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PubMed1989

[Use of solid phase extraction for rapid sample preparation in the determination of food constituents. I. Quinine in beverages].

A routine method was developed for the determination of quinine in spirits and alcohol-free beverages. Using ion pair chromatography quinine was separated from interfering substances by high-performance liquid chromatography on a RP 18 phase and analysed by UV and fluorescence detection. In contrast to the analysis of alcohol-free beverages, sample preparation was necessary in the study of alcoholic beverages. Solid-phase extraction on phenyl sorbens was found to be a rapid, specific and simple technique.

Beverages↗

PubMed2003

Solid-phase extraction and sample stacking-micellar electrokinetic capillary chromatography for the determination of multiresidues of herbicides and metabolites.

Micellar electrokinetic capillary chromatography (MEKC) with diode array detection was used for the separation of 13 compounds (eight herbicides widely used in agriculture: metribuzin, lenacil, ethofumesate, atrazine, terbutryn, isoproturon, chlorotoluron and linuron, and five of their principal degradation products; namely, deethylatrazine, 2-hydroxyatrazine, deethyl-2-hydroxyatrazine, deisopropylatrazine and 3-chloro-4-methylphenylurea). Peak separation for the 13 analytes was not successful when a single surfactant system was employed, neither sodium dodecyl sulfate (SDS) nor dioctyl sulfosuccinate (DOSS) sodium salt. However, a mixture of these herbicides was successfully separated using a mixed micellar system involving SDS-DOSS in less than 14 min. An application study of an on-line concentration technique for MEKC was carried out to enhance sensitivity. The optimized on-line stacking procedure consisted simply of the addition of 50 mM of sodium chloride to the injection sample, the stacking effect being more intensive as analyte polarity increased. When this stacking procedure was combined with an off-line sample preconcentration step, based on solid-phase extraction, analytes could be detected in the ppb range. The whole method was applied to ultra-high-quality and natural waters. Linear relationships between the analytical signal and the initial analyte concentration were found to be independent of the type of water, except for the more polar analytes for which small differences were observed.

Chromatography, Micellar Electrokinetic Capillary↗

PubMed1997

Simultaneous solid phase extraction, derivatization, and gas chromatographic mass spectrometric quantification of thromboxane and prostacyclin metabolites, prostaglandins, and isoprostanes in urine.

The current analytical methods for the various prostanoids require a separate and extended sample workup, derivatization, and gas chromatographic/mass spectrometric detection of each compound. Therefore, we developed and validated a rapid method for the common purification, derivatization, and GC/MS determination of 11-dehydrothromboxane B2, 2,3-dinor-6-keto-PGF1a, PGF2A, PGE2, PGD2, and isoprostanes in urine. A single reversed-phase solid-phase extraction step and modified reaction conditions yielded excellent sample purification at high recoveries and efficient derivatization for all compounds in one vial. The method allows, for the first time, the simultaneous quantification of these index metabolites of systemic thromboxane and prostacyclin synthesis, renal prostaglandin formation, and nonenzymatic in vivo lipid peroxidation in a single GC/MS run with high sensitivity and precision.

6-Ketoprostaglandin F1 alpha↗

PubMed2006

Determination of rabeprazole enantiomers and their metabolites by high-performance liquid chromatography with solid-phase extraction.

Here, we describe the development of a rapid, simple and sensitive high-performance liquid chromatography (HPLC) method for the simultaneous quantitative determination of rabeprazole enantiomers (1a,b) and their metabolites, rabeprazole-thioether (2) and rabeprazole sulfone (3), in human plasma. Analytes and the internal standard (omeprazole-thioether) were separated using a mobile phase of 0.5 M NaClO4-acetonitrile (6:4, v/v) over a Chiral CD-Ph column. Analysis required only 100 microl of plasma and involved solid-phase extraction with an Oasis HLB cartridge, which gave high recovery (>91.8%) with good selectivity for all analytes. The lower limit of quantification was 5 ng/ml for analytes 1a, 1b and 3 and 10 ng/ml for 2. Linearity of this assay was determined to lie between 5 and 1000 ng/ml for 1a, 1b and 3 and 10 and 1000 ng/ml for 2 (r2>0.982 of the regression line). Inter- and intra-day coefficients of variation were less than 7.8% and accuracies were within 8.4% over the linear range for all analytes. Our results indicate that this method is applicable to the simultaneous monitoring of plasma levels of rabeprazole enantiomers and associated metabolites in human plasma.

