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PubMed2003

Sample preparation for routine high-performance liquid chromatographic determination of retinol palmitate in emulsified nutritional supplements by solid-phase extraction using monosodium L-glutamate as dissolving agent.

Retinol palmitate (vitamin A, 73.3 microg/g) in an emulsified nutritional supplement was determined by solid-phase extraction (SPE) and high-performance liquid chromatography (HPLC) with fluorescence detection (excitation 350 nm, emission 480 nm) using monosodium L-glutamate as a dissolving agent to obtain higher recovery of vitamin A from the emulsified sample solution. A Bond Elut C2 cartridge (500 mg) was chosen for SPE after comparison with 16 other types. A sample solution was applied to a conditioned Bond Elut C2 cartridge and then vitamin A was eluted with ethanol followed by HPLC. The proposed method was simple, rapid (sample preparation time by SPE: ca. 8 min, retention time: ca. 8 min), sensitive [detection limit: ca. 0.1 pg/injection (100 microl) at a signal-to-noise ratio of 3:1], highly selective and reproducible (relative standard deviation (RSD): ca. 2.9% (n = 5), between-day RSD ca. 3.7 (5 days). The recovery of vitamin A was over 90% by the standard addition method.

Chromatography, High Pressure Liquid↗

PubMed1997

Liquid chromatography-mass spectrometry with on-line solid-phase extraction by a restricted-access C18 precolumn for direct plasma and urine injection.

In this paper, the on-line coupling of solid-phase extraction, based on a restricted-access support with liquid chromatography-mass spectrometry (LC-MS), for the analysis of biological samples is described. The system was tested with cortisol and prednisolone for plasma analysis and arachidonic acid for urine analysis. A precolumn packed with a 25-micron C18 alkyl-diol support is used for direct plasma or urine injection. Using column-switching techniques, the analytes enriched on the precolumn are eluted to the analytical column without transfer loss. An on-line heart-cut technique was employed and only the analyte-containing fraction eluting from the LC column is directed to the MS to protect the LC-MS interface and ion-source from contamination. The whole system is operated in a parallel mode, that is, sample pre-treatment and LC-MS analysis are performed simultaneously to provide the shortest possible analysis time. The only off-line sample pre-treatment step required was centrifugation to remove particulate matter. With the fully automated system, total analysis times of 5 and 9.5 min were achieved for cortisol in serum and arachidonic acid in urine, respectively. Cortisol and related compounds were quantitatively recovered from plasma with a detection limit for prednisolone (direct injection of 100 microliters on restricted-access precolumn) of 2 ng/ml.

Arachidonic Acid↗

PubMed1999

On-line coupling of solid-phase extraction with mass spectrometry for the analysis of biological samples. I. Determination of clenbuterol in urine.

The potential of the direct coupling of solid-phase extraction (SPE) with mass spectrometry (MS) for the analysis of biological samples is demonstrated. For SPE a cartridge exchanger is used and the eluate is directly introduced into the mass spectrometer. This system has been investigated for the determination of clenbuterol in urine. With mixed-mode cartridges, a considerable ion suppression has been obtained. The mass spectrum at the elution time of clenbuterol is dominated by that of creatinine and adduct formation of clenbuterol and creatinine has been observed. The whole procedure including injection of 1 ml urine, washing and desorption has been developed with cartridges containing 8-microm C18-bonded silica. If only a single MS step is used, the selectivity and, therefore, the sensitivity are insufficient. The detection limit is about 100 ng/ml. However, with atmospheric pressure chemical ionisation and the tandem MS mode the detection limit has been decreased to about 2 ng/ml and the ion suppression is only about 10%. For the electrospray ionisation the detection limit is about 10-times higher and the ion suppression is less favourable. The repeatability for the SPE-MS-MS procedure was 6.5% at 10 ng/ml (n=5) and the difference between the response factors at 10 ng/ml and 100 ng/ml was only 2.5%. The MS behaviour of clenbuterol and the matrix under the present conditions is discussed.

Adrenergic beta-Agonists↗

PubMed2003

LC-MS method for the determination of albuterol enantiomers in human plasma using manual solid-phase extraction and a non-deuterated internal standard.

