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111.
Priyanka Trivedi Jonnala Kotesh Kumar Arvind Singh Negi Karuna Shanker 《Biomedical chromatography : BMC》2011,25(6):697-706
Extraction and pre‐concentration of a bioactive marker compound, phenyl‐1,3,5‐heptatriyne from Bidens pilosa, prior to HPLC has been demonstrated using both organic and ecofriendly solvents. Non‐ionic surfactants, viz. Triton X‐100, Triton X‐114 and Genapol X‐80, were used for extraction. No back‐extraction or liquid chromatographic steps were required to remove the target phytochemical from the surfactant‐rich extractant phase. The optimized cloud point extraction procedure has been shown to be a potentially useful methodology for the preconcentration of the target analyte, with a preconcentration factor of 4–99. Moreover, the method is simple, sensitive, rapid and consumes lesser solvent than traditional methods. An isocratic chromatographic separation and quantitation was accomplished on a C18 column with acetonitrile–acidified aqueous as mobile phase at a flow rate of 1.0 mL/min, UV detection at 254 nm and specificity with photo diode‐array detector (PDA) and MS. Under the optimum experimental conditions recovery was satisfactory (99.18–100.33%) without interference from the surfactant. The method seems to be reliable with intraday precision and interday precision below 2.0%. Good linearity was obtained in the working range from 7.5 to 30 µg/mL with correlation coefficient >0.99. The limits of detection and quantitation were 1.84 and 6.13 µg/mL, respectively. The method was validated following international guidelines and successfully applied for quantitative assays of cytotoxic compound phenyl‐1,3,5‐heptatriyne in Bidens pilosa. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
112.
Summary An on-line flow injection-solid-phase extraction-capillary zone electrophoresis (FI-SPE-CZE) method has been developed for
determination of cimetidine in human plasma. Sodium dodecylsulfate (SDS) was used as dynamic chemical modifier for elimination
of capillary contamination by biological macromolecules. FI on-line preconcentration and cleaning of the analyte by means
of a C18 microcolumn was performed automatically and CZE separation was performed consecutively without interruption of the applied
voltage and between-run-washing of the capillary. A detection limit of 8 μgL−1 (3×σ) was achieved at a sample throughput of 12h−1. The approach was successfully used for a pharmacokinetic study of cimetidine. 相似文献
113.
Gerhard Friedrich Thorsten Rose Alexander Wawkuschewski Sabine Kafert-Kasting Britta Laube Lubomir Arseniev Klaus Rissler 《Chromatographia》2008,67(1-2):31-39
In a recently published paper development of a sensitive automated “on-line” solid-phase extraction (SPE)/RP-HPLC assay for
6β-hydroxytestosterone (6β-OHT) with corticosterone as the internal standard (IS) was reported and its potential for quantification
of various testosterone metabolites in culture media reflecting metabolic activity of cultured human and animal hepatocytes
demonstrated [1]. In this following contribution the technique has been extended to determination of another five testosterone metabolites
in cultured rat hepatocytes using an identical “on-line” SPE/RP-HPLC procedure and detection by tandem MS-MS with an atmospheric
pressure chemical ionization (APCI) source in the selected reaction monitoring (SRM) mode as that described in [1]. All six testosterone metabolites, namely 2α-OHT, 2β-OHT, 6α-OHT, 6β-OHT, 7α-OHT and 16α-OHT, could be sufficiently separated
from each other and thus an unequivocal assignment to the individual structures was achieved. Validation data are presented
specifying the limits of quantitation as well as the mean values of the coefficients of variation (CV) for the target analytes
and the accuracy obtained at five different days. Regio- and stereoselective testosterone hydroxylation by rat hepatocytes
was measured in a long-term culture system with and without exposure to rifampicin as an inducer of liver CYP 3A4 activity.
In addition, testosterone hydroxylation was analyzed in cultures of cryopreserved hepatocytes that had been stored at −196 °C.
The rat hepatocytes were cultured after thawing for up to 11 days and induction of testosterone hydroxylase activity could
be demonstrated in cultures which underwent a new cryopreservation protocol.
This paper is dedicated to Professor Hinrich Cramer on the occasion of his 75th birthday. 相似文献
114.
Wilhelm Blödorn Robert Krismer Hugo M. Ortner Jens Stummeyer Peter Wilhartitz Gerold Wünsch 《Mikrochimica acta》1989,99(3-6):423-432
Trace metals (20 elements) in high-purity chromium, molybdenum and tungsten are collected and preconcentrated by precipitation and adsorption on cellulose collectors. The compound methods allow the application of AAS and ICP-AES as determination methods for the production control of highly pure refractory metals under routine conditions.Presented in part at the 1989 European Winter Conference on Plasma Spectrochemistry, Reutte, Austria 相似文献
115.
