Dispersive liquid-liquid microextraction prior to field-amplified sample injection for the sensitive analysis of 3,4- methylenedioxymetamphetamine, phencyclidine and lysergic acid diethylamide by capillary electrophoresis in human urine

Posted on 13 November, 2012 by fqm302

A novel capillary zone electrophoresis (CZE) with ultraviolet detection method has been developed and validated for the analysis of 3,4-methylenedioxymethamphetamine (MDMA), lysergic acid diethylamide (LSD) and phencyclidine (PCP) in human urine. The separation of these three analytes has been achieved in less than 8 min in a 72-cm effective length capillary with 50-μm internal diameter. 100 mM NaH2PO4/Na2HPO4, pH 6.0 has been employed as running buffer, and the separation has been carried out at temperature and voltage of 20 °C, and 25 kV, respectively. The three drugs have been detected at 205 nm. Field amplified sample injection (FASI) has been employed for on-line sample preconcentration. FASI basically consists in a mismatch between the electric conductivity of the sample and that of the running buffer and it is achieved by electrokinetically injecting the sample diluted in a solvent of lower conductivity than that of the carrier electrolyte. Ultrapure water resulted to be the better sample solvent to reach the greatest enhancement factor. Injection voltage and time have been optimized to 5 kV and 20 s, respectively. The irreproducibility associated to electrokinetic injection has been correcting by using tetracaine as internal standard. Dispersive liquid–liquid microextraction (DLLME) has been employed as sample treatment using experimental design and response surface methodology for the optimization of critical variables. Linear responses were found for MDMA, PCP and LSD in presence of urine matrix between 10.0 and 100 ng/mL approximately, and LODs of 1.00, 4.50, and 4.40 ng/mL were calculated for MDMA, PCP and LSD, respectively. The method has been successfully applied to the analysis of the three drugs of interest in human urine with satisfactory recovery percentages.

Posted in Biological fluids, CZE, DLLME, Drugs, Electrophoresis, FASI, UV-vis, Urine | Tagged | Comments Off on Dispersive liquid-liquid microextraction prior to field-amplified sample injection for the sensitive analysis of 3,4- methylenedioxymetamphetamine, phencyclidine and lysergic acid diethylamide by capillary electrophoresis in human urine

Analysis of amino acids in latent fingerprint residue by capillary electrophoresis-mass spectrometry

Posted on 5 November, 2012 by fqm302

The analysis of the chemical composition of fingerprints is important for the development and improvement of existing fingerprint enhancement techniques. This study demonstrates the first analysis of a latent fingerprint sample, using an optimized CE-MS method. In total 12 amino acids were detected in the fingerprint sample. MS/MS fragmentation was used to provide additional identity confirmation, for which eight of the twelve detected amino acids generated confirmatory product ions. Nine amino acids were quantified and their relative abundances were consistent with previous studies with serine and glycine being the most abundant. The successful detection of amino acids from latent fingerprints demonstrates that CE-MS is a potential future technique for further study of such compounds in fingerprint samples.

Posted in Amino acids, CZE, Electrophoresis, Fingerprints, Mass spectrometry | Tagged , | Comments Off on Analysis of amino acids in latent fingerprint residue by capillary electrophoresis-mass spectrometry

Advances in the determination of β-lactam antibiotics by liquid chromatography

Posted on 15 August, 2012 by fqm302

β-lactam antibiotics have been the most widely used antimicrobial drugs for more than 80 years and still constitute the most important group of antibiotics. Their extensive use in veterinary medicine practices as growth promoters, and chemotherapeutic and/or prophylactic agents causes numerous residues in foodstuffs which present a serious health hazard. For this reason, sensitive and specific methods for the quantification of these compounds in numerous matrices have been published.

This article reviews the current status of the application of liquid-chromatography-based analytical methods in the analysis of β-lactam antibiotics. These methods are classified according to the different detection systems used: UV-visible spectrophotometry, mass spectrometry and other detection techniques such as fluorescence or chemiluminescence. We include applications in different fields (e.g., food, environmental, clinical and pharmaceutical).

Posted in Antibiotics, Chromatography, Drugs, Review, β-lactams | Tagged , | Comments Off on Advances in the determination of β-lactam antibiotics by liquid chromatography

Analysis of cephalosporin residues in environmental waters by capillary zone electrophoresis with off-line and on-line preconcentration

