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PubMed1995

Determination of antipyrine metabolites in human plasma by solid-phase extraction and micellar liquid chromatography.

A rapid solid-phase extraction (SPE) procedure was developed for the quantitative isolation of three important antipyrine (dipyrone) metabolites from human plasma: 4-formylaminoantipyrine (FAA), 4-aminoantipyrine (AA) and 4-methylaminoantipyrine (MAA). Separation and quantitation were performed using micellar liquid chromatography (MLC) with a 0.1 mol l-1 sodium dodecyl sulfate (SDS)-2.5% pentanol mobile phase and UV detection at 262 nm. The metabolites were well resolved in less than 5 min using an octadecyl silica-bonded stationary phase. The extraction procedure involved passing 0.3 ml of plasma sample through a disposable SPE cartridge packed with C18 bonded porous silica. The adsorbed metabolites were removed from the cartridge with methanol. The eluent was evaporated to dryness and the residue was reconstituted with mobile phase and injected into the chromatographic system. The cartridge blank interferent peaks, the effects on reproducibility of sample loading in the cartridge and volume needed for desorption of metabolites were evaluated. The concentration of metabolites ranged between 2.4 and 4 micrograms ml-1. The present procedure yields recoveries for the three metabolites ranging from 93 to 100%. The relative standard deviation (Sr) ranged between 1.2 and 13.6%. Limits of detection (LODs) were 10.5, 11.5 and 17.0 ng ml-1 for FAA, AA and MAA, respectively.

Aminopyrine↗
PubMed2000

Determination of organochlorine and organophosphorus pesticide residues in low moisture, nonfatty products using a solid phase extraction cleanup and gas chromatography.

A multiresidue solid-phase extraction (SPE) method for the isolation and subsequent gas chromatographic determination of organochlorine and organophosphorus pesticide residues in low-moisture, nonfatty products is described. Residues are extracted from samples with an acetonitrile/water mixture. Cleanup of the extract is performed using graphitized carbon black and anion exchange SPE columns, and analysis is performed by gas chromatography with Hall electrolytic conductivity and flame photometric detection. Recovery data was obtained by fortifying corn, oats and wheat with pesticides. The average recoveries were 79-123% for eight organochlorine and 51-122% for 28 organophosphorus pesticide residues. The limit of quantitation for chlorpyriphos was 0.05 ppm using the Hall electrolytic conductivity detector and < 0.005 ppm using the flame photometric detector.

Animal Feed↗
PubMedDate not supplied

Screening procedure for organochlorine and organophosphorus pesticide residues in eggs using a solid-phase extraction cleanup and gas chromatographic detection.

A solid-phase extraction (SPE) screening procedure for the isolation and gas chromatographic (GC) determination of organochlorine and organophosphorus pesticide residues in eggs is described. Eggs are extracted with acetonitrile. The extract is subjected to a cleanup on tandem C18 and Florisil SPE columns. Organochlorine and organophosphorus pesticide residues are determined by GC with electron capture and flame photometric detection, respectively. Because the injected extracts are free from matrix interferences, the amount of residue present is easy to calculate. The average recoveries of 9 spiked organochlorine pesticide residues (0.01-1.0 ppm) ranged from 80.9 to 91.1%. The average recoveries of 7 spiked organophosphorus pesticide residues (0.02-0.50 ppm) ranged from 80.3 to 89.5%. The SPE method results in a 90% reduction in organic solvent consumption and an 85% reduction in hazardous waste production compared with the AOAC methodology.

Acetonitriles↗
PubMed2005

A rapid and reliable solid-phase extraction method for high-performance liquid chromatographic analysis of opium alkaloids from papaver plants.

A rapid and reliable solid-phase extraction method for HPLC analysis of opium alkaloids from Papaver plants was established. Fifty mg of dried and powdered plant sample was extracted with 5 ml of 5% acetic acid for 30 min under sonication. After centrifugation, 3 ml of the supernatant was loaded on a reversed-phase cation-exchange solid-phase extraction cartridge. After seriate washings with 0.1 M hydrochloric acid and methanol, alkaloids were eluted with a mixture of 28% ammonia and methanol (1:19). The eluate was concentrated under nitrogen stream at 40 degrees C and the residue was dissolved in 50% aqueous methanol for high performance liquid chromatographic analysis. With this solid-phase extraction method, the recovery of morphine, codeine, oripavine, thebaine, papaverine, noscapine and sanguinarine was from 99.94 to 112.18% when the standard alkaloids were added to the plant samples. Opium alkaloids of a variety of genus Papaver plants cultivated in a field and phytotron were analyzed by this method.

