Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Liquid Phase Microextraction”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 451 records · Page 25Linked to original sources
PubMed2006

Determination of sulfonamide antibiotics in wastewater: a comparison of solid phase microextraction and solid phase extraction methods.

In recent years, pharmaceutical and personal care products (PPCPs) have been detected in diverse environments (including groundwater, river water, and municipal wastewater). In order to evaluate their environmental impact, PPCPs must first be accurately determined. In this study, we focused on developing methods to accurately determine 10 sulfonamide antibiotics: sulfaguanidine, sulfacetamide, sulfadiazine, sulfathiazine, sulfapyridine, sulfamerazine, sulfamethazine, sulfamethoxazole, sulfadimethoxine, and sulfasalazine. While sulfonamides can easily be determined in pure water, wastewater influent and effluent collected from sewage treatment plants in Burlington and Toronto (Ontario) were found to generate confounding matrix effects. In an effort to overcome these matrix effects, we developed a solid phase microextraction (SPME) method to determine sulfonamides. Of the five different fiber assemblies investigated, the carbowax/divinylbenzene (CW/DVB) fiber produced the optimal response to sulfonamides. The SPME method was further optimized for sorption time (20min), solution salinity (10%, w/v, KCl), pH (4.5), and static desorption time (30min). When compared to solid phase extraction (SPE) using MCX cartridges, we observed that despite having higher MDLs and poorer sensitivity, SPME possessed the advantage of speed and reduced solvent usage. Most importantly, in contrast to SPE, when we applied the SPME method to fortified wastewater samples, we were generally able to accurately determine (i.e., recover) those sulfonamides that were present. Therefore, we conclude that SPME is a viable method for overcoming matrix effects in environmental samples.

Anti-Bacterial Agents↗
PubMed2004

Biotransformation of (R)-(+)- and (S)-(-)-citronellol by Aspergillus sp. and Penicillium sp., and the use of solid-phase microextraction for screening.

The biotransformation of (R)-(+)- and (S)-(-)-citronellol by fungi was studied. For screening experiments, solid-phase microextraction (SPME) was used as analytical sampling technique. It was found that sporulated surface cultures of Aspergillus niger were able to convert the substrate into cis- and trans-rose oxides and nerol oxide. The relative contents in the headspace SPME extract of the three bioconversion products cis- and trans-rose oxide and nerol oxide were up to 54, 21 and 12%, respectively. Rose oxide is found in minor amounts in some essential oils, such as Bulgarian rose oil and geranium oil and contributes to its unique odor. It is one of the most important fragrance materials in perfumery in creating rosy notes. Other bioconversion products were 6-methyl-5-hepten-2-one, 6-methyl-5-hepten-2-ol, limonene, terpinolene, linalool and alpha-terpineol. These bioconversion reactions were confirmed by sporulated surface cultures on larger scale and sampling by dynamic headspace sweep and steam distillation solvent extraction. The same conversions were noticed with A. tubingensis and Penicillium roqueforti. This bioconversion was enantioselective since more of the chiral cis- than trans-rose oxide was obtained (cisitrans ratio up to 95/5). Submerged liquid cultures of P. roqueforti yielded two unidentified metabolites after conversion of citronellol (yield up to 5%). The stability and acid-catalyzed conversion of citronellol was also investigated. No chemical oxidation or auto-oxidation products were detected in acidified liquid control broths up to pH 3.5. However, when control tests were run with solid media, acid-catalyzed conversion of the substrate to small amounts of cis- and trans-rose oxides, nerol oxide, linalool and alpha-terpineol was observed at pH 3.5 and when heat treatment (steam distillation solvent extraction) was applied.

Acyclic Monoterpenes↗
PubMed2005

Solid-phase microextraction for qualitative and quantitative determination of migrated degradation products of antioxidants in an organic aqueous solution.

