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PubMed2003

A simple method for nicardipine hydrochloride quantification in plasma using solid-phase extraction and reversed-phase high-performance liquid chromatography.

A simple and sensitive reversed-phase liquid chromatography method was developed and validated for the determination of nicardipine hydrochloride (NC) in rabbit plasma. Nicardipine hydrochloride and nimodipine, used as internal standard, were initially extracted from plasma by a rapid solid-phase extraction using C(18) cartridges. After extraction, nicardipine hydrochloride was separated by HPLC on a C(18) column and quantified by ultraviolet detection at 254 nm. A mixture of acetonitrile-0.02 M sodium phosphate buffer-methanol (45:40:15) with 0.2% of triethylamine of pH of 6.1 was used as mobile phase. The mean (+/-SD) extraction efficiency of NC was 77.56 +/- 5.4, 84.23 +/- 4.32 and 83.94 +/- 3.87% for drug concentrations of 5, 25 and 100 ng/mL, respectively. The method proved to be linear in the range of 5-100 ng/mL with a regression coefficient of 0.9993. The relative standard deviations of intra- and inter-day analysis for NC in plasma were 3.26-6.52% (n = 5) and 4.71-9.38% (n = 5), respectively. The differences of the mean value measured from the concentration prepared, expressed in percentages (bias percentage), were only - 5.2, 0.4 and 0.8% at NC 5, 25 and 50 ng/mL, which confirmed the accuracy of the method. The analytical technique was used to determine NC plasma concentration after drug oral administration to rabbits. The results inferred that NC is rapidly absorbed in rabbits and has a short half-life (t(1/2) = 1.34 h).

Administration, Oral↗
PubMed2006

Application of molecularly imprinted polymers to solid-phase extraction of analytes from real samples.

A review is presented of recent developments in the use of molecularly imprinted polymers (MIPs) as selective materials for solid-phase extraction. Compared with traditional sorbents, MIPs can not only concentrate but also selectively separate the target analytes from real samples, which is crucial for the quantitatively determination of analytes in complex samples. Consequently, as one of the most effective sorbents, MIPs have been successfully applied to the pretreatment of analytes in foods, drugs, and biological and environmental samples in the past five years.

Biocompatible Materials↗
PubMed2001

A clinical trial on a plate? The potential of 384-well format solid phase extraction for high-throughput bioanalysis using liquid chromatography/tandem mass spectrometry.

The application of 384-well format solid phase extraction (SPE) for bioanalysis using liquid chromatography/tandem mass spectrometry (LC/MS/MS) is reported and a 384-well SPE method for the 5-HT agonist sumatriptan in human plasma described. Plasma samples were extracted on a prototype low-density polyethylene 384-well SPE block using a packed bed of 5 mg Oasistrade mark HLB. Liquid handling was automated by a combination of a robotic sampler processor and a 96/384 multi-channel dispensing station. Samples and SPE reagents were drawn through the SPE block by centrifugation. The extracts were analysed by LC/MS/MS with thermally and pneumatically assisted electrospray ionisation and selected reaction monitoring. The method is used to illustrate and discuss the feasibility and viability of sample preparation techniques in high-density microtitre plate format for routine bioanalysis.

Blood Chemical Analysis↗
PubMed2001

Determination of trace quaternary ammonium surfactants in water by combining solid-phase extraction with surface-assisted laser desorption/ionization mass spectrometry.

This study demonstrates the feasibility of combining solid-phase extraction (SPE) with surface-assisted laser desorption/ionization (SALDI) mass spectrometry to determine trace quaternary ammonium surfactants in water. The trace surfactants in water were directly concentrated on the surface of activated carbon sorbent in SPE. The activated carbon sorbent was then mixed with the SALDI liquid for SALDI analysis. No SPE elution procedure was necessary. Experimental results indicate that the surfactants with longer chain alkyl groups exhibit higher sensitivities than those with shorter chain alkyl groups in SPE-SALDI analysis. The detection limit for hexadecyltrimethylammonium bromide is around 10 ppt in SPE-SALDI analysis by sampling 100 mL of aqueous solution, while that of tetradecyltrimethylammonium bromide is about 100 ppt. The detection limit for decyltrimethylammonium bromide and dodecyltrimethylammonium bromide is in the low-ppb range.

Indicators and Reagents↗
PubMed1993

Evaluation of a solid-phase extraction system for determining pesticide residues in milk.

