Search results for "performance"
showing 10 items of 4457 documents
Automated Fourier Transform near Infrared Determination of Buprofezin in Pesticide Formulations
2005
An automated procedure has been developed for Fourier transform near infrared (FT-NIR) determination of buprofezin in pesticide formulations. This methodology is based on on-line pesticide extraction with acetonitrile from solid samples and its determination by using peak area absorbance measurements between 2147 and 2132 nm, corrected with a horizontal baseline established at 2091 nm. The repeatability, as a relative standard deviation of five independent analyses of 18.9 mg g−1 of buprofezin, was 0.06% and the limit of detection 5 mg L−1. The reagent consumption was clearly reduced compared with a chromatographic reference procedure from 40.4 mL acetonitrile per sample, required by high …
Determination of water-soluble UV-filters in sunscreen sprays by liquid chromatography.
2002
Abstract Liquid chromatography was used for the determination of the three most used water-soluble UV filters, benzophenone-4 (BZ4), terephthalylidene dicamphor sulfonic acid (TDS), and phenylbenzimidazole sulphonic acid (PBS), in aqueous sunscreen sprays. A C 18 stationary phase and an isocratic mobile phase of EtOH–20 m M sodium acetate buffer of pH 4.6 (30:70, v/v) were used at a flow-rate of 0.5 ml min −1 . Mobile phase was also used as solvent for samples and standards. UV detection was at 313 nm. The analytical run took 5.5 min. The limits of detection were 0.5, 0.9 and 2 μg ml −1 for BZ4, TDS and PBS, respectively. The proposed method does not involve highly toxic solvents.
Quantification of nortriptyline in plasma by HPLC and fluorescence detection
2009
Abstract A simple, sensitive and specific high-performance liquid chromatography method has been developed for the determination of nortriptyline (NT) in plasma samples. The assay involved derivatization with 9H-fluoren-9-ylmethyl chloroformate (Fmoc-Cl) and isocratic reversed-phase (C 18 ) chromatography with fluorescence detection. The developed method required only 100 μl of plasma sample, deproteinized and derivatized in one step. Calibration curves were lineal over the concentration range of 5–5000 ng/ml. The derivatization reaction was performed at room temperature in 20 min and the obtained NT derivative was stable for at least 48 h at room temperature. The within-day and between-day…
Sensitive determination of free benzophenone-3 in human urine samples based on an ionic liquid as extractant phase in single-drop microextraction pri…
2007
Abstract Benzophenone-3 (BZ3), one of the compounds most commonly used as UV filter in cosmetic products, can be absorbed through the skin into the human body, since it can be found at trace levels in urine from users of cosmetic products that contain BZ3. Moreover, different undesirable effects have been attributed to this compound. Thus, sensitive analytical methods to monitor urinary excretion of this compound should be developed. This paper presents a selective and sensitive methodology for BZ3 determination at ultratrace levels in human urine samples. The methodology is based on a novel microextraction technique, known as single-drop microextraction (SDME). An ionic liquid (IL) has bee…
A microanalytical method for ammonium and short-chain primary aliphatic amines using precolumn derivatization and capillary liquid chromatography.
2007
Abstract A new microscale method is presented for the determination of ammonium and primary short-chain aliphatic amines (methylamine, ethylamine, propylamine, n -butylamine and n -pentylamine) in water. The assay uses precolumn derivatization with the reagent o -phthaldialdehyde (OPA) in combination with the thiol N -acetyl- l -cysteine (NAC), and capillary liquid chromatography with UV detection at 330 nm. The described method is very simple and rapid as no preconcentration of the analytes is necessary, and the volume of sample required is only 0.1 mL. Under the proposed conditions good linearity has been obtained up to a concentration of the analytes of 10.0 mg L −1 , the limits of detec…
Improved Solid Phase Extraction Procedure for Assay of Cephalosporins in Human Urine Samples
1998
Abstract Solid phase extraction technique has been evaluated for the treatment of urine samples in the analysis of cephalosporins before injection into an HP-Hypersil ODS-C18 column. Cephalexin, cefotaxime, cefazolin, cefuroxime, and cefoxitin were tested with seven different reversed-phase extraction column cartridges and the obtained urine extracts were not clean. However, 3M Empore extraction disk cartridges packed with octadecyl (C18) bonded silica provided clean extracts with a single extraction. The recoveries of the five cephalosporins ranged from 56 to 60 % in the 1.25–500 g/mL concentration range. The assay was accurate, precise, and adequate for testing the drug content in urine s…
Determination of clenbuterol in urine by azo-dye precolumn derivatization and micellar liquid chromatography
1997
Clenbuterol has been determined in urine by solidphase extraction on a C18 cartridge, diazotization of the eluate with nitrite, coupling of the diazonium ion with 1-(naphthyl)ethylenediamine, and separation of the azo dye formed by HPLC with a C18 column and a micellar mobile phase containing 0.1 M sodium dodecyl sulphate, 12%n-butanol and 0.05 M citrate buffer, pH 3. Recoveries higher than 90% were obtained by mixing the samples with a 20% 0.2 M NaOH before extraction. Limits of detection of 51 and 6.7 ng L−1 were obtained with spectrophotometric and thermal lens spectrometric detection, respectively; respective repeatabilities were 3.1% (5 μg mL−1) and 5.6% (0.16 μg mL−1).
Determination of catecholamines in urine by micellar liquid chromatography with coulometric detection
1994
The determination of catecholamines by HPLC with a sodium dodecyl-sulphate (SDS), micellar mobile phase on a C18 column and with coulometric detection was studied. The eluate was conditioned at +0.25 and +0.00 V, and the current at −0.16V was recorded. A previously developed model which describes the chromatographic behaviour of solutes in HPLC with hybrid, micellar mobile phases was used to optimize the SDS and ethanol concentrations. A mobile phase of 0.15M SDS in a phosphate buffer of pH 3.4 and without ethanol is recommended. The limits of detection were 0.4–0.7 ng ml−1. The procedure was applied to the determination of unconjugated L-dopa, norepinephrine and dopamine in urine. Direct i…
Sequential injection spectrophotometric determination of oxybenzone in lipsticks
2001
A sequential injection (SI) procedure for the spectrophotometric determination of oxybenzone in lipsticks is reported. The colorimetric reaction between nickel and oxybenzone was used. SI parameters such as sample solution volume, reagent solution volume, propulsion flow rate and reaction coil length were studied. The limit of detection was 3 microg ml(-1). The sensitivity was 0.0108+/-0.0002 ml microg(-1). The relative standard deviations of the results were between 6 and 12%. The real concentrations of samples and the values obtained by HPLC were comparable. Microwave sample pre-treatment allowed the extraction of oxybenzone with ethanol, thus avoiding the use of toxic organic solvents. E…
Simultaneous detection of three antiviral and four antibiotic compounds in source-separated urine with liquid chromatography
2013
An analytical method for the simultaneous screening of three antiviral agents (nevirapine, zidovudine, lamivudine), four antibiotics (sulfamethoxazole, trimethoprim, ciprofloxacin, rifampicin) and one reference compound (carbamazepine) in human urine was developed. Separation was achieved with a Kinetex XB-C18 (75 × 4.6 mm, 2.6 μm) column after the extraction of pharmaceuticals from urine with SPE. Gradient elution with a mobile phase consisting of acetonitrile and 10 mM KH2 PO4 (pH 2.5), and diode array detection with monitoring at 210 and 264 nm was applied. The developed method was validated in terms of selectivity, linearity, stability and sensitivity. Repeatability (n = 3) and between-…