Low molecular weight aromatic substances may migrate out from plastic packaging to their contents, especially if they consist of organic aqueous solutions or oils. It is, therefore, extremely important to be able to identify and quantify any migrated substances in such solutions, even at very low concentrations. We have in this work investigated and evaluated the use of solid-phase microextraction for the specific task of extraction from an organic aqueous solution such as a simulated pharmaceutical solution consisting of 10 vol.% ethanol in water. The goal was furthermore to investigate the possibility of simultaneously identifying and quantifying the substances in spite of differences in their chemical structures. Methods were developed and evaluated for extraction both with direct sampling and with headspace sampling. Difficulties appeared due to the ethanol in the solution and the minute amounts of substances present. We have shown that a simultaneous quantification of migrated low molecular weight degradation products of antioxidants using only one fibre is possible if the extraction method and temperature are adjusted in relation to the concentration levels of the analytes. Comparions were made with solid-phase extraction.

Antioxidants↗
PubMed1999

[The study of carbonaceous adsorbent for solid-phase microextraction and the comparison with commercial device].

The parameters governing solid-phase microextraction have been investigated, and the development of carbonaceous adsorbent for SPME is presented because it is durable and inexpensive. The time profile curves were determined for several organic pesticides having a wide range of water solubilities and the effect of salt was also investigated. The method of SPME-GC-ECD to analyse trace level of the organic pesticide in water is established by the determination of optimum parameters. The comparison with commercial SPME device shows that the carbonaceous adsorbent having been treated with physical or chemical method for SPME can get lower limits of detection than polyacrylate and polydimethylsiloxane, although there are still some work to be done to improve its precision. The results shows that this new SPME device has great application potential.

Acrylic Resins↗
PubMed2000

[Determination of phthalic diesters in water by solid phase microextraction-capillary gas chromatography].

The solid phase microextraction (SPME) has the advantages of high efficiency, high sensitivity, simple operation and solvent free operation for analyzing environmental samples. An optical fiber coated with mixed stationary phase of polysiloxane and polymeric fullerene (in ratio of 4:1) was used to extract 5 phthalic diesters by HS-SPME-GC. The operating conditions of SPME such as the extraction temperature, ionic strength of solution, adsorption time and desorption time have been studied. It was compared with commercial polymer coating PDMS fiber through headspace SPME combined with GC. The results indicated that OV-1/PSO-C60 was better than PDMS in extracting high boiling point and semi-volatile phthalic diesters. For phthalic diesters, the detection limits were in the range of 0.331 ng/L-12.5 micrograms/L, and relative standard deviations were below 12% except for dinonyl phthalate.

Chromatography, Gas↗
PubMedDate not supplied

Solid-phase microextraction and GC-ECD of benzophenones for detection of benzodiazepines in urine.

Benzodiazepines are common drugs that cause intoxication. Benzodiazepines and their metabolites can be converted by hydrolysis in acid to the corresponding benzophenones, which are easier to be separated from matrices because of their hydrophobic properties. In this study, a new separation technique called solid-phase microextraction (SPME), which can integrate extraction, concentration, sampling and sample introduction into one single procedure, has been employed to extract the products of benzodiazepines from urine after acid hydrolysis. The extracts were determined by gas chromatography with electron-capture detection (GC-ECD). The hydrolysis conditions were optimized by a statistic orthogonal design. Factors influencing direct-immersion (DI)-SPME process were also checked and chosen experimentally. The method was evaluated with spiked human urine samples. The recoveries of nine benzodiazepines ranged from 1 to 25%, with the highest for oxazolam and the lowest for bromazepam. The calibration curves were linear from 10 to 500 ng/mL for oxazolam, haloxazolam, flunitrazepam, nimetazepam, and clonazepam and from 20 to 1000 ng/mL for the others except bromazepam. The detection limits were 2-20 ng/mL for most drugs tested. The intraday and interday coefficients of variation of the developed method were within 10 and 17%, respectively. In addition, the utility of the method was confirmed by determining two ingested benzodiazepines (flunitrazepam and oxazolam) in a volunteer's urine; urine flunitrazepam was still detectable 32 h after a therapeutic dose (1.2 mg) of the drug. Finally, the DI-SPME was compared with the conventional liquid-liquid extraction with regard to detection limits and extraction efficiency of the analytes. By DI-SPME, more amounts of analytes could be introduced into GC column than by conventional liquid-liquid extraction, and thus lower detection limits of the analytes were reached, although benzophenone recoveries by DI-SPME were rather low.