A simple and rapid procedure based on reversed solid-phase extraction with octadecylsilica was developed for determining chlorinated pesticide residues in milk. The need for an agent that breaks the fat globules was first investigated and the method variables were optimized on whole homogenized milk (3.6% fat content). Recovery experiments performed for 26 organochlorine pesticides at levels of 3-40 micrograms/l gave > 80% recoveries for all the compounds. The method was validated and evaluated by comparison with two widely used liquid-liquid extraction methods. The performance was checked by analysis of a certified standard with natural low endogenous levels (CMR 187) and different kinds of milk (skimmed, 2%, powdered, evaporated and condensed) spiked with the 26 pesticides. The procedure was used to analyse 45 commercial milks in which the presence of organochlorine residues had been detected. The proposed method offers advantages such as low cost and simplicity and the fact that the extracts obtained do not require a purification step.

Animals↗
PubMed1993

Application of solid-phase extraction in the determination of U-82217 in rat serum, urine and brain.

The techniques of solid-phase extraction (SPE) were applied in the analytical method development for the determination of U-82217, 3-(5-cyclopropyl-1,2,4-oxadiazol-3-yl)-5-[(4-methoxyphenyl)methyl] -imidazo[1,5-a]quinoxalin-4(5H)-one, in rat serum, urine and brain. Samples of serum, urine or brain homogenate containing U-82217 were loaded on C18 SPE columns and eluted with acetonitrile (300 microliters). The prepared samples were analyzed by reversed-phase HPLC using an ODS column with a mobile phase of acetonitrile-water (45:55, v/v) containing 0.12% of acetic acid (pH 6.0 +/- 0.1). The UV absorbance of the column effluent was monitored at a wavelength of 318 nm. The absolute extraction recovery from serum, urine and brain samples was ca. 90%. Linear calibration graphs were obtained over the ranges 5 ng/ml-20 micrograms/ml (serum), 20 ng/ml-20 micrograms/ml (urine) and 50 ng/g-200 micrograms/g (brain). The intra- and inter-assay precision and accuracy were all found to be < 13% at the concentrations evaluated. The strategy in SPE development and the application of this method to the determination of U-82217 in rat serum and brain for a pharmacokinetic study are also discussed.

Animals↗
PubMed1995

Solid-phase extraction on C18 in the trace determination of selected polychlorinated biphenyls in milk.

The utility of solid-phase extraction with octadecylsilica for determining fifteen polychlorinated biphenyl (PCB) congeners from milk samples was examined. Recoveries higher than 80% and relative standard deviations better than 10% were obtained for PCBs from different kinds of milk (whole, skimmed, 2%, powdered, breast and evaporated). A comparison with other procedures was made. The described method provides better detection limits than those attainable with the liquid-liquid extractions currently used as standard methods, when capillary gas-liquid chromatography is used for the final determination. A study of the separation was also performed using six different fused-silica capillary columns and an electron-capture detector.

Animals↗
PubMed1996

High-performance liquid chromatographic determination of penicillins by means of automated solid-phase extraction and photochemical degradation with electrochemical detection.

An automated precolumn exchange system for on-line solid-phase extraction (OPS-2) coupled to liquid chromatography with photochemical degradation and electrochemical detection was used for the determination of residual amounts of penicillin G, penicillin V, oxacillin, cloxacillin and dicloxacillin. A 5-10-fold increase in sensitivity was obtained when compared with direct UV detection of penicillins at 225 nm. The system is recommended for samples that have received an immunoaffinity clean-up. Analysis of bovine muscle tissue indicated, however, that this procedure could also be suitable for the determination of penicillin G at its maximum residue limit of 50 micrograms/kg even with conventional solvent partitioning for the first clean-up steps.

Animals↗
PubMed1991

Determination of 6-chloro-3-(3-cyclopropyl 1,2,4-oxadiazol-5-yl)-5-methyl-imidazo less than 1,5-a greater than-quinoxalin-4(5h)-one in rat serum, urine and brain by solid-phase extraction and liquid chromatography.

A simple, rapid, and accurate liquid chromatographic method with ultraviolet detection and solid-phase extraction is described for the quantitation of 6-chloro-3-(3-cyclopropyl 1,2,4-oxadiazol-5-yl)-5-methyl-imidazo less than 1,5-a greater than-quinoxalin-4(5h)-one (I, U-80447) in rat serum, urine and brain. Linear calibration curves were obtained in the concentration ranges of 5 ng ml-1-20 micrograms ml-1 (serum), 20 ng ml-1-20 micrograms ml-1 (urine), and 50 ng g-1-200 micrograms g-1 (brain). Intra- and inter-assay precision and accuracy were all found to be less than 10% at the three concentrations evaluated. The absolute extraction recovery each from serum, urine and brain was greater than or equal to 90%. Application of this method to the quantitation of the title compound in rat serum and brain for a pharmacokinetic study is reported.