Alkaloids↗
PubMed2004

Trace level analysis of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and its biodegradation intermediates in liquid media by solid-phase extraction and high-pressure liquid chromatography analysis.

The use of solid-phase extraction for the analysis of liquid media containing low microg/L levels of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), mononitroso-RDX (MNX), dinitroso-RDX (DNX), and trinitroso-RDX (TNX) is examined. Aqueous samples (100 mL) consisting of water and a microbiological basal medium are spiked with known concentrations of RDX, MNX, DNX, and TNX. The compounds are extracted from the liquid media using a Porapak RDX cartridge and then eluted from the cartridge with 5 mL of acetonitrile. The eluent is concentrated to 1 mL before analysis by high-pressure liquid chromatography (HPLC). The method detection limits for RDX are 0.1 microg/L in water and 0.5 microg/L in the basal medium after a 100-fold concentration. For MNX, DNX, and TNX, the method detection limits are approximately 0.5 microg/L in water and approximately 1 microg/L in the basal medium after a 100-fold concentration. Interferences in the basal medium and a contaminant in the standard made quantitation for MNX and TNX, respectively, is less accurate below the 1 microg/L level. Solid-phase extraction of the liquid media gave good recoveries of nitramines and nitroso intermediates from a microbiological basal medium, allowing HPLC detection of RDX and the nitroso intermediates in the low microg/L (ppb) range.

Biodegradation, Environmental↗
PubMed1996

High-performance liquid chromatography using on-line solid-phase extraction: determination of furosemide in human serum.

An on-line solid-phase extraction technique based on column switching (heart-cutting) was developed for direct injection analysis of furosemide in human serum. In order to minimize the influence of deterioration in pre-treatment column efficiency, which was caused by protein precipitation with repeated injections of serum, furosemide was completely enriched at the top of the analytical column by ion-pair formation with tetra-n-butylammonium ion during heart-cutting. The robustness of the established on-line solid-phase extraction system was confirmed under routine conditions. As a result, almost comparable chromatograms could be obtained even though 50 repeated injections of a 100-microliter volume of serum were carried out using one pre-treatment column. The linearity of the calibration curves was demonstrated by the correlation coefficient which was greater than 0.99999 (5-1000 ng/ml). The relative errors and C.V. of quality control samples were within 4.00 and 5.88%, respectively (furosemide concentrations: 5, 100 and 1000 ng/ml).

Chromatography, High Pressure Liquid↗
PubMed2003

Quantitation of estrogens in ground water and swine lagoon samples using solid-phase extraction, pentafluorobenzyl/trimethylsilyl derivatizations and gas chromatography-negative ion chemical ionization tandem mass spectrometry.

A method was developed for the confirmed identification and quantitation of 17beta-estradiol, estrone, 17alpha-ethynylestradiol and 16alpha-hydroxy-17beta-estradiol (estriol) in ground water and swine lagoon samples. Centrifuged and filtered samples were extracted using solid-phase extraction (SPE), and extracts were derivatized using pentafluorobenzy] bromide (PFBBR) and N-trimethylsilylimidazole (TMSI). Analysis was done using negative ion chemical ionization (NICI) gas chromatography-mass spectrometry-mass spectrometry (GC-MS-MS). Deuterated analogs of each of the estrogens were used as isotope dilution standards (IDS) and were added to the samples before extraction. A limit of quantitation of 1 ng/l in ground water was obtained using 500 ml of ground water sample, 1.0 ml of extract volume and the lowest calibration standard of 0.5 pg/microl. For a 25 ml swine lagoon sample, the limit of quantitation was 40 ng/l. The average recovery of the four estrogens spiked into 500 ml of distilled water and ground water samples (n = 16) at 2 ng/l was 103% (S.D. 14%). For 25 ml of swine lagoon samples spiked at 500, 1000 and 10,000 ng/l, the average recovery for the four estrogens was 103% (S.D. 15%). The method detection limits (MDLs) of the four estrogens spiked at 2 ng/l in a 500 ml of ground water sample ranged from 0.2 to 0.6 ng/l. In swine lagoon samples from three different types of swine operations, estrone was found at levels up to 25,000 ng/l, followed by estriol and estradiol up to levels at 10,000 and 3000 ng/l, respectively. It was found that pretreatment of swine lagoon samples with formaldehyde was necessary to prevent conversion of estradiol to estrone.

Animals↗
PubMed1997

Evaluation of an on-line solid-phase extraction method for determination of almokalant, an antiarrhythmic drug, by liquid chromatography.

