Search results for "Performance."
showing 10 items of 4178 documents
Sensitive determination of probenecid in urine samples by reversed-phase liquid chromatography and UV-visible detection using solid-phase extraction …
1993
This study describes a rapid method for the determination of probenecid in human urine by liquid chromatography with UV detection at 254 nm, after clean-up through a C8 solid-phase extraction column. Liquid chromatography was carried out on a C18-bonded phase using an acetonitrile-acetate buffer (pH=4) gradient elution. Ethacrynic acid was used as internal standard. The system has been applied to the determination of probenecid in the 0.10–100.0 μg/ml concentration range; the limit of detection was 5 ng/mL.
Supercritical fluid extraction and high performance liquid chromatography determination of homosalate in lipsticks
2001
Supercritical fluid extraction of homosalate is reported for the first time. Extraction parameters such as pressure, time of extraction, use of modifier, temperature and sample mass were studied. The proposed method was assayed for the extraction of homosalate in sunscreen lipsticks. Efficient recoveries were obtained after 5 min of dynamic extraction with supercritical CO2 and 15% ethanol as modifier at 300 bar and 60°C, flow rate 4 mL min−1. Extracts were dissolved in ethanol, and homosalate determined by HPLC using water—acetic acid—ethanol mobile phase and flow rate of 1 mL min−1. UV detection was at 309 nm using homosalate in ethanol solutions as standards, limit of detection 4 μg mL−1…
Analysis of organic pollutants in water at trace levels using fully automated solid-phase extraction coupled to high-performance liquid chromatography
1997
A method has been developed for the determination of trace levels of 32 pesticides, 19 explosives and 16 polycyclic aromatic hydrocarbons (PAH) in water in three individual steps. Solid-phase enrichment (SPE) is coupled to high-performance liquid chromatography (HPLC) with a fully automated system. The organic pollutants are enriched on reusable cartridges packed with adsorbent materials: pesticides and explosives on a mixed bed of divinylbenzene-ethylvinylbenzene copolymers (LiChrolut EN®) and perfluorinated polyethylene (PolyF®), and polycyclic aromatic hydrocarbons on C18-modified silica (Zorbax® ODS1). Thermally assisted desorption (TAD) has been shown to increase the recovery of analyt…
High-performance liquid chromatographic determination of sumatriptan after in vitro transdermal diffusion studies.
2004
A simple, accurate, precise and rapid HPLC method with UV detection has been validated in order to determine the in vitro transdermal absorption of sumatriptan succinate. The HPLC method is a modification of that described by Nozal et al. [M.J. Nozal, J.L. Bernal, L. Toribio, M.T. Martin, F.J. Diez, J. Pharm. Biomed. Anal. 30 (2002) 285-291]. Separation was carried out on a 250 mm Kromasil C18 column at room temperature. The detector response, at 282.7 nm, was found to be linear in a concentration range between 0.145 and 145 microM. The limit of detection (LOD) was 0.019 microM and the limit of quantification (LOQ) was 0.145 microM.
A rapid procedure for the determination of caffeine, theophylline and theobromine in urine by micellar liquid chromatography and direct sample inject…
1995
Abstract A liquid chromatographic procedure for the determination of caffeine, theophylline and theobromine in urine samples is described. The proposed system uses a Spherisorb octadecyl-silane ODS-2 C18 analytical column and a guard column of similar characteristics. The UV detector was set at 273 nm. A study to adequately select the composition of the micellar mobile phase for the separation of these compounds in urine samples is performed. Maximum resolution was achieved with a 0.075 M sodium dodecylsulphate-1.5% propanol eluent. Limits of detection at 273 nm ranged between 0.4 μg/ml for theobromine and theophylline and 1.2 μg/ml for caffeine. The procedure allows the determination of th…
High-performance liquid chromatographic determination of tocopherols in infant formulas
2002
A method for the simultaneous determination of alpha-tocopherol acetate and alpha-, delta-, and gamma-tocopherols by normal-phase high-performance liquid chromatography (HPLC) with a fluorescent detector in infant formula is proposed. The values obtained in the determination of the analytical parameters: linearity, precision, limit of detection and accuracy (analysis of a standard reference material, SRM 1846), confirm the quality of the method. The proposed method is useful for the determination of alpha-, delta-, and gamma-tocopherols and alpha-tocopherol acetate in infant formulas at a low cost and in a total time of 2 h.
Fourier transform infrared determination of Fluometuron in pesticide formulations
2003
Abstract A single method has been developed for Fourier transform infrared (FTIR) determination of Fluometuron in pesticide formulations. Samples were ultrasonically shaken with CHCl3 for 5 min and the FTIR spectra of sample extracts and standards were obtained at a nominal resolution of 4 cm−1 from 4000 to 900 cm−1 accumulating 25 scans. Fluometuron determination is based on the measure of peak area from 1342 to 1321 cm−1 corrected using a baseline defined from 1352 to 1294 cm−1. This procedure provided a limit of detection of 6.5 μg g−1, a sensitivity of 0.852 a.u. g mg−1 for a pathlength of 0.11 mm, a relative standard deviation of 1.6% for three analysis of a sample containing 50.4% (w/…
Quantitative determination of moniliformin in vegetable foods and feeds
1984
A suitable and simple method for the quantitative determination of moniliformin in vegetable foods and feeds is described. The mycotoxin was extracted by Soxhlet extraction with methanol from mouldy maize, rice, rye, oats, wheat and barley samples. Moniliformin was determined by thin-layer chromatography (TLC) using N-methylbenzthiazolon-2-hydrazone (MBTH) as a new derivatization reagent for this mycotoxin. The moniliformin derivative was assayed at 518 nm. Quantification could be performed after calibration. A linear relationship between mycotoxin amount and peak area was found from 100 to 400 ng/spot. The detection limit is 75 ng/spot.
Selective determination of ammonium in water based on HPLC and chemiluminescence detection
2005
Abstract A selective and sensitive method has been developed for liquid chromatographic determination of ammonium in water samples. The analyte is derivatized with Dansyl Chloride prior to injection into HPLC. Optimal solution derivatization conditions have been established. The dansyl derivative is separated with the aid of a chromatographic column and post-column mixed with peroxyoxalate (TCPO) and H 2 O 2 in order to perform chemiluminescence detection. The detection limit achieved is 8 μg/L and linear response from 0.027 to 0.750 mg/L of ammonium was obtained. Ammonium ion was determined within 2.4 min under optimum chromatographic conditions. The method is fast, and near 10 derivatized…
Use of micellar mobile phases for the chromatographic determination of clorazepate, diazepam, and diltiazem in pharmaceuticals
2001
An ODS-2 column, a micellar mobile phase of high elution strength containing 0.1M sodium dodecyl sulfate and 3% (v/v) butanol, and ultraviolet detection at 230 nm are used for the determination of either of two benzodiazepines (clorazepate and diazepam) and a benzothiazepine (diltiazem) in pharmaceuticals. The procedure is shown to be competitive against conventional chromatography with methanol-water mobile phases, especially for diltiazem. The composition of the micellar mobile phase is selected using a predictive strategy based on an accurate retention model and assisted by computer simulation. Calibration graphs are linear at least in the 2.5 to 20 microg/mL, 4 to 20 microg/mL, and 5 to…