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PubMed2001

Determination of rutin in human plasma by high-performance liquid chromatography utilizing solid-phase extraction and ultraviolet detection.

An HPLC method for determining a flavonol glycoside, rutin, in human plasma is presented for application to the pharmacokinetic study. Isocratic reversed-phase HPLC was employed for the quantitative analysis by using kaempferol-3-rutinoside as an internal standard. Solid-phase extraction was performed on an Oasis MAX cartridge possessing reversed-phase and anion-exchange functions (recovery, approximately 80%). The HPLC assay was carried out using a Luna ODS-2 column (150 x 2.1 mm I.D., 5 microm particle size). The mobile phase was acetonitrile-10 mM ammonium acetate solution containing 0.3 mM EDTA-glacial acetic acid (16.5:82.5:1, v/v, pH 3.8). The flow-rate was 0.3 ml/min. The detection wavelength was set at 370 nm. Calibration of the overall analytical procedure gave a linear signal (r>0.9999) over a concentration range of 3-1,000 ng/ml of rutin in plasma. The lower limit of quantification was ca. 5 ng/ml of rutin in plasma. The detection limit (defined as signal-to-noise ratio of about 3) was approximately 0.75 ng/ml. A preliminary experiment to investigate the plasma concentration of rutin after oral administration of 500 mg of rutin to a healthy volunteer demonstrated that the present method was suitable for determining rutin in human plasma.

Calibration↗
PubMed2005

Simple liquid chromatographic method for the rapid and simultaneous determination of propoxur and its major metabolite isopropoxy phenol in rat blood and urine using solid-phase extraction.

This research paper describes the development and validation of an analytical method for the simultaneous determination of propoxur and isopropoxy phenol (IPP, a major metabolite) in both blood and urine of rat using reversed-phase high-performance liquid chromatography (HPLC) employing solid-phase extraction (SPE). Sample purification was performed using a weak cation-exchange cartridge (Isolute CBA). Separation was achieved by HPLC with UV detection at 270 nm. Recoveries of propoxur and IPP from blood and urine by SPE exceeded 85%. The validated calibration range for propoxur is from 0.5 to 100 microg/L and 2 to 100 microg/L for IPP in both rat blood and urine. The limit of quantitation for propoxur in blood and urine is 0.5 and 0.8 pg/L, respectively, and 2.0 and 4.2 microg/L, respectively, for IPP. Validation results on specificity, sensitivity, linearity, precision, accuracy, and stability are shown. The applicability of the method was demonstrated by the analysis of urine and blood from rats that were orally fed propoxur at minimum dose.

Administration, Oral↗
PubMed2006

Determination of sulfonamide antibiotics in wastewater: a comparison of solid phase microextraction and solid phase extraction methods.

In recent years, pharmaceutical and personal care products (PPCPs) have been detected in diverse environments (including groundwater, river water, and municipal wastewater). In order to evaluate their environmental impact, PPCPs must first be accurately determined. In this study, we focused on developing methods to accurately determine 10 sulfonamide antibiotics: sulfaguanidine, sulfacetamide, sulfadiazine, sulfathiazine, sulfapyridine, sulfamerazine, sulfamethazine, sulfamethoxazole, sulfadimethoxine, and sulfasalazine. While sulfonamides can easily be determined in pure water, wastewater influent and effluent collected from sewage treatment plants in Burlington and Toronto (Ontario) were found to generate confounding matrix effects. In an effort to overcome these matrix effects, we developed a solid phase microextraction (SPME) method to determine sulfonamides. Of the five different fiber assemblies investigated, the carbowax/divinylbenzene (CW/DVB) fiber produced the optimal response to sulfonamides. The SPME method was further optimized for sorption time (20min), solution salinity (10%, w/v, KCl), pH (4.5), and static desorption time (30min). When compared to solid phase extraction (SPE) using MCX cartridges, we observed that despite having higher MDLs and poorer sensitivity, SPME possessed the advantage of speed and reduced solvent usage. Most importantly, in contrast to SPE, when we applied the SPME method to fortified wastewater samples, we were generally able to accurately determine (i.e., recover) those sulfonamides that were present. Therefore, we conclude that SPME is a viable method for overcoming matrix effects in environmental samples.

