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PubMed2004

Automated sample preparation based on the sequential injection principle. Solid-phase extraction on a molecularly imprinted polymer coupled on-line to high-performance liquid chromatography.

A molecularly imprinted polymer (MIP) prepared using caffeine, as a template, was validated as a selective sorbent for solid-phase extraction (SPE), within an automated on-line sample preparation method. The polymer produced was packed in a polypropylene cartridge, which was incorporated in a flow system prior to the HPLC analytical instrumentation. The principle of sequential injection was utilised for a rapid automated and efficient SPE procedure on the MIP. Samples, buffers, washing and elution solvents were introduced to the extraction cartridge via a peristaltic pump and a multi-position valve, both controlled by appropriate software developed in-house. The method was optimised in terms of flow rates, extraction time and volume. After extraction, the final eluent from the extraction cartridge was directed to the injection loop and was subsequently analysed on HPLC. The overall set-up facilitated unattended operation, operation and improved both mixing fluidics and method development flexibility. This system may be readily built in the laboratory and can be further used as an automated platform for on-line sample preparation.

Automation↗
PubMed1998

Interference of 6 beta-hydroxycortisol in the quantitation of urinary free cortisol by immunoassay and its elimination by solid phase extraction.

OBJECTIVE: To study the cross-reactivity of 6 beta-hydroxycortisol (6 beta-OHF) with anticortisol antibodies and subsequent interference with urinary free cortisol (UFC) quantitation in commercial immunoassay kits. A solid-phase-extraction (SPE) technique was evaluated for removal of 6 beta-OHF from the specimen. METHODS: Interference by 6 beta-OHF was studied in three enzyme immunoassay and three radioimmunoassay kits. Interference was assessed by the multiple regression equation derived from a 4 x 4 matrix composed of four levels of cortisol and four levels of 6 beta-OHF. Sep-Pak Plus C18 cartridges were used to remove 6 beta-OHF from the specimens, and optimum conditions for fractionating 6 beta-OHF from cortisol were determined by eluting the cartridge with a stepwise increment in methanol concentration. HPLC was used to monitor cortisol and 6 beta-OHF in the sample and cartridge eluates. RESULTS: Cross-reactivity of 6 beta-OHF with anticortisol antibodies was variable and depended on the cortisol kit used with a range from 0.1 to 10%. Multiple regression analysis indicated that 6 beta-OHF interfered positively with the cortisol assay regardless of cortisol concentrations. Extraction of UFC by methylene chloride as recommended by some immunoassay kits yielded a significant constant error to the UFC results which was nearly proportional to the added levels of 6 beta-OHF. SPE of samples completely removed 6 beta-OHF from the specimen when a 40% methanol elution step was included. Consequently, specimens processed in this manner did not show interference in UFC measurements even in samples spiked with 2.38 mumol/L of 6 beta-OHF. CONCLUSIONS: Elevated urinary 6 beta-OHF may be a significant source of interference in UFC immunoassays. SPE of samples prior to analysis would be a simple and inexpensive means for removing 6 beta-OHF from urine specimens, therefore, increasing accuracy and precision in UFC measurements by immunoassay.

Chemical Fractionation↗
PubMed1989

Quantitative and pharmacokinetic analysis of naloxone in plasma using high-performance liquid chromatography with electrochemical detection and solid-phase extraction.

In this study we present a method for measuring naloxone in plasma after intravenous and oral administration of naloxone to humans, in order to study its pharmacokinetic profile. The method consists of a solid-phase extraction step followed by detection on a high-performance liquid chromatographic (HPLC) system equipped with an electrochemical dual-electrode detector. The extraction step employs cyanopropyl columns optimized for naloxone extraction to allow for elution of naloxone by the HPLC mobile phase; this eluate is then directly injected in the HPLC instrument. The HPLC system employs a radial compression phenyl column with a mobile phase containing 18% (v/v) acetonitrile and pentanesulfonic acid as ion-pairing agent; this system shows extraordinary high plate counts for naloxone. The detection limit is 3 ng (signal-to-noise ratio = 3) free naloxone per ml plasma. Following intravenous injection of 30 mg naloxone hydrochloride in two subjects, it was possible to determine the free naloxone concentration in the plasma for 8 h, more than four times the half-life of naloxone in plasma in humans.

