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PubMedDate not supplied

Solid-phase extraction and optimized separation of doxorubicin, epirubicin and their metabolites using reversed-phase high-performance liquid chromatography.

A reversed-phase isocratic high-performance liquid chromatographic method is described in which a formal structured procedure was applied to predict the mobile phase composition giving optimal baseline resolution of the clinically important anticancer agents doxorubicin and 4'-epidoxorubicin (epirubicin), their principal metabolites, and daunorubicin (internal standard). These formal statistical procedures included the simultaneous techniques of solvent selectivity triangle and factorial design for range-finding preliminary studies, followed by use of the modified simplex, a sequential procedure. These were used to select the parameters of organic modifier, buffer strength and pH necessary for use with a Spherisorb ODS 1 column, to achieve optimal separation of eight anthracycline solutes. Ultraviolet and fluorescence detection was used (lambda ex = 254 nm, lambda em = 560 nm), and the latter gave a low detection limit for doxorubicin in serum of 1 ng ml-1. The optimal mobile phase composition was determined to be acetonitrile-0.06 M Na2 HPO4 containing 0.05% (v/v) triethylamine adjusted to pH 4.6 with 0.03 M citric acid (35:65, v/v). A solid-phase extraction method was developed to enable the selective isolation of anthracyclines by adsorption onto C8 Bond-Elut cartridges, and is based on extraction of serum spiked with a mixture of the anthracycline solutes. The anthracyclines were eluted using acetonitrile-0.2 M Na2 HPO4 containing 0.05% (v/v) triethylamine adjusted to pH 3.6 with 0.1 M citric acid (67.5:32.5, v/v). Reproducible recoveries for doxorubicin (94 +/- 8%) and for epirubicin (96 +/- 8%) were obtained (n = 5). In particular, recoveries for the 7-deoxyaglycone metabolite (99%) were higher than other extraction methods cited.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption↗
PubMed2005

Development of a validated HPLC method for the determination of iodotyrosines and iodothyronines in pharmaceuticals and biological samples using solid phase extraction.

Identification, separation and quantitation of iodoaminoacids, is essential for the biological research and the clinical diagnosis of thyroid gland disease. Under this aspect a reversed-phase high-performance liquid chromatographic method was developed for the determination of thyroid gland hormones and some of their primary metabolites, 3,3',5,5'-tetra-iodo-L-thyronine (L-thyroxine), 3,3',5-tri-iodo-L-thyronine, 3,5-di-iodo-L-thyronine, L-thyronine, 3,5-di-iodo-L-tyrosine, 3-iodo-L-tyrosine and l-tyrosine. Analysis was performed on an Inertsil C(18) column with photodiode-array detection, using a 25 min gradient scale program of a binary mobile phase consisted of 0.1% aqueous solution of trifluoroacetic acid at pH 3 as solvent A and acetonitrile as solvent B, at a flow rate of 1 mL/min. Quantitation was performed using were obtained using theophylline as internal standard. The method was applied to commercial pharmaceuticals and biological samples (serum, urine and tissue). Drug-free urine and serum samples were spiked with known concentrations of the analytes standards and pretreated by solid phase extraction to remove matrix interferences. C(18) cartridges were used, yielding recoveries ranging from 87.1% to 107.6% for serum samples and from 92.1% to 98.7% for urine samples. With regard to total-T(4) concentrations in serum samples, results are cross-validated with RIA and found to agree well.

Chromatography, High Pressure Liquid↗
PubMed2005

Simultaneous determination of phenytoin and dextromethorphan in urine by solid-phase extraction and HPLC-DAD.