2-Pyridinylmethylsulfinylbenzimidazoles↗

PubMed2006

Multiresidue analytical method using dispersive solid-phase extraction and gas chromatography/ion trap mass spectrometry to determine pharmaceuticals in whole blood.

A convenient analytical method for the simultaneous determination of more than 40 pharmaceuticals belonging to various therapeutic categories in whole blood has been developed. Exemplarily, the method was fully validated for eight different pharmaceuticals. The procedure entails addition of acetonitrile, magnesium sulfate and sodium chloride to a small amount of blood, then the mixture is shaken intensively and centrifuged for phase separation. An aliquot of the organic layer is cleaned up by dispersive solid-phase extraction employing bulk sorbents as well as magnesium sulfate for the removal of residual water. This method was based on the QuEChERS approach developed for pesticide residue analysis in food. Gas chromatography/ion trap mass spectrometry (GC/MS) with electron (EI) and chemical (CI) ionisation was then used for qualitative and quantitative determination of the pharmaceuticals. The dispersive SPE with PSA (sorbent functionalized with primary and secondary amines) was found more suitable than aminopropyl and a styrene-divinylbenzene sorbent for sample clean-up before drug level determination in whole blood and plasma, as it was found that most of endogenous matrix components were removed and the analytes were isolated from spiked samples with recoveries above 80%. Variation coefficients of the repeatability typically smaller than 10% have been achieved for a wide range of the investigated substances. The used analytical conditions allowed to separate successively a variety of drugs and poisons with the typical limit of detection at <20 ng mL(-1) levels using 1 microL injection of equivalent blood sample in whole blood. The method is simple, rapid, cheap and very effective for therapeutic drug monitoring and forensic chemistry.

Absorption↗

PubMed2005

Assessment of the quantitative determination of paralytic shellfish poisoning toxins by pre-column derivatization and elimination of interfering compounds by solid-phase extraction.

Monitoring programmes for paralytic shellfish poisoning toxins in bivalve molluscs still rely heavily on the use of mouse bioassays (MBA) for consumer protection. A high-performance liquid chromatography (HPLC) methodology (Lawrence method) was implemented in 1996 in the Portuguese monitoring programme as a complementary means of analysis. Comparison between MBA and HPLC was done at the time only by a qualitative approach due to the scarce number of positive samples tested. More quantitative data were obtained recently when studying toxin profiles in Moroccan shellfish, and the correlation found between these two methodologies is reported here for the first time. Two different matrices were studied: blue mussel and the giant cockle Acanthocardia tuberculatum. A good linear correlation was obtained for both matrices. However, a second-degree polynomial best fitted the data at both low and high extremes of toxicity. According to the HPLC quantitative results, 13% of false-negatives could be obtained by MBA due to an underestimation of toxicity near the limit of detection of the MBA. Difficulties on relying solely on HPLC for consumer protection have been aroused with uncommon matrices, such as imported clams or crustaceans, due to the presence of high concentrations of interfering compounds. The solid-phase extraction step of the Lawrence method was implemented to eliminate an unknown compound that could be mistaken for saxitoxin, and an 80% reduction of another common unknown compound eluting close to decarbamoylsaxitoxin. The implementation of the HPLC methodology achieved so far allows a high degree of consumer protection without the need to resource to animal sacrifice.

Animals↗

PubMed2002

Effects of organic solvents on the high performance liquid chromatographic analysis of the cyanobacterial toxin cylindrospermopsin and its recovery from environmental eutrophic waters by solid phase extraction.