Anti-Bacterial Agents↗
PubMed2004

A comparative solid-phase extraction study for the simultaneous determination of fluvoxamine, mianserin, doxepin, citalopram, paroxetine, and etoperidone in whole blood by capillary gas-liquid chromatography with nitrogen-phosphorus detection.

This paper reports a simple and reliable gas chromatographic method with nitrogen-phosphorus detection without derivatization for the simultaneous detection of fluvoxamine, mianserin, doxepin, citalopram, paroxetine, and etoperidone in whole blood as part of a systematic toxicological analysis (STA). All drugs were studied at concentration levels of 100-2000 ng/mL, except paroxetine for which it was necessary to study at concentration levels of 400-8000 ng/mL. A comparative and validation study using two solid-phase extraction (SPE) columns, Chem Elut and Bond Elut Certify, was developed regarding their recovery, precision, sensitivity, and matrix purification efficiency. The Chem Elut columns, diatomaceous earth, are closely related to conventional liquid-liquid extraction. The Bond Elut Certify columns, more recently developed in the market, are mixed SPE (reversed-phase and cation exchange sorbent). Recoveries for the antidepressants using Chem Elut columns at 500 ng/mL (2000 ng/mL for paroxetine) were in the range 43-72% with intra- and interassay precisions of less than 10% and 16%, respectively. Limits of detection (LODs) and quantitation (LOQs) for fluvoxamine, mianserin, doxepin, citalopram, and etoperidone ranged from 18 to 236 ng/mL and 60 to 786 ng/mL, respectively. LOD and LOQ for paroxetine were 303 and 1009 ng/mL, respectively. Recoveries of these compounds using Bond Elut Certify columns at 500 ng/mL (2000 ng/mL for paroxetine) were in the range 52-83% with intra- and interassay precisions of less than 6% and 8%, respectively. LODs and LOQs for fluvoxamine, mianserin, doxepin, citalopram, and etoperidone ranged from 7 to 28 ng/mL and 23 to 93 ng/mL, respectively. LOD and LOQ for paroxetine were 113 and 376 ng/mL, respectively. An excellent linearity was observed with both procedures from the LOQs up to the upper studied concentration level. In general, higher recoveries, cleaner extracts, better sensitivity, better precision, and reduced solvent consumption and disposal were achieved for the screening of these antidepressants with the use of the mixed SPE Bond Elut Certify compared with Chem Elut columns. The application of these methods on a forensic case study is also presented.

Aged↗
PubMed1997

Enantioselective determination of S-(+)- and R-(-)-ondansetron in human serum using derivatized cyclodextrin-modified capillary electrophoresis and solid-phase extraction.

A high-performance capillary electrophoresis (HPCE) assay method for the quantitation of S-(+)- and R-(-)-ondansetron in human serum was developed. Resolution was achieved using 15 mM heptakis-(2, 6-di-O-methyl)-beta-cyclodextrin (DM-beta-CD) in 100 mM phosphate buffer (pH 2.5). A 72-cm untreated fused-silica capillary, at a constant voltage of 20 kV, was used for the analysis. A 0.03-mM cationic detergent was used as a buffer additive to decrease the adsorption of endogenous substances onto the silica wall. The analytes of interest were isolated from endogenous substances using a solid-phase extraction procedure. The cyanopropyl cartridge gave good recoveries in excess of 85% for both S-(+)- and R-(-)-ondansetron, without any interferences. To decrease the limits of detection of the analytes, an on-capillary sample concentration technique was employed. The detection limit was 10 ng/ml using 2 ml of serum and the limit of quantitation was 15 ng/ml. The calibration curve was linear over a range of 15-250 ng/ml, with procainamide as the internal standard, and the coefficients of determination obtained were greater than 0.999 (n = 3). Precision and accuracy of the method were 2.76-5.80 and 2.10-5.00%, respectively, for S-(+)-ondansetron, and 3.10-6.57 and 2.50-4.35%, respectively, for R-(-)-ondansetron. The HPCE method is a useful alternative to existing chiral high-performance liquid chromatographic methods.