A rapid and simple high-performance liquid chromatographic method with photodiode array detection was developed for the separation and the simultaneous determination of phenytoin and dextromethorphan in human urine. Analysis was performed in less than 4.5 min in isocratic mode on a reversed-phase C18 column (5 microm; 150 x 4.6 mm) using a mobile phase composed of acetonitrile-buffer phosphate 0.01 M (60:40, v/v) adjusted to pH 6.0, at 1 mL/min flow rate and UV absorbance at 210 nm. The elution order of analytes was dextromethorphan (DXM), Internal Standard (IS), and phenytoin (PHT). Calibration curves were linear in the 7.5-25 microg/mL range for PHT and in the 10-30 microg/mL range for DXM. Spike recoveries for urine samples prepared at three spiking levels ranged from 97.8 to 102.3% for PHT and from 94.8 to 100.4% for DXM. The detection limit (LOD) values ranged from 0.08 microg/mL for PHT to 0.5 microg/mL for DXM. The quantitation limit (LOQ) values ranged from 0.3 microg/mL for PHT to 1.6 microg/mL for DXM. The sample preparation method involves a rapid and simple procedure based on solid-phase extraction using a C18 reversed-phase column. Validation of the optimised method was carried out according to the ICH guidelines. The method developed in this study allows the reliable simultaneous analysis of PHT and DXM, drugs that were never quantified together in previously reported analytical methods. The described method has the advantage of being rapid and easy and it could be applied in therapeutic monitoring of these drugs in human urine of epileptic patients.

Anticonvulsants↗
PubMed2005

Automated solid-phase extraction and high-performance liquid chromatographic determination of nitrosamines using post-column photolysis and tris(2,2'-bipyridyl) ruthenium(III) chemiluminescence.

A sensitive and selective post-column detection system for nitrosamines is described. The principle upon which the detector works is that UV irradiation of aqueous solutions of nitrosamines leads to cleavage of the N-NO bond. The amine generated is subsequent detected by chemiluminescence using tris(2,2'-bipyridyl) ruthenium(III), which is on-line generated by photo-oxidation of the ruthenium(II) complex in the presence of peroxydisulfate. Factors affecting the photochemical and chemiluminescent reactions were optimized to minimise their contribution to the total band-broadening. This detection system was tested for N-nitrosodimethylamine, N-nitroso-diethylamine, N-nitrosomorpholine, N-nitrosopiperidine and N-nitrosopyrrolidine, which were separated on an ODS column by isocratic reversed-phase chromatography with acetonitrile-water containing 5 mM acetate buffer at pH 4.0. A linear relationship between analyte concentration and peak area was obtained within the range 0.13-500 microg l(-1) with correlation coefficients greater than 0.9995 and detection limits of between 0.03 and 0.76 microg l(-1). Intra- and inter-day precision values of about 1.2% RSD (n = 11) and 2.5% RSD (n = 10), respectively, were obtained. The sensitivity may increase from 9 to 280 times with respect to UV detection, depending on the nitrosamine in question. An automated solid-phase extraction (SPE) system was used in conjunction with HPLC to determine nitrosamine residues in waters. Detection limits within the range 0.10-3.0 ng l(-1) were achieved for only 250 ml of sample.

2,2'-Dipyridyl↗
PubMed2007

A solid-phase extraction method for high-performance liquid chromatographic determination of salvianolic acid B in rabbit plasma: application to pharmacokinetic study.

A sensitive solid-phase extraction/high-performance liquid chromatographic method with ultraviolet detection was established for the analysis of salvianolic acid B in rabbit plasma. The analyte was separated on a reversed-phase column with trifluoroacetic acid-methanol-acetonitrile (70:10:20, v/v/v) as mobile phase at a flow rate of 1 mL/min, and ultraviolet detection at 315 nm. The calibration curve for salvianolic acid B was linear over the range 35-1400 microg/L with coefficients of correlation >0.999. The inter-day and intra-day precisions of analysis were <15%, and assay accuracy ranged from 95.3 to 109.1%. This method is suitable for determining salvianolic acid B in plasma and thus investigating the pharmacokinetics of salvianolic acid B.

Animals↗
PubMed2003

Aminopropyl solid phase extraction and 2 D TLC of neutral glycosphingolipids and neutral lysoglycosphingolipids.

