Peña Farfal, Carlos

Confocal laser scanning microscopy (CLSM) supported with multivariate analysis is proposed as hyperspectral imaging technique to identify, locate, and quantify, in a direct way, active pharmaceutical ingredients (APIs) in synthetic tablets, with the aim of establishing a new analysis methodology that collects qualitative and quantitative information from the surface and inner layers of solid dosage forms. This method is proposed as a novel, non-destructive, rapid, and highly sensitive hyperspectral imaging technique, with an excellent spatial resolution at the microscopic level. Two chemical systems comprising pharmaceutical mixtures of acetaminophen–caffeine–excipients and digoxin–excipients were analyzed by multivariate curve resolution-alternating least squares (MCR-ALS) using emission spectra obtained from microscopic images with the pixel sizes of 512 μm × 512 μm to localize the APIs in the tablets. In addition, partial least squares (PLS) regression models were developed and used for calibration to obtain the concentration of the fluorescent active ingredients. The analysis by MCR-ALS delivered excellent results in localizing the fluorescent compounds; meanwhile, PLS achieved good error parameters for prediction of the external validation set for the quantification of caffeine and less successful quantification of digoxin. The performance of CLSM was evaluated by estimation of the analytical figures of merit of the technique to assess the quantification of APIs, including calculations of the uncertainty in the signal, sensitivity, analytical sensitivity, and ranges of detection and quantification limits. Use of CLSM as hyperspectral imaging attempts to increase the application of this technique in direct analysis of solid samples, showing that autofluorescent compounds can be analyzed for qualitative and quantitative purposes in presence of interferents by application of chemometrics.

The study and determination of the antioxidant capacity of the Greigia Sphacelata fruit were carried out. G. sphacelata is an endemic fruit of central-southern Chile, better known as Chupón or Quiscal. Spectrophotometric and modified ORAC test were developed for antioxidant capacity d eterminations, and later an electrochemical method was developed by differential impulse voltammetry (DPV) with a vitreous carbon electrode for the quantification of the antioxidant capacity expressed in equivalent of the Trolox standard in µmolL-1. Once the voltammetric test was developed, the correlation study between both methods used to determine the antioxidant capacity of Greigia sphacelata was carried out. The results of the determination of the antioxidant capacity of Greigia sphacelata by ORAC test report an antioxidant capacity of 3525 µmol/100g equivalents of Trolox. Concerning the concentration obtained by the electrochemical methodology, 724 µmol/100g Trolox equivalents is obtained for a linear correlation r = 0.969 with the spectrophotometric method.

The anodic oxidation (AO) of 30 pharmaceuticals including antibiotics, hormones, antihistaminics, anti-inflammatories, antidepressants, antihypertensives, and antiulcer agents, in solutions containing different supporting electrolytes media (0.05 M Na2SO4, 0.05 M NaCl, and 0.05 M Na2SO4 + 0.05 M NaCl) at natural pH was studied. A boron-doped diamond (BDD) electrode and a stainless-steel electrode were used as anode and cathode, respectively, and three current densities of 6, 20, and 40 mA cm−2 were applied. The results showed high mineralization rates, above 85%, in all the tested electrolytic media. 25 intermediaries produced during the electrooxidation were identified, depending on the supporting electrolyte together with the formation of carboxylic acids, NO3−, SO42− and NH4+ ions. The formation of intermediates in chloride medium produced an increase in absorbance. Finally, a real secondary effluent spiked with the 30 pharmaceuticals was treated by AO applying 6 mA cm−2 at natural pH and without addition of supporting electrolyte, reaching c.a. 90% mineralization after 300 min, with an energy consumption of 18.95 kW h m−3 equivalent to 2.90 USD m−3. A degradation scheme for the mixture of emerging contaminants in both electrolytic media is proposed. Thus, the application of anodic oxidation generates a high concentration of hydroxyl radicals that favors the mineralization of the pharmaceuticals present in the spiked secondary effluent sample.

Food packaging for traditional foods mainly serves to isolate foods from external environmental. For this reason, it is a growing interest in developing active packaging materials that can extend foodstuff shelf-life. Also, it could counteract the level of contamination by plastic in the environment using biodegradable polymers. For this purpose, poly(3-hydroxybutyrate) (PHB)-thermoplastic starch (TPS)/ organically modified montmorillonite (OMMT)/eugenol bionanocomposites were prepared by melt blending. Morphology, thermal, and mechanical properties were determined by comparing the concentration influence of eugenol and clay on the PHB-TPS blend and PHB. X-ray diffraction measurements revealed the existence of exfoliated morphology in the bionanocomposites. Atomic force microscopy imaging (AFM) showed the difference in morphological characteristics of the pure PHB and the prepared bionanocomposites. Roughness analysis from the AFM data indicates that the presence of clay and TPS increases the roughness with respect to PHB. Dynamic mechanical thermal analysis (DMTA) showed that bionanocomposites have an improved storage module. Finally, properties such as hardness and elastic modulus studied by nanoindentation showed a decrease with respect to PHB. The presence of eugenol in the bionanocomposites does not show a significant effect on the different properties.