A fully automated liquid chromatographic method based on a Prospekt solid-phase extraction unit is described for determination of the antiarrhythmic drug almokalant in plasma. The assay comprises solid-phase extraction on a C2 phase and separation on a C18 column with fluorometric detection. In the original procedure 40 samples a day could be run unattended but by modifying the sequence in the solid-phase extraction process it was possible to increase this number to 70. The method gives an absolute recovery of 92% and a repeatability (C.V.) of 2.9% at 75 nmol/l of plasma. The limit of quantitation is 2 nmol/l of plasma (C.V. < 20%). As regards accuracy and precision the performance of the method is as good as the manual method based on liquid-liquid extraction. The Prospekt method is, above all, faster and requires far less manual effort.

Anti-Arrhythmia Agents↗
PubMed1995

Automated high-performance liquid chromatographic assay for lesopitron, a novel anxiolytic, in human plasma using on-line solid-phase extraction.

A totally automated liquid chromatographic assay method based on a Prospekt solid-phase extraction unit was developed for the analysis of lesopitron and its metabolite 5-hydroxylesopitron in human plasma. On-line solid-phase extraction of lesopitron, 5-hydroxylesopitron and its internal standard in human plasma was carried out using C2 cartridges. After washing, the test substances were eluted with mobile phase onto an ODS-2 Inertsil column and measured by fluorescence detection. The total time for one analysis was 25 min. The method developed was selective and linear in the concentration range from 1 to 40 ng/ml for both parent drug and metabolite. Recovery of lesopitron and 5-hydroxylesopitron were higher than 80% and the quantification limits were 1 ng/ml for both compounds. Coefficients of variation obtained for precision parameters were all below 14.5% and 13.9% for parent drug and metabolite, respectively. Good values of accuracy were also obtained.

Anti-Anxiety Agents↗
PubMed2003

Interlaboratory comparison of extraction efficiency of pesticides from surface and laboratory water using solid-phase extraction disks.

A continuation of an earlier interlaboratory comparison was conducted (1) to assess solid-phase extraction (SPE) using Empore disks to extract atrazine, bromacil, metolachlor, and chlorpyrifos from various water sources accompanied by different sample shipping and quantitative techniques and (2) to compare quantitative results of individual laboratories with results of one common laboratory. Three replicates of a composite surface water (SW) sample were fortified with the analytes along with three replicates of deionized water (DW). A nonfortified DW sample and a nonfortified SW sample were also extracted. All samples were extracted using Empore C(18) disks. After extraction, part of the samples were eluted and analyzed in-house. Duplicate samples were evaporated in a 2-mL vial, shipped dry to a central laboratory (SDC), redissolved, and analyzed. Overall, samples analyzed in-house had higher recoveries than SDC samples. Laboratory x analysis type and laboratory x water source interactions were significant for all four compounds. Seven laboratories participated in this interlaboratory comparison program. No differences in atrazine recoveries were observed from in-house samples analyzed by laboratories A, B, D, and G compared with the recovery of SDC samples. In-house atrazine recoveries from laboratories C and F were higher when compared with recovery from SDC samples. However, laboratory E had lower recoveries from in-house samples compared with SDC samples. For each laboratory, lower recoveries were observed for chlorpyrifos from the SDC samples compared with samples analyzed in-house. Bromacil recovery was <65% at two of the seven laboratories in the study. Bromacil recoveries for the remaining laboratories were >75%. Three laboratories showed no differences in metolachlor recovery; two laboratories had higher recoveries for samples analyzed in-house, and two other laboratories showed higher metolachlor recovery for SDC samples. Laboratory G had a higher recovery in SW for all four compounds compared with DW. Other laboratories that had significant differences in pesticide recovery between the two water sources showed higher recovery in DW than in the SW regardless of the compound. In comparison to earlier work, recovery of these compounds using SPE disks as a temporary storage matrix may be more effective than shipping dried samples in a vial. Problems with analytes such as chlorpyrifos are unavoidable, and it should not be assumed that an extraction procedure using SPE disks will be adequate for all compounds and transferrable across all chromatographic conditions.

Acetamides↗
PubMed2002

Analysis of ethyl carbamate in wines using solid-phase extraction and multidimensional gas chromatography/mass spectrometry.