Chromatography, High Pressure Liquid↗
PubMed2002

Sensitive determination of benzalkonium chloride in blood and tissues using high-performance liquid chromatography with solid-phase extraction.

A sensitive and simple high-performance liquid chromatography assay for benzalkonium chloride (BZK) in biological samples was developed. The biological samples, spiked with domiphen used as an internal standard, were purified by solid-phase extraction. The major homologues of BZK in pharmaceutical products (C(12) and C(14)) were eluted at 24 and 36 min using a YMC-Pack CN column (4.6 x 250 mm, 5 microm) with a mobile phase, mixture of acetonitrile and sodium acetate buffer (48:52), and monitored at 254 nm. The most dominant component C(12) was selected as an indicator to quantify BZK, and adjustment was then done based on the proportion of C(12) in the BZK product. Good linearity was obtained in the range of 0.1-3 microg, and the limit of detection was 20 ng as a loaded amount on column. The recoveries of BZK in serum and tissues ranged from 54 to 90%. In a practical case, 0.16 microg/ml of BZK was quantified in serum collected several hours after accidental ingestion. The method is simple, sensitive and reliable for determining BZK levels in practical biological samples.

Journal Article↗
PubMed1993

Sample cleanup by solid-phase extraction for the ultratrace determination of polychlorinated dibenzo-p-dioxins and dibenzofurans in biological samples.

A sample cleanup method for the isolation of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) by solid-phase extraction is described. A C18 bonded silica cartridge is used for the initial extraction and enrichment of the analytes. Subsequent cleanup is achieved with a dual-cartridge arrangement consisting of a bonded benzenesulfonic acid cartridge in series with a silica cartridge. A Florisil cartridge is employed for the final cleanup step. Sample preparation procedures used for blood plasma and animal tissues are described. The precision and accuracy of the method is validated by determining recoveries of 2,3,7,8-substituted PCDD and PCDF congeners spiked at various levels in blood plasma and in animal tissues. The effectiveness of the cleanup method is shown by the analysis of wild bird eggs which are highly contaminated with a variety of pesticides and polychlorinated biphenyls. The application of this cleanup method to human plasma containing PCDDs/PCDFs at parts-per-quadrillion levels and results of analyses by high-resolution mass spectrometry and low-resolution mass spectrometry are presented. The validity of this method is demonstrated by the comparable results obtained from this method and from other established methods.

Animals↗
PubMed2006

Determination of phosphoric acid mono- and diesters in municipal wastewater by solid-phase extraction and ion-pair liquid chromatography-tandem mass spectrometry.

The first analytical method for the determination of 13 phosphoric acid mono- and diesters from aqueous samples is presented. The method consists of solid-phase extraction (SPE) and ion-pair liquid chromatographic separation with tri-n-butylamine coupled to electrospray ionization tandem mass spectrometry in the negative ion mode. Due to a lack of pure standards, only 3 of the 13 esters could be quantified. SPE recoveries ranged from 71 to 112% for di-n-butyl phosphate, diphenyl phosphate, and di-(2-ethylhexyl) phosphate (DEHP) with limits of quantification from 7 to 14 ng/L for 100-mL samples. At analyte concentrations >or=1 microg/L, aqueous samples can be analyzed by direct injection without extraction. In municipal wastewater, six diesters and one monoester were unambiguously identified by comparison with synthesized reference material. DEHP showed highest concentrations of 60 and 5 microg/L in raw and treated wastewater, respectively. The detection of monoethylhexyl phosphate was confirmed by LC-Q-TOF-MS analysis, and it was found at a concentration level comparable to DEHP. Laboratory degradation tests show that phosphoric acid diesters can be formed as intermediates in the microbial degradation of trialkyl phosphates that are being used as flame retardants and plasticizers.

Journal Article↗
PubMed1998

Use of automated solid-phase extraction equipment for the determination of ivermectin residues in animal liver by HPLC.

