On-line preconcentration strategy for the simultaneous quantification of three local anaesthetics in human urine using capillary zone electrophoresis

Posted on 15 December, 2015 by fqm302

The simultaneous determination of usually employed anaesthetics (procaine, lidocaine and bupivacaine) has been developed and validated using capillary electrophoresis with ultraviolet detection at 212 nm. The separation of these three drugs has been achieved in less than 7 min, using a temperature of 25º C and 25 kV, with a 150 mM citrate buffer (pH 2.5) as background electrolyte. Field amplified sample injection (FASI) has been used for on-line sample preconcentration. Ultrapure water and acetonitrile 50/50 (v/v) mixture gave the greatest enhancement factor when it was employed as injection solvent. Injection voltage and time were optimized, being 13 kV and 13 s, the optimum values respectively. To avoid the possible irreproducibility associated with the electrokinetic injection, an internal standard such as tetracaine, was employed. The instrumental detection limits (LOD s/n = 3) for the compounds ranged between 2.6 and 7.0 μg L−1 and the quantitation limits (LOQ s/n = 10) between 37.8 and 55.9 μg L−1. The detection limits obtained in real human urine samples ranged between 55.2 and 83.6 μg L−1 and the quantitation limits between 196.0 and 276.0 μg L−1. The proposed method has demonstrated its applicability to the analysis of these local anaesthetics in urine samples without any pretreatment, allowing the rapid determination of these target analytes.

Posted in Anaesthetics, CZE, FASI, UV-vis, Urine | Comments Off on On-line preconcentration strategy for the simultaneous quantification of three local anaesthetics in human urine using capillary zone electrophoresis

Advances in the application of chemiluminescence detection in liquid chromatography

Posted on 21 November, 2015 by fqm302

Recently, chemiluminescence (CL)-based detection has become a very useful detection system in high-performance liquid chromatography (HPLC) due to its simplicity, low cost, high sensitivity and high selectivity. Some methods such as the use of photochemically induced CL reactions, the application of nanoparticles and new sample treatments have been combined either with well-known CL reactions based on the use of luminol, tris(2,2-bipyridine) ruthenium (II) and peroxyoxalate as CL precursors or with direct oxidations. This review presents some important contributions published during the last 5 years.

Posted in Chemiluminescence, P12-AGR-1647, Review | Tagged | Comments Off on Advances in the application of chemiluminescence detection in liquid chromatography

Determination of aminoglycosides in honey by capillary electrophoresis tandem mass spectrometry and extraction with molecularly imprinted polymers

Posted on 26 August, 2015 by fqm302

A new analytical method based on capillary zone electrophoresis-tandem mass spectrometry is proposed and validated for the identification and simultaneous quantification of nine aminoglycosides in honey samples. Detection using an ion trap mass analyzer operating in the multiple reaction monitoring mode was used. Different parameters were optimized in order to obtain an adequate separation combined with the highest sensitivity. In order to achieve high selectivity in the sample treatment, a commercially-available molecularly imprinted polymer has been used for the solid phase extraction of the analytes. Under optimum conditions, recoveries for fortified samples ranged from 88.2 to 99.8 %, with relative standard deviations lower than 8%. The limits of detection ranged from 0.4 to 28.5 μg kg−1.Furthermore, the decision limit and the detection capability were evaluated, ranging from 3.5 to 60.5 μg kg-1 and from 6.0 to 103.1 μg kg-1, respectively, demonstrating the sensitivity and applicability of this fast and simple method.

Posted in Aminoglycosides, CZE, Honey, MIPs, Mass spectrometry, P12-AGR-1647 | Tagged | Comments Off on Determination of aminoglycosides in honey by capillary electrophoresis tandem mass spectrometry and extraction with molecularly imprinted polymers

Hollow-fiber liquid-phase microextraction combined with capillary HPLC for the selective determination of six sulfonylurea herbicides in environmental waters

Posted on 15 October, 2013 by fqm302

A three-phase hollow-fiber liquid-phase microextraction combined with a capillary LC method using diode array detection was proposed for the determination of six sulfonylurea herbicides, triasulfuron, metsulfuron-methyl, chlorsulfuron, flazasulfuron, chlorimuron-ethyl, and primisulfuron-methyl, in environmental water samples. Different factors that can affect the extraction process such as extraction solvent, acidity of the donor phase, composition and pH of the acceptor phase, salt addition, stirring speed, and extraction time were optimized. Under the optimum conditions, detection and quantitation limits between 0.1–1.7 and 0.3–5.7 μg/L, respectively, and enrichment factors ranging from 71 to 548 were obtained. The calibration curves were linear within the range of 0.3–40 μg/L. Intra- and interday RSDs were <6.3 and 8.4%, respectively. The relative recoveries of the spiked ground and river water samples were in the range of 69.4–119.2 and 77.4–111.7%, respectively. The results of the study revealed that the developed methodology involves an efficient sample pretreatment allowing the preconcentration of analytes, combined with the use of a miniaturized separation technique, suitable for the accurate determination of sulfonylurea herbicides in water.