The effect of organic solvents on the high performance liquid chromatography (HPLC) analysis of cylindrospermopsin using photodiode array detection was examined since organic solvents are commonly used to extract this toxin from cyanobacteria and in the mobile phase compositions used in HPLC. Increasing concentrations of methanol resulted in an increase in the UV absorbance of purified cylindrospermopsin according to spectrometry, but to a marked decrease during HPLC analysis when the concentration of this solvent was greater than 50% methanol, or when acetonitrile concentrations exceeded 30% (v/v). Precipitation of cylindrospermopsin at these high concentrations of organic solvents was not observed. Solid phase extraction methods were developed to recover the toxin from spent extracellular growth medium after laboratory culture of Cylindrospermopsis raciborskii strain CR3 as an aid to toxin purification and from spiked environmental water samples. Using C18 and polygraphite carbon cartridges in series, 100% recoveries of cylindrospermopsin were achieved for lake waters spiked at 1 micro g l(-1).

Alkaloids↗

PubMed2004

Direct injection of solid-phase extraction eluents onto silica columns for the analysis of polar compounds isoniazid and cetirizine in plasma using hydrophilic interaction chromatography with tandem mass spectrometry.

Isoniazid and cetirizine do not retain well on reversed-phase columns due to their high polarity. Silica columns, when operated under hydrophilic interaction conditions, do provide excellent retention of these compounds. We have developed simple and proof of concept analytical methods for the analysis of isoniazid and cetirizine in animal and human plasma, respectively. Both methods employed the approach of direct injection of solid-phase extraction (SPE) organic eluents onto silica columns for analysis, thus eliminating evaporation and reconstitution steps that are typically needed for reversed-phase liquid chromatographic analysis. Isoniazid was extracted from animal plasma samples using a Waters Oasis HLB 96-well plate and then eluted with acetonitrile, while cetirizine was extracted from human plasma with a Waters MCX mu-Elute plate and then eluted with acetonitrile containing 5% concentrated ammonium hydroxide. The direct injection of the SPE eluent onto the analytical column was necessary since significant loss of isoniazid was found during the evaporation and reconstitution steps. The method for isoniazid also enabled ultra-fast analysis due to the relatively low back-pressure exhibited by silica columns even under high flow conditions. Both methods show good linearity, accuracy and precision covering the range of 10-2000 ng/mL of isoniazid, and 1-1000 ng/mL of cetirizine in plasma. Substantial time savings were realized as a result of both the elimination of the evaporation and reconstitution steps and the fast chromatographic analysis.

Animals↗

PubMed2001

Determination of alkylphenols and alkylphenol polyethoxylates by reversed-phase high-performance liquid chromatography and solid-phase extraction.

A simple, accurate and reproducible reversed-phase high-performance liquid chromatography (HPLC) method was developed for the separation and characterisation of alkylphenols (APs) and alkylphenol polyethoxylates (APEOs), using a C18 octadecyl silica (ODS) column. APs and each APEO oligomer were separated successfully within a reasonable time without gradient elution. An excellent resolution was obtained, even for mixtures of APs and low EO number APEOs, which are otherwise difficult to separate using conventional normal-phase HPLC methods. This method, combined with solid-phase extraction, was highly applicable for the simultaneous determination of alkylphenols and alkylphenol ethoxylates in real samples.

Journal Article↗

PubMed1999

Comparison of turbulent-flow chromatography with automated solid-phase extraction in 96-well plates and liquid-liquid extraction used as plasma sample preparation techniques for liquid chromatography-tandem mass spectrometry.