Methods for isolation of neutral lysoglycosphingolipids (n-lyso-GSLs) such as glucosylsphingosine and galactosylsphingosine normally involve mild alkaline or acid hydrolysis followed by multiple chromatography steps, yielding relatively low recoveries of n-lyso-GSLs and neutral glycosphingolipids (n-GSLs). We now describe a new technique for isolating these compounds using one chromatography step, resulting in quantitative recovery of n-GSLs and n-lyso-GSLs. Lipids are extracted using a modified Folch procedure in which recovery is optimized by reextracting the Folch upper phase with water-saturated butanol. The extract is applied to an aminopropyl solid phase column from which both n-GSLs and n-lyso-GSLs elute in the same fraction. Separation is achieved using a new two-dimensional thin-layer chromatography procedure. The usefulness of this technique for biological samples was tested by examining Glc[4,5-(3)H]ceramide and Glc[4,5-(3)H]sphingosine accumulation in metabolically-labeled neurons treated with an inhibitor of lysosomal glucocerebrosidase. Accurate quantification of both lipids was obtained with Glc[4,5-(3)H]ceramide and Glc[4,5-(3)H]sphingosine accumulating at levels of 20 nmol/mg DNA and 40 pmol/mg DNA, respectively. This simple and rapid technique can therefore be used for the analysis of lyso-GSLs and GSLs in the same tissue, which may permit the determination of their metabolic pathways in normal and in pathological tissues, such as those taken from Gaucher and Krabbe's disease patients.

Animals↗
PubMed1992

High-performance liquid chromatographic determination of spironolactone and its metabolites in human biological fluids after solid-phase extraction.

A simple and sensitive high-performance liquid chromatographic procedure to determine spironolactone and its three major metabolites in biological specimens is described. The assay involves sequential extraction on C18 and CN solid phases, and subsequent separation on a reversed-phase column. In plasma samples, spironolactone and its metabolites were completely separated within 8 min using an isocratic mobile phase, while in urine samples a methanol gradient was necessary to achieve a good separation within 14 min. Recoveries for all analytes were greater than 80% in plasma and 72% in urine. Linear responses were observed for all compounds in the range 6.25-400 ng/ml for plasma and 31.25-2000 ng/ml for urine. The plasma and urine methods were precise (coefficient of variation from 0.8 to 12.5%) and accurate (-12.1% to 7.4% of the nominal values) for all compounds. The assay proved to be suitable for the pharmacokinetic study of spironolactone in healthy human subjects.

Chromatography, High Pressure Liquid↗
PubMed1999

A rapid and reliable solid-phase extraction--LC/MS/MS assay for the determination of two novel human leukocyte elastase inhibitors, SYN-1390 and SYN-1396, in rat plasma.

A rapid and rugged solid-phase extraction-liquid chromatographic-electrospray tandem mass spectrometric method has been developed to quantitate two novel human leukocyte elastase inhibitors, SYN-1390 and SYN-1396, in rat plasma. A reversed-phase column and an isocratic mobile phase consisting of acetonitrile-water-formic acid (70:30:0.2, v/v/v) were used. The mass spectrometer was operated in the multiple reaction monitoring mode. For both analytes, standard curves were linear over a working range of 0.1-20 microg ml(-1) (r> or =0.995) and the limit of quantitation was 0.1 microg ml(-1) with a 150 microl plasma volume. This assay proved to be useful for the determination of SYN-1390 and SYN-1396 in plasma samples from pharmacokinetic study.

Animals↗
PubMed2006

Resolution of an intense sweetener mixture by use of a flow injection sensor with on-line solid-phase extraction. Application to saccharin and aspartame in sweets and drinks.