Antiemetics↗
PubMed2004

Automated solid-phase extraction and measurement of perfluorinated organic acids and amides in human serum and milk.

Organic fluorochemicals are used in multiple commercial applications including surfactants, lubricants, paints, polishes, food packaging, and fire-retarding foams. Recent scientific findings suggest that several perfluorochemicals (PFCs), a group of organic fluorochemicals, are ubiquitous contaminants in humans and animals world wide. Furthermore, concern has increased about the toxicity of these compounds. Therefore, monitoring human exposure to PFCs is important. We have developed a high-throughput method for measuring trace levels of 13 PFCs (2 perfluorosulfonates, 8 perfluorocarboxylates, and 3 perfluorosulfonamides) in serum and milk using an automated solid-phase extraction (SPE) cleanup followed by high-performance liquid chromatography-tandem mass spectrometry. The method is sensitive, with limits of detection between 0.1 and 1 ng in 1 mL of serum or milk, is not labor intensive, involves minimal manual sample preparation, and uses a commercially available automated SPE system. Our method is suitable for large epidemiologic studies to assess exposure to PFCs. We measured the serum levels of these 13 PFCs in 20 adults nonoccupationally exposed to these compounds. Nine of the PFCs were detected in at least 75% of the subjects. Perfluorooctanesulfonate (PFOS), perfluorohexanesulfonate (PFHxS), 2-(N-methylperfluorooctane-sulfonamido)acetate (Me-PFOSA-AcOH), perfluorooctanoate (PFOA), and perfluorononanoate (PFNA) were found in all of the samples. The concentration order and measured levels of PFOS, PFOA, Me-PFOSA-AcOH, and PFHxS compared well with human serum levels previously reported. Although no human data are available for the perfluorocarboxylates (except PFOA), the high frequency of detection of PFNA and other carboxylates in our study suggests that human exposure to long-alkyl-chain perfluorocarboxylates may be widespread. We also found PFOS in the serum and milk of rats administered PFOS by gavage, but not in the milk of rats not dosed with PFOS. Furthermore, we did not detect most PFCs in two human milk samples. These findings suggest that PFCs may not be as prevalent in human milk as they are in serum. Additional studies are needed to determine whether environmental exposure to PFCs can result in PFCs partitioning into milk. Large epidemiological studies to determine the levels of PFCs among the U.S. general population are warranted.

Animals↗
PubMed2000

Solid-phase extraction applied to the determination of ochratoxin A in wines by reversed-phase high-performance liquid chromatography.

A reversed-phase high-performance liquid chromatographic method is described for the analysis of Ochratoxin A at low microg l(-1) levels in samples of artificially contaminated wines. The method involves solid-phase extraction of samples using octadecylsilane cartridges and an additional preconcentration step prior to chromatography with isocratic elution and fluorimetric detection. The method was evaluated for accuracy and precision with relative standard deviations lower than 10%. Recoveries of ochratoxin A added to commercial wines over the range 0.1-3.0 microg l(-1) were higher than 80% in the assays. The performance of the octadecylsilane cartridge method tested compared very favourably with results of other published studies of ochratoxin A which use immunoaffinity columns or solvent extraction techniques.

Chromatography, High Pressure Liquid↗
PubMedDate not supplied

Solid phase extraction purification of carboxylic acid products from 96-well format solution phase synthesis with DOWEX 1x8-400 formate anion exchange resin.

