J. Peris-Vicente

Characterization of proteinaceous glues in old paintings by separation of the o-phtalaldehyde derivatives of their amino acids by liquid chromatography with fluorescence detection.

A HPLC-fluorescence method for characterization of proteinaceous glues from binding media used in pictorial works of art prior to conservation or restoration treatment is proposed. Fluorescence derivatization of amino acids released by acid hydrolysis of standard proteins is studied. The derivatization reagent was o-phtalaldehyde with 2-mercaptoethanol as catalyst. Mobile phase was a programmed gradient among two eluents (water buffered at pH 5.8 wit 5% THF, and methanol) and is able to satisfactorily resolve the amino acid derivatives in 45min. Peak area ratios among amino acid derivatives and the leucine derivative are useful to characterize the proteins. The method shows good sensitivity and adequate linearity between 2.0x10(-3) and 3.3mmol/l of each amino acid, with a limit of detection of 6.0x10(-4)mmol/l. The proposed method has been successfully applied to artistic samples from items of the cultural heritage of Valencia (Spain).

Analytical and mineralogical studies of ore and impurities from a chromite mineral using X-ray analysis, electrochemical and microscopy techniques.

A wide analytical study of South African chromite ore, material with high interest in ceramic industry, has been carried out. With this purpose, an accurate chemical identification and mineralogical characterization of the mineral and the gangue have been performed using X-ray fluorescence (XRF), voltammetry, X-ray diffraction (XRD), light microscopy (LM), and scanning electron microscopy (SEM/EDX). The elemental composition of the sample (ore and gangue) has been obtained by XRF. The voltammetric analysis has allowed to demonstrate that iron in the sample was as Fe(II). The main compound of the chromite ore was a spinel (magnesiochromite ferroan), identified by XRD from the sample, which constitutes the chromite ore. This technique has also been useful to characterize some silicates as impurities in the chromite ore sample. Light microscopy has allowed the detection of the spinel and the identification of a silicate impurity (chrome chlorite), by means of their colouration. On the other hand, the other silicate impurity was identified as labradorite by means of X-ray microscopy by SEM/EDX. Finally, a strategy was developed to calculate the composition of each mineral in the unknown sample. The obtained results were: chromite spinel 82.89%, chlorite 12.79% and labradorite 4.32%.

Determination of Paroxetine in Pharmaceutical Preparations Using HPLC with Electrochemical Detection

A reliable and sensitive high performance liquid chromatographic method for the determination of widely prescribed antidepressant has been developed. Paroxetine is a potent selective serotonin reuptake inhibitor used for the treatment of depression and various mood disorders. The optimum mobile phase was prepared using a combination of 40% acetonitrile and phosphate buffer 0.01 M to pH 3 and running under isocratic mode at a flow rate of 1.0 ml/min. with electrochemical detection at 0.9V. The applicability of the developed method is in the field of quality control as well as for monitoring the level of drug at various concentrations during synthesis of the parent drug. The suggested methodology was validated following the guidelines of the FDA in terms of: sensitivity (LOD and LOQ, 0.005 and 0.01 ng/mL, respectively), linearity between 0.5 - 50 ng/mL (r 2 > 0.9999), inter- and intraday precision (< 0.259% and < 0.538%), robustness (less than 5.0%) and recovery (99.7 - 100.7%). The developed method is specific, rapid (less than 10 min), precise, reliable, accurate, cheap and suitable for routine analysis for the determination of paroxetine in pharmaceutical preparations.

Development of a method to determine axitinib, lapatinib and afatinib in plasma by micellar liquid chromatography and validation by the European Medicines Agency guidelines

A method based on micellar liquid chromatography to quantify the tyrosine kinase inhibitors axitinib, lapatinib and afatinib in plasma is reported. The sample pretreatment was a simple 1/5-dilution in a pure micellar solution, filtration and direct injection, without requiring extraction or purification steps. The three drugs were resolved from the matrix in 17min, using an aqueous solution of 0.07M sodium dodecyl sulfate - 6.0% 1-pentanol, buffered at pH7 with 0.01M phosphate salt as mobile phase, running under isocratic mode at 1mL/min through a C18 column. The detection was performed by absorbance at 260nm. An accurate mathematical relationship was established between the retention factor of each drug and the surfactant/organic solvent concentration in the mobile phase, achieved with a limited number of experiments, in order to optimize these factors. A binding behavior of the analytes face to the micelles was found out. The method was successfully validated by the guidelines of the European Medicines Agency in terms of: selectivity, linearity (r2>0.9995), calibration range (0.5 to 10mg/L), limit of detection (0.2mg/L), carry-over effect, accuracy (-8.1 to +6.9%), precision (<13.8%), dilution integrity, matrix effect, stability and robustness. The procedure was found reliable, practical, economic, accessible, short-time, easy-to-handle, inexpensive, environmental-friendly, safe, useful for the analysis of many samples per day. Finally, the method was applied to the analysis of incurred, using quality control samples in the same analytical run, with adequate results. Therefore, it can be implementable for routine analysis in clinical laboratories.

Analytical Study of a Resinous Material Used as Sealing in Ancient Pottery Found in an Archaeological Site by Thermally Assisted Hydrolysis Methylation–Gas Chromatography–Mass Spectrometry, Vibrational Spectroscopy and Light Microscopy

Abstract A resin sample was found in the archaeological site of Lixus (Morocco), belonging to the second century BC. The resinous material was found inside an amphora containing iron remains used in the plug as sealing material to hermetically close the pottery. The resinous sample was studied by several analytical techniques, as thermally assisted hydrolysis and methylation–gas chromatography–mass spectrometry (THM–GC–MS), Fourier transformed infrared spectroscopy (FTIR), and light microscopy. The material was identified as a Pinaceae resin. Therefore, a modern pine resin was also analyzed to consider the influence of aging in the archaeological sample. The ancient material was found not too oxidized, owing to the conservation conditions inside the amphora, protected from air and moisture.

Electrochemical characterization of solid state reaction kinetics using voltammetry of microparticles. Application to thermal decomposition of iron chromites

The voltammetry of microparticles is applied to characterize the electrocatalytic ability of solids towards selected electrochemical processes. The variation of catalytic currents under fixed electrochemical conditions permits to obtain composition/time data to be fitted with solid state kinetic models. This methodology is applied to analyze the thermal decomposition of magnesiochromite ferroan and chlorite chromian standards and a South Africa iron chromite ore on the basis of the significant catalytic effect on the electrochemical oxygen evolution reaction (OER) in aqueous alkaline media at mineral-modified graphite electrodes. Measurement of the time variation of catalytic current for OER provides a direct estimate of fractional conversion of the reactant in the course of the reaction of thermal decomposition enabling for testing different reaction kinetic models.