Adult↗
PubMed2000

Automated in-tube solid phase microextraction coupled with HPLC-ES-MS for the determination of catechins and caffeine in tea.

A polypyrrole (PPY) coated capillary and several commercially available capillaries (capillary GC columns) were used to evaluate their extraction efficiencies for catechins and caffeine. Compared with commercial capillaries that were currently used for in-tube solid phase microextraction (SPME), the PPY coated capillary showed better extraction efficiency for all of the compounds studied. Electrospray mass spectrometric (ES-MS) detection conditions were also investigated. After optimization of the extraction and detection conditions, a method for the sensitive and selective determination of catechins and caffeine was developed by coupling the PPY coated capillary in-tube SPME with HPLC-ES-MS. Catechins could be determined in both positive and negative ion detection modes. The detection limit (S/N = 3) for each of the studied catechins was < 0.5 ng mL-1. Caffeine could only be determined under positive ES-MS detection conditions and its detection limit was 0.01 ng mL-1. Caffeine and the five catechins in several tea samples were determined using the developed method. Small amounts of catechins were also detected in grape juice and wine samples.

Caffeine↗
PubMed2006

Solid-liquid extraction fluorescence line narrowing spectroscopy of fluoroquinolones in aqueous samples.

We present a simple, selective, and sensitive method for the analysis of fluoroquinolones in water samples without previous separation. Octadecyl silica membranes are used with the dual purpose of sample preconcentration and solid substrate for fluorescence line narrowing spectroscopy. Measurements at liquid helium temperature (4.2 K) are easily made with the aid of a cryogenic fiber-optic probe. The entire procedure takes less than 15 minutes per sample and it consumes only 100 microL of organic solvent. Unambiguous fluoroquinolone determination is accomplished via wavelength-time matrices, which provide simultaneous information on spectral peak purity and fluorescence lifetime. We show that 10 mL of water sample are enough to detect analyte concentrations at parts-per-billion levels. The potential of this approach for the analysis of real world samples is demonstrated with the analysis of a synthetic mixture of seven fluoroquinolones spiked in a heavily contaminated water sample.

Algorithms↗
PubMed2005

Enantiomeric determination of amphetamines: exploring a novel one-step solid-phase microextraction-based approach.

The recent advances in fiber manufacturing technology, solid-phase microextraction (SPME) is now widely studied for its effectiveness for the pretreatment of various categories of samples. This study explores a novel SPME approach for enantiomeric analysis of amphetamines, in which absorption/derivatization are accomplished in one step. Specifically, (S)-(-)-N-(Trifluoroacetyl)-prolyl chloride was adopted as the chiral derivatizing reagent and added directly into the sample matrix. Analytical parameters, such as temperature, absorption/desorption duration, and the amount of derivatizing reagent, were studied to determine their effects on the yield of analytes. The derivatization products resulting from this study show excellent desorption characteristics on the polydimethylsiloxane-coated fiber adopted in this study. Optimal operational parameters (absorption: 70 degrees C for 10 min; injection: 250 degrees C for 5 min) cause minimal negative impact on the fiber, allowing repeated use of the fiber for more than 30 times. For quantitation, data were collected under selected ion monitoring (SIM) mode using m/z 237 and 251 to designate derivatized amphetamine and methamphetamine. This method was evaluated and proved to be effective in (a) quantitative determination of the enantiomeric pairs of amphetamine and methamphetamine--in terms of repeatability, linearity, and limits of detection and quantitation; and (b) generating case-specimen data comparable to those derived from a conventional Liquid-liquid extraction approach. Good linearity for the calibration curves were established in the range of 1000-50 ng/mL for both analytes. The limits of detection for these analytes were 30 ng/mL.