An integrated solid-phase spectrophotometry-FIA method is proposed for simultaneous determination of the mixture of saccharin (1,2-benzisothiazol-3(2H)-one-1,1-dioxide; E-954) (SA) and aspartame (N-L-alpha-aspartyl-L-phenylalanine-1-methyl ester; E-951) (AS). The procedure is based on on-line preconcentration of AS on a C18 silica gel minicolumn and separation from SA, followed by measurement, at lambda = 210 nm, of the absorbance of SA which is transiently retained on the adsorbent Sephadex G-25 placed in the flow-through cell of a monochannel FIA setup using pH 3.0 orthophosphoric acid-dihydrogen phosphate buffer, 3.75x10(-3) mol L(-1), as carrier. Subsequent desorption of AS with methanol enables its determination at lambda = 205 nm. With a sampling frequency of 10 h(-1), the applicable concentration range, the detection limit, and the relative standard deviation were from 1.0 to 200.0 microg mL(-1), 0.30 microg mL(-1), and 1.0% (80 microg mL(-1), n = 10), respectively, for SA and from 10.0 to 200.0 microg mL(-1), 1.4 microg mL(-1), and 1.6% (100 microg mL(-1), n = 10) for AS. The method was used to determine the amounts of aspartame and saccharin in sweets and drinks. Recovery was always between 99 and 101%. The method enabled satisfactory determination of blends of SA and AS in low-calorie and dietary products and the results were compared with those from an HPLC reference method.

Aspartame↗
PubMed2001

[Advances in the fiber coating of solid phase micro-extraction].

Solid phase micro-extraction (SPME) is a simple and effective sample preparation technique and fiber coatings play a very important role in SPME process. The discussion begins with a brief historical perspective from the very early work conducted almost a decade ago. At the moment, more than 20 alternatives of fiber coatings and size are available. In this paper, the coatings are divided into two categories: commercial fibers and custom-made fibers. A novel so-gel method has been introduced for the preparation of the coatings.

Adsorption↗
PubMed1986

Solid-phase extraction and high-performance liquid chromatography analysis of lipoxygenase pathway products.

Liquid chromatography methods for quantitation of leukotrienes and HETEs (hydroxyeicosatetraenoic acids) in biological samples are described. Extraction is accomplished by acetonitrile precipitation of proteins followed by selective acetonitrile elution from a solid-phase C18 extraction cartridge. Isocratic elution of extracts from short reverse-phase columns with 3 microns C18-bonded silica results in elution of all components of interest in less than 10 min. The addition of the mobile-phase additives, trifluoroacetic acid and triethylamine, enable the peptido-leukotrienes to be eluted with excellent peak shape and unique elution times. As little as 1 pmol of each metabolite can be detected by uv spectrophotometry with a wavelength change from 280 to 235 nm midway through the chromatographic run. This method is demonstrated by the extraction and analysis of leukotriene and HETE standards from human serum.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed2002

Determination of the angiotensin-converting enzyme inhibitor quinapril and its metabolite quinaprilat in pharmaceuticals and urine by capillary zone electrophoresis and solid-phase extraction.

Quinapril is an antihypertensive drug commonly used in the treatment of hypertension and congestive heart failure. In this work, a capillary zone electrophoresis system is optimized for the analysis of quinapril and its active metabolite quinaprilat in urine, as well as for the determination of the drug and its combination with hydrochlorothiazide in pharmaceuticals. The separation takes place in a fused-silica capillary. The running electrolyte consists of a 60 mM borate buffer solution, pH 9.5. The analysis of urine samples requires a previous extraction step using C8 solid-phase cartridges. Under the optimum experimental conditions, the separation of the two analytes and the internal standard takes less than 5 min. The detection limits obtained (75 and 95 ng/mL for quinapril and quinaprilat, respectively) allow the application of the electrophoretic method to the determination of the drug and its metabolite in urine samples obtained from four patients treated with quinapril.

Adult↗
PubMed2007

Solid phase extraction as a faster alternative to HPLC: application to MS analysis of metabolic stability samples.

