Carmen Cruces Blanco

Laser induced fluorescence coupled to capillary electrophoresis for the determination of fluoroquinolones in foods of animal origin using molecularly imprinted polymers.

A method for the simultaneous determination of four fluoroquinolones of veterinary use (ciprofloxacin, danofloxacin, enrofloxacin and sarafloxacin) in two complex matrixes, such as bovine raw milk and pig kidney, has been established and validated. The method is based on the use of capillary electrophoresis (CE) coupled with a very sensitive detection mode, such as laser induced fluorescence (LIF) detection, due to the fact the all the compounds selected show native fluorescence. In order to achieve high selectivity in the sample treatment procedure, a commercially available molecularly imprinted polymer has been used for the solid phase extraction of the analytes. Once the retention and elution processes were optimized, the final extract was analyzed by CE-LIF using a 325 nm He-Cd laser. Optimum separation was obtained in a 70 cm x75 microm capillary using a 125 mM phosphoric acid solution at pH 2.8 with 36% methanol as background electrolyte. The method provided very low detection limits, ranging from 0.17 to 0.98 microg/kg for milk and 1.10 to 10.5 microg/kg for kidney, with acceptable precision and satisfactory recoveries.

An innovative way of obtaining room-temperature phosphorescence signals in solution

This manuscript presents an innovative way of obtaining room temperature phosphorescence (RTP) in solution. For the first time, the RTP of naphthalene derivatives have been observed in solution without using any kind of organized media. The RTP signals are a consequence of intermolecular protection when analytes are exclusively in the presence of a heavy atom salt and sodium sulfite is employed as an oxygen scavenger to minimize RTP quenching. A rigorous study of numerous experimental and instrumental variables has been carried out.

Variable-angle scanning fluorescence spectrometry for the simultaneous determination of three diuretic drugs

Abstract The applicability of variable-angle synchronous scanning (VASS) fluorescence spectroscopy has been demonstrated for the resolution of mixtures of three diuretics (furosemide, triamterene, piretamide) with closely overlapping fluorescence profiles. This technique permits linear or non-linear paths to be scanned at preselected angles through the excitation-emission matrix by scanning both monochromators at different speeds, in order to obtain the best variable-angle scanning spectra (highest signal values and interference-free bands). Such an approach has permitted the simultaneous determination of the three compounds at the μg to ng ml −1 level, with a relative standard deviation ≤ 5% ( n = 10). When applied to commercial pharmaceutical dosage forms, recoveries of the original drug between 98–101% have been obtained.

Application of variable-angle synchronous phosphorimetry in a microemulsion medium for the simultaneous determination of three polyaromatic hydrocarbons

The applicability of variable-angle synchronous scanning (VASS) phosphorimetry at room temperature has been demonstrated, for the first time, for the simultaneous determination of the polycyclic aromatic hydrocarbons phenanthrene, fluoranthene and benz[a]anthracene. This technique permits linear or non-linear paths to be scanned at preselected angles through the excitation-emission phosphorescence matrix in order to obtain the highest signal values and interference-free bands. The phosphorescence emissions of the three compounds have been obtained using microemulsion aqueous solutions in an apolar solvent. In order to obtain the optimum spectrophosphorimetric responses, a statistical model of central composite design type was applied. The increased selectivity afforded by the VASS technique has permitted the simultaneous determination of the three phosphorescent compounds with closely overlapping profiles added to coffee samples giving mean recoveries of 94% with a relative standard deviation of 1.5%.

Capillary electrochromatography-mass spectrometry for the determination of 5-nitroimidazole antibiotics in urine samples.