A sensitive enantioselective liquid chromatography-mass spectrometry (LC-MS) assay using a manual solid-phase extraction (SPE) procedure, a non-deuterated internal standard and an ion trap LC-MS was developed to measure (R)- and (S)-albuterol in plasma. Sample extraction from plasma was achieved by a manual SPE extraction procedure with methoxyphenamine added as the internal standard. Chiral separation was achieved using a teicoplanin-based stationary phase and a mobile phase consisting of methanol, acetic acid and 28% (w/v) ammonia (1000:5:1, v/v/v). Samples were analyzed by selected reaction monitoring of product ions from the protonated molecular ions. The detection limit of the assay was 0.1 ng/ml with a conservative lower limit of quantification of 0.25 ng/ml for each enantiomer. Recovery of albuterol enantiomers from plasma spiked at 10 ng/ml of racemate was determined to be 89+/-5.8% (mean+/-S.D.). Reproducibility at 10 ng/ml of racemate assessed by the coefficient of variation was found to be 6.5% (n=5). Instrument precision (measured as coefficient of variation) was 1.4% (n=5). The correlation coefficient r(2) determined from the calibration curve over the range 0.5-50.0 ng/ml racemate in plasma was 0.998. This assay allows adequate sensitivity, recovery and reproducibility for the application to studies of inhaled albuterol.

Albuterol↗

PubMed2002

Determination of methylnaltrexone in clinical samples by solid-phase extraction and high-performance liquid chromatography for a pharmacokinetics study.

A high-performance liquid chromatographic (HPLC) method with electrochemical detection and solid-phase extraction (SPE) using cartridges of weak cation-exchange capacity as the primary retention mechanism is described for the separation and determination of methylnaltrexone (MNTX) in small clinical samples of plasma or urine. The procedure was performed using a Phenomenex Prodigy ODS-2, 5 microm, 150x3.2 mm analytical column and 50 mM potassium acetate buffer, with 11% methanol as organic modifier at pH* 4.5 at a flow-rate of 0.5 ml/min. The detection potential was 700 mV. The six-point standard calibration curves were linear over three consecutive days in the range from 2 to 100 ng/ml. The average goodness of fit (r) was 0.9993. The lower limit of detection (LOD) and limit of quantification (LOQ) were found to be 2.0 and 5.0 ng/ml, respectively. At the LOQ, the coefficient of variation for the entire method was 8.0% and the accuracy was 10.0% (n = 10). Recovery of the drug from plasma was in the region of 94%. The method was applied to a pharmacokinetics study of methylnaltrexone after subcutaneous administration and in numerous assays of analytes in blood plasma and urine. The pharmacokinetics parameters for a single dose of 0.1 or 0.3 mg/kg in plasma were C(max) = 110 (+/-55) and 287 (+/-101) ng/ml and t(max) = 16.7 (+/-10.8) and 20.0 (+/-9.5) min, respectively. The method is simple, yet sensitive for the detection and determination of methylnaltrexone in biological samples at the level of the physiological response.

Calibration↗

PubMed1992

Simultaneous determination of some antibacterial drugs in isosensitest broth using high-performance liquid chromatography with solid-phase extraction.

A method is described for the simultaneous determination of combinations of some antibacterial drugs in a matrix of isosensitest broth. A double solid-phase extraction procedure is described in which trimethoprim and dibromopropamidine isethionate together with 4-chlorophenylbiguanide as internal standard are freed from endogenous components by a cation-exchange extraction cartridge and subsequently removed and individually separated by reversed-phase ion-pair chromatography. Sulfadiazine, sulfamerazine and p-aminobenzoic acid, unretained by ion exchange, are similarly isolated for chromatography by adsorption on a CH-bonded phase cartridge and individually assayed using the same chromatographic system. The rationale of the pre-treatment and chromatography is described and the quantitative aspects of the analyses of selected combinations of these drugs are reported.

4-Aminobenzoic Acid↗

PubMedDate not supplied

Mixed-mode solid-phase extraction procedures for the determination of MDMA and metabolites in urine using LC-MS, LC-UV, or GC-NPD.

A solid-phase extraction (SPE) procedure was developed for the liquid chromatographic-mass spectrometric (LC-MS) analysis of 3,4-methylenedioxymethamphetamine (MDMA) and its metabolites 3,4-methylenedioxyamphetamine (MDA) and N,alpha-dimethyl-(3-methoxy-4-hydroxybenzene) (HMMA) ethanamine in urine. The procedure, with modifications, was also demonstrated using LC-UV and GC-nitrogen-phosphorus detection (NPD). A mixed-mode cation exchange SPE cartridge was effective for both reducing matrix impurities and for preconcentrating the analytes for the analysis. The concentration range investigated spanned from 0.10 to 20 microg/mL with recoveries ranging from 88% to 108% for all analytes using LC-MS. Both LC methods and the GC method allow for complete resolution of MDMA, MDA, and HMMA, as well as the internal standards (MDMA-d5 and 3,4-methylenedioxypropylamphetamine) in less than 10 min. Lower limits of quantitation (LLOQ) for the LC-MS method were 0.1 microg/mL for MDMA and MDA and 0.04 microg/mL for HMMA. Compared with LC-UV and GC-NPD, the LC-MS method requires the least amount of sample manipulation and provided the highest sample throughput. GC-NPD gave comparable selectivity, but the extra sample manipulation steps required contributed to lower recovery, lower precision, and increased time for the analysis. LC-MS analysis demonstrated better selectivity for the determination of HMMA in incurred samples compared with LC-UV analysis.