Amphetamines↗
PubMed2003

Determination of linear alkylbenzensulfonates in aqueous matrices by ion-pair solid-phase microextraction-in-port derivatization-gas chromatography-mass spectrometry.

Trace determination (low ng/ml) of linear alkylbenzensulfonates (LASs) in water was achieved by solid-phase microextraction (SPME) of ion-pairs formed with tetrabutylammonium. This ion-pairing reagent served two purposes. First, it allowed the extraction of LAS with the polydimethylsiloxane fiber by counterion association and second, the derivatization of the formed LAS ion pairs in the GC injection port at 300 degrees C to form the corresponding sulfonated butyl esters. The methodology developed allows the isomer specific determination of LAS at low detection limits (0.16-0.8 ng/ml), depending on the alkyl chain lengths of LASs with RSDs of 10-12%. Furthermore, the developed methodology was applied to urban wastewater and sea water and compared with a solid-phase extraction (SPE) method (e.g. C18 and strong anion-exchange sorbent) to obtain concordant values for urban wastewater. Moreover, the developed SPME methodology overcame the procedural blank and matrix-dependent recoveries found in the SPE methodologies at low LAS concentrations.

Alkanesulfonic Acids↗
PubMed2000

High-temperature solid-phase microextraction procedure for the detection of drugs by gas chromatography-mass spectrometry.

High-temperature headspace solid-phase microextraction (SPME) with simultaneous ("in situ") derivatisation (acetylation or silylation) is a new sample preparation technique for the screening of illicit drugs in urine and for the confirmation analysis in serum by GC-MS. After extraction of urine with a small portion of an organic solvent mixture (e.g., 2 ml of hexane-ethyl acetate) at pH 9, the organic layer is separated and evaporated to dryness in a small headspace vial. A SPME-fiber (e.g., polyacrylate) doped with acetic anhydride-pyridine (for acetylation) is exposed to the vapour phase for 10 min at 200 degrees C in a blockheater. The SPME fiber is then injected into the GC-MS for thermal desorption and analysis. After addition of perchloric acid and extraction with n-hexane to remove lipids, the serum can be analysed after adjusting to pH 9 as described for urine. Very clean extracts are obtained. The various drugs investigated could be detected and identified in urine by the total ion current technique at the following concentrations: amphetamines (200 microg/l), barbiturates (500 microg/l), benzodiazepines (100 microg/l), benzoylecgonine (150 microg/l), methadone (100 microg/l) and opiates (200 microg/l). In serum all drugs could be detected by the selected ion monitoring technique within their therapeutic range. As compared to liquid-liquid extraction only small amounts of organic solvent are needed and larger amounts of the pertinent analytes could be transferred to the GC column. In contrast to solid-phase extraction (SPE), the SPME-fiber is reusable several times (as there is no contamination by endogenous compounds). The method is time-saving and can be mechanised by the use of a dedicated autosampler.

Gas Chromatography-Mass Spectrometry↗
PubMed1999

Fishing for a drug: solid-phase microextraction for the assay of clozapine in human plasma.