An improvement of the method commonly used for the determination of ivermectin is proposed. An automatic system is used for the solid-phase extraction column purification stage in order to provide more efficient and fast sample preparation, prior to separation and quantification by HPLC. Some tests were performed to obtain recovery and repeatability data. The mean recovery for spiked samples (five replicates twice at three concentration levels) was more than 90% in the concentration range 7.5-30 ng g-1. The tests for accuracy (five replicates at three concentration levels) gave a standard error of -2.0% at the highest and -19.2% at the lowest concentration. Concerning repeatability data (five replicates twice at three concentration levels), in the concentration range 7.5-30 ng g-1 the RSD varied from 9.29 to 2.15%. The described method was used in a survey on the presence of ivermectin in food-producing animals in two regions of southern Italy; no positives out of 250 liver samples were found.

Animals↗
PubMed2002

A simple and rapid in situ preconcentration method using solid-phase extraction for the determination of dissolved manganese in brackish lake water samples.

A simple and rapid in situ preconcentration method for the determination of dissolved manganese in environmental waters has been developed based on solid-phase extraction using a Sep-Pak C18 cartridge. Manganese in water samples, which was taken into a graduated syringe to easily perform the operation for collecting manganese at sampling sites, was converted into a stable complex with 4-(2-pyridylazo)resorcinol (PAR) at pH 10 immediately after sample collection. The formed Mn-PAR complex was collected by a Sep-Pak C18 cartridge, which was packed with C18-bonded silica. The complex was stable in the Sep-Pak C18 cartridge for at least one month. The retained complex was quantitatively eluted with 0.5 M hydrochloric acid. The manganese was determined by graphite-furnace AAS. The proposed method was successfully applicable to brackish lake water samples to investigate the behavior of dissolved manganese in brackish lakes.

Adsorption↗
PubMed1996

Analysis of low-dose benzodiazepines by HPLC with automated solid-phase extraction.

We describe a simple, specific, and sensitive reversed-phase HPLC method with automated solid-phase extraction (SPE) for analyzing alprazolam, clonazepam, and nitrazepam concentrations in human serum or plasma. We prepare samples and calibrators with an automated sample preparer, using 100-mg Bond-Elut C18 SPE columns. The HPLC method uses isocratic elution with acetonitrile:methanol:dipotassium hydrogen phosphate, 10 nmol/L, pH 3.7 (30:2:100 by vol), at a flow rate of 1.5 mL/min to separate the drugs. We detect the benzodiazepines with diode-array detector at 240 nm; analyses of peak purity are performed at 210-365 nm. The recoveries were between 94% and 100%. The intraassay and interassay CVs were between 1.0% and 4.1%. The detection limit is 5 nmol/L. The antiepileptic and antidepressant drugs tested did not interfere with the assay. We developed the method for use in a clinical laboratory for therapeutic drug monitoring.

Alprazolam↗
PubMed2005

[Study on solid phase extraction and spectrophotometric determination of uranium in water with 2-(2-quinolylazo)-5-dimthylaminophenol].

A new chromogenic reagent 2-(2-quinolylazo)-5-Dimthylaminophenol (QADMAP) was synthesized, and its structure was verified by elemental analysis, infrared spectrum, 1H nuclear magnetic resonance spectrum, mass spectrumand UV-spectrum. The color reaction of QADMAP with uranium was studied. In the presence of pH 7.8 buffer solution, when fluorin ion and TritonX-100 medium exist, QADMAP can react with uranium and fluorin to form a stable 1 : 1 : 1 stable complex [F- :QADMAP : U(VI)]. The molar absorptivity is 1.05 x 10(5) L x mol(-1) x cm(-1) at 590 nm. Beer's law is obeyed in range of 0-20 microg/10 mL. The uranium in samples can be enriched and separated by solid phase extraction with TBP resin cartridge. This method is applied to the determination of uranium in water sample. The relative standard deviations are 2.2%-3.6%, and the recoveries are 94%-105%.

Aza Compounds↗
PubMedDate not supplied

Comparison of various dilutions and solid-phase extraction cleanup on the determination of ephedrine-type alkaloids and internal standard recovery in ephedra botanical raw material and powdered extract.