Turbulent flow chromatography (TFC) combined with the high selectivity and sensitivity of tandem mass spectrometry (MS-MS) is a new technique for the fast direct analysis of drugs from crude plasma. TFC in the 96-well plate format reduces significantly the time required for sample clean-up in the laboratory. For example, for 100 samples the workload for a technician is reduced from about 8 h by a manual liquid-liquid extraction (LLE) assay to about 1 h in the case of TFC. Sample clean-up and analysis are performed on-line on the same column. Similar chromatographic performance and validation results were achieved using HTLC Turbo-C18 columns (Cohesive Technologies) and Oasis HLB extraction columns (Waters). One 96-well plate with 96 plasma samples is analyzed within 5.25 h, corresponding to 3.3 min per sample. Compared to this LLE and analysis of 96 samples takes about 16 h. Two structurally different and highly protein bound compounds, drug A and drug B, were analyzed under identical TFC conditions and the assays were fully validated for the application to toxicokinetics studies (compliant with Good Laboratory Practices-GLP). The limit of quantitation was 1.00 microg/l and the linear working range covered three orders of magnitude for both drugs. In the case of drug A the quality of analysis by TFC was similar to the reference LLE assay and slightly better than automated solid-phase extraction in 96-well plates. The accuracy was -3.1 to 6.7% and the precision was 3.1 to 6.8% in the case of drug A determined for dog plasma by TFC-MS-MS. For drug B the accuracy was -3.7 to 3.5% and the precision was 1.6 to 5.4% for rat plasma, which is even slightly better than what was achieved with the validated protein precipitation assay.

Animals↗

PubMed2006

A simple method to separate red wine nonpolymeric and polymeric phenols by solid-phase extraction.

Simple polyphenols and tannins differ in the way that they contribute to the organoleptic profile of wine and their effects on human health. Very few straightforward techniques to separate red wine nonpolymeric phenols from the polymeric fraction are available in the literature. In general, they are complex, time-consuming, and generate large amounts of waste. In this procedure, the separation of these compounds was achieved using C18 cartridges, three solvents with different elution strengths, and pH adjustments of the experimental matrices. Two full factorial 2(3) experimental designs were performed to find the optimal critical variables and their values, allowing for the maximization of tannin recovery and separation efficiency (SE). Nonpolymeric phenols such as phenolic acids, monomers, and oligomers of flavonol and flavan-3-ols and anthocyanins were removed from the column by means of an aqueous solvent followed by ethyl acetate. The polymeric fraction was then eluted with a combination of methanol/acetone/water. The best results were attained with 1 mL of wine sample, a 10% methanol/water solution (first eluant), ethyl acetate (second eluant), and 66% acetone/water as the polymeric phenols-eluting solution (third eluant), obtaining a SE of ca. 90%. Trials with this method on fruit juices also showed high separation efficiency. Hence, this solid-phase extraction method has been shown to be a simple and efficient alternative for the separation of nonpolymeric phenolic fractions and the polymeric ones, and this method could have important applications to sample purification prior to biological testing due to the nonspecific binding of polymeric phenolics to nearly all enzymes and receptor sites.

Acetone↗

PubMed2006

Development of an HPLC method for the determination of nifedipine in human plasma by solid-phase extraction.

Nifedipine, a dihydropyridine calcium channel antagonist, is widely used in the treatment of hypertension and other cardiovascular disorders. A selective, sensitive and accurate high-performance liquid chromatographic method has been developed, validated and applied for determination of nifedipine in human plasma samples. A series of studies were conducted in order to investigate the effects of mobile phase composition, buffer concentration, mobile phase pH and concentration of organic modifiers, and to develop a convenient and easy-to-use method for quantitative analysis of nifedipine. The method involves solid-phase extraction on C18 cartridges. The chromatographic separation was accomplished on a Lichrocart Lichrospher 60 RP selectB column with a mobile phase composed of 0.020 mol/L KH2PO4 (pH 4.8) and acetonitrile (42:58, v/v). UV detection was set at 240 nm. The calibration curve was linear in the concentration range of 5.0-200.0 ng/mL for nifedipine in plasma and the limit of quantification was 5.0 ng/mL.

Biological Assay↗

PubMed2006

Simultaneous determination of the antipsychotic drugs levomepromazine and clozapine and their main metabolites in human plasma by a HPLC-UV method with solid-phase extraction.