The anion exchange resin DOWEX 1x8-400 formate has been developed for the isolation or resin capture of carboxylic acids from solution phase reactions in a 96-well format using a batchwise solid phase extraction technique. Eleven different anion exchange resins (formate forms) were evaluated for their efficiency at scavenging aryl and aliphatic carboxylic acids from solution. The model carboxylic acids had pK(a)s ranging from 3.40 to 4.89. Exchange efficiency onto the resin was pK(a) dependent with the carboxylic acids but not with their diisopropylethylammonium salts. Exchange off of the resin also showed pK(a) dependence with the stronger acids requiring more concentrated solvent acid for exchange. DOWEX 1x8-400 formate was determined to have superior capacity and the fastest exchange rate. Solvents suitable for exchanging the acids onto the resin were CH2Cl2, methanol, and various solvent/water mixtures. Solvents suitable for exchanging the carboxylic acids off of the resin were TFA/solvent or HCO2H/solvent mixtures. The resin was found to swell best in CH2Cl2 and in polar protic solvents such as water, alcohols, and acids. Application of this technique to the crude product mixtures from an arrayed reductive amination and an arrayed Stille reaction provided product carboxylic acids in yields averaging 57% and purities averaging 89%.

Journal Article↗
PubMed1997

High-performance liquid chromatographic assay of dilazep in plasma after solid-phase extraction.

A new, simple and accurate high-performance liquid chromatography method is presented for measuring dilazep in plasma, using a reversed-phase technique and UV absorption at 267 nm. Dilazep and papaverine (the internal standard) added to plasma were successfully isolated using a solid-phase extraction procedure (CN cartridges). The method was linear between 2.5-12.5 micrograms ml-1. Over the tested concentration range the intra-day coefficient of variation for replicate analyses of plasma ranged from 2.38 to 5.27% (the day-to-day CV ranged from 2.52 to 7.99%). The detection limit for the analysis of dilazep in plasma was 50 ng with 20 microliters injection.

Chromatography, High Pressure Liquid↗
PubMed2002

On-line solid-phase extraction and determination of paclitaxel in human plasma.

The application of coupled-column liquid chromatographic analysis to pharmacokinetic studies eliminates the need for sample clean-up from plasma. Considering lipophilic antineoplastic agents, we tested this approach to analyze paclitaxel under unfavourable circumstances (i.e., weekly low-dose regimen, plasma protein binding >90%, UV detection at 229 nm). The excellent quality control data (recovery: 95.6-100.7%, inter-assay relative standard deviation on 5 days: 1.3-3.2%, accuracy: 0.9-2.7%) and the detection limit of 19 nM indicates the usefulness of this method for the analysis of paclitaxel in plasma using on-line solid-phase extraction.

Antineoplastic Agents, Phytogenic↗
PubMed2005

Analysis of N7-(benzo[a]pyrene-6-yl)guanine in urine using two-step solid-phase extraction and isotope dilution with liquid chromatography/tandem mass spectrometry.

Analysis of urinary N7-(benzo[a]pyren-6-yl)guanine (BP-6-N7Gua), a DNA adduct induced by benzo[a]pyrene, may serve as a risk-associated biomarker for exposure to polyaromatic hydrocarbons (PAHs). In this study a highly sensitive and specific analytical method, incorporating on-line sample preparation coupled with isotope-dilution liquid chromatography and tandem mass spectrometry (LC/MS/MS), was developed to quantitate this adduct in human urine. In order to achieve accurate quantitation, 15N5-labeled BP-6-N7Gua was synthesized to serve as the internal standard, and a two-step solid-phase extraction (SPE) procedure using C8 and SCX cartridges was used for sample cleanup. BP-6-7-N7Gua was analyzed using positive ion LC/MS/MS operated in multiple reaction monitoring (MRM) mode. The [M+H]+ ions at m/z 402 and 407 and the common fragment ion of [M+H]+ at m/z 252 were monitored for quantification. The recovery of this analyte after two-step SPE was 90%, and the limit of detection was 2.5 fmol/mL in 10 mL of urine. This highly specific and sensitive method for BP-6-N7Gua in urine may be applied to assess exposure to PAHs in coke-oven workers for future molecular epidemiology studies on health effects of PAHs.

Benzopyrenes↗
PubMed2004

Stability of fluoroquinolone antibiotics in river water samples and in octadecyl silica solid-phase extraction cartridges.