On-line scheduling with non-crossing constraints 总被引:1,自引:0,他引:1
We consider the problem of on-line scheduling with non-crossing constraints. The objective is to minimize the latest completion time. We provide optimal competitive ratio heuristics for the on-line list and on-line time problems with unit processing times, and a 3-competitive heuristic for the general on-line time problem. 相似文献
116.
Narayanan Prakash Georg Csanády Markus R. A. Michaelis Günter Knapp 《Mikrochimica acta》1989,99(3-6):257-265
Automated preconcentration techniques for off/on-line determination with ICP-OES have been developed for various metal ions of environmental interest. Preconcentration studies were performed on two different types of chemically bonded chelating ion-exchangers, namely EDTrA-cellulose (iminoacetate groups) and HSO3 · oxine-cellulose. Enrichment studies were carried out at various preconcentration factors and also at different loadings.Presented in part at the 1989 European Winter Conference on Plasma Spectrochemistry, Reutte, Austria 相似文献
117.
118.
Raúl A. Gil José A. Salonia José A. Gásquez Alejandro C. Olivieri Roberto Olsina Luis D. Martinez 《Microchemical Journal》2010,95(2):306-310
A novel method for the determination of Pb by on-line cloud point extraction coupled to inductively coupled plasma optical emission spectrometry with ultrasonic nebulization (USN–ICP OES) is presented. The cloud point system was formed in the presence of non-ionic micelles of polyethyleneglycolmono-p-nonylphenylether (PONPE 7.5) and was retained in a minicolumn filled with particles of PTFE. Since the micelles of PONPE were able to extract Pb from the solutions, the use of a complexing reagent was not necessary. Afterwards, the surfactant-rich phase containing the analyte was removed from the minicolumn with nitric acid and introduced into the ultrasonic nebulizer. A total enhancement factor of 150 was obtained for a preconcentration time of 3.3 min, with respect to the direct determination of Pb by conventional ICP OES. The values of the detection (3σ) and quantification (10σ) limits for the preconcentration of 10 mL of sample solution were 0.09 µg L− 1 and 0.2 µg L− 1 respectively. The precision, expressed as the relative standard deviation (RSD), for 10 replicate determinations at 5.0 µg L− 1 Pb level was 6.0%. Verification of the accuracy was carried out by analysis of two certified reference materials (NIST SRM 1640e and VKI QC Metal LL1). The method was successfully applied to the determination of Pb in drinking water samples. 相似文献
119.
A rapid micro‐analytical multiresidue method was developed for analysis of pyrethroids (kadethrin K, cypermethrin C and permethrin P) in soil micro‐sample (200 mg). It uses on‐line flow‐through extraction of soil micro‐samples (packed into a short glass column) with a methanol‐aqueous citric acid buffer mixture, successive on‐line SPE preconcentration of analytes from the extract and on‐line RP‐HPLC analysis with UV photometric detection. The separation of pyrethroids is performed on a Purospher RP‐18e column with methanol/water as mobile phase. Effects of sorbent placed at the bottom of a short column holding the soil sample and different kinds of on‐line SPE columns were tested. Besides, the influence of volume of the effluent on the pyrethroids recovery was also studied. Calibration curves were linear over the range assayed from 0.01 to 0.2 μg/mL with correlation coefficients of linear regression (least‐squares method) in the range 0.998–0.999. Recovery studies were carried out at 0.25–1.00 μg/g dry soil fortification level and obtained recoveries were for K 81–84%, C 56–59% and for P 58–63%. Achieved LOD (confidence band) of studied pyrethroids were for large‐volume injection (1 mL) 4.5 ng K, 3.7 ng C, 3.6 ng P or 27 ng/g K, 32 ng/g C and 29 ng/g P in dry soil “solid sampling HPLC”. 相似文献
120.
Hong Heng See Peter C. Hauser Wan Aini Wan Ibrahim Mohd Marsin Sanagi 《Electrophoresis》2010,31(3):575-582
Rapid and direct online preconcentration followed by CE with capacitively coupled contactless conductivity detection (CE‐C4D) is evaluated as a new approach for the determination of glyphosate, glufosinate (GLUF), and aminophosphonic acid (AMPA) in drinking water. Two online preconcentration techniques, namely large volume sample stacking without polarity switching and field‐enhanced sample injection, coupled with CE‐C4D were successfully developed and optimized. Under optimized conditions, LODs in the range of 0.01–0.1 μM (1.7–11.1 μg/L) and sensitivity enhancements of 48‐ to 53‐fold were achieved with the large volume sample stacking‐CE‐C4D method. By performing the field‐enhanced sample injection‐CE‐C4D procedure, excellent LODs down to 0.0005–0.02 μM (0.1–2.2 μg/L) as well as sensitivity enhancements of up to 245‐ to 1002‐fold were obtained. Both techniques showed satisfactory reproducibility with RSDs of peak height of better than 10%. The newly established approaches were successfully applied to the analysis of glyphosate, glufosinate, and aminophosphonic acid in spiked tap drinking water. 相似文献