Posted in Capillary HPLC, Hollow-fiber liquid-phase microextraction, Sulfonylurea, UV-vis, Water | Tagged , , | Comments Off on Hollow-fiber liquid-phase microextraction combined with capillary HPLC for the selective determination of six sulfonylurea herbicides in environmental waters

Ultrasound-assisted surfactant-enhanced emulsification microextraction for the determination of carbamates in wines by ultra-high performance liquid chromatography–tandem mass spectrometry

Posted on 14 October, 2013 by fqm302

A new sensitive multiresidue method based on ultra-high performance liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS) has been developed for the detection, confirmation and quantification of twenty five carbamates in wine samples. The separation was achieved in 5.5 min, using a Zorbax Eclipse plus RRHD C18 column (50 mm × 2.1 mm, 1.8 μm), with a mobile phase of water and methanol, both of them with 0.01% formic acid. The analytes were detected in positive mode with multiple reaction monitoring mode. Ultrasound-assisted surfactant-enhanced emulsification microextraction (UASEME), using a low-density extraction solvent has been optimized for the satisfactory extraction of carbamates and clean-up of extracts. The matrix effect was studied, showing that the proposed procedure provides very clean extracts. Under optimum conditions, recoveries for fortified wine samples ranged from 74 to 102%, with relative standard deviations lower than 6%. Limits of quantification ranged from 0.15 to 0.92 μg l−1, showing the high sensitivity of this fast and simple method and its compliance with current requirements.

Posted in Carbamates, Mass spectrometry, UASEME, UHPLC, Wine | Tagged , | Comments Off on Ultrasound-assisted surfactant-enhanced emulsification microextraction for the determination of carbamates in wines by ultra-high performance liquid chromatography–tandem mass spectrometry

Green methodology based on dispersive liquid–liquid microextraction and micellar electrokinetic chromatography for 5-nitroimidazole analysis in water samples

Posted on 19 September, 2013 by fqm302
Dispersive liquid–liquid microextraction has been proposed as an extraction technique combined with micellar  electrokinetic chromatography (MEKC) for the analysis of eight 5-nitroimidazole compounds, including some metabolites, in water samples. Determination has been carried out using a diode array detector, employing 20 mM sodium phosphate and150 mM SDS as separation buffer. Separation has taken place under a voltage of 25 kV anda temperature of 20 C. Samples were prepared in a buffer without micelles and they were hydrodynamically injected at 50 mbar for 25 s, producing a sweeping effect on the analytes for increasing sensitivity. Different factors involved in the dispersive liquid–liquid microextraction procedure were optimized, such as sample pH, nature, and volume of extraction and dispersive solvents in the mixture, percentage of NaCl added to sample and shaking time after the injection of the extraction and dispersive solvents. The method was characterized for water samples, achieving detection limits lower than 2.4g/L. Trueness was checked in river, tap, and bottled water. Dispersive liquid–liquid microextraction combined with MEKC constitutes an easy, cheap, and green alternative for 5-nitroimidazole analysis in environmental water samples.
Posted in 5-nitroimidazoles, DLLME, MEKC, Sweeping, UV-vis, Water | Tagged , | Comments Off on Green methodology based on dispersive liquid–liquid microextraction and micellar electrokinetic chromatography for 5-nitroimidazole analysis in water samples

Micellar electrokinetic chromatography–electrospray ionization mass spectrometry employing a volatile surfactant for the analysis of amino acids in human urine

Posted on 12 September, 2013 by fqm302

A new MEKC-ESI-MS method for the analysis of amino acids (AAs) in human urine was developed employing ammonium perfluorooctanoate (APFO) as volatile surfactant. The influence of APFO on the MS signal of AAs was evaluated by infusion experiments, which showed that APFO hardly affects analyte responses and presents significantly less ion suppression than equal concentrations of ammonium acetate. In order to obtain efficient separation of AAs, MEKC parameters such as the pH and APFO concentration of the BGE, were optimized. Optimum AA resolution, including baseline separation of leucine and isoleucine, was obtained using 150 mM APFO (pH 9.0) as BGE, representing a considerable selectivity improvement over CE using 50 mM ammonium acetate (pH 9.0). Optimization of CE-MS parameters, such as sheath liquid composition and flow rate, and ESI and MS settings, led to LODs ranging from 9 to 26 ng/mL for the 20 tested AAs, which is highly favorable for an MEKC-MS method. Good linearity (r2 > 0.99) and repeatability were obtained for all AAs tested with RSD values of 3.0–6.7% for peak area and <1.5% for migration time. The applicability of the MEKC-MS method was demonstrated by the quantitative determination of AAs in urine employing only a 1:1 dilution with BGE as sample pretreatment. All AAs could selectively be detected and quantified obtaining relevant concentration values for normal human urine.