Intensive use of antibiotics in human and veterinarian medicine and in industrial farming (food additives) has resulted in the transport of important quantities of the active ingredients to environmental waters. Environmental analysis usually requires sample storage for certain periods of time and, consequently, it is of great importance to know the stability of antibiotics in these kinds of sample. Thus, in this work the stability in river water of oxolinic acid (Oxo) and ciprofloxacin (Cip), taken as representatives of fluoroquinolone and quinolone antibiotics respectively, has been evaluated. The stability of these compounds in river water has been studied both in containers and on C(18) solid-phase extraction cartridges (SPE) under different storage conditions (time, light, and temperature). Data analysis revealed that Cip and Oxo have different degradation profiles with different degradation kinetics in river water. It was also concluded that these antibiotics are stable both in the containers and on SPE cartridges for at least 2 weeks at ambient temperature, and stability can be increased substantially if samples are stored at low temperatures (4 and -18 degrees C).

Anti-Bacterial Agents↗
PubMed1998

Solid-phase extraction and high-performance liquid chromatography procedures for the analysis of paralytic shellfish toxins.

Paralytic shellfish poisoning (PSP) toxins are produced by certain dinoflagellate species such as Gymnodinium catenatum and Alexandrium tamarensis, during certain periods of the year influenced by several environmental factors, affecting the aquaculture industry and mainly bivalve molluscs. HPLC with fluorescence detection is a powerful analytical technique for the analysis of such toxins; several HPLC alternatives have been developed in order to improve the liquid chromatographic analysis, but due to the complexity of the sample matrix, important work has been focused recently on the clean-up of samples prior to HPLC analysis. Solid-phase extraction procedures offer advantages for this clean-up. In this work we focus on the study of three different clean-up methods prior to HPLC with fluorescence detection analysis of PSP toxin present in contaminated mussel samples; by spiking uncontaminated mussel samples with two different PSP toxin standards and by calculating the recovery values for these experiments. These recoveries must be taken into account in order to quantify the exact amount of PSP toxins present in the contaminated samples.

Animals↗
PubMed2000

Comparison of different commercial solid-phase extraction cartridges used to extract heterocyclic amines from a lyophilised meat extract.

Heterocyclic amines are a group of potent mutagenic compounds which are generated when muscle meat is cooked. Since they are possible human carcinogens, these mutagens have received considerable attention in recent years, and several analytical techniques have been developed for their quantification. Although the purification step is one of the most important, there are a great number of variables influencing the recovery of the amines, especially when real samples are analysed. In this work we studied the influence of sample spiking mode on the recoveries. Furthermore, on the basis of a previously developed clean-up method, the effect of changing commercial source and structure of the sorbents used in two solid-phase extraction steps was examined. This purification method was applied to the quantification of the heterocyclic aromatic amines present in a lyophilised meat extract by means of liquid chromatography-mass spectrometry.

Amines↗
PubMed1998

Determination of glycolic acid in cosmetic products by solid-phase extraction and reversed-phase ion-pair high-performance liquid chromatography.

A procedure has been developed for the assay of glycolic acid in cosmetic products by reversed-phase high-performance liquid chromatography using an ion-pairing method. After dissolution in tetrahydrofuran-water (90:10, v/v), samples were purified by solid-phase extraction using silica-based strong anion-exchange cartridges and analysed directly on an Ultrasphere ODS column with UV detection at 210 nm and methanol-phosphate buffer (2:98, v/v), containing tetrabutylammonium iodide, as the mobile phase. Recovery of glycolic acid from different cosmetic matrices was between 92.4 and 96.2% and the precision of the method was better than 5.4% relative standard deviation. The procedure is rapid, simple, selective and it is suitable for routine analyses of commercial cosmetics.

Buffers↗
PubMed1998

Determination of the molecular species composition of diacylglycerols in human adipose tissue by solid-phase extraction and gas chromatography on a polar phase.