A study was conducted to determine the effect of 3 dilution levels on the precision of the ephedra alkaloid method when used in conjunction with a solid-phase extraction (SPE) column. For the dilutions studied, SPE column cleanup is necessary because it promotes a greater recovery of the internal standard. However, overall, target precision values were not obtained on the test materials. It was determined that the SPE column is not the cause of the lower recovery in the more concentrated solutions. Significant signal suppression of the internal standard occurs in more concentrated solutions within the mass spectrometer. It is hypothesized that this lack of performance on the part of the SPE column may be linked to its inability to fully clean contaminants from the higher concentration solutions and/or a mass spectrometer overload, which resulted in the internal standard not fully correcting for signal suppression in more concentrated solutions. An internal standard is necessary, especially for accuracy, for the determination of all alkaloids, and only dilute solutions can be accurately analyzed. Due to the sensitivity of the mass spectrometer, it is recommended that the determination of ephedrine alkaloids in dietary supplements and botanicals should be studied using a standard graph at a level 10 x less than the current method. It is also recommended that the SPE column used should be evaluated on its need for the sample dilutions made to fit the newly recommended standard graph.

Alkaloids↗
PubMed1998

A radioimmunoassay combined with solid-phase extraction for the determination (pg ml-1) of AR-C15849XX) in human plasma.

A radioimmunoassay has been developed for the determination of AR-C15849KF, a CCK-8 analogue, in human plasma. The method incorporates solid-phase sample extraction, is suitable for the determination of the analyte at pg ml-1 concentrations and is based on a method developed and validated for dog plasma. The solid-phase extraction, using ion-exchange aminopropyl and octadecyl sorbents sequentially, was retained for this procedure to remove matrix interferences in the plasma and to enhance method sensitivity. The calibration range is 10-500 pg ml-1, using a 1 ml sample of undiluted human plasma. The method has been successfully used to generate early human pharmacokinetic data during a programme of exploratory development.

Animals↗
PubMed2003

Trace explosive detection in aqueous samples by solid-phase extraction ion mobility spectrometry (SPE-IMS).

Law enforcement agencies use ion mobility spectrometers for the detection of explosives, drugs of abuse, and chemical warfare agents. Ion mobility spectrometry (IMS) has the advantages of short analysis times, detections in the parts per billion concentrations, and high sensitivity. On-site environmental analysis of explosives or explosive residues in water is possible with ion mobility spectrometers. Unfortunately, the direct analysis of low levels of explosives in water is difficult. Extraction provides a method for pre-concentrating the analytes and removing interferents. Coupling solid-phase extraction (SPE) with IMS is useful for the identification of trace amounts of explosives in water. Commercially available SPE disks were used. After extraction, the sample disk is inserted into the ion mobility spectrometer, where the analytes are thermally desorbed from the disk. Concentrations as low as one part per trillion were detected with a Barringer Ionscan 350. An external computer and acquisition software (LabVIEW, National Instruments) were used to collect data. SIMPLISMA (SIMPLe-to-use-Interactive Self-modeling Mixture Analysis) was applied to the data to resolve features that vary with respect to time.

Aniline Compounds↗
PubMed2006

[Study on solid phase extraction and spectrophotometric determination of cadmium with 2-[2-(5-bromoquinolinylazo)]-5-diethylaminophenol].

A new chromogenic reagent 2-[2-(5-bromoquinolinylazo)]-5-diethylaminophenol (5-Br-QADEAP) was synthesized, and its structure was verified by elemental analysis, infrared spectrum, and 1H nuclear magnetic resonance spectrum. The color reaction of 5-Br-QADEAP with cadmium was studied. In the presence of pH 8.0 buffer solution and Triton X-100 medium, 5-Br-QADEAP can react with cadmium(II) to form a stable 2 : 1 complex (5-Br-QADEAP: Cd(II). The molar absorptivity is 1.60 x 10(5) L x mol(-1) x cm(-1) at 595 nm. Beer's law is obeyed in the range of 0-1.0 microg x mL(-1). The cadmium ion in the samples can be enriched and separated by solid phase extraction with anion exchange resin cartridge. This method was applied to the determination of cadmium in water and food. The relative standard deviations are 2.5%-3.2%, and the recoveries are 96%-105%. The results are satisfactory.

Animals↗
PubMed2003

Study on the determination of polyphenols in tobacco by HPLC coupled with ESI-MS after solid-phase extraction.