Due to recent advances in high throughput organic synthesis, discovery teams now need to profile increased numbers of analogs in vitro for their absorption, distribution, metabolism, and excretion (ADME) properties. Consequently, pharmaceutical companies are developing lower cost and higher throughput methods for ADME testing. As demands for metabolic stability testing have increased in our laboratory, the time required to analyze samples using high-pressure liquid chromatography-mass spectrometry (HPLC-MS) has grown rapidly and ultimately limited our data output. In this study we show that solid phase extraction-mass spectrometry (SPE-MS) is a viable alternative to HPLC-MS for monitoring small molecule stability in liver microsomes. Using the SPE-MS approach, samples can be analyzed in 24 s compared to 2.5 min on the HPLC-MS without compromising data quality, thereby alleviating the analytical bottleneck.

Animals↗
PubMed2006

Solid phase extraction of lead on octadecyl bonded silica membrane disk modified with Cyanex302 and determination by flame atomic absorption spectrometry.

A simple, reliable and rapid method for preconcentration and determination of lead using octadecyl bonded silica membrane disk impregnated with Cyanex302 and flame atomic absorption spectrometry is presented. The influence of aqueous phase pH, type of eluent, flow rates of sample solution and eluent, volume of eluent and amount of extractant has been investigated. The break through volume is greater than 4.0 dm(3) with an enrichment factor of more than 400 and a detection limit of 1.0microg dm(-3). The method developed for determination of lead is good as six replicate determinations using 100cm(3) solution containing lead in the range 1-4900microg provides a relative standard deviation (R.S.D.) of 0.4%. The selectivity of the proposed method was confirmed from the interference studies. The developed procedure was successfully applied for the determination of lead in spiked sea water, USGS standard soil sample, sludge and industrial effluents, medicinal formulation, plant, some food products and wine.

Adsorption↗
PubMed2006

A new solid phase extraction clean-up method for the determination of 12 type A and B trichothecenes in cereals and cereal-based food by LC-MS/MS.

A new reliable and cost-efficient solid phase extraction-based clean-up method for the determination of 12 type A and B trichothecenes [deoxynivalenol (DON), nivalenol, 3-acetyldeoxynivalenol, 15-acetyldeoxynivalenol, fusarenon-X, T-2 toxin, HT-2 toxin, neosolaniol, monoacetoxy-scirpenol, diacetoxyscirpenol, T-2 triol and T-2 tetraol] in cereals and cereal-based food is presented. Furthermore, the suitability for the simultaneous determination of zearalenone is examined. Toxins were extracted from cereal samples using ACN/water (80/20, v/v), purified by means of a new Bond Elut Mycotoxin column and analyzed via liquid chromatography-electrospray ionization tandem mass spectrometry. Limits of detection were calculated for the matrix wheat and ranged from 0.3 to 5 ng/g, depending on the toxin. Average recovery rates for the tested compounds in seven cereal-based matrices have been determined ranging from 65 to 104%. The relative standard deviations of the complete method ranged from 2.67 (DON, wheat) to 20.0% (T-2 toxin, oats).

Chromatography, Liquid↗
PubMed1991

Determination of a novel steroidal androgen receptor antagonist (Win 49596) in human plasma using solid-phase extraction and high-performance liquid chromatography with ultraviolet detection.

A rapid, sensitive and selective method was developed for the determination of a novel steroidal androgen receptor antagonist (Win 49596, I) in human plasma. The procedure involved extraction from plasma using a solid-phase phenyl support and elution directly onto a reversed-phase C8 column using a mobile phase consisting of 0.2 mol/l sodium acetate buffer at pH 7-acetonitrile (45:55, v/v). Drug was monitored by ultraviolet detection at a wavelength of 238 nm. Linear responses were observed for standards over the range 0.01-5.0 micrograms/ml. The minimum quantifiable level was 0.02 microgram/ml, using a 0.5-ml plasma sample. The precision was 5.5% and the accuracy ranged from -9.4% to 0.23%. The analytical method has been used to quantify I in plasma from dogs and rats and is projected for use with human plasma from clinical trials.

Androgen Antagonists↗