Chromatography, Gas↗

PubMed2006

A larval medaka (Oryzias latipes) acute toxicity assay combined with solid-phase extraction to efficiently determine the toxicity of organic contaminants in river water.

Using a larval medaka (Oryzias latipes) acute toxicity assay combined with solid-phase extraction, we proposed a method for efficiently determining the fish toxicity of organic contaminants in river water. Organic toxicants were 10, 20, 50 and 100-fold concentrated from 4 L of the sample with adsorption cartridges. The lethal effect was observed by exposing every ten individuals of 48-72 h old larval medaka to 20 mL of each solution for 48h. The median lethal concentration rate (LCR50) was used as an indicator for the toxicity. With the developed toxicity test method, more than seven times difference was found in the LCR50 of the river water samples. LCR50 distribution profiles were compared with 125 samples in two typical rivers. The result revealed a lower toxicity level in the mainstream than in the confluences, and a lower toxicity level in Sagami River than in Ayase River. LCR50 proved unique as a toxicity indicator, which was impossible to speculate from the conventional water quality indicator of the dissolved organic carbon concentration. As an effective screening test for priority settings, the method can help us with an efficient planning for the environmental investigation and management.

Animals↗

PubMedDate not supplied

Single laboratory validation of a method for the determination of hydroxymethylfurfural in honey by using solid-phase extraction cleanup and liquid chromatography.

A method is described for the determination of hydroxymethylfurfural (HMF) in honey. The method, which is based on solid-phase extraction cleanup followed by liquid chromatography (LC) with UV absorbance detection, was tested on a variety of different honey types: liquid, set, blended, filtered, crystalline, and comb honey. A sample of honey fortified with a known amount of HMF acted as an in-house reference material. LC with diode-array detection showed that the HMF peak did not contain any peaks of coeluting interfering species. Stability studies showed that honey samples should not be repeatedly frozen and thawed because the temperature changes caused a gradual increase in the HMF concentration. It was also shown that aqueous HMF standard solutions should be kept in the dark at 4 degrees C to avoid degradation of the HMF. The method was internally validated, and the measurement uncertainty was estimated to be +/-9.0 at 40 mg/kg, the legal limit. A comparison of the relative standard uncertainty with the Horwitz relative standard deviation showed that the method was suitable for its purpose and should be validated by a collaborative trial.

Chemistry Techniques, Analytical↗

PubMed1989

A high-performance liquid chromatographic method for the determination of encainide and its major metabolites in urine and serum using solid-phase extraction.

A high-performance liquid chromatography (HPLC) procedure used to quantitate encainide and two of its active metabolites, O-desmethylencainide (ODE) and 3-methoxy-O-desmethylencainide (MODE), is described. All three compounds were simultaneously extracted from urine and serum using an octyl (C-8) solid-phase extraction column. The compounds were then separated by reverse-phase HPLC on a cyanopropylsilane column using ultraviolet detection at 260 nm. Serum samples were quantified over a concentration range of 25-400 ng/ml and urine over a range of 150-10,000 ng/ml. Total run time for the assay was less than 12 min. Within-day and between-day precision and relative error were less than 10% in serum and less than 13% in urine for all three compounds. The lower limit of quantitation was 10 ng/ml for encainide and ODE and 15 ng/ml for MODE. This HPLC procedure represents a quick and reliable method of measuring encainide and its major metabolites in both urine and serum, making the assay applicable as an aid for therapeutic drug monitoring of patients receiving encainide therapy.

Anilides↗

PubMed1997

Derivatization of amphetamine and methamphetamine with 1,2-naphthoquinone 4-sulfonic acid into solid-phase extraction cartridges. Determination of amphetamine in pharmaceutical and urine samples.

The derivatization of amphetamine and methamphetamine with 1,2-naphthoquinone-4-sulfonate (NQS) into solid-phase extraction cartridges (C18) is described. Optimum conditions were the use of carbonate-hydrogencarbonate buffer of pH 10, a 10 min reaction time at 25 degrees C and an NQS concentration of 9.6 x 10(-3) M. The accuracy and the precision of the method were tested. The results obtained with the proposed liquid-solid procedure were compared with those obtained with a traditional liquid-liquid extraction with hexane-ethyl acetate. The procedure was used to measure amphetamine in pharmaceutical and urine samples.