Solid-phase microextraction (SPME) was investigated as a sample preparation method for assaying the neuroleptic drug clozapine in human plasma. A mixture of human plasma, water, loxapine (as internal standard) and aqueous NaOH was extracted with a 100-micron polydimethylsiloxane (PDMS) fiber (Supelco). Desorption of the fiber was performed in the injection port of a gas chromatograph at 260 degrees C (HP 5890; 30 m x 0.53 mm I.D., 1 micron film capillary; nitrogen-phosphorous selective detection). Fibers were used repeatedly in up to about 75 analyses. The recovery was found to be 3% for clozapine from plasma after 30 min of extraction. However, in spite of the low recovery, the analyte was well separated and the calibration was linear between 100 and 1000 ng/ml. The within-day and between-day precision was consistently about 8 to 15% at concentrations of 200 ng/ml to 1000 ng/ml. No interfering drug was found. The limit of detection was 30 ng/ml. The sample volume was 250 microliters. The influence of the concentration of proteins, triglycerides and salt, i.e., changes in the matrix on the peak areas and peak-area ratios was studied. The method is not impaired by physiological changes in the composition of the matrix. Good agreement was found with a liquid-liquid extraction-gas-liquid chromatography (LLE-GLC) standard method and an on-line column-switching high-performance liquid chromatography (HPLC) method for patients' samples and spiked samples, respectively. It is concluded that the method can be used in the therapeutic drug monitoring of clozapine because the therapeutic window of clozapine is from 350 to 600 ng/ml.

Chromatography, Gas↗
PubMed2006

Headspace-solid-phase microextraction in the analysis of the volatile fraction of aromatic and medicinal plants.

Headspace (HS)-solid-phase microextraction (SPME) has assumed an ever increasing importance as a technique for HS sampling to study the composition of the HS of medicinal and aromatic plants. HS-SPME has mainly been applied for (a) studying the composition of the volatile fraction, including in addition to or as an alternative to other sampling techniques; (b) monitoring the biological phenomena involved with the volatile fraction of a plant; (c) discriminating between species, subspecies, varieties, cultivars, or chemotypes; and (d) quality control of plant samples. A review of 108 articles published during 2000-2005 is presented covering the use of HS-SPME in the field of aromatic and medicinal plants, selection of the most effective fiber and sampling conditions, comparison of HS-SPME and other volatile fraction sample preparation techniques, and the advantages and limits of HS-SPME when applied to medicinal and aromatic plants.

Chromatography, Liquid↗
PubMed2001

Comparison of simultaneous distillation extraction and solid-phase microextraction for the determination of volatile flavor components.

Traditional simultaneous distillation extraction (SDE) and solid-phase microextraction (SPME) techniques were compared for their effectiveness in the extraction of volatile flavor compounds from various mustard paste samples. Each method was used to evaluate the responses of some analytes from real samples and calibration standards in order to provide sensitivity comparisons between the two techniques. Experimental results showed traditional SDE lacked the sensitivity needed to evaluate certain flavor volatiles, such as 1,2-propanediol. Dramatic improvements in the extraction ability of the SPME fibers over the traditional SDE method were noted. Different SPME fibers were investigated to determine the selectivity of the various fibers to the different flavor compounds present in the mustard paste samples. Parameters that might affect the SPME, such as the duration of absorption and desorption, temperature of extraction, and the polarity and structure of the fiber were investigated. Of the various fibers investigated, the PDMS-DVB fiber proved to be the most desirable for these analytes.

Chromatography, Liquid↗
PubMed2003

Determination of organochlorine pesticides in water using microwave assisted headspace solid-phase microextraction and gas chromatography.