The method describes a rapid and accurate procedure for the analysis of ethyl carbamate in wines. The separation of the ethyl carbamate (EC), the target analyte, from alcohol and the sample matrix is a challenge to many analytical chemists. After alcohol removal from the sample, EC was extracted and concentrated by solid-phase extraction. For analysis of EC, large-volume injection on a programmable temperature vaporization (PTV) inlet was used followed by multidimensional gas chromatography/mass spectrometry (MDGC/MS) using electron-impact ionization (EI). For quantitation, the ratio of ions produced during EI at m/z 62 (EC) and 64 (isotopically labeled EC) was monitored. The use of solid-phase extraction and MDGC/MS removes the majority of the matrix interference encountered in other methods. A linear dynamic range was established from 0.387 to 1160 ng/mL, with a limit of detection at 0.1 ng/mL and limit of quantitation at 1 ng/mL.

Gas Chromatography-Mass Spectrometry↗
PubMed2004

A new molecularly imprinted polymer for the selective extraction of naproxen from urine samples by solid-phase extraction.

A non-covalent molecularly imprinted polymer (MIP) was synthesised using naproxen (a non-steroidal, anti-inflammatory drug (NSAID)) as a template molecule. The MIP was chromatographically evaluated to confirm the imprinting effect, and was then applied as a selective sorbent in solid-phase extraction (SPE) to selectively extract naproxen. After this study, the MIP was used to extract naproxen from urine samples; it was demonstrated that by applying a selective washing step with acetonitrile (ACN) the compounds in the sample that were structurally related to naproxen could be eliminated.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2005

Determination of fluorescent whitening agents in laundry detergents and surface waters by solid-phase extraction and ion-pair high-performance liquid chromatography.

A simple method was developed to detect four stilbene-type disulfonate and one distyrylbiphenyl-type fluorescent whitening agents (FWAs) in household laundry detergents and surface waters by ion-pair high-performance liquid chromatography. The FWA concentrations in detergents were measured directly. The contents of FWAs in water samples were extracted by solid-phase extraction (C18-SPE) with ion-pairing reagent, and were then determined by an isocratic ion-pair chromatography (IPC) using a C18 column, applying tetrabutylammonium hydrogensulfate (TBA) as the ion-pairing reagent in mobile phase, and equipped with fluorescence detection. Water samples at various pH conditions for SPE were evaluated. Experimental results indicate that the proposed method is precise and sensitive in analyzing FWAs, and enables quantitation of 0.01-0.1 microg/l in 100 ml water samples. The recovery rates of FWAs in spiked water samples were between 73 and 89%, and the precision (RSD) ranged from 2.6 to 8.9%. Over 7200 microg/g of 4,4'-bis(2-sulfostryl)-biphenyl (DSBP) and 2320 microg/g of 4,4'-bis[(4-anilino-6-morpholino-1,3,5-triazine-2-yl)-amino]stilbene-2,2'-disulfonate (DAS1) were detected in household laundry detergents. Trace amounts of DSBP were detected in surface water samples ranging from 0.2 to 3.7 microg/l.

Chromatography, High Pressure Liquid↗
PubMed2002

Advanced solid phase extraction using molecularly imprinted polymers for the determination of quercetin in red wine.

Solid phase extraction (SPE) based on molecularly imprinted polymers (MIPs) is a novel approach for sample preparation and preconcentration, gaining increased interest in the fields of environmental, clinical, and food analysis. The first application combining MIPs with SPE for advanced beverage analysis is reported. MIPs for the flavonoid quercetin have been generated, using quercetin as a template molecule in a self-assembly approach and yielding imprinting of 1% of the used template. The MIP achieved a capacity of 0.4 g quercetin per gram polymer and a recovery rate of 98.2%. The application of these synthetic receptors as SPE material for the selective extraction and preconcentration of quercetin from synthetic and red wine samples was investigated. Red wine samples from a French Merlot were directly applied onto the SPE cartridge. The collected fractions were analyzed by high-pressure liquid chromatography. For verification of the obtained results, a similarly prepared nonimprinted polymer and a classical octadecyl silane reversed-phase cartridge were applied as the SPE matrix during control experiments. The MIP enabled the selective extraction of quercetin from a complex matrix, such as red wine, spiked with 8.8 mg per liter quercetin, demonstrating the potential of molecularly imprinted solid phase extraction for rapid, selective, and cost-effective sample pretreatment.

Acetonitriles↗
PubMedDate not supplied

Extraction of fipronil and thiobencarb from anaerobic water samples using solid-phase extraction.