Amphetamine↗

PubMedDate not supplied

Solid-phase extraction of 11-nor-delta9-tetrahydrocannabinol-9-carboxylic acid from urine drug-testing specimens with the cerex polycrom-THC column.

Confirmation of drugs of abuse by gas chromatography-mass spectrometry (GC-MS) is the most time-consuming process used by drug-testing laboratories. Cost effectiveness and competitive turnaround times for testing results demand fast, efficient, and reliable extraction methods. We applied the Cerex Polycrom-THC solid-phase extraction (SPE) column to the extraction of 11-nor-delta9-tetrahydrocannabinol carboxylic acid (9-THCA) from urine. This column uses an anion exchange divinyl-benzene copolymer, which requires no pH adjustment after hydrolysis of the THC-glucuronide with base, as is necessary with many other SPE columns. With urine, no preconditioning of the SPE column was necessary. After extraction, trimethylsilation derivatization was performed with N-methyl-N-(trimethylsilyl) trifluoroacetamide. This further improved efficiency because no heated incubation was required. A method correlation to an existing liquid-liquid extraction was performed. Analysis was on a Finnigan Voyager GC-MS with a 2.5-min run time per injection. Using 9-THCA-d9 deuterated internal standard, the assay was linear from 2 to 2000 ng/mL. Total precision at the 15-ng/mL cutoff concentration was 4.4%. The Cerex column was also evaluated for interference using two common drug-test adulterants, Klear and Urine Luck. Considerably less interference was observed when compared to an existing liquid-liquid method.

Cost-Benefit Analysis↗

PubMed1997

Determination of melanotan II in rabbit urine using solid-phase extraction sample preparation followed by reversed-phase high-performance liquid chromatography.

A solid-phase extraction (SPE) method has been developed for the isolation of melanotan II from rabbit urine. The proposed extraction method makes it possible to selectively isolate melanotan II without significant loss of the peptide. Standard curves obtained from high-performance liquid chromatographic (HPLC) analysis of spiked urine extracts are linear from 0.1 to 4.0 micrograms/ml. The analytical method is shown to be highly reproducible, giving a relative standard deviation of less than 5% for both between-day and same-day analyses. The accuracy of the method obtained from standard plots ranges from -3.3 to 3.1%.

Animals↗

PubMed1998

High-performance liquid chromatographic determination of modafinil and its two metabolites in human plasma using solid-phase extraction.

A simple procedure for the simultaneous determination of modafinil, its acid and sulfone metabolites in plasma is described. The assay involved an extraction of the drug, metabolites and internal standard from plasma with a solid-phase extraction using C18 cartridges. These compounds were eluted by methanol. The extract was evaporated to dryness at 40 degrees C under a gentle stream of nitrogen. The residue was redissolved in 250 microl of mobile-phase and a 30 microl aliquot was injected via an automatic sampler into the liquid chromatograph and eluted with the mobile-phase (26%, v/v acetonitrile in 0.05 M orthophosphoric acid buffer adjusted to pH 2.6) at a flow-rate of 1.1 ml/min on a C8 Symmetry cartridge column (5 microm, 150 mm x 3.9 mm, Waters) at 25 degrees C. The eluate was detected at 225 nm. Intra-day coefficients of variation ranged from 1.0 to 2.9% and inter-day coefficients from 0.9 to 6.1%. The limits of detection and quantitation of the assay were 0.01 microg/ml and 0.10 microg/ml respectively.

Administration, Oral↗

PubMed1997

Combination of solid-phase extraction and field-amplified concentration for trace analysis of organonitrogen pesticides by micellar electrokinetic chromatography.

An analytical method based on the combination of solid-phase extraction (SPE) and field-amplified concentration (FAC), with micellar electrokinetic chromatography (MEKC) was developed to extract, concentrate, separate, and quantitate six organonitrogen pesticides (metribuzin, bromacil, terbacil, hexazinone, triadimefon, and DEET) in drainage water. The recovery of the first five pesticides was over 85%, and the limit of detection was 0.8 ppb. Four advantages (enhanced enrichment and recoveries, reduced extraction time and interferences) of combining SPE with FAC for trace analysis of pesticides at the ppb level were demonstrated.