The separation of eight antibiotics belonging to 5‐nitroimidazole family was carried out by means of CEC coupled with MS. Preliminary experiments were carried out with ultraviolet detection in order to select the proper stationary and mobile phase. Among the different stationary phases studied (namely Lichrospher C18, 5 μm particle size; CogentTM Bidentate C18, 4.2 μm; Pinnacle II™ Phenyl, 3 μm; Pinnacle II™ Cyano, 3 μm), Cogent™ Bidentate C18 (4.2 μm) gave the best performance. For CEC‐MS coupling, a laboratory assembled liquid‐junction‐nano‐spray interface was used. In order to achieve a good sensitivity, special attention was paid to both optimization of the sheath liquid composition as well as selection of the injection mode. Under optimized CEC‐ESI‐MS conditions, the separation was accomplished within 22 min by using a column packed with a mixture of Bidentate C18:Lichrospher Silica‐60 (5 μm) 3:1 w/w, an inlet pressure of 11 bar, a voltage of 15 kV, and a mobile phase composed by 45:10:45 v/v/v ACN/MeOH/water containing ammonium acetate (5 mM pH 5). A combined hydrodynamic and electrokinetic injection of 8 bar, 15 kV, and 96 s was adopted. The method was validated in terms of repeatability and intermediate precision of retention times and peak areas, linearity, and LODs and LOQs. RSDs values were <2.9% for retention times and <16.1% for peak areas in both intraday and interday experiments. LOQ values were between 0.09 and 0.42 μg/mL for all compounds. Finally, the method was applied to the determination of three most employed 5‐nitroimidazole antibiotics (metronidazole, secnidazole, and ternidazole) in spiked urine samples, subjected to a SPE procedure. Recovery values in the 67–103% range were obtained. Furthermore, for the selected antibiotics, CEC‐MS2 spectra were obtained providing the unambiguous confirmation of these drugs in urine samples.

Simultaneous microemulsion room temperature phosphorimetric determination of five polycyclic aromatic hydrocarbons by variable-angle synchronous scanning

Abstract Five polycyclic aromatic hydrocarbons, i.e. acenaphthene, fluoranthene, pyrene, benz[a]anthracene and benzo[a]pyrene were simultaneously determined by variable-angle synchronous scanning (VASS) microemulsion phosphorimetry at room temperature. The phosphorescence emissions of the five compounds have been obtained using sodium sulphite as O2 scavenger and thallium(I) nitrate as heavy atom salt perturbation in sodium dodecyl sulphate (SDS) microemulsion aqueous solutions. In order to obtain the optimum phosphorescence responses, a statistical model of central composite design type, was applied. Despite the closely overlapping profiles of the five phosphorescent compounds, the increased selectivity afforded by the VASS technique has permitted their simultaneous determination after addition to road dust samples giving mean recoveries of 87.6% with a relative standard deviation of 3.0%, (n = 5).

Experimental Studies of the Factors That Influence 1-Naphthaleneacetamide Determination by Micelle-stabilized Room-temperature Phosphorescence

A micelle-stabilized room-temperature phosphorescence (MS-RTP) method was developed for the determination of the phytohormone 1-naphthaleneacetamide residues in fortified pear samples. The proposed method is based on the use of a micellar medium obtained by the surfactant sodium dodecyl sulfate in the presence of thallium nitrate as an external heavy atom salt. To avoid oxygen quenching, sodium sulfite solution was used. To establish the optimum experimental variables, a complete and exhaustive statistical analysis of the experimental data by a multivariate optimization approach was performed. MS-RTP spectra were obtained and successfully used to determine 1-naphthaleneacetamide by the established method without further separation, with a detection limit of 25 ng ml - 1 . The precision (RSD ≤ 2.55%) and recovery (≥ 91.9%) were satisfactory.

Application of derivative variable-angle synchronous scanning phosphorimetry in a microemulsion medium for the simultaneous determination of 2-naphthoxyacetic acid and 1-naphthalenacetamide

The applicability of derivative variable-angle synchronous scanning (DVASS) microemulsion phosphorimetry at room temperature (ME-RTP) was demonstrated for the simultaneous determination of the plant growth regulators 2-naphthoxyacetic acid and 1-naphthalenacetamide in soil samples. This technique permits linear or non-linear paths to be scanned at preselected angles through the excitation–emission phosphorescence matrix in order to obtain the highest signal values and interference-free bands. The phosphorescence emission of the two compounds was obtained using sodium sulfite as an O 2 scavenger and thallium nitrate as an external heavy atom salt perturbed in sodium docecyl sulfate microemulsion aqueous solutions. A statistical model of the central composite design type to obtain the optimum phosphorescence responses was applied. The increased selectivity afforded by the DVASS technique permitted the demonstration of its applicability to the simultaneous determination of phosphorescent signals of these two compounds obtained in a microemulsion medium which show closely overlapped profiles giving mean recoveries of 89.0% (n = 5) for 1-naphthalenacetamide and 103.5% (n = 5) for 2-naphthoxyacetic acid, with an RSD of 7.35 and 5.90%, respectively, in real samples.