by HPLC, using a reverse phase ODS column (mu-Bondapak C18). The analytical mean recovery of clonazepam added to the blank serum averaged 99.9%. The detection limit was as high as approximately 2 ng/ml in the serum. The reproducibilities were 2.3-8.6 CV % in the within-day assay and 6.5 CV % in the between-day assay, indicating that the analysis method was effective in the determination of clonazepam serum levels. Accordingly, we suggest that the present method, using a solid phase extraction column, may be useful for the routine monitoring of clonazepam serum levels in epileptic patients.

Chromatography, High Pressure Liquid↗