Animals↗
PubMed2005

Application of solid-phase extraction to quantitatively determine cyproconazole and tebuconazole in treated wood using liquid chromatography with UV detection.

Solid-phase extraction (SPE) procedures were developed to avoid interference during the quantitative determination of cyproconazole and tebuconazole co-existing in wood extractives. Five species of wood were used, Japanese cedar (Cryptomeria japonica), Japanese larch (Larix leptolepis), Yezo spruce (Picea jezoensis), Sakhalin fir (Abies sachalinensis), and western hemlock (Tsuga heterophylla). Methanol extractives from the heartwood of all wood samples, except western hemlock, interfered with the quantitative determination of cyproconazole and tebuconazole using liquid chromatography (LC) with UV detection (LC-UV). SPE with Oasis MCX was effective in avoiding this interference. This method also reduced the time and volume of mobile phase required for LC-UV, since wood extractives with long retention times were also removed.

Chromatography, Liquid↗
PubMed2003

Determination of metformin in plasma using a new ion pair solid phase extraction technique and ion pair liquid chromatography.

This article describes the development of the first ion pair solid phase extraction technique (IPSPE), which has been applied to the extraction of metformin from plasma samples. In addition an ion pair chromatographic method was developed for the specific HPLC determination of metformin. Several extraction and HPLC methods have been described previously for metformin, however, most of them did not solve the problems associated with the high polarity of this drug. Drug recovery in the developed method was found to be more than 98%. The limit of detection and limit of quantification was 3 and 5 ng/ml, respectively. The intraday and interday precision (measured by coefficient of variation, CV%) was always less than 9%. The accuracy (measured by relative error, R.E.%) was always less than 6.9%. Stability analysis showed that metformin is stable for at least 3 months when stored at -70 degrees C. The method has been applied to 150 patient samples as part of a medication adherence study.

Chromatography, High Pressure Liquid↗
PubMed2005

A solid phase extraction procedure for indium prior to its graphite furnace atomic absorption spectrometric determination.

A procedure based on solid phase extraction of indium ions at trace level on Chromosorb 108 resin as bathocuproinedisulfonic acid chelate is presented for its preconcentration. The optimum pH value for quantitative sorption is 8.0-9.0, and desorption can be achieved by using 10.0 ml of 2 M HNO3. The effects of diverse ions on the sorption and recovery of indium have been studied. The capacity of sorbent was 3.78 mg In/g resin. Recoveries for indium from water samples were in the range 95-105%. The accuracy of procedure was confirmed by indium determination in certified reference materials. The method developed was applied with varying results to the analysis of real samples including metallic zinc with satisfactory results.

Indium↗
PubMed2000

Comparison of different sorbent materials for on-line solid-phase extraction with liquid chromatography-atmospheric pressure chemical ionization mass spectrometry of phenols.

On-line solid-phase extraction (SPE) was interfaced to liquid chromatography with atmospheric pressure chemical ionization mass spectrometry (HPLC-APCI-MS) for the determination of US Environmental Protection Agency (EPA) phenols. The system, allowing fully automated operation, was used to evaluate different SPE cartridge materials and dimensions. Six different SPE materials (C18 HD, Polymer Labs PLRP-s, Hamilton PRP-1, Hysphere GP, Hysphere SH and Waters Oasis) were tested. Criteria for their comparison were first the recovery for the different phenols and its reproducibility, but also chromatographically relevant items like peakshape in the on-line elution mode. High recoveries and good relative standard deviations were obtained particularly for the newer, strongly retaining SPE materials that have become commercially available recently (the Hysphere materials and Waters Oasis) compared to the well known silica-based and weaker polymeric adsorbents like PLRP-s and PRP-1. These advantages are, however, traded in for good chromatographic peakshape, since the stronger adsorbents give rise to notable peak broadening in on-line elution. This is particularly true when using APCI-MS detection which on the one hand offers excellent selectivity and sensitivity, but imposes additional restrictions on the mobile phase composition in order not to suppress the response significantly. The influence of these parameters on the on-line-SPE-HPLC-MS determination of EPA phenols is discussed and present limitations are pointed out.

Atmospheric Pressure↗
PubMed2000

Solid-phase extraction coupling to capillary electrophoresis with emphasis on environmental analysis.