A high-performance liquid chromatography method coupled with electrospray ionization-mass spectrometry for the determination of polyphenols in tobacco is studied. The polyphenols are extracted from a tobacco sample by being refluxed in a boiling water bath with 80% methanol and purified by solid-phase extraction with a C18 cartridge. The chlorogenic acid, rutin, scopoletin, caffeic acid, scopolin, and other polyphenols are satisfactorily separated on a Nova-Pak C18 chromatographic column (3.9 x 150 mm) with methanol and 0.05 mol/L potassium dihydrogen phosphate buffer solution gradient elution as mobile phase at a flow rate of 0.5 mL/min. Each of the polyphenols is monitored by photodiode array detector at its maximum wavelength: chlorogenic acid, 326.1 nm; rutin, 354.8 nm; scopoletin, 344.0 nm; caffeic acid, 323.7 nm; and scopolin, 365.2 nm. The limits of detection are: 100 ng/mL for chlorogenic acid, 125 ng/mL for rutin, 60 ng/mL for scopoletin, 50 ng/mL for caffeic acid, and 100 ng/mL for scopolin. The key polyphenols in tobacco are identified by comparing the retention time, the UV-spectrum, and the mass spectra with those of the standards. The recovery of tobacco polyphenols is 94-105%, and the relative standard deviations are 1.28-1.49%. This method is successfully applied to qualitatively and quantitatively analyze the polyphenols in tobacco with good results.

Chromatography, High Pressure Liquid↗
PubMed1989

Determination of pipecolic acid in serum or plasma by solid-phase extraction and isotope dilution mass spectrometry.

The determination of pipecolic acid in serum or plasma by positive chemical ionization gas chromatography/mass spectrometry is assessed. This quantitative method involves stable isotope dilution and cation-exchange solid-phase extraction. Several derivatives of pipecolic acid and its octadeuterated analogue were investigated for their mass spectrometric characteristics. The heptafluorobutyric methyl ester derivatives afford optimal resolution on gas chromatography of biological extracts. Moreover, the derivatizing reagent (methanolic HCl) allows a combined elution and derivatization. Selected ion monitoring is performed on the [M + H]+ ions of both analyte and internal standard, at m/z 340 and 348, respectively. Serum or plasma samples from healthy subjects and patients suspected of peroxisomal diseases have been examined.

Child↗
PubMed2001

A simple and rapid in situ preconcentration method for the determination of phosphate in environmental waters by use of solid-phase extraction, and its applications to brackish lake waters.

A simple and rapid in situ preconcentration method for the determination of phosphate in environmental waters has been developed for field analysis. This method is based on solid-phase extraction on a zirconium-loaded Sep-Pack Accell CM cartridge (Zr-SP) and is applicable to studies in which sampling is performed by use of a graduated syringe to prevent contamination and to ensure easy operation at sampling sites. The Zr-SP cartridge was prepared by passing 0.1 mol L(-1) zirconium solution through a Sep-Pak Accell CM cartridge, packed with cation exchange sorbent based on a silica matrix. The adsorption of phosphate and its desorption depend only on the pH of the solution. A water sample containing phosphate was adjusted to pH 2 and passed through the Zr-SP cartridge to collect it. The retained phosphate was quantitatively eluted with 0.5 mol L(-1) sodium hydroxide solution. The phosphate retained in the Zr-SP cartridge was stable for at least one month. The established preconcentration method was successfully applied to brackish lake waters to investigate seasonal changes in the distribution and behavior of phosphate in a brackish lake.

Environmental Monitoring↗
PubMed1996

Determination of penicillin-V in human plasma by high-performance liquid chromatography and solid-phase extraction.

A high-performance liquid chromatographic method has been developed for the determination of penicillin-V concentrations between 0.1 and 19 micrograms/ml in human plasma. Penicillin-V was isolated from plasma by solid-phase extraction on a C18/OH cartridge. The extracts were injected onto a reversed-phase HPLC system. A 125 x 4 mm C18 column was used to separate penicillin-V from its main metabolites, 5R- and 5S-penicilloic acid and endogenous compounds. The eluent consisted of 66% 0.02 M phosphoric acid buffer, to which tetrabutylammonium dihydrogenphosphate and 34% acetonitrile were added. The column effluent was monitored by ultraviolet spectrophotometry at 269 nm. Using this method, penicillin-V concentrations in plasma could be determined with an accuracy between -5.4 and 5.2% and a precision between 0.8 and 1.6%. The method has proved to be reliable and was used in bioavailability studies for the development of a new oral penicillin-V formulation.

Calibration↗