Anaerobic water samples containing levels of soluble Fe(II) may form insoluble Fe(III) particulates that could hinder subsequent extraction and analysis. Solid-phase extraction (SPE) cartridges could become blocked by this material, reducing the volume that can be processed. The ability of ascorbic acid to reduce these Fe(III) colloids and/or to prevent further oxidation of Fe(II) by dissolved oxygen during sampling was investigated and compared to sample stabilization with hydrochloric acid. Ascorbic acid (5%, w/v) proved the most effective treatment because it prevented 95% of the dissolved iron in the sample from precipitating during processing, compared to 40% in untreated samples. The effect of ascorbic acid addition on degradation of 2 rice pesticides, fipronil and thiobencarb, was investigated and compared to degradation rates in water. Pesticide reduction by ascorbic acid over a 3 h period was insignificant compared to the natural degradation occurring in deionized water. While this method was shown to increase sample processing time, it also allowed the processing of large-volume anaerobic water samples (150 mL) that were previously not extractable due to rapid obstruction of the SPE cartridge.

Ascorbic Acid↗
PubMed2000

Analysis of steroids in environmental water samples using solid-phase extraction and ion-trap gas chromatography-mass spectrometry and gas chromatography-tandem mass spectrometry.

This paper describes an improved method for the extraction and determination of three steroids, oestrone, 17beta-oestradiol, and the synthetic contraceptive steroid 17alpha-ethinyloestradiol in aqueous matrices. Samples of wastewater and environmental water were spiked with internal standards, comprising isotopically labelled analogues of the steroids to be determined. The samples were extracted using solid-phase extraction disks and the extracts were then derivatized to form tert.-butyldimethylsilyl derivatives. The derivatised steroids were determined in the final extracts by GC-MS or GC-MS-MS allowing an operational detection limit for each steroid in effluent samples of 1 ng l(-1).

Chromatography, Gas↗
PubMed2000

A method for separation of phosphatidylcholine, triacylglycerol, non-esterified fatty acids and cholesterol esters from plasma by solid-phase extraction.

Efficient isolation of individual lipid classes is a critical step in the analysis of plasma and lipoprotein fatty acid compositions. Whilst good separations of total lipid extracts are possible by TLC, this method is time consuming and a major rate-limiting step when processing large numbers of specimens. A method for rapid separation of phosphatidylcholine (PC), non-esterified fatty acids (NEFA), cholesterol ester (CE) and triacylglycerol (TAG) from total plasma lipid extracts by solid-phase extraction (SPE) using aminopropyl silica columns has been developed and validated. Following initial separation of polar and neutral lipids, individual classes were isolated by application of solvents with increasing polarity. Recoveries for combined plasma extraction with chloroform-methanol and SPE were (%): PC 74.2 (SD 7.5), NEFA 73.6 (SD 8.3), CE 84.9 (SD 4.9), and TAG 86.8 (SD 4.9), which were significantly greater for TAG and NEFA than by TLC Both GC-flame ionisation detector and GC-MS analysis of fatty acid methyl esters demonstrated that there was no cross-contamination between lipid classes. Measurements of repeatability of fatty acid composition for TAG, PC, CE and NEFA fractions showed similar CV for each fatty acid. The magnitude of the CV appeared to be related inversely to the fractional fatty acid concentration, and was greatest at concentrations of less than 1 g/100 g total fatty acids. There was no evidence of selective elution of individual fatty acid or CE species. In conclusion, this method represents an efficient, rapid alternative to TLC for isolation of these lipid classes from plasma.

Cholesterol Esters↗
PubMed1985

Re-examination of the assay for plasma prostanoids by solid-phase extraction, and radioimmunoassay.

A method for the routine assay of plasma thromboxane and prostacyclin metabolites, thromboxane B2 and 6 keto-prostaglandin F1 alpha (employing solid phase extraction to remove the metabolites from interfering substances) and using commercially available antisera for their radioimmunoassay has been investigated. Modifications of previously published procedures have been explored, including the use of non-explosive solvents in the extraction procedure, and inclusion of a non-cross reacting internal standard, prostaglandin D2, to estimate recovery through the extraction procedures. Both the original and modified procedures can produce high blank values, which apparently result from the solid-phase extraction. These high backgrounds are constant for a given lot of solid phase extraction cartridges and can be corrected by subtraction. The modified method is linear with volume of plasma assayed to as little as one ml, and all cross-reacting material in normal human plasma was found to co-chromatograph with authentic standards on reverse-phase high performance liquid chromatography. Values for normal adult plasmas were found to be 0.44 +/- .15 pmol/ml 6 keto PGF1 alpha (mean +/- SD) and .103 +/- .07 for thromboxane B2. The method reported provides a convenient, reproducible way to assay these important plasma prostanoids.

Adolescent↗