A HPLC method with UV detection has been developed for the simultaneous determination of levomepromazine, clozapine and their main metabolites: N-desmethyl-levomepromazine, levomepromazine sulphoxide, O-desmethyl-levomepromazine, N-desmethylclozapine and clozapine N-oxide. The analytes were separated on a C8 reversed-phase column using a mobile phase composed of acetonitrile and a pH 2.0, 34 mM phosphate buffer containing 0.3% triethylamine (29:71, v/v). Loxapine was used as the internal standard. A reliable biological sample pre-treatment procedure by means of solid-phase extraction on C1 cartridges was implemented, which allows to obtain good extraction yields (>91%) for all analytes and appropriate sample purification from endogenous interference. The method was validated in terms of extraction yield, precision and accuracy. These assays gave RSD% values for precision always lower than 4.9% and mean accuracy values higher than 92%. The method is suitable for the therapeutic drug monitoring (TDM) of patients undergoing polypharmacy with levomepromazine and clozapine.

Antipsychotic Agents↗

PubMed2003

Liquid chromatographic analysis of the cis(Z)- and trans(E)-isomers of clopenthixol in human plasma using a novel solid phase extraction procedure.

A simple and highly sensitive high-performance liquid chromatographic (HPLC) method for the simultaneous determination of cis(Z)-clopenthixol and trans(E)-clopenthixol in human plasma has been developed. The chromatographic analysis was carried out isocratically on a reversed-phase column (C(8) 150 x 4.6 mm I.D., 5 microm) using a mixture of 25 mM phosphate buffer and acetonitrile (65:35 v/v, pH* 3.0) as the mobile phase, and ultraviolet detection at 230 nm. Plasma sample pretreatment was accomplished by means of an original solid-phase extraction (SPE) procedure carried out on cyanopropyl cartridges, with a high extraction yield and good selectivity. Under the optimum conditions, calibration graphs of spiked human plasma samples were obtained over the concentration ranges 1-300 ng ml(-1) for cis(Z)-clopenthixol and 1-200 ng ml(-1) for trans(E)-clopenthixol. The limit of detection (LOD) was 0.3 ng ml(-1) for both cis(Z)- and trans(E)-isomers of clopenthixol. The method was successfully applied to the determination of cis(Z)-clopenthixol and trans(E)-clopenthixol in plasma samples of schizophrenic patients undergoing therapy with zuclopenthixol.

Antipsychotic Agents↗

PubMed2006

Solid-phase extraction and analysis of 20 antidepressant drugs in human plasma by LC/MS with SSI method.

A simultaneous determination of 20 antidepressant drugs (imipramine, amitriptyline, desipramine, trimipramine, nortriptyline, clomipramine, amoxapine, lofepramine, dosulepin, maprotiline, mianserin, setiptiline, trazodone, fluvoxamine, paroxetine, milnacipran, sulpiride, tandspirone, methylphenidate and melitracen) in human plasma was developed using LC/MS with sonic spray ionization (SSI) method. These drugs showed good separation and sensitivity by LC-MS using an Inertsil C-8 column with methanol:10mM ammonium acetate (pH 5.0):acetonitrile (70:20:10) as mobile phase at 0.10 mL/min at 35 degrees C. Solid-phase extraction of these drugs added to the human plasma was performed with an Oasis HLB cartridge column. Recovery and limit of detection of these drugs were between 69 and 102% and between 0.03 and 0.63 microg/mL, respectively. The present procedure offers an easier and more convenient screening method for antidepressants, and will be useful for forensic toxicology investigations.

Antidepressive Agents↗

PubMed1993

Direct determination of ibuprofen and ibuprofen acyl glucuronide in plasma by high-performance liquid chromatography using solid-phase extraction.