A coupled technique, microwave-assisted headspace solid-phase microextraction (MA-HS-SPME), was investigated for one-step in situ sample pretreatment for organochlorine pesticides (OCPs) prior to gas chromatographic determination. The OCPs, aldrin, o,p'-DDE, p,p'-DDE, o,p'-DDT, p,p'-DDT, dieldrin, alpha-endosulfan, beta-endosulfan, endosulfan sulfate, endrin, delta-HCH, gamma-HCH, heptachlor, heptachlor epoxide, methoxychlor and trifluralin were collected by the proposed method and analyzed by gas chromatography with electron-capture detection (GC-ECD). To perform the MA-HS-SPME, six types of SPME fibers were examined and compared. The parameters affecting the efficiency in MA-HS-SPME process such as sampling time and temperature, microwave irradiation power, desorption temperature and time were studied to obtain the optimal conditions. The method was developed using spiked water samples such as field water and with 0.05% humic acid in a concentration range of 0.05-2.5 microg/l except endosulfan sulfate in 0.25-2.5 microg/l. The detection was linear over the studied concentration range with r2>0.9978. The detection limits varied from 0.002 to 0.070 microg/l based on S/N=3 and the relative standard deviations for repeatability were <15%. A certified reference sample of OCPs in aqueous solution was analyzed by the proposed method and compared with the conventional liquid-liquid extraction procedure. These results are in good agreement. The results indicate that the proposed method provides a very simple, fast, and solvent-free procedure to achieve sample pretreatment prior to the trace-level screening determination of organochloride pesticides by gas chromatography.

Chromatography, Gas↗
PubMed2001

Solid phase microextraction.

Solid Phase Microextraction (SPME) uses a small volume of sorbent dispersed typically on the surface of small fibres, to isolate and concentrate analytes from sample matrix. After contact with sample, analytes are absorbed or adsorbed by the fibre phase (depending on the nature of the coating) until an equilibrium is reached in the system. The amount of an analyte extracted by the coating at equilibrium is determined by the magnitude of the partition coefficient of the analyte between the sample matrix and the coating material. After the extraction step, the fibres are transferred, with the help of a syringe-like handling device, to analytical instrument, for separation and quantitation of target analytes. This technique integrates sampling, extraction and sample introduction and is a simple way of facilitating on-site monitoring. Applications of this technique include environmental monitoring, industrial hygiene, process monitoring, clinical, forensic, food, flavour, fragrance and drug analyses, in laboratory and on-site analysis.

Chemistry Techniques, Analytical↗
PubMed2005

Application of solid-phase microextraction in the investigation of protein binding of pharmaceuticals.

Protein-drug interactions of seven common pharmaceuticals were studied using solid-phase microextraction (SPME). SPME can be used in such investigations on the condition that no analyte depletion occurs. In multi-compartment systems (e.g. a proteinaceous matrix) only the free portion of the analyte is able to partition into the SPME fiber. In addition if no sample depletion occurs, the bound drug-free drug equilibria are not disturbed. In the present study seven pharmaceuticals (quinine, quinidine, naproxen, ciprofloxacin, haloperidol, paclitaxel and nortriptyline) were assayed by SPME. For quantitative purposes SPME was validated first in the absence of proteins. Calibration curves were constructed for each drug by HPLC-fluorescence and HPLC-UV analysis. SPME was combined to HPLC off-line, desorption occurring in HPLC inserts filled with 200 microL methanol. Binding of each drug to human serum albumin was studied independently. Experimental results were in agreement with literature data and ultrafiltration experiments, indicating the feasibility of the method for such bioanalytical purposes.

Binding, Competitive↗
PubMed2003

Solid-phase microextraction from small volumes of sample in a glass capillary.

A new sampling method is proposed for solid-phase microextraction (SPME), in which the extraction is carried out in a glass capillary containing a few microliters of sample. When an adsorption-type fiber is used for SPME, the equilibrium between aqueous sample and coating can be described by a Langmuir isotherm. Since the total amount of analytes and coexisting substances stays at a low level in a small volume of sample, the linear concentration range of analytes will be extended for SPME to be applied in quantification and the interference caused by sample matrix will be reduced. In addition, sampling in a capillary has a short diffusion distance and extraction equilibrium is established in 5-10 min. It is important in clinical analysis and therapeutic drug monitoring to be able to analyse sample volumes of samples. The feasibility of the new sampling method is demonstrated by the extractions of p-hydroxybenzaldehyde and a synthetic solution containing 1-naphthol, paeonol and 1-naphthylamine.

Chromatography, Gas↗