Search results for "liquid"
showing 10 items of 4351 documents
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…
Simultaneous quantification of 18 different phytocannabinoids in serum using a highly sensitive liquid chromatography-tandem mass spectrometry (LC-MS…
2021
Abstract The potential therapeutic effects of various phytocannabinoids and the availability of multiple cannabis-based medicines make it desirable to have an analytical method that simultaneously quantifies a wide range of cannabinoids in blood, beyond delta-9-tetrahydrocannabinol and its metabolites. A liquid chromatography tandem mass spectrometry (LC-MS/MS) method for quantification of 18 phytocannabinoids and cannabinoid metabolites in serum was developed and validated. The method enables simultaneous detection of delta-9-tetrahydrocannabinol, cannabidiol, cannabinol, cannabigerol, cannabichromene, cannabicyclol, tetrahydrocannabivarin and cannabidivarin and their acidic precursors tet…
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…
On-line in-tube solid phase microextraction-capillary liquid chromatography method for monitoring degradation products of di-(2-ethylhexyl) phthalate…
2014
Abstract The main di-(2-ethylhexyl) phthalate (DEHP) degradation products, (2-ethylhexyl) phthalate (MEHP), diethyl phthalate (DEP) and dibutyl phthalate (DBP), have been tested. The proposed cost-effective method combines on-line, in-tube solid-phase micro extraction (IT-SPME) in in-valve configuration and capillary liquid chromatography with UV diode array detection (Cap-LC-DAD). Acidification of the samples at pH 3 improved markedly the estimation of MEHP. Aliquots of 4 mL of acidified water samples were directly processed. After sample loading, the analytes were desorbed with the mobile-phase and transferred to the monolithic capillary column. Satisfactory linearity and precision, absen…
Simple and commercial readily-available approach for the direct use of ionic liquid-based single-drop microextraction prior to gas chromatography
2009
A simple and commercial readily-available approach that enables the direct use of ionic liquid (IL)-based single-drop microextraction (SDME) prior to gas chromatography (GC) is presented. The approach is based on thermal desorption (TD) of the analytes from the IL droplet to the GC system, by using a robust and commercially-available thermodesorption system. For this purpose, a two-glass-tube concentrically disposed system was designed. The inner tube is a laboratory-cut Pyrex tube (20mm length) that houses the ionic liquid droplet from the SDME process, and the outer tube is a commercially-available TD glass tube (187 mm length) commonly employed for stir-bar sorptive extractions (SBSE). I…
RAPID LIQUID CHROMATOGRAPHIC DETERMINATION OF TETRACYCLINES IN ANIMAL FEEDS USING A SURFACTANT SOLUTION AS MOBILE PHASE
2002
ABSTRACT A chromatographic procedure was developed for the determination of oxytetracycline (OTC), tetracycline (TC), chlortetracycline (CTC), doxycycline (DC) and minocycline (MINO) in animal feeds. Clear analyte-rich extracts were obtained using a 1 : 1 acetonitrile/water mixture buffered at pH 3. The extracts were injected into a conventional unprotected C18 chromatographic column and eluted with a mobile phase of 0.05 M sodium dodecyl sulfate/5% 1-butanol/0.01 M oxalic acid at pH 3. Good resolution was achieved for the five compounds, whereas OTC and TC coeluted with an optimized aqueous-organic mobile phase of methanol/acetonitrile/0.01 M oxalic acid at pH 3. Mean recoveries from spike…
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…