Posted on 1 August, 2012 by fqm302

A sensitive and reliable method using capillary zone electrophoresis with UV-diode array detection (CZE-DAD) has been developed and validated for trace determination of cephalosporin antibiotics in spring water, groundwater and river water matrices. Due to the lack of sensitivity of the UV-Vis detection method, a solid-phase extraction (SPE) method has been applied for off-line preconcentration and cleanup of water samples, in combination with an on-line preconcentration methodology named large volume sample stacking (LVSS) with polarity switching. The simultaneous determination of five cephalosporins of veterinary use, namely cephalexin (CFL), cephoperazone (CFPR), ceftiofur (CFTF), cephapirin (CFP) and cephazolin (CFZ) has been accomplished in environmental water samples using 70 mM acetate buffer, pH 7.0, applying a voltage of 22.5 kV at 25 °C and using cephadroxil (a cephalosporin for human use) as the internal standard. For the SPE procedure a HLB sorbent column was used. The combination of both off-line and on-line preconcentration procedures provided a significant improvement in sensitivity, obtaining detection limits of 0.1 μg L−1 for CFL; 0.2 μg L−1 for CFPR, CFTF and CFP, and 0.3 μg L−1 for CFZ. The SPE-LVSS-CZE-DAD procedure is suitable for monitoring these compounds in water samples with high sensitivity and precision and satisfactory recoveries.

Posted in Antibiotics, CZE, Cephalosporins, LVSS, SPE, UV-vis, Water | Tagged | Comments Off on Analysis of cephalosporin residues in environmental waters by capillary zone electrophoresis with off-line and on-line preconcentration

Determination of 5-nitroimidazoles and metabolites in environmental samples by micellar electrokinetic chromatography

Posted on 13 July, 2012 by fqm302

A method based on micellar electrokinetic chromatography (MEKC) with UV detection has been developed for the determination of nine 5-nitroimidazoles (5-NDZs), including metabolites in river water samples. Due to the relative insensitivity of UV detection in MEKC, a solid-phase extraction (SPE) method has been proposed that preconcentrates water samples fiftyfold and cleans them up off-line. An on-line preconcentration approach based on sweeping and the use of an extended light path fused-silica capillary (64.5 cm × 50 μm i.d., 56 cm effective length) was also found to improve the sensitivity of the method. Separation was carried out in <21 min using 20 mM phosphate buffer (pH 6.5) and 150 mM SDS as the background electrolyte (BGE). The temperature of the capillary was kept constant at 20°C, a voltage of 25 kV was applied (normal mode), and a detected wavelength of 320 nm was utilized. Hydrodynamic injection (50 mbar for 15 s) of the samples, which were dissolved in 20 mM phosphate (pH 6.5), was employed. The limits of detection were lower than 1.1 μg L−1. Recoveries of >80% from spiked river water samples were obtained for most of the analytes at three different concentration levels with acceptable precision. This method could provide an efficient and economical alternative to the use of chromatographic methods to monitor nitroimidazole residues, thus supplementing the relatively few methods available for the analysis of these compounds in environmental samples.

Posted in 5-nitroimidazoles, MEKC, SPE, Sweeping, UV-vis, Water | Tagged | Comments Off on Determination of 5-nitroimidazoles and metabolites in environmental samples by micellar electrokinetic chromatography

Convenient solid phase extraction of cephalosporins in milk using a molecularly imprinted polymer

Posted on 26 June, 2012 by fqm302

In this paper, a molecularly imprinted polymer (MIP) for cephalosporin molecules (cephalexin (CFL) and cephapirin (CFP)), was prepared by non covalent molecular imprinting approach and applied to solid phase extraction (SPE). For MIP synthesis, a tributylammonium cefadroxil salt (TBA–CFD) was used as template with methacrylic acid and ethylene glycol dimethacrylate as monomer and cross-linker, respectively, in acetone–methanol 92/8 (v/v) mixture. The selectivity of MIP versus non imprinted polymer (NIP) was confirmed for CFL, CFD and CFP in standard solutions as well as in milk samples. The efficiency of the synthesized MIP was evaluated by means of the application of the proposed MIP–SPE procedure to spiked milk samples previous to the HPLC method for the detection of cephalosporins. The MIP–SPE recoveries were higher than 60% for the three target analytes in spiked milk.

Posted in Cephalosporins, MIPs, Milk | Tagged | Comments Off on Convenient solid phase extraction of cephalosporins in milk using a molecularly imprinted polymer

Determination of ochratoxin A in wines by capillary liquid chromatography with laser induced fluorescence detection using dispersive liquid–liquid microextraction

Posted on 26 June, 2012 by fqm302

A method based on reverse phase capillary high performance liquid chromatography (capillary HPLC) coupled to laser-induced fluorescence detection (LIF) has been proposed for the determination of ochratoxin A (OTA) in wine samples. An anionic micellar medium was added to the mobile phase for increasing the fluorescence intensity and peak efficiency. Dispersive liquid–liquid microextraction (DLLME) has been used as a simple and efficient sample pretreatment method for the analysis of OTA in wines, being optimised by means of experimental design. The limit of detection was 5.5 ng L−1 (3 × S/N) and recoveries for different wines ranged from 91.7 to 98.1%. The proposed methodology could be classified as a green analytical chemistry alternative, combining the low organic solvent volumes required in the DLLME with the reduced consumption of mobile phase in capillary HPLC. The use of LIF as detector provided an extremely sensitive method for the determination of OTA in wines.