This article reviews the status of solid-phase extraction (SPE) coupled with capillary electrophoresis (CE). It focuses on some of the organic pollutants which have captured the interest of analytical chemists--phenols, surfactants, dyes, polynuclear aromatic hydrocarbons (PAHs), aromatic and aliphatic amines, aromatic acids and aromatic sulfonic acids--and, in particular, on monitoring pesticides from different sources. It shows that the coupling of SPE to CE has considerable potential in the analysis of environmental pollutants.

Amines↗
PubMed1998

Gas chromatographic determination of aromatic amines in water samples after solid-phase extraction and derivatization with iodine. II. Enrichment.

A procedure for the enrichment of aromatic amines via solid-phase extraction was developed. A HR-P phase based on styrene-divinylbenzene was used for the investigations, generally followed by derivatization with iodine and determination via GC-ECD. The recoveries of 53 aromatic amines in a drinking water matrix at pH 9 were determined. Most anilines showed relative recoveries between 80-120% with relative standard deviations of< or = 5% at concentration levels between 10 and 20 micrograms 1(-1). The comparison with a wastewater matrix led to similar results. The enrichment procedure was applied to real samples, e.g., samples of ammunition wastewater.

Amines↗
PubMed1999

Semi-automated solid-phase extraction procedure for the high-performance liquid chromatographic determination of alinastine in biological fluids.

A solid-phase extraction (SPE) method for sample clean-up followed by a reversed-phase HPLC procedure for the assay of alinastina (pINN) in biological fluids is reported. The effects of the sample pH, composition of the washing and elution solvents and the nature of the SPE cartridge on recovery were evaluated. The selectivity of SPE was examined using spiked rat urine and plasma samples and the CH and PH cartridges gave rise to the cleanest extracts. The recoveries obtained in spiked rat urine and plasma samples were 91.2+/-2.7 and 99.9+/-2.8%, respectively. The proposed SPE method coupled off-line with a reserved-phase HPLC system with fluorimetric detection was applied to the quantitation of alinastine in real rat urine samples. The analytical method was also applied and validated for the determination of alinastine in dog plasma. The recovery from spiked dog plasma samples using the PH cartridge was around 65%. The within-day and between-day precisions were 7 and 12%, respectively. The detection and quantitation limits in dog plasma were 0.024 and 0.078 microg/ml, respectively.

Animals↗
PubMed2004

Immunoaffinity solid-phase extraction for pharmaceutical and biomedical trace-analysis-coupling with HPLC and CE-perspectives.

Immunoaffinity solid-phase extraction (SPE) technique is based upon a molecular recognition mechanism. The high affinity and the high selectivity of the antigen-antibody interactions allow the specific extraction and the concentration of the analytes of interest in one step. In pharmaceutical and biological fields, where most often matrices are complex and analytes at trace-levels, this approach constitutes a unique tool for fast and solvent-free sample preparation. This review presents a general description of this extraction technique and gives numerous examples of its applications in pharmaceutical and biomedical fields. It emphasizes the on-line coupling with chromatographic and electrophoretic separation techniques and introduces new developments. The future directions, especially with regards to the current development of analytical microsystems, are discussed.

Antibodies↗
PubMed2003

On-line coupling of solid-phase extraction with mass spectrometry for the analysis of biological samples. III. Determination of prednisolone in serum.

Solid-phase extraction (SPE) was directly coupled to mass spectrometry (MS) to assess the feasibility of the system for the rapid determination of prednisolone in serum. A C(18) stationary phase allowed washing of the cartridge with 25% methanol. Elution was performed by switching the methanol percentage from 25% in the washing step to 50% during elution. The high flow-rates during the extraction (5.0 ml/min) combined with ion-trap MS detection resulted in a total analysis time of 4 min. Some tailing of the prednisolone peak was observed. However, the tailing was found acceptable, since by this elution procedure most matrix compounds were prevented from eluting from the cartridge. Some matrix interference was still observed with a triple-quadrupole MS, even in the multiple reaction monitoring mode. This resulted in a detection limit (LOD) of about 10 ng/ml. The matrix interference and the LOD were similar for atmospheric pressure chemical ionisation and atmospheric pressure photo ionisation. Applying an ion-trap MS in the MS-MS mode resulted in cleaner chromatograms. Due to extensive fragmentation of prednisolone, the LOD was not lower than about 5 ng/ml prednisolone in serum, and a limit of quantitation of about 10 ng/ml (relative standard deviation <15%) was observed.

Glucocorticoids↗