Posted in Amino acids, MEKC, Mass spectrometry, Urine | Tagged , | Comments Off on Micellar electrokinetic chromatography–electrospray ionization mass spectrometry employing a volatile surfactant for the analysis of amino acids in human urine

Mass spectrometric and contactless conductivity detection approaches in the determination of muscle relaxants by capillary electrophoresis

Posted on 12 September, 2013 by fqm302

Novel and rapid capillary electrophoresis-coupled tandem mass spectrometry (CE-MS/MS) and capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C4D) methods have been developed for the separation and determination of three neuromuscular blocking agents: pancuronium, vecuronium, and rocuronium. In both cases, the separation was conducted in background electrolytes based on acidic acetate-ammonium buffers to avoid possible decomposition of the analytes that are known to be unstable in alkaline media. Baseline resolution of the analytes was achieved in the presence of modified γ-cyclodextrin by CE with C4D detection. The two detection techniques were compared with regard to analytical figures of merit including linear dynamic range, limit of detection, limit of quantification, precision, and accuracy. The calibration curves showed good linearity for both detection methods examined (characterized by r2 ≥ 0.9908). The LODs of the CE-MS/MS and the CE-C4D methods differed at least by two orders of magnitude considering all analytes. The differences in precision and accuracy of these methods were evaluated and discussed. The assays of pancuronium, vecuronium, and rocuronium in commercial injection solutions by CE-MS/MS and CE-C4D were performed and the results compared.

Posted in C4D, CZE, Cyclodextrins, Mass spectrometry, Muscle relaxants, Pharmaceutical formulations | Tagged , | Comments Off on Mass spectrometric and contactless conductivity detection approaches in the determination of muscle relaxants by capillary electrophoresis

Novel solid phase extraction method for the analysis of 5-nitroimidazoles and metabolites in milk samples by capillary electrophoresis

Posted on 9 September, 2013 by fqm302

A new sample treatment has been developed for the extraction of 5-nitroimidazole (5-NDZ) drugs in milk samples previous to their determination by micellar electrokinetic chromatography (MEKC). Fat removing and protein precipitation were simultaneously carried out by the addition of trichloroacetic acid (TCA) and subsequent centrifugation. Clean-up and off-line concentration were achieved by a novel solid-phase extraction (SPE) method employing mixed cation exchange (MCX) cartridges, obtaining an off-line concentration factor of 18. Analyses were performed in less than 18 min employing 20 mM phosphate buffer (pH 6.5) and 150 mM SDS as background electrolyte (BGE). During the separation procedure a temperature of 20 °C and a voltage of 25 kV (normal mode) were applied. Due to sweeping effects, an on-line concentration was achieved for all the studied compounds and detection limits lower than 1.8 μg L−1 were obtained. This method has been successfully applied to milk samples of different origins, including raw ewe milk.

Posted in 5-nitroimidazoles, MEKC, Milk, SPE, Sweeping, UV-vis | Tagged , | Comments Off on Novel solid phase extraction method for the analysis of 5-nitroimidazoles and metabolites in milk samples by capillary electrophoresis

On-line anion exchange solid-phase extraction coupled to liquid chromatography with fluorescence detection to determine quinolones in water and human urine

Posted on 5 September, 2013 by fqm302

An analytical method based on on-line solid-phase extraction coupled to liquid chromatography with fluorescence detection has been developed to determine quinolones in tap water and human urine. A home-made setup was used to percolate 10 mL of sample through a solid-phase extraction column. Analytes were retained onto the sorbent by an anion exchange mechanism which ensures an optimum compatibility with the subsequent chromatographic separation. A C-18 column containing core-shell particles (2.6 μm) was used to achieve peak efficiencies up to 200,000 plates/m, at a flow rate of 1.2 mL/min and without the need for special pumps. The method allowed the determination of 11 quinolones directly in tap water samples in less than 20 min and with limits of detection ranging between 7 and 110 ng/L. The sensitivity achieved made possible the direct determination of 9 quinolones in human urine without any sample treatment, just dilution with water. Relative recoveries between 94 and 109% were obtained meaning that the matrix effect in human urine is negligible after dilution. Satisfactory results were also obtained in terms of precision since relative standard deviations were always below 13%.

Posted in Fluorescence, Quinolones, Urine, Water, on-line SPE | Tagged , | Comments Off on On-line anion exchange solid-phase extraction coupled to liquid chromatography with fluorescence detection to determine quinolones in water and human urine