Posted in Capillary HPLC, DLLME, LIF, Mycotoxins, Wine | Tagged | Comments Off on Determination of ochratoxin A in wines by capillary liquid chromatography with laser induced fluorescence detection using dispersive liquid–liquid microextraction

Dispersive liquid-liquid microextraction using a low density extraction solvent for the determination of 17 N-methylcarbamates by micellar electrokinetic chromatography-electrospray-mass spectrometry employing a volatile surfactant

Posted on 23 June, 2012 by fqm302

A new analytical method based on micellar electrokinetic chromatography tandem mass spectrometry (MEKC–ESI–MS/MS) employing a MS friendly surfactant (ammonium perfluorooctanoate) is proposed and validated for the identification and simultaneous quantification of 17 N-methylcarbamate pesticides in environmental and drinking water samples. MS/MS detection using an ion trap as analyzer operating in the multiple reaction monitoring mode was used. Different parameters were optimized in order to obtain an adequate CE separation combined with the highest sensitivity in MS/MS. Dispersive liquid–liquid microextraction (DLLME) using a low-density extraction solvent has been proposed for extraction, obtaining a preconcentration factor of 10. Under optimum conditions, recoveries for fortified samples ranged from 83% to 101%, with relative standard deviations lower than 8%. The limits of detection ranged from 1 to 144 ng l−1, demonstrating the sensitivity and applicability of this fast, simple, and environmentally friendly method.

Posted in Carbamates, DLLME, MEKC, Mass spectrometry, Water | Tagged | Comments Off on Dispersive liquid-liquid microextraction using a low density extraction solvent for the determination of 17 N-methylcarbamates by micellar electrokinetic chromatography-electrospray-mass spectrometry employing a volatile surfactant

Determination of quinolones of veterinary use in bee products by ultra-high performance liquid chromatography–tandem mass spectrometry using a QuEChERS extraction procedure

Posted on 28 February, 2012 by fqm302

A reliable and rapid ultra high performance liquid chromatography tandem mass spectrometry (UHPLC–MS/MS) method has been developed for the determination of the eight quinolones of veterinary use regulated by European Union (marbofloxacin, ciprofloxacin, danofloxacin, enrofloxacin, sarafloxacin, difloxacin, flumequine and oxolinic acid). Chromatographic conditions were optimized in order to increase sample throughput and sensitivity. The antibiotics were detected by electrospray ionization in positive ion mode with multiple reaction monitoring (MRM) and MS/MS conditions were optimized in order to increase selectivity, selecting the corresponding product ions for quantification and identification. The separation was achieved in 3 min, using a Zorbax Eclipse Plus C18 column (50 mm × 2.1 mm, 1.8 μm), with a mobile phase of 0.02% aqueous formic acid solution and acetonitrile. A dispersive solid phase extraction methodology, often referred to as the “QuEChERS” (quick, easy, cheap, effective, rugged, and safe) method, was optimized for extraction of the quinolones from honey and also it was evaluated for other bee products such as royal jelly and propolis. The method was validated for each matrix in terms of linearity, trueness, precision, limits of detection (LODs) and quantification (LOQ). LODs ranged between 0.2 and 4.1 μg/kg with precision lower than 12% and satisfactory recoveries in most cases. The method was also applied for studying the occurrence of these antibiotics in several market samples.

Posted in Honey, Mass spectrometry, Propolis, QuEChERS, Quinolones, Royal jelly, UHPLC | Comments Off on Determination of quinolones of veterinary use in bee products by ultra-high performance liquid chromatography–tandem mass spectrometry using a QuEChERS extraction procedure

Capillary electrophoresis for the analysis of drugs of abuse in biological specimens of forensic interest

Posted on 21 December, 2011 by fqm302

We review analytical methodologies using capillary electrophoresis and related  techniques (micellar electrokinetic chromatography and capillary electrochromatography) with detection systems (ultraviolet-visible spectrometry, fluorescence, laser-induced fluorescence and mass spectrometry) for quantification of drugs of abuse and their metabolites in biological specimens of interest in forensic toxicology (e.g., blood, urine and hair). Despite some drawbacks that still need to be addressed and finally overcome when using this technique in forensic laboratories, the coupling of capillary electrophoresis and mass spectrometry generally provides a powerful option for detection and determination of very low concentrations of these compounds in some forensic matrices (e.g., hair).

Posted in Drugs, Electrophoresis, Review | Comments Off on Capillary electrophoresis for the analysis of drugs of abuse in biological specimens of forensic interest