Bromouracil↗

PubMed2003

Determination of didanosine in human serum by on-line solid-phase extraction coupled to high-performance liquid chromatography with electrospray ionization tandem mass spectrometric detection: application to a bioequivalence study.

A method based on solid-phase extraction coupled to liquid chromatography with positive ion electrospray ionization and tandem mass spectrometric detection was developed for the determination of didanosine in human serum, using lamivudine as internal standard. The acquisition was performed in the multiple reaction monitoring mode, monitoring the transitions m/z 237 --> 136.7 for didanosine and m/z 230 --> 111.7 for lamivudine. The method was linear over the range studied (10-1500 ng ml(-1)), with r(2) > 0.98, and the run time was 5 min. The intra- and inter-assay precisions were < or =10% and the intra- and inter-assay accuracies were >95%. The absolute recoveries were 99.8% (10 ng ml(-1)), 98.4% (30 ng ml(-1)), 91.5% (700 ng ml(-1)) and 94.7% (1200 ng ml(-1)). The limits of detection and quantitation were 5 and 10 ng ml(-1), respectively. The method was applied to a bioequivalence study, in which 24 healthy adult volunteers (12 men) received single oral doses (200 mg) of reference and test didanosine formulations (buffered powder for oral solutions), in an open, two-way, randomized, crossover protocol. The 90% confidence interval of the individual ratios (test formulation/reference formulation) for C(max) (peak serum concentration) and AUC(0-inf) (area under the serum concentration versus time curve from time zero to infinity) were within the range 80-125%, which supports the conclusion that the two formulations are bioequivalent regarding the rate and extent of didanosine absorption.

Administration, Oral↗

PubMed2005

A novel on-line solid-phase extraction approach integrated with a monolithic column and tandem mass spectrometry for direct plasma analysis of multiple drugs and metabolites.

An on-line solid-phase extraction liquid chromatography/tandem mass spectrometry (SPE LC/MS/MS) assay using a newly developed SPE column and a monolithic column was developed and validated for direct analysis of plasma samples containing multiple analytes. This assay was developed in an effort to increase bioanalysis throughput and reduce the complexity of on-line SPE LC/MS/MS systems. A simple column-switching configuration that requires only one six-port valve and one HPLC pumping system was employed for on-line plasma sample preparation and subsequent gradient chromatographic separation. The resulting analytical method couples the desired sensitivity with ease of use. The method was found to perform satisfactorily for direct plasma analysis with respect to assay linearity, specificity, sensitivity, precision, accuracy, carryover, and short-term stability of an eight-analyte mixture in plasma. A gradient LC condition was applied to separate the eight analytes that cannot be distinctly differentiated by MS/MS. With a run time for every injection of 2.8 min, a minimum of 300 direct plasma injections were made on one on-line SPE column without noticeable changes in system performance. Due to the ruggedness and simplicity of this system, generic methods can be easily developed and applied to analyze a wide variety of compounds in a high-throughput manner without laborious off-line sample preparation.

Chromatography, High Pressure Liquid↗

PubMed2007

Optimization of microfabricated nanoliter-scale solid-phase extraction device for detection of gel-separated proteins in low abundance by matrix-assisted laser desorption/ionization mass spectrometry.

A nano-scale solid-phase extraction (SPE) device was developed for the detection of gel-separated proteins in low abundance by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) with a simplified microfabrication technology. By using SU-8 photoresist instead of epoxy glue to connect the microchannel and transfer capillary, polymeric contaminant signals in MS analysis were significantly reduced. Micro SPE columns with different capacities and geometric characteristics were investigated in order to increase the detection sensitivity and decrease spot size for MALDI-TOF-MS analysis. It is shown that enhancements in sensitivities for the detection of proteins in low abundance were correlated with the reduction in column capacity and increase in column aspect ratio. Fifty nanoliters of matrix solution were sufficient to elute the sample completely from the optimized micro SPE column with 3.5 nL capacity. The mass spectrum of a 5 fmol in-gel tryptic digest of bovine serum albumin (BSA), processed by the micro SPE column, demonstrated that 29 peptides matched the protein giving a sequence coverage of 51%, which was better than that obtained from analysis of 25 fmol of the same sample prepared by the dried-droplet method. With the micro SPE column treatment of 2 microL of digestion supernatant of a gel spot of the IQGAP1 protein, 15 peptides were detected from the mass spectrum with the highest individual score of 111, while, with a ZipTip procedure, only nine peaks were detected with the highest individual score of 71. Analytical results demonstrated that this approach greatly improved the sequence coverage and identification specificity for the tested protein. It can serve as a very useful tool in proteomics studies, especially for low abundance proteins.

Animals↗