The free diacylglycerols (DAGs) in adipose tissue are involved in the metabolism of stored lipids and hence are related to the supply of fatty acids for other tissues. This paper describes a simple, fast, and reproducible method for the identification and quantification of different molecular species of DAGs in human adipose tissue. The method comprised solid-phase extraction on a diol-bonded phase column combined with capillary GC analysis of silylated DAG derivatives on a polar phase (65% phenylmethylsilicone). Separation of the DAGs was achieved based on chain length, isomeric structure (1,2- and 1,3-DAGs), and degree of unsaturation. The main DAGs were 1,2-OO, 1,2-OP, 1,2-LO and 1,2-LP. The composition was corroborated by analysis of the component fatty acids of the DAGs, 18:1(n-9), 16:0, and 18:2(n-6) being the three major fatty acids obtained.

Adipose Tissue↗
PubMed1999

Determination of acyclovir in plasma by solid-phase extraction and column liquid chromatography.

After oral administration, valacyclovir, the L-valyl ester of acyclovir, converts to the antiherpes virus drug, acyclovir. The bioavailability of acyclovir after valacyclovir administration is between 3- to 4.5-fold higher than that achieved after oral acyclovir administration. Therefore, despite the drug's short terminal half-life (3 hours), acyclovir plasma concentrations obtained after oral administration of the prodrug offer a more convenient dosage regimen in patients with herpes zoster than that required after acyclovir administration. Acyclovir is also used for viral infection prophylaxis in patients with hematologic disorders and in those who have undergone solid organ transplantation. We have described a simple and selective liquid chromatographic method for the determination of acyclovir in plasma using a new polymeric reversed-phase sorbent for solid-phase extraction. A mean acyclovir absolute recovery of 90% was found after elution of the drug from the cartridge with the mobile phase. This procedure allowed us to measure 62.5 ng/mL of acyclovir with an acceptable precision using a plasma volume of 250 microL, and no drug was found to interfere with the assay. This method is suitable for the therapeutic monitoring of acyclovir in patients who have been given a wide variety of coadministered drugs.

Acyclovir↗
PubMed2000

Routine determination of sulfonylurea, imidazolinone, and sulfonamide herbicides at nanogram-per-liter concentrations by solid-phase extraction and liquid chromatography/mass spectrometry.

Sulfonylurea (SU), imidazolinone (IMI), and sulfonamide (SA) herbicides are new classes of low-application-rate herbicides increasingly used by farmers. Some of these herbicides affect both weed and crop species at low dosages and must be carefully used. Less is known about the effect of these compounds on non-crop plant species, but a concentration of 100 ng/l in water has been proposed as the threshold for possible plant toxicity for most of these herbicides. Hence, analytical methods must be capable of detecting SUs, IMIs, and SAs at concentrations less than 100 ng/l in ambient water samples. The authors developed a two-cartridge, solid-phase extraction method for isolating 12 SU, 3 IMI, and 1 SA herbicides by using high-performance liquid chromatography/electrospray ionization-mass spectrometry (HPLC/ESI-MS) to identify and quantify these herbicides to 10 ng/l. This method was used to analyze 196 surface- and ground-water samples collected from May to August 1998 throughout the Midwestern United States, and more than 100 quality-assurance and quality-control samples. During the 16 weeks of the study, the HPLC/ESI-MS maintained excellent calibration linearity across the calibration range from 5 to 500 ng/l, with correlation coefficients of 0.9975 or greater. Continuing calibration verification standards at 100-ng/l concentration were analyzed throughout the study, and the average measured concentrations for individual herbicides ranged from 93 to 100 ng/l. Recovery of herbicides from 27 reagent-water samples spiked at 50 and 100 ng/l ranged from 39 to 92%, and averaged 73%. The standard deviation of recoveries ranged from 14 to 26%, and averaged 20%. This variability reflects multiple instruments, operators, and the use of automated and manual sample preparation. Spiked environmental water samples had similar recoveries, although for some herbicides, the sample matrix enhanced recoveries by as much as 200% greater than the spiked concentration. This matrix enhancement was sample- and compound-dependent. Concentrations of herbicides in unspiked duplicate environmental samples were typically within 25% of each other. The results demonstrate the usefulness of HPLC/ESI-MS for determining low-application-rate herbicides at ambient concentrations.

Chromatography, High Pressure Liquid↗