A method for the simultaneous determination of ibuprofen and its labile, reactive metabolite, ibuprofen acyl glucuronide, in plasma is described. Reversed-phase high-performance liquid chromatography (HPLC) employed a C18 column using methanol-10 mM trifluoroacetic acid as the mobile phase with ultraviolet detection at 225 or 214 nm. It is essential that blood is handled rapidly and plasma is acidified upon collection prior to freezing. Plasma samples first are deproteinated with acetonitrile, the supernatant is diluted with phosphate buffer, and ibuprofen, ibuprofen glucuronide, and ibufenac (internal standard) are initially isolated by solid-phase extraction on C18 cartridges. Upon elution, the residue is evaporated, dissolved and injected onto the HPLC system. Recovery is 94 +/- 8 and 70 +/- 9% for ibuprofen glucuronide and ibuprofen, respectively. The measurable concentration range is linear from 0.1 to 10 micrograms/ml for ibuprofen glucuronide and from 0.5 to 100 micrograms/ml for ibuprofen. The method is satisfactory for the analysis of ibuprofen and ibuprofen glucuronide from pharmacokinetic studies in humans. The direct determination of ibuprofen glucuronide allows accurate measurement of this conjugate at low levels relative to the parent compound, ibuprofen, a distinct advantage compared to previously employed indirect methods.

Chromatography, High Pressure Liquid↗

PubMed2003

Automated solid-phase extraction and liquid chromatography-electrospray ionization-mass spectrometry for the determination of flunitrazepam and its metabolites in human urine and plasma samples.

A sensitive and specific method using reversed-phase liquid chromatography coupled with electrospray ionization-mass spectrometry (LC-ESI-MS) has been developed for the quantitative determination of flunitrazepam (F) and its metabolites 7-aminoflunitrazepam (7-AF), N-desmethylflunitrazepam (N-DMF) and 3-hydroxyflunitrazepam (3-OHF) in biological fluids. After the addition of deuterium labelled standards of F,7-AF and N-DMF, the drugs were isolated from urine or plasma by automated solid-phase extraction, then chromatographed in an isocratic elution mode with a salt-free eluent. The quantification was performed using selected ion monitoring of protonated molecular ions (M+H(+)). Experiments were carried out to improve the extraction recovery (81-100%) and the sensitivity (limit of detection 0.025 ng/ml for F and 7-AF, 0.040 ng/ml for N-DMF and 0.200 ng/ml for 3-OHF). The method was applied to the determination of F and metabolites in drug addicts including withdrawal urine samples and in one date-rape plasma and urine sample.

Adult↗

PubMed2002

Study on determination of iron, cobalt, nickel, copper, zinc and manganese in drinking water by solid-phase extraction and RP-HPLC with 2-(2-quinolinylazo)-5-diethylaminophenol as precolumn derivatizing reagent.

A new method for the determination of iron, cobalt, nickel, copper, zinc and manganese in drinking water by the reversed-phase high-performance liquid chromatography (RP-HPLC) with 2-(2-quinolinylazo)-5-diethylaminophenol (QADEAP) as precolumn derivatizing reagent was studied in this paper. The iron, cobalt, nickel, copper, zinc, and manganese ions react with QADEAP to form color chelates in the presence of cetyl trimethylammonium bromide (CTMAB) and acetic acid-sodium acetic buffer solution medium of pH 4.0. These chelates were enriched by solid-phase extraction with a Waters Nova-Pak C18 cartridge and eluted the retained chelates from the cartridge with tetrahydrofuran (THF). The enrichment factor of 100 was achieved. Then the chelates were separated on a Waters Nova-Pak C18 column (3.9 x 150 mm, 5 microm) by gradient elution with methanol (containing 0.2% of acetic acid and 0.1% of CTMAB) and 0.05 mol L(-1) acetic acid-sodium acetic buffer solution (containing 0.1% of CTMAB) (pH 4.0) as mobile phase at a flow rate of 0.5 ml min(-1), and monitored with a photodiode array detector from 450 approximately 700 nm. The detection limits (S/N = 3) of iron, cobalt, nickel, copper, zinc and manganese are 0.8, 1.1, 0.9, 1.1, 1.5 and 2.0 ng L(-1), respectively, in the original sample. This method can be applied to determination at the microg L(-1) level of iron, cobalt, nickel, copper, zinc and manganese in drinking water